Library import 16 (#2433)

Co-authored-by: robot-piglet <robot-piglet@yandex-team.com>
Co-authored-by: deshevoy <deshevoy@yandex-team.com>
Co-authored-by: robot-contrib <robot-contrib@yandex-team.com>
Co-authored-by: thegeorg <thegeorg@yandex-team.com>
Co-authored-by: robot-ya-builder <robot-ya-builder@yandex-team.com>
Co-authored-by: svidyuk <svidyuk@yandex-team.com>
Co-authored-by: shadchin <shadchin@yandex-team.com>
Co-authored-by: robot-ratatosk <robot-ratatosk@yandex-team.com>
Co-authored-by: innokentii <innokentii@yandex-team.com>
Co-authored-by: arkady-e1ppa <arkady-e1ppa@yandex-team.com>
Co-authored-by: snermolaev <snermolaev@yandex-team.com>
Co-authored-by: dimdim11 <dimdim11@yandex-team.com>
Co-authored-by: kickbutt <kickbutt@yandex-team.com>
Co-authored-by: abdullinsaid <abdullinsaid@yandex-team.com>
Co-authored-by: korsunandrei <korsunandrei@yandex-team.com>
Co-authored-by: petrk <petrk@yandex-team.com>
Co-authored-by: miroslav2 <miroslav2@yandex-team.com>
Co-authored-by: serjflint <serjflint@yandex-team.com>
Co-authored-by: akhropov <akhropov@yandex-team.com>
Co-authored-by: prettyboy <prettyboy@yandex-team.com>
Co-authored-by: ilikepugs <ilikepugs@yandex-team.com>
Co-authored-by: hiddenpath <hiddenpath@yandex-team.com>
Co-authored-by: mikhnenko <mikhnenko@yandex-team.com>
Co-authored-by: spreis <spreis@yandex-team.com>
Co-authored-by: andreyshspb <andreyshspb@yandex-team.com>
Co-authored-by: dimaandreev <dimaandreev@yandex-team.com>
Co-authored-by: rashid <rashid@yandex-team.com>
Co-authored-by: robot-ydb-importer <robot-ydb-importer@yandex-team.com>
Co-authored-by: r-vetrov <r-vetrov@yandex-team.com>
Co-authored-by: ypodlesov <ypodlesov@yandex-team.com>
Co-authored-by: zaverden <zaverden@yandex-team.com>
Co-authored-by: vpozdyayev <vpozdyayev@yandex-team.com>
Co-authored-by: robot-cozmo <robot-cozmo@yandex-team.com>
Co-authored-by: v-korovin <v-korovin@yandex-team.com>
Co-authored-by: arikon <arikon@yandex-team.com>
Co-authored-by: khoden <khoden@yandex-team.com>
Co-authored-by: psydmm <psydmm@yandex-team.com>
Co-authored-by: robot-javacom <robot-javacom@yandex-team.com>
Co-authored-by: dtorilov <dtorilov@yandex-team.com>
Co-authored-by: sennikovmv <sennikovmv@yandex-team.com>
Co-authored-by: hcpp <hcpp@ydb.tech>

1 files changed, 2596 insertions, 0 deletions

diff --git a/contrib/tools/python3/Modules/_struct.c b/contrib/tools/python3/Modules/_struct.c
new file mode 100644
index 0000000000..55efc0c6cf
--- /dev/null
+++ b/contrib/tools/python3/Modules/_struct.c
@@ -0,0 +1,2596 @@
+/* struct module -- pack values into and (out of) bytes objects */
+
+/* New version supporting byte order, alignment and size options,
+   character strings, and unsigned numbers */
+
+#ifndef Py_BUILD_CORE_BUILTIN
+#  define Py_BUILD_CORE_MODULE 1
+#endif
+
+#define PY_SSIZE_T_CLEAN
+
+#include "Python.h"
+#include "pycore_moduleobject.h"  // _PyModule_GetState()
+#include "structmember.h"         // PyMemberDef
+#include <ctype.h>
+
+/*[clinic input]
+class Struct "PyStructObject *" "&PyStructType"
+[clinic start generated code]*/
+/*[clinic end generated code: output=da39a3ee5e6b4b0d input=9b032058a83ed7c3]*/
+
+typedef struct {
+    PyObject *cache;
+    PyObject *PyStructType;
+    PyObject *unpackiter_type;
+    PyObject *StructError;
+} _structmodulestate;
+
+static inline _structmodulestate*
+get_struct_state(PyObject *module)
+{
+    void *state = _PyModule_GetState(module);
+    assert(state != NULL);
+    return (_structmodulestate *)state;
+}
+
+static struct PyModuleDef _structmodule;
+
+#define get_struct_state_structinst(self) \
+    (get_struct_state(PyType_GetModuleByDef(Py_TYPE(self), &_structmodule)))
+#define get_struct_state_iterinst(self) \
+    (get_struct_state(PyType_GetModule(Py_TYPE(self))))
+
+/* The translation function for each format character is table driven */
+typedef struct _formatdef {
+    char format;
+    Py_ssize_t size;
+    Py_ssize_t alignment;
+    PyObject* (*unpack)(_structmodulestate *, const char *,
+                        const struct _formatdef *);
+    int (*pack)(_structmodulestate *, char *, PyObject *,
+                const struct _formatdef *);
+} formatdef;
+
+typedef struct _formatcode {
+    const struct _formatdef *fmtdef;
+    Py_ssize_t offset;
+    Py_ssize_t size;
+    Py_ssize_t repeat;
+} formatcode;
+
+/* Struct object interface */
+
+typedef struct {
+    PyObject_HEAD
+    Py_ssize_t s_size;
+    Py_ssize_t s_len;
+    formatcode *s_codes;
+    PyObject *s_format;
+    PyObject *weakreflist; /* List of weak references */
+} PyStructObject;
+
+#define PyStruct_Check(op, state) PyObject_TypeCheck(op, (PyTypeObject *)(state)->PyStructType)
+
+/* Define various structs to figure out the alignments of types */
+
+
+typedef struct { char c; short x; } st_short;
+typedef struct { char c; int x; } st_int;
+typedef struct { char c; long x; } st_long;
+typedef struct { char c; float x; } st_float;
+typedef struct { char c; double x; } st_double;
+typedef struct { char c; void *x; } st_void_p;
+typedef struct { char c; size_t x; } st_size_t;
+typedef struct { char c; _Bool x; } st_bool;
+
+#define SHORT_ALIGN (sizeof(st_short) - sizeof(short))
+#define INT_ALIGN (sizeof(st_int) - sizeof(int))
+#define LONG_ALIGN (sizeof(st_long) - sizeof(long))
+#define FLOAT_ALIGN (sizeof(st_float) - sizeof(float))
+#define DOUBLE_ALIGN (sizeof(st_double) - sizeof(double))
+#define VOID_P_ALIGN (sizeof(st_void_p) - sizeof(void *))
+#define SIZE_T_ALIGN (sizeof(st_size_t) - sizeof(size_t))
+#define BOOL_ALIGN (sizeof(st_bool) - sizeof(_Bool))
+
+/* We can't support q and Q in native mode unless the compiler does;
+   in std mode, they're 8 bytes on all platforms. */
+typedef struct { char c; long long x; } s_long_long;
+#define LONG_LONG_ALIGN (sizeof(s_long_long) - sizeof(long long))
+
+#ifdef __powerc
+#pragma options align=reset
+#endif
+
+/*[python input]
+class cache_struct_converter(CConverter):
+    type = 'PyStructObject *'
+    converter = 'cache_struct_converter'
+    c_default = "NULL"
+
+    def parse_arg(self, argname, displayname):
+        return """
+            if (!{converter}(module, {argname}, &{paramname})) {{{{
+                goto exit;
+            }}}}
+            """.format(argname=argname, paramname=self.name,
+                       converter=self.converter)
+
+    def cleanup(self):
+        return "Py_XDECREF(%s);\n" % self.name
+[python start generated code]*/
+/*[python end generated code: output=da39a3ee5e6b4b0d input=d6746621c2fb1a7d]*/
+
+static int cache_struct_converter(PyObject *, PyObject *, PyStructObject **);
+
+#include "clinic/_struct.c.h"
+
+/* Helper for integer format codes: converts an arbitrary Python object to a
+   PyLongObject if possible, otherwise fails.  Caller should decref. */
+
+static PyObject *
+get_pylong(_structmodulestate *state, PyObject *v)
+{
+    assert(v != NULL);
+    if (!PyLong_Check(v)) {
+        /* Not an integer;  try to use __index__ to convert. */
+        if (PyIndex_Check(v)) {
+            v = _PyNumber_Index(v);
+            if (v == NULL)
+                return NULL;
+        }
+        else {
+            PyErr_SetString(state->StructError,
+                            "required argument is not an integer");
+            return NULL;
+        }
+    }
+    else
+        Py_INCREF(v);
+
+    assert(PyLong_Check(v));
+    return v;
+}
+
+/* Helper routine to get a C long and raise the appropriate error if it isn't
+   one */
+
+static int
+get_long(_structmodulestate *state, PyObject *v, long *p)
+{
+    long x;
+
+    v = get_pylong(state, v);
+    if (v == NULL)
+        return -1;
+    assert(PyLong_Check(v));
+    x = PyLong_AsLong(v);
+    Py_DECREF(v);
+    if (x == (long)-1 && PyErr_Occurred()) {
+        return -1;
+    }
+    *p = x;
+    return 0;
+}
+
+
+/* Same, but handling unsigned long */
+
+static int
+get_ulong(_structmodulestate *state, PyObject *v, unsigned long *p)
+{
+    unsigned long x;
+
+    v = get_pylong(state, v);
+    if (v == NULL)
+        return -1;
+    assert(PyLong_Check(v));
+    x = PyLong_AsUnsignedLong(v);
+    Py_DECREF(v);
+    if (x == (unsigned long)-1 && PyErr_Occurred()) {
+        return -1;
+    }
+    *p = x;
+    return 0;
+}
+
+/* Same, but handling native long long. */
+
+static int
+get_longlong(_structmodulestate *state, PyObject *v, long long *p)
+{
+    long long x;
+
+    v = get_pylong(state, v);
+    if (v == NULL)
+        return -1;
+    assert(PyLong_Check(v));
+    x = PyLong_AsLongLong(v);
+    Py_DECREF(v);
+    if (x == (long long)-1 && PyErr_Occurred()) {
+        return -1;
+    }
+    *p = x;
+    return 0;
+}
+
+/* Same, but handling native unsigned long long. */
+
+static int
+get_ulonglong(_structmodulestate *state, PyObject *v, unsigned long long *p)
+{
+    unsigned long long x;
+
+    v = get_pylong(state, v);
+    if (v == NULL)
+        return -1;
+    assert(PyLong_Check(v));
+    x = PyLong_AsUnsignedLongLong(v);
+    Py_DECREF(v);
+    if (x == (unsigned long long)-1 && PyErr_Occurred()) {
+        return -1;
+    }
+    *p = x;
+    return 0;
+}
+
+/* Same, but handling Py_ssize_t */
+
+static int
+get_ssize_t(_structmodulestate *state, PyObject *v, Py_ssize_t *p)
+{
+    Py_ssize_t x;
+
+    v = get_pylong(state, v);
+    if (v == NULL)
+        return -1;
+    assert(PyLong_Check(v));
+    x = PyLong_AsSsize_t(v);
+    Py_DECREF(v);
+    if (x == (Py_ssize_t)-1 && PyErr_Occurred()) {
+        return -1;
+    }
+    *p = x;
+    return 0;
+}
+
+/* Same, but handling size_t */
+
+static int
+get_size_t(_structmodulestate *state, PyObject *v, size_t *p)
+{
+    size_t x;
+
+    v = get_pylong(state, v);
+    if (v == NULL)
+        return -1;
+    assert(PyLong_Check(v));
+    x = PyLong_AsSize_t(v);
+    Py_DECREF(v);
+    if (x == (size_t)-1 && PyErr_Occurred()) {
+        return -1;
+    }
+    *p = x;
+    return 0;
+}
+
+
+#define RANGE_ERROR(state, f, flag) return _range_error(state, f, flag)
+
+
+/* Floating point helpers */
+
+static PyObject *
+unpack_halffloat(const char *p,  /* start of 2-byte string */
+                 int le)         /* true for little-endian, false for big-endian */
+{
+    double x = PyFloat_Unpack2(p, le);
+    if (x == -1.0 && PyErr_Occurred()) {
+        return NULL;
+    }
+    return PyFloat_FromDouble(x);
+}
+
+static int
+pack_halffloat(_structmodulestate *state,
+               char *p,      /* start of 2-byte string */
+               PyObject *v,  /* value to pack */
+               int le)       /* true for little-endian, false for big-endian */
+{
+    double x = PyFloat_AsDouble(v);
+    if (x == -1.0 && PyErr_Occurred()) {
+        PyErr_SetString(state->StructError,
+                        "required argument is not a float");
+        return -1;
+    }
+    return PyFloat_Pack2(x, p, le);
+}
+
+static PyObject *
+unpack_float(const char *p,  /* start of 4-byte string */
+         int le)             /* true for little-endian, false for big-endian */
+{
+    double x;
+
+    x = PyFloat_Unpack4(p, le);
+    if (x == -1.0 && PyErr_Occurred())
+        return NULL;
+    return PyFloat_FromDouble(x);
+}
+
+static PyObject *
+unpack_double(const char *p,  /* start of 8-byte string */
+          int le)         /* true for little-endian, false for big-endian */
+{
+    double x;
+
+    x = PyFloat_Unpack8(p, le);
+    if (x == -1.0 && PyErr_Occurred())
+        return NULL;
+    return PyFloat_FromDouble(x);
+}
+
+/* Helper to format the range error exceptions */
+static int
+_range_error(_structmodulestate *state, const formatdef *f, int is_unsigned)
+{
+    /* ulargest is the largest unsigned value with f->size bytes.
+     * Note that the simpler:
+     *     ((size_t)1 << (f->size * 8)) - 1
+     * doesn't work when f->size == sizeof(size_t) because C doesn't
+     * define what happens when a left shift count is >= the number of
+     * bits in the integer being shifted; e.g., on some boxes it doesn't
+     * shift at all when they're equal.
+     */
+    const size_t ulargest = (size_t)-1 >> ((SIZEOF_SIZE_T - f->size)*8);
+    assert(f->size >= 1 && f->size <= SIZEOF_SIZE_T);
+    if (is_unsigned)
+        PyErr_Format(state->StructError,
+            "'%c' format requires 0 <= number <= %zu",
+            f->format,
+            ulargest);
+    else {
+        const Py_ssize_t largest = (Py_ssize_t)(ulargest >> 1);
+        PyErr_Format(state->StructError,
+            "'%c' format requires %zd <= number <= %zd",
+            f->format,
+            ~ largest,
+            largest);
+    }
+
+    return -1;
+}
+
+
+
+/* A large number of small routines follow, with names of the form
+
+   [bln][up]_TYPE
+
+   [bln] distinguishes among big-endian, little-endian and native.
+   [pu] distinguishes between pack (to struct) and unpack (from struct).
+   TYPE is one of char, byte, ubyte, etc.
+*/
+
+/* Native mode routines. ****************************************************/
+/* NOTE:
+   In all n[up]_<type> routines handling types larger than 1 byte, there is
+   *no* guarantee that the p pointer is properly aligned for each type,
+   therefore memcpy is called.  An intermediate variable is used to
+   compensate for big-endian architectures.
+   Normally both the intermediate variable and the memcpy call will be
+   skipped by C optimisation in little-endian architectures (gcc >= 2.91
+   does this). */
+
+static PyObject *
+nu_char(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    return PyBytes_FromStringAndSize(p, 1);
+}
+
+static PyObject *
+nu_byte(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    return PyLong_FromLong((long) *(signed char *)p);
+}
+
+static PyObject *
+nu_ubyte(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    return PyLong_FromLong((long) *(unsigned char *)p);
+}
+
+static PyObject *
+nu_short(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    short x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyLong_FromLong((long)x);
+}
+
+static PyObject *
+nu_ushort(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned short x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyLong_FromLong((long)x);
+}
+
+static PyObject *
+nu_int(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    int x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyLong_FromLong((long)x);
+}
+
+static PyObject *
+nu_uint(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned int x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyLong_FromUnsignedLong((unsigned long)x);
+}
+
+static PyObject *
+nu_long(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    long x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyLong_FromLong(x);
+}
+
+static PyObject *
+nu_ulong(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyLong_FromUnsignedLong(x);
+}
+
+static PyObject *
+nu_ssize_t(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    Py_ssize_t x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyLong_FromSsize_t(x);
+}
+
+static PyObject *
+nu_size_t(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    size_t x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyLong_FromSize_t(x);
+}
+
+static PyObject *
+nu_longlong(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    long long x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyLong_FromLongLong(x);
+}
+
+static PyObject *
+nu_ulonglong(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long long x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyLong_FromUnsignedLongLong(x);
+}
+
+static PyObject *
+nu_bool(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    _Bool x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyBool_FromLong(x != 0);
+}
+
+
+static PyObject *
+nu_halffloat(_structmodulestate *state, const char *p, const formatdef *f)
+{
+#if PY_LITTLE_ENDIAN
+    return unpack_halffloat(p, 1);
+#else
+    return unpack_halffloat(p, 0);
+#endif
+}
+
+static PyObject *
+nu_float(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    float x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyFloat_FromDouble((double)x);
+}
+
+static PyObject *
+nu_double(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    double x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyFloat_FromDouble(x);
+}
+
+static PyObject *
+nu_void_p(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    void *x;
+    memcpy((char *)&x, p, sizeof x);
+    return PyLong_FromVoidPtr(x);
+}
+
+static int
+np_byte(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    long x;
+    if (get_long(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 0);
+        }
+        return -1;
+    }
+    if (x < -128 || x > 127) {
+        RANGE_ERROR(state, f, 0);
+    }
+    *p = (char)x;
+    return 0;
+}
+
+static int
+np_ubyte(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    long x;
+    if (get_long(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 1);
+        }
+        return -1;
+    }
+    if (x < 0 || x > 255) {
+        RANGE_ERROR(state, f, 1);
+    }
+    *(unsigned char *)p = (unsigned char)x;
+    return 0;
+}
+
+static int
+np_char(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    if (!PyBytes_Check(v) || PyBytes_Size(v) != 1) {
+        PyErr_SetString(state->StructError,
+                        "char format requires a bytes object of length 1");
+        return -1;
+    }
+    *p = *PyBytes_AS_STRING(v);
+    return 0;
+}
+
+static int
+np_short(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    long x;
+    short y;
+    if (get_long(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 0);
+        }
+        return -1;
+    }
+    if (x < SHRT_MIN || x > SHRT_MAX) {
+        RANGE_ERROR(state, f, 0);
+    }
+    y = (short)x;
+    memcpy(p, (char *)&y, sizeof y);
+    return 0;
+}
+
+static int
+np_ushort(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    long x;
+    unsigned short y;
+    if (get_long(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 1);
+        }
+        return -1;
+    }
+    if (x < 0 || x > USHRT_MAX) {
+        RANGE_ERROR(state, f, 1);
+    }
+    y = (unsigned short)x;
+    memcpy(p, (char *)&y, sizeof y);
+    return 0;
+}
+
+static int
+np_int(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    long x;
+    int y;
+    if (get_long(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 0);
+        }
+        return -1;
+    }
+#if (SIZEOF_LONG > SIZEOF_INT)
+    if ((x < ((long)INT_MIN)) || (x > ((long)INT_MAX)))
+        RANGE_ERROR(state, f, 0);
+#endif
+    y = (int)x;
+    memcpy(p, (char *)&y, sizeof y);
+    return 0;
+}
+
+static int
+np_uint(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    unsigned long x;
+    unsigned int y;
+    if (get_ulong(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 1);
+        }
+        return -1;
+    }
+    y = (unsigned int)x;
+#if (SIZEOF_LONG > SIZEOF_INT)
+    if (x > ((unsigned long)UINT_MAX))
+        RANGE_ERROR(state, f, 1);
+#endif
+    memcpy(p, (char *)&y, sizeof y);
+    return 0;
+}
+
+static int
+np_long(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    long x;
+    if (get_long(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 0);
+        }
+        return -1;
+    }
+    memcpy(p, (char *)&x, sizeof x);
+    return 0;
+}
+
+static int
+np_ulong(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    unsigned long x;
+    if (get_ulong(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 1);
+        }
+        return -1;
+    }
+    memcpy(p, (char *)&x, sizeof x);
+    return 0;
+}
+
+static int
+np_ssize_t(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    Py_ssize_t x;
+    if (get_ssize_t(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 0);
+        }
+        return -1;
+    }
+    memcpy(p, (char *)&x, sizeof x);
+    return 0;
+}
+
+static int
+np_size_t(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    size_t x;
+    if (get_size_t(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 1);
+        }
+        return -1;
+    }
+    memcpy(p, (char *)&x, sizeof x);
+    return 0;
+}
+
+static int
+np_longlong(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    long long x;
+    if (get_longlong(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            PyErr_Format(state->StructError,
+                         "'%c' format requires %lld <= number <= %lld",
+                         f->format,
+                         LLONG_MIN,
+                         LLONG_MAX);
+        }
+        return -1;
+    }
+    memcpy(p, (char *)&x, sizeof x);
+    return 0;
+}
+
+static int
+np_ulonglong(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    unsigned long long x;
+    if (get_ulonglong(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            PyErr_Format(state->StructError,
+                         "'%c' format requires 0 <= number <= %llu",
+                         f->format,
+                         ULLONG_MAX);
+        }
+        return -1;
+    }
+    memcpy(p, (char *)&x, sizeof x);
+    return 0;
+}
+
+
+static int
+np_bool(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    int y;
+    _Bool x;
+    y = PyObject_IsTrue(v);
+    if (y < 0)
+        return -1;
+    x = y;
+    memcpy(p, (char *)&x, sizeof x);
+    return 0;
+}
+
+static int
+np_halffloat(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+#if PY_LITTLE_ENDIAN
+    return pack_halffloat(state, p, v, 1);
+#else
+    return pack_halffloat(state, p, v, 0);
+#endif
+}
+
+static int
+np_float(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    float x = (float)PyFloat_AsDouble(v);
+    if (x == -1 && PyErr_Occurred()) {
+        PyErr_SetString(state->StructError,
+                        "required argument is not a float");
+        return -1;
+    }
+    memcpy(p, (char *)&x, sizeof x);
+    return 0;
+}
+
+static int
+np_double(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    double x = PyFloat_AsDouble(v);
+    if (x == -1 && PyErr_Occurred()) {
+        PyErr_SetString(state->StructError,
+                        "required argument is not a float");
+        return -1;
+    }
+    memcpy(p, (char *)&x, sizeof(double));
+    return 0;
+}
+
+static int
+np_void_p(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    void *x;
+
+    v = get_pylong(state, v);
+    if (v == NULL)
+        return -1;
+    assert(PyLong_Check(v));
+    x = PyLong_AsVoidPtr(v);
+    Py_DECREF(v);
+    if (x == NULL && PyErr_Occurred())
+        return -1;
+    memcpy(p, (char *)&x, sizeof x);
+    return 0;
+}
+
+static const formatdef native_table[] = {
+    {'x',       sizeof(char),   0,              NULL},
+    {'b',       sizeof(char),   0,              nu_byte,        np_byte},
+    {'B',       sizeof(char),   0,              nu_ubyte,       np_ubyte},
+    {'c',       sizeof(char),   0,              nu_char,        np_char},
+    {'s',       sizeof(char),   0,              NULL},
+    {'p',       sizeof(char),   0,              NULL},
+    {'h',       sizeof(short),  SHORT_ALIGN,    nu_short,       np_short},
+    {'H',       sizeof(short),  SHORT_ALIGN,    nu_ushort,      np_ushort},
+    {'i',       sizeof(int),    INT_ALIGN,      nu_int,         np_int},
+    {'I',       sizeof(int),    INT_ALIGN,      nu_uint,        np_uint},
+    {'l',       sizeof(long),   LONG_ALIGN,     nu_long,        np_long},
+    {'L',       sizeof(long),   LONG_ALIGN,     nu_ulong,       np_ulong},
+    {'n',       sizeof(size_t), SIZE_T_ALIGN,   nu_ssize_t,     np_ssize_t},
+    {'N',       sizeof(size_t), SIZE_T_ALIGN,   nu_size_t,      np_size_t},
+    {'q',       sizeof(long long), LONG_LONG_ALIGN, nu_longlong, np_longlong},
+    {'Q',       sizeof(long long), LONG_LONG_ALIGN, nu_ulonglong,np_ulonglong},
+    {'?',       sizeof(_Bool),      BOOL_ALIGN,     nu_bool,        np_bool},
+    {'e',       sizeof(short),  SHORT_ALIGN,    nu_halffloat,   np_halffloat},
+    {'f',       sizeof(float),  FLOAT_ALIGN,    nu_float,       np_float},
+    {'d',       sizeof(double), DOUBLE_ALIGN,   nu_double,      np_double},
+    {'P',       sizeof(void *), VOID_P_ALIGN,   nu_void_p,      np_void_p},
+    {0}
+};
+
+/* Big-endian routines. *****************************************************/
+
+static PyObject *
+bu_short(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long x = 0;
+
+    /* This function is only ever used in the case f->size == 2. */
+    assert(f->size == 2);
+    Py_ssize_t i = 2;
+    const unsigned char *bytes = (const unsigned char *)p;
+    do {
+        x = (x<<8) | *bytes++;
+    } while (--i > 0);
+    /* Extend sign, avoiding implementation-defined or undefined behaviour. */
+    x = (x ^ 0x8000U) - 0x8000U;
+    return PyLong_FromLong(x & 0x8000U ? -1 - (long)(~x) : (long)x);
+}
+
+static PyObject *
+bu_int(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long x = 0;
+
+    /* This function is only ever used in the case f->size == 4. */
+    assert(f->size == 4);
+    Py_ssize_t i = 4;
+    const unsigned char *bytes = (const unsigned char *)p;
+    do {
+        x = (x<<8) | *bytes++;
+    } while (--i > 0);
+    /* Extend sign, avoiding implementation-defined or undefined behaviour. */
+    x = (x ^ 0x80000000U) - 0x80000000U;
+    return PyLong_FromLong(x & 0x80000000U ? -1 - (long)(~x) : (long)x);
+}
+
+static PyObject *
+bu_uint(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long x = 0;
+    Py_ssize_t i = f->size;
+    const unsigned char *bytes = (const unsigned char *)p;
+    do {
+        x = (x<<8) | *bytes++;
+    } while (--i > 0);
+    return PyLong_FromUnsignedLong(x);
+}
+
+static PyObject *
+bu_longlong(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long long x = 0;
+
+    /* This function is only ever used in the case f->size == 8. */
+    assert(f->size == 8);
+    Py_ssize_t i = 8;
+    const unsigned char *bytes = (const unsigned char *)p;
+    do {
+        x = (x<<8) | *bytes++;
+    } while (--i > 0);
+    /* Extend sign, avoiding implementation-defined or undefined behaviour. */
+    x = (x ^ 0x8000000000000000U) - 0x8000000000000000U;
+    return PyLong_FromLongLong(
+        x & 0x8000000000000000U ? -1 - (long long)(~x) : (long long)x);
+}
+
+static PyObject *
+bu_ulonglong(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long long x = 0;
+    Py_ssize_t i = f->size;
+    const unsigned char *bytes = (const unsigned char *)p;
+    do {
+        x = (x<<8) | *bytes++;
+    } while (--i > 0);
+    return PyLong_FromUnsignedLongLong(x);
+}
+
+static PyObject *
+bu_halffloat(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    return unpack_halffloat(p, 0);
+}
+
+static PyObject *
+bu_float(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    return unpack_float(p, 0);
+}
+
+static PyObject *
+bu_double(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    return unpack_double(p, 0);
+}
+
+static PyObject *
+bu_bool(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    return PyBool_FromLong(*p != 0);
+}
+
+static int
+bp_int(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    long x;
+    Py_ssize_t i;
+    unsigned char *q = (unsigned char *)p;
+    if (get_long(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 0);
+        }
+        return -1;
+    }
+    i = f->size;
+    if (i != SIZEOF_LONG) {
+        if ((i == 2) && (x < -32768 || x > 32767))
+            RANGE_ERROR(state, f, 0);
+#if (SIZEOF_LONG != 4)
+        else if ((i == 4) && (x < -2147483648L || x > 2147483647L))
+            RANGE_ERROR(state, f, 0);
+#endif
+    }
+    do {
+        q[--i] = (unsigned char)(x & 0xffL);
+        x >>= 8;
+    } while (i > 0);
+    return 0;
+}
+
+static int
+bp_uint(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    unsigned long x;
+    Py_ssize_t i;
+    unsigned char *q = (unsigned char *)p;
+    if (get_ulong(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 1);
+        }
+        return -1;
+    }
+    i = f->size;
+    if (i != SIZEOF_LONG) {
+        unsigned long maxint = 1;
+        maxint <<= (unsigned long)(i * 8);
+        if (x >= maxint)
+            RANGE_ERROR(state, f, 1);
+    }
+    do {
+        q[--i] = (unsigned char)(x & 0xffUL);
+        x >>= 8;
+    } while (i > 0);
+    return 0;
+}
+
+static int
+bp_longlong(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    int res;
+    v = get_pylong(state, v);
+    if (v == NULL)
+        return -1;
+    res = _PyLong_AsByteArray((PyLongObject *)v,
+                              (unsigned char *)p,
+                              8,
+                              0, /* little_endian */
+                              1  /* signed */);
+    Py_DECREF(v);
+    if (res == -1 && PyErr_Occurred()) {
+        PyErr_Format(state->StructError,
+                     "'%c' format requires %lld <= number <= %lld",
+                     f->format,
+                     LLONG_MIN,
+                     LLONG_MAX);
+        return -1;
+    }
+    return res;
+}
+
+static int
+bp_ulonglong(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    int res;
+    v = get_pylong(state, v);
+    if (v == NULL)
+        return -1;
+    res = _PyLong_AsByteArray((PyLongObject *)v,
+                              (unsigned char *)p,
+                              8,
+                              0, /* little_endian */
+                              0  /* signed */);
+    Py_DECREF(v);
+    if (res == -1 && PyErr_Occurred()) {
+        PyErr_Format(state->StructError,
+                     "'%c' format requires 0 <= number <= %llu",
+                     f->format,
+                     ULLONG_MAX);
+        return -1;
+    }
+    return res;
+}
+
+static int
+bp_halffloat(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    return pack_halffloat(state, p, v, 0);
+}
+
+static int
+bp_float(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    double x = PyFloat_AsDouble(v);
+    if (x == -1 && PyErr_Occurred()) {
+        PyErr_SetString(state->StructError,
+                        "required argument is not a float");
+        return -1;
+    }
+    return PyFloat_Pack4(x, p, 0);
+}
+
+static int
+bp_double(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    double x = PyFloat_AsDouble(v);
+    if (x == -1 && PyErr_Occurred()) {
+        PyErr_SetString(state->StructError,
+                        "required argument is not a float");
+        return -1;
+    }
+    return PyFloat_Pack8(x, p, 0);
+}
+
+static int
+bp_bool(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    int y;
+    y = PyObject_IsTrue(v);
+    if (y < 0)
+        return -1;
+    *p = (char)y;
+    return 0;
+}
+
+static formatdef bigendian_table[] = {
+    {'x',       1,              0,              NULL},
+    {'b',       1,              0,              nu_byte,        np_byte},
+    {'B',       1,              0,              nu_ubyte,       np_ubyte},
+    {'c',       1,              0,              nu_char,        np_char},
+    {'s',       1,              0,              NULL},
+    {'p',       1,              0,              NULL},
+    {'h',       2,              0,              bu_short,       bp_int},
+    {'H',       2,              0,              bu_uint,        bp_uint},
+    {'i',       4,              0,              bu_int,         bp_int},
+    {'I',       4,              0,              bu_uint,        bp_uint},
+    {'l',       4,              0,              bu_int,         bp_int},
+    {'L',       4,              0,              bu_uint,        bp_uint},
+    {'q',       8,              0,              bu_longlong,    bp_longlong},
+    {'Q',       8,              0,              bu_ulonglong,   bp_ulonglong},
+    {'?',       1,              0,              bu_bool,        bp_bool},
+    {'e',       2,              0,              bu_halffloat,   bp_halffloat},
+    {'f',       4,              0,              bu_float,       bp_float},
+    {'d',       8,              0,              bu_double,      bp_double},
+    {0}
+};
+
+/* Little-endian routines. *****************************************************/
+
+static PyObject *
+lu_short(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long x = 0;
+
+    /* This function is only ever used in the case f->size == 2. */
+    assert(f->size == 2);
+    Py_ssize_t i = 2;
+    const unsigned char *bytes = (const unsigned char *)p;
+    do {
+        x = (x<<8) | bytes[--i];
+    } while (i > 0);
+    /* Extend sign, avoiding implementation-defined or undefined behaviour. */
+    x = (x ^ 0x8000U) - 0x8000U;
+    return PyLong_FromLong(x & 0x8000U ? -1 - (long)(~x) : (long)x);
+}
+
+static PyObject *
+lu_int(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long x = 0;
+
+    /* This function is only ever used in the case f->size == 4. */
+    assert(f->size == 4);
+    Py_ssize_t i = 4;
+    const unsigned char *bytes = (const unsigned char *)p;
+    do {
+        x = (x<<8) | bytes[--i];
+    } while (i > 0);
+    /* Extend sign, avoiding implementation-defined or undefined behaviour. */
+    x = (x ^ 0x80000000U) - 0x80000000U;
+    return PyLong_FromLong(x & 0x80000000U ? -1 - (long)(~x) : (long)x);
+}
+
+static PyObject *
+lu_uint(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long x = 0;
+    Py_ssize_t i = f->size;
+    const unsigned char *bytes = (const unsigned char *)p;
+    do {
+        x = (x<<8) | bytes[--i];
+    } while (i > 0);
+    return PyLong_FromUnsignedLong(x);
+}
+
+static PyObject *
+lu_longlong(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long long x = 0;
+
+    /* This function is only ever used in the case f->size == 8. */
+    assert(f->size == 8);
+    Py_ssize_t i = 8;
+    const unsigned char *bytes = (const unsigned char *)p;
+    do {
+        x = (x<<8) | bytes[--i];
+    } while (i > 0);
+    /* Extend sign, avoiding implementation-defined or undefined behaviour. */
+    x = (x ^ 0x8000000000000000U) - 0x8000000000000000U;
+    return PyLong_FromLongLong(
+        x & 0x8000000000000000U ? -1 - (long long)(~x) : (long long)x);
+}
+
+static PyObject *
+lu_ulonglong(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    unsigned long long x = 0;
+    Py_ssize_t i = f->size;
+    const unsigned char *bytes = (const unsigned char *)p;
+    do {
+        x = (x<<8) | bytes[--i];
+    } while (i > 0);
+    return PyLong_FromUnsignedLongLong(x);
+}
+
+static PyObject *
+lu_halffloat(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    return unpack_halffloat(p, 1);
+}
+
+static PyObject *
+lu_float(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    return unpack_float(p, 1);
+}
+
+static PyObject *
+lu_double(_structmodulestate *state, const char *p, const formatdef *f)
+{
+    return unpack_double(p, 1);
+}
+
+static int
+lp_int(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    long x;
+    Py_ssize_t i;
+    unsigned char *q = (unsigned char *)p;
+    if (get_long(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 0);
+        }
+        return -1;
+    }
+    i = f->size;
+    if (i != SIZEOF_LONG) {
+        if ((i == 2) && (x < -32768 || x > 32767))
+            RANGE_ERROR(state, f, 0);
+#if (SIZEOF_LONG != 4)
+        else if ((i == 4) && (x < -2147483648L || x > 2147483647L))
+            RANGE_ERROR(state, f, 0);
+#endif
+    }
+    do {
+        *q++ = (unsigned char)(x & 0xffL);
+        x >>= 8;
+    } while (--i > 0);
+    return 0;
+}
+
+static int
+lp_uint(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    unsigned long x;
+    Py_ssize_t i;
+    unsigned char *q = (unsigned char *)p;
+    if (get_ulong(state, v, &x) < 0) {
+        if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
+            RANGE_ERROR(state, f, 1);
+        }
+        return -1;
+    }
+    i = f->size;
+    if (i != SIZEOF_LONG) {
+        unsigned long maxint = 1;
+        maxint <<= (unsigned long)(i * 8);
+        if (x >= maxint)
+            RANGE_ERROR(state, f, 1);
+    }
+    do {
+        *q++ = (unsigned char)(x & 0xffUL);
+        x >>= 8;
+    } while (--i > 0);
+    return 0;
+}
+
+static int
+lp_longlong(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    int res;
+    v = get_pylong(state, v);
+    if (v == NULL)
+        return -1;
+    res = _PyLong_AsByteArray((PyLongObject*)v,
+                              (unsigned char *)p,
+                              8,
+                              1, /* little_endian */
+                              1  /* signed */);
+    Py_DECREF(v);
+    if (res == -1 && PyErr_Occurred()) {
+        PyErr_Format(state->StructError,
+                     "'%c' format requires %lld <= number <= %lld",
+                     f->format,
+                     LLONG_MIN,
+                     LLONG_MAX);
+        return -1;
+    }
+    return res;
+}
+
+static int
+lp_ulonglong(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    int res;
+    v = get_pylong(state, v);
+    if (v == NULL)
+        return -1;
+    res = _PyLong_AsByteArray((PyLongObject*)v,
+                              (unsigned char *)p,
+                              8,
+                              1, /* little_endian */
+                              0  /* signed */);
+    Py_DECREF(v);
+    if (res == -1 && PyErr_Occurred()) {
+        PyErr_Format(state->StructError,
+                     "'%c' format requires 0 <= number <= %llu",
+                     f->format,
+                     ULLONG_MAX);
+        return -1;
+    }
+    return res;
+}
+
+static int
+lp_halffloat(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    return pack_halffloat(state, p, v, 1);
+}
+
+static int
+lp_float(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    double x = PyFloat_AsDouble(v);
+    if (x == -1 && PyErr_Occurred()) {
+        PyErr_SetString(state->StructError,
+                        "required argument is not a float");
+        return -1;
+    }
+    return PyFloat_Pack4(x, p, 1);
+}
+
+static int
+lp_double(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
+{
+    double x = PyFloat_AsDouble(v);
+    if (x == -1 && PyErr_Occurred()) {
+        PyErr_SetString(state->StructError,
+                        "required argument is not a float");
+        return -1;
+    }
+    return PyFloat_Pack8(x, p, 1);
+}
+
+static formatdef lilendian_table[] = {
+    {'x',       1,              0,              NULL},
+    {'b',       1,              0,              nu_byte,        np_byte},
+    {'B',       1,              0,              nu_ubyte,       np_ubyte},
+    {'c',       1,              0,              nu_char,        np_char},
+    {'s',       1,              0,              NULL},
+    {'p',       1,              0,              NULL},
+    {'h',       2,              0,              lu_short,       lp_int},
+    {'H',       2,              0,              lu_uint,        lp_uint},
+    {'i',       4,              0,              lu_int,         lp_int},
+    {'I',       4,              0,              lu_uint,        lp_uint},
+    {'l',       4,              0,              lu_int,         lp_int},
+    {'L',       4,              0,              lu_uint,        lp_uint},
+    {'q',       8,              0,              lu_longlong,    lp_longlong},
+    {'Q',       8,              0,              lu_ulonglong,   lp_ulonglong},
+    {'?',       1,              0,              bu_bool,        bp_bool}, /* Std rep not endian dep,
+        but potentially different from native rep -- reuse bx_bool funcs. */
+    {'e',       2,              0,              lu_halffloat,   lp_halffloat},
+    {'f',       4,              0,              lu_float,       lp_float},
+    {'d',       8,              0,              lu_double,      lp_double},
+    {0}
+};
+
+
+static const formatdef *
+whichtable(const char **pfmt)
+{
+    const char *fmt = (*pfmt)++; /* May be backed out of later */
+    switch (*fmt) {
+    case '<':
+        return lilendian_table;
+    case '>':
+    case '!': /* Network byte order is big-endian */
+        return bigendian_table;
+    case '=': { /* Host byte order -- different from native in alignment! */
+#if PY_LITTLE_ENDIAN
+        return lilendian_table;
+#else
+        return bigendian_table;
+#endif
+    }
+    default:
+        --*pfmt; /* Back out of pointer increment */
+        /* Fall through */
+    case '@':
+        return native_table;
+    }
+}
+
+
+/* Get the table entry for a format code */
+
+static const formatdef *
+getentry(_structmodulestate *state, int c, const formatdef *f)
+{
+    for (; f->format != '\0'; f++) {
+        if (f->format == c) {
+            return f;
+        }
+    }
+    PyErr_SetString(state->StructError, "bad char in struct format");
+    return NULL;
+}
+
+
+/* Align a size according to a format code.  Return -1 on overflow. */
+
+static Py_ssize_t
+align(Py_ssize_t size, char c, const formatdef *e)
+{
+    Py_ssize_t extra;
+
+    if (e->format == c) {
+        if (e->alignment && size > 0) {
+            extra = (e->alignment - 1) - (size - 1) % (e->alignment);
+            if (extra > PY_SSIZE_T_MAX - size)
+                return -1;
+            size += extra;
+        }
+    }
+    return size;
+}
+
+/*
+ * Struct object implementation.
+ */
+
+/* calculate the size of a format string */
+
+static int
+prepare_s(PyStructObject *self)
+{
+    const formatdef *f;
+    const formatdef *e;
+    formatcode *codes;
+
+    const char *s;
+    const char *fmt;
+    char c;
+    Py_ssize_t size, len, num, itemsize;
+    size_t ncodes;
+
+    _structmodulestate *state = get_struct_state_structinst(self);
+
+    fmt = PyBytes_AS_STRING(self->s_format);
+    if (strlen(fmt) != (size_t)PyBytes_GET_SIZE(self->s_format)) {
+        PyErr_SetString(state->StructError,
+                        "embedded null character");
+        return -1;
+    }
+
+    f = whichtable(&fmt);
+
+    s = fmt;
+    size = 0;
+    len = 0;
+    ncodes = 0;
+    while ((c = *s++) != '\0') {
+        if (Py_ISSPACE(c))
+            continue;
+        if ('0' <= c && c <= '9') {
+            num = c - '0';
+            while ('0' <= (c = *s++) && c <= '9') {
+                /* overflow-safe version of
+                   if (num*10 + (c - '0') > PY_SSIZE_T_MAX) { ... } */
+                if (num >= PY_SSIZE_T_MAX / 10 && (
+                        num > PY_SSIZE_T_MAX / 10 ||
+                        (c - '0') > PY_SSIZE_T_MAX % 10))
+                    goto overflow;
+                num = num*10 + (c - '0');
+            }
+            if (c == '\0') {
+                PyErr_SetString(state->StructError,
+                                "repeat count given without format specifier");
+                return -1;
+            }
+        }
+        else
+            num = 1;
+
+        e = getentry(state, c, f);
+        if (e == NULL)
+            return -1;
+
+        switch (c) {
+            case 's': /* fall through */
+            case 'p': len++; ncodes++; break;
+            case 'x': break;
+            default: len += num; if (num) ncodes++; break;
+        }
+
+        itemsize = e->size;
+        size = align(size, c, e);
+        if (size == -1)
+            goto overflow;
+
+        /* if (size + num * itemsize > PY_SSIZE_T_MAX) { ... } */
+        if (num > (PY_SSIZE_T_MAX - size) / itemsize)
+            goto overflow;
+        size += num * itemsize;
+    }
+
+    /* check for overflow */
+    if ((ncodes + 1) > ((size_t)PY_SSIZE_T_MAX / sizeof(formatcode))) {
+        PyErr_NoMemory();
+        return -1;
+    }
+
+    self->s_size = size;
+    self->s_len = len;
+    codes = PyMem_Malloc((ncodes + 1) * sizeof(formatcode));
+    if (codes == NULL) {
+        PyErr_NoMemory();
+        return -1;
+    }
+    /* Free any s_codes value left over from a previous initialization. */
+    if (self->s_codes != NULL)
+        PyMem_Free(self->s_codes);
+    self->s_codes = codes;
+
+    s = fmt;
+    size = 0;
+    while ((c = *s++) != '\0') {
+        if (Py_ISSPACE(c))
+            continue;
+        if ('0' <= c && c <= '9') {
+            num = c - '0';
+            while ('0' <= (c = *s++) && c <= '9')
+                num = num*10 + (c - '0');
+        }
+        else
+            num = 1;
+
+        e = getentry(state, c, f);
+
+        size = align(size, c, e);
+        if (c == 's' || c == 'p') {
+            codes->offset = size;
+            codes->size = num;
+            codes->fmtdef = e;
+            codes->repeat = 1;
+            codes++;
+            size += num;
+        } else if (c == 'x') {
+            size += num;
+        } else if (num) {
+            codes->offset = size;
+            codes->size = e->size;
+            codes->fmtdef = e;
+            codes->repeat = num;
+            codes++;
+            size += e->size * num;
+        }
+    }
+    codes->fmtdef = NULL;
+    codes->offset = size;
+    codes->size = 0;
+    codes->repeat = 0;
+
+    return 0;
+
+  overflow:
+    PyErr_SetString(state->StructError,
+                    "total struct size too long");
+    return -1;
+}
+
+static PyObject *
+s_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
+{
+    PyObject *self;
+
+    assert(type != NULL);
+    allocfunc alloc_func = PyType_GetSlot(type, Py_tp_alloc);
+    assert(alloc_func != NULL);
+
+    self = alloc_func(type, 0);
+    if (self != NULL) {
+        PyStructObject *s = (PyStructObject*)self;
+        s->s_format = Py_NewRef(Py_None);
+        s->s_codes = NULL;
+        s->s_size = -1;
+        s->s_len = -1;
+    }
+    return self;
+}
+
+/*[clinic input]
+Struct.__init__
+
+    format: object
+
+Create a compiled struct object.
+
+Return a new Struct object which writes and reads binary data according to
+the format string.
+
+See help(struct) for more on format strings.
+[clinic start generated code]*/
+
+static int
+Struct___init___impl(PyStructObject *self, PyObject *format)
+/*[clinic end generated code: output=b8e80862444e92d0 input=192a4575a3dde802]*/
+{
+    int ret = 0;
+
+    if (PyUnicode_Check(format)) {
+        format = PyUnicode_AsASCIIString(format);
+        if (format == NULL)
+            return -1;
+    }
+    else {
+        Py_INCREF(format);
+    }
+
+    if (!PyBytes_Check(format)) {
+        Py_DECREF(format);
+        PyErr_Format(PyExc_TypeError,
+                     "Struct() argument 1 must be a str or bytes object, "
+                     "not %.200s",
+                     _PyType_Name(Py_TYPE(format)));
+        return -1;
+    }
+
+    Py_SETREF(self->s_format, format);
+
+    ret = prepare_s(self);
+    return ret;
+}
+
+static int
+s_clear(PyStructObject *s)
+{
+    Py_CLEAR(s->s_format);
+    return 0;
+}
+
+static int
+s_traverse(PyStructObject *s, visitproc visit, void *arg)
+{
+    Py_VISIT(Py_TYPE(s));
+    Py_VISIT(s->s_format);
+    return 0;
+}
+
+static void
+s_dealloc(PyStructObject *s)
+{
+    PyTypeObject *tp = Py_TYPE(s);
+    PyObject_GC_UnTrack(s);
+    if (s->weakreflist != NULL)
+        PyObject_ClearWeakRefs((PyObject *)s);
+    if (s->s_codes != NULL) {
+        PyMem_Free(s->s_codes);
+    }
+    Py_XDECREF(s->s_format);
+    freefunc free_func = PyType_GetSlot(Py_TYPE(s), Py_tp_free);
+    free_func(s);
+    Py_DECREF(tp);
+}
+
+static PyObject *
+s_unpack_internal(PyStructObject *soself, const char *startfrom,
+                  _structmodulestate *state) {
+    formatcode *code;
+    Py_ssize_t i = 0;
+    PyObject *result = PyTuple_New(soself->s_len);
+    if (result == NULL)
+        return NULL;
+
+    for (code = soself->s_codes; code->fmtdef != NULL; code++) {
+        const formatdef *e = code->fmtdef;
+        const char *res = startfrom + code->offset;
+        Py_ssize_t j = code->repeat;
+        while (j--) {
+            PyObject *v;
+            if (e->format == 's') {
+                v = PyBytes_FromStringAndSize(res, code->size);
+            } else if (e->format == 'p') {
+                Py_ssize_t n = *(unsigned char*)res;
+                if (n >= code->size)
+                    n = code->size - 1;
+                v = PyBytes_FromStringAndSize(res + 1, n);
+            } else {
+                v = e->unpack(state, res, e);
+            }
+            if (v == NULL)
+                goto fail;
+            PyTuple_SET_ITEM(result, i++, v);
+            res += code->size;
+        }
+    }
+
+    return result;
+fail:
+    Py_DECREF(result);
+    return NULL;
+}
+
+
+/*[clinic input]
+Struct.unpack
+
+    buffer: Py_buffer
+    /
+
+Return a tuple containing unpacked values.
+
+Unpack according to the format string Struct.format. The buffer's size
+in bytes must be Struct.size.
+
+See help(struct) for more on format strings.
+[clinic start generated code]*/
+
+static PyObject *
+Struct_unpack_impl(PyStructObject *self, Py_buffer *buffer)
+/*[clinic end generated code: output=873a24faf02e848a input=3113f8e7038b2f6c]*/
+{
+    _structmodulestate *state = get_struct_state_structinst(self);
+    assert(self->s_codes != NULL);
+    if (buffer->len != self->s_size) {
+        PyErr_Format(state->StructError,
+                     "unpack requires a buffer of %zd bytes",
+                     self->s_size);
+        return NULL;
+    }
+    return s_unpack_internal(self, buffer->buf, state);
+}
+
+/*[clinic input]
+Struct.unpack_from
+
+    buffer: Py_buffer
+    offset: Py_ssize_t = 0
+
+Return a tuple containing unpacked values.
+
+Values are unpacked according to the format string Struct.format.
+
+The buffer's size in bytes, starting at position offset, must be
+at least Struct.size.
+
+See help(struct) for more on format strings.
+[clinic start generated code]*/
+
+static PyObject *
+Struct_unpack_from_impl(PyStructObject *self, Py_buffer *buffer,
+                        Py_ssize_t offset)
+/*[clinic end generated code: output=57fac875e0977316 input=cafd4851d473c894]*/
+{
+    _structmodulestate *state = get_struct_state_structinst(self);
+    assert(self->s_codes != NULL);
+
+    if (offset < 0) {
+        if (offset + self->s_size > 0) {
+            PyErr_Format(state->StructError,
+                         "not enough data to unpack %zd bytes at offset %zd",
+                         self->s_size,
+                         offset);
+            return NULL;
+        }
+
+        if (offset + buffer->len < 0) {
+            PyErr_Format(state->StructError,
+                         "offset %zd out of range for %zd-byte buffer",
+                         offset,
+                         buffer->len);
+            return NULL;
+        }
+        offset += buffer->len;
+    }
+
+    if ((buffer->len - offset) < self->s_size) {
+        PyErr_Format(state->StructError,
+                     "unpack_from requires a buffer of at least %zu bytes for "
+                     "unpacking %zd bytes at offset %zd "
+                     "(actual buffer size is %zd)",
+                     (size_t)self->s_size + (size_t)offset,
+                     self->s_size,
+                     offset,
+                     buffer->len);
+        return NULL;
+    }
+    return s_unpack_internal(self, (char*)buffer->buf + offset, state);
+}
+
+
+
+/* Unpack iterator type */
+
+typedef struct {
+    PyObject_HEAD
+    PyStructObject *so;
+    Py_buffer buf;
+    Py_ssize_t index;
+} unpackiterobject;
+
+static void
+unpackiter_dealloc(unpackiterobject *self)
+{
+    /* bpo-31095: UnTrack is needed before calling any callbacks */
+    PyTypeObject *tp = Py_TYPE(self);
+    PyObject_GC_UnTrack(self);
+    Py_XDECREF(self->so);
+    PyBuffer_Release(&self->buf);
+    PyObject_GC_Del(self);
+    Py_DECREF(tp);
+}
+
+static int
+unpackiter_traverse(unpackiterobject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(Py_TYPE(self));
+    Py_VISIT(self->so);
+    Py_VISIT(self->buf.obj);
+    return 0;
+}
+
+static PyObject *
+unpackiter_len(unpackiterobject *self, PyObject *Py_UNUSED(ignored))
+{
+    Py_ssize_t len;
+    if (self->so == NULL)
+        len = 0;
+    else
+        len = (self->buf.len - self->index) / self->so->s_size;
+    return PyLong_FromSsize_t(len);
+}
+
+static PyMethodDef unpackiter_methods[] = {
+    {"__length_hint__", (PyCFunction) unpackiter_len, METH_NOARGS, NULL},
+    {NULL,              NULL}           /* sentinel */
+};
+
+static PyObject *
+unpackiter_iternext(unpackiterobject *self)
+{
+    _structmodulestate *state = get_struct_state_iterinst(self);
+    PyObject *result;
+    if (self->so == NULL)
+        return NULL;
+    if (self->index >= self->buf.len) {
+        /* Iterator exhausted */
+        Py_CLEAR(self->so);
+        PyBuffer_Release(&self->buf);
+        return NULL;
+    }
+    assert(self->index + self->so->s_size <= self->buf.len);
+    result = s_unpack_internal(self->so,
+                               (char*) self->buf.buf + self->index,
+                               state);
+    self->index += self->so->s_size;
+    return result;
+}
+
+static PyType_Slot unpackiter_type_slots[] = {
+    {Py_tp_dealloc, unpackiter_dealloc},
+    {Py_tp_getattro, PyObject_GenericGetAttr},
+    {Py_tp_traverse, unpackiter_traverse},
+    {Py_tp_iter, PyObject_SelfIter},
+    {Py_tp_iternext, unpackiter_iternext},
+    {Py_tp_methods, unpackiter_methods},
+    {0, 0},
+};
+
+static PyType_Spec unpackiter_type_spec = {
+    "_struct.unpack_iterator",
+    sizeof(unpackiterobject),
+    0,
+    (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+     Py_TPFLAGS_IMMUTABLETYPE | Py_TPFLAGS_DISALLOW_INSTANTIATION),
+    unpackiter_type_slots
+};
+
+/*[clinic input]
+Struct.iter_unpack
+
+    buffer: object
+    /
+
+Return an iterator yielding tuples.
+
+Tuples are unpacked from the given bytes source, like a repeated
+invocation of unpack_from().
+
+Requires that the bytes length be a multiple of the struct size.
+[clinic start generated code]*/
+
+static PyObject *
+Struct_iter_unpack(PyStructObject *self, PyObject *buffer)
+/*[clinic end generated code: output=172d83d0cd15dbab input=6d65b3f3107dbc99]*/
+{
+    _structmodulestate *state = get_struct_state_structinst(self);
+    unpackiterobject *iter;
+
+    assert(self->s_codes != NULL);
+
+    if (self->s_size == 0) {
+        PyErr_Format(state->StructError,
+                     "cannot iteratively unpack with a struct of length 0");
+        return NULL;
+    }
+
+    iter = (unpackiterobject *) PyType_GenericAlloc((PyTypeObject *)state->unpackiter_type, 0);
+    if (iter == NULL)
+        return NULL;
+
+    if (PyObject_GetBuffer(buffer, &iter->buf, PyBUF_SIMPLE) < 0) {
+        Py_DECREF(iter);
+        return NULL;
+    }
+    if (iter->buf.len % self->s_size != 0) {
+        PyErr_Format(state->StructError,
+                     "iterative unpacking requires a buffer of "
+                     "a multiple of %zd bytes",
+                     self->s_size);
+        Py_DECREF(iter);
+        return NULL;
+    }
+    iter->so = (PyStructObject*)Py_NewRef(self);
+    iter->index = 0;
+    return (PyObject *)iter;
+}
+
+
+/*
+ * Guts of the pack function.
+ *
+ * Takes a struct object, a tuple of arguments, and offset in that tuple of
+ * argument for where to start processing the arguments for packing, and a
+ * character buffer for writing the packed string.  The caller must insure
+ * that the buffer may contain the required length for packing the arguments.
+ * 0 is returned on success, 1 is returned if there is an error.
+ *
+ */
+static int
+s_pack_internal(PyStructObject *soself, PyObject *const *args, int offset,
+                char* buf, _structmodulestate *state)
+{
+    formatcode *code;
+    /* XXX(nnorwitz): why does i need to be a local?  can we use
+       the offset parameter or do we need the wider width? */
+    Py_ssize_t i;
+
+    memset(buf, '\0', soself->s_size);
+    i = offset;
+    for (code = soself->s_codes; code->fmtdef != NULL; code++) {
+        const formatdef *e = code->fmtdef;
+        char *res = buf + code->offset;
+        Py_ssize_t j = code->repeat;
+        while (j--) {
+            PyObject *v = args[i++];
+            if (e->format == 's') {
+                Py_ssize_t n;
+                int isstring;
+                const void *p;
+                isstring = PyBytes_Check(v);
+                if (!isstring && !PyByteArray_Check(v)) {
+                    PyErr_SetString(state->StructError,
+                                    "argument for 's' must be a bytes object");
+                    return -1;
+                }
+                if (isstring) {
+                    n = PyBytes_GET_SIZE(v);
+                    p = PyBytes_AS_STRING(v);
+                }
+                else {
+                    n = PyByteArray_GET_SIZE(v);
+                    p = PyByteArray_AS_STRING(v);
+                }
+                if (n > code->size)
+                    n = code->size;
+                if (n > 0)
+                    memcpy(res, p, n);
+            } else if (e->format == 'p') {
+                Py_ssize_t n;
+                int isstring;
+                const void *p;
+                isstring = PyBytes_Check(v);
+                if (!isstring && !PyByteArray_Check(v)) {
+                    PyErr_SetString(state->StructError,
+                                    "argument for 'p' must be a bytes object");
+                    return -1;
+                }
+                if (isstring) {
+                    n = PyBytes_GET_SIZE(v);
+                    p = PyBytes_AS_STRING(v);
+                }
+                else {
+                    n = PyByteArray_GET_SIZE(v);
+                    p = PyByteArray_AS_STRING(v);
+                }
+                if (n > (code->size - 1))
+                    n = code->size - 1;
+                if (n > 0)
+                    memcpy(res + 1, p, n);
+                if (n > 255)
+                    n = 255;
+                *res = Py_SAFE_DOWNCAST(n, Py_ssize_t, unsigned char);
+            } else {
+                if (e->pack(state, res, v, e) < 0) {
+                    if (PyLong_Check(v) && PyErr_ExceptionMatches(PyExc_OverflowError))
+                        PyErr_SetString(state->StructError,
+                                        "int too large to convert");
+                    return -1;
+                }
+            }
+            res += code->size;
+        }
+    }
+
+    /* Success */
+    return 0;
+}
+
+
+PyDoc_STRVAR(s_pack__doc__,
+"S.pack(v1, v2, ...) -> bytes\n\
+\n\
+Return a bytes object containing values v1, v2, ... packed according\n\
+to the format string S.format.  See help(struct) for more on format\n\
+strings.");
+
+static PyObject *
+s_pack(PyObject *self, PyObject *const *args, Py_ssize_t nargs)
+{
+    char *buf;
+    PyStructObject *soself;
+    _structmodulestate *state = get_struct_state_structinst(self);
+
+    /* Validate arguments. */
+    soself = (PyStructObject *)self;
+    assert(PyStruct_Check(self, state));
+    assert(soself->s_codes != NULL);
+    if (nargs != soself->s_len)
+    {
+        PyErr_Format(state->StructError,
+            "pack expected %zd items for packing (got %zd)", soself->s_len, nargs);
+        return NULL;
+    }
+
+    /* Allocate a new string */
+    _PyBytesWriter writer;
+    _PyBytesWriter_Init(&writer);
+    buf = _PyBytesWriter_Alloc(&writer, soself->s_size);
+    if (buf == NULL) {
+        _PyBytesWriter_Dealloc(&writer);
+        return NULL;
+    }
+
+    /* Call the guts */
+    if ( s_pack_internal(soself, args, 0, buf, state) != 0 ) {
+        _PyBytesWriter_Dealloc(&writer);
+        return NULL;
+    }
+
+    return _PyBytesWriter_Finish(&writer, buf + soself->s_size);
+}
+
+PyDoc_STRVAR(s_pack_into__doc__,
+"S.pack_into(buffer, offset, v1, v2, ...)\n\
+\n\
+Pack the values v1, v2, ... according to the format string S.format\n\
+and write the packed bytes into the writable buffer buf starting at\n\
+offset.  Note that the offset is a required argument.  See\n\
+help(struct) for more on format strings.");
+
+static PyObject *
+s_pack_into(PyObject *self, PyObject *const *args, Py_ssize_t nargs)
+{
+    PyStructObject *soself;
+    Py_buffer buffer;
+    Py_ssize_t offset;
+    _structmodulestate *state = get_struct_state_structinst(self);
+
+    /* Validate arguments.  +1 is for the first arg as buffer. */
+    soself = (PyStructObject *)self;
+    assert(PyStruct_Check(self, state));
+    assert(soself->s_codes != NULL);
+    if (nargs != (soself->s_len + 2))
+    {
+        if (nargs == 0) {
+            PyErr_Format(state->StructError,
+                        "pack_into expected buffer argument");
+        }
+        else if (nargs == 1) {
+            PyErr_Format(state->StructError,
+                        "pack_into expected offset argument");
+        }
+        else {
+            PyErr_Format(state->StructError,
+                        "pack_into expected %zd items for packing (got %zd)",
+                        soself->s_len, (nargs - 2));
+        }
+        return NULL;
+    }
+
+    /* Extract a writable memory buffer from the first argument */
+    if (!PyArg_Parse(args[0], "w*", &buffer))
+        return NULL;
+    assert(buffer.len >= 0);
+
+    /* Extract the offset from the first argument */
+    offset = PyNumber_AsSsize_t(args[1], PyExc_IndexError);
+    if (offset == -1 && PyErr_Occurred()) {
+        PyBuffer_Release(&buffer);
+        return NULL;
+    }
+
+    /* Support negative offsets. */
+    if (offset < 0) {
+         /* Check that negative offset is low enough to fit data */
+        if (offset + soself->s_size > 0) {
+            PyErr_Format(state->StructError,
+                         "no space to pack %zd bytes at offset %zd",
+                         soself->s_size,
+                         offset);
+            PyBuffer_Release(&buffer);
+            return NULL;
+        }
+
+        /* Check that negative offset is not crossing buffer boundary */
+        if (offset + buffer.len < 0) {
+            PyErr_Format(state->StructError,
+                         "offset %zd out of range for %zd-byte buffer",
+                         offset,
+                         buffer.len);
+            PyBuffer_Release(&buffer);
+            return NULL;
+        }
+
+        offset += buffer.len;
+    }
+
+    /* Check boundaries */
+    if ((buffer.len - offset) < soself->s_size) {
+        assert(offset >= 0);
+        assert(soself->s_size >= 0);
+
+        PyErr_Format(state->StructError,
+                     "pack_into requires a buffer of at least %zu bytes for "
+                     "packing %zd bytes at offset %zd "
+                     "(actual buffer size is %zd)",
+                     (size_t)soself->s_size + (size_t)offset,
+                     soself->s_size,
+                     offset,
+                     buffer.len);
+        PyBuffer_Release(&buffer);
+        return NULL;
+    }
+
+    /* Call the guts */
+    if (s_pack_internal(soself, args, 2, (char*)buffer.buf + offset, state) != 0) {
+        PyBuffer_Release(&buffer);
+        return NULL;
+    }
+
+    PyBuffer_Release(&buffer);
+    Py_RETURN_NONE;
+}
+
+static PyObject *
+s_get_format(PyStructObject *self, void *unused)
+{
+    return PyUnicode_FromStringAndSize(PyBytes_AS_STRING(self->s_format),
+                                       PyBytes_GET_SIZE(self->s_format));
+}
+
+static PyObject *
+s_get_size(PyStructObject *self, void *unused)
+{
+    return PyLong_FromSsize_t(self->s_size);
+}
+
+PyDoc_STRVAR(s_sizeof__doc__,
+"S.__sizeof__() -> size of S in memory, in bytes");
+
+static PyObject *
+s_sizeof(PyStructObject *self, void *unused)
+{
+    size_t size = _PyObject_SIZE(Py_TYPE(self)) + sizeof(formatcode);
+    for (formatcode *code = self->s_codes; code->fmtdef != NULL; code++) {
+        size += sizeof(formatcode);
+    }
+    return PyLong_FromSize_t(size);
+}
+
+/* List of functions */
+
+static struct PyMethodDef s_methods[] = {
+    STRUCT_ITER_UNPACK_METHODDEF
+    {"pack",            _PyCFunction_CAST(s_pack), METH_FASTCALL, s_pack__doc__},
+    {"pack_into",       _PyCFunction_CAST(s_pack_into), METH_FASTCALL, s_pack_into__doc__},
+    STRUCT_UNPACK_METHODDEF
+    STRUCT_UNPACK_FROM_METHODDEF
+    {"__sizeof__",      (PyCFunction)s_sizeof, METH_NOARGS, s_sizeof__doc__},
+    {NULL,       NULL}          /* sentinel */
+};
+
+static PyMemberDef s_members[] = {
+    {"__weaklistoffset__", T_PYSSIZET, offsetof(PyStructObject, weakreflist), READONLY},
+    {NULL}  /* sentinel */
+};
+
+static PyGetSetDef s_getsetlist[] = {
+    {"format", (getter)s_get_format, (setter)NULL, "struct format string", NULL},
+    {"size", (getter)s_get_size, (setter)NULL, "struct size in bytes", NULL},
+    {NULL} /* sentinel */
+};
+
+PyDoc_STRVAR(s__doc__,
+"Struct(fmt) --> compiled struct object\n"
+"\n"
+);
+
+static PyType_Slot PyStructType_slots[] = {
+    {Py_tp_dealloc, s_dealloc},
+    {Py_tp_getattro, PyObject_GenericGetAttr},
+    {Py_tp_setattro, PyObject_GenericSetAttr},
+    {Py_tp_doc, (void*)s__doc__},
+    {Py_tp_traverse, s_traverse},
+    {Py_tp_clear, s_clear},
+    {Py_tp_methods, s_methods},
+    {Py_tp_members, s_members},
+    {Py_tp_getset, s_getsetlist},
+    {Py_tp_init, Struct___init__},
+    {Py_tp_alloc, PyType_GenericAlloc},
+    {Py_tp_new, s_new},
+    {Py_tp_free, PyObject_GC_Del},
+    {0, 0},
+};
+
+static PyType_Spec PyStructType_spec = {
+    "_struct.Struct",
+    sizeof(PyStructObject),
+    0,
+    (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
+     Py_TPFLAGS_BASETYPE | Py_TPFLAGS_IMMUTABLETYPE),
+    PyStructType_slots
+};
+
+
+/* ---- Standalone functions  ---- */
+
+#define MAXCACHE 100
+
+static int
+cache_struct_converter(PyObject *module, PyObject *fmt, PyStructObject **ptr)
+{
+    PyObject * s_object;
+    _structmodulestate *state = get_struct_state(module);
+
+    if (fmt == NULL) {
+        Py_SETREF(*ptr, NULL);
+        return 1;
+    }
+
+    if (state->cache == NULL) {
+        state->cache = PyDict_New();
+        if (state->cache == NULL)
+            return 0;
+    }
+
+    s_object = PyDict_GetItemWithError(state->cache, fmt);
+    if (s_object != NULL) {
+        *ptr = (PyStructObject *)Py_NewRef(s_object);
+        return Py_CLEANUP_SUPPORTED;
+    }
+    else if (PyErr_Occurred()) {
+        return 0;
+    }
+
+    s_object = PyObject_CallOneArg(state->PyStructType, fmt);
+    if (s_object != NULL) {
+        if (PyDict_GET_SIZE(state->cache) >= MAXCACHE)
+            PyDict_Clear(state->cache);
+        /* Attempt to cache the result */
+        if (PyDict_SetItem(state->cache, fmt, s_object) == -1)
+            PyErr_Clear();
+        *ptr = (PyStructObject *)s_object;
+        return Py_CLEANUP_SUPPORTED;
+    }
+    return 0;
+}
+
+/*[clinic input]
+_clearcache
+
+Clear the internal cache.
+[clinic start generated code]*/
+
+static PyObject *
+_clearcache_impl(PyObject *module)
+/*[clinic end generated code: output=ce4fb8a7bf7cb523 input=463eaae04bab3211]*/
+{
+    Py_CLEAR(get_struct_state(module)->cache);
+    Py_RETURN_NONE;
+}
+
+
+/*[clinic input]
+calcsize -> Py_ssize_t
+
+    format as s_object: cache_struct
+    /
+
+Return size in bytes of the struct described by the format string.
+[clinic start generated code]*/
+
+static Py_ssize_t
+calcsize_impl(PyObject *module, PyStructObject *s_object)
+/*[clinic end generated code: output=db7d23d09c6932c4 input=96a6a590c7717ecd]*/
+{
+    return s_object->s_size;
+}
+
+PyDoc_STRVAR(pack_doc,
+"pack(format, v1, v2, ...) -> bytes\n\
+\n\
+Return a bytes object containing the values v1, v2, ... packed according\n\
+to the format string.  See help(struct) for more on format strings.");
+
+static PyObject *
+pack(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+{
+    PyObject *s_object = NULL;
+    PyObject *format, *result;
+
+    if (nargs == 0) {
+        PyErr_SetString(PyExc_TypeError, "missing format argument");
+        return NULL;
+    }
+    format = args[0];
+
+    if (!cache_struct_converter(module, format, (PyStructObject **)&s_object)) {
+        return NULL;
+    }
+    result = s_pack(s_object, args + 1, nargs - 1);
+    Py_DECREF(s_object);
+    return result;
+}
+
+PyDoc_STRVAR(pack_into_doc,
+"pack_into(format, buffer, offset, v1, v2, ...)\n\
+\n\
+Pack the values v1, v2, ... according to the format string and write\n\
+the packed bytes into the writable buffer buf starting at offset.  Note\n\
+that the offset is a required argument.  See help(struct) for more\n\
+on format strings.");
+
+static PyObject *
+pack_into(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+{
+    PyObject *s_object = NULL;
+    PyObject *format, *result;
+
+    if (nargs == 0) {
+        PyErr_SetString(PyExc_TypeError, "missing format argument");
+        return NULL;
+    }
+    format = args[0];
+
+    if (!cache_struct_converter(module, format, (PyStructObject **)&s_object)) {
+        return NULL;
+    }
+    result = s_pack_into(s_object, args + 1, nargs - 1);
+    Py_DECREF(s_object);
+    return result;
+}
+
+/*[clinic input]
+unpack
+
+    format as s_object: cache_struct
+    buffer: Py_buffer
+    /
+
+Return a tuple containing values unpacked according to the format string.
+
+The buffer's size in bytes must be calcsize(format).
+
+See help(struct) for more on format strings.
+[clinic start generated code]*/
+
+static PyObject *
+unpack_impl(PyObject *module, PyStructObject *s_object, Py_buffer *buffer)
+/*[clinic end generated code: output=48ddd4d88eca8551 input=05fa3b91678da727]*/
+{
+    return Struct_unpack_impl(s_object, buffer);
+}
+
+/*[clinic input]
+unpack_from
+
+    format as s_object: cache_struct
+    /
+    buffer: Py_buffer
+    offset: Py_ssize_t = 0
+
+Return a tuple containing values unpacked according to the format string.
+
+The buffer's size, minus offset, must be at least calcsize(format).
+
+See help(struct) for more on format strings.
+[clinic start generated code]*/
+
+static PyObject *
+unpack_from_impl(PyObject *module, PyStructObject *s_object,
+                 Py_buffer *buffer, Py_ssize_t offset)
+/*[clinic end generated code: output=1042631674c6e0d3 input=6e80a5398e985025]*/
+{
+    return Struct_unpack_from_impl(s_object, buffer, offset);
+}
+
+/*[clinic input]
+iter_unpack
+
+    format as s_object: cache_struct
+    buffer: object
+    /
+
+Return an iterator yielding tuples unpacked from the given bytes.
+
+The bytes are unpacked according to the format string, like
+a repeated invocation of unpack_from().
+
+Requires that the bytes length be a multiple of the format struct size.
+[clinic start generated code]*/
+
+static PyObject *
+iter_unpack_impl(PyObject *module, PyStructObject *s_object,
+                 PyObject *buffer)
+/*[clinic end generated code: output=0ae50e250d20e74d input=b214a58869a3c98d]*/
+{
+    return Struct_iter_unpack(s_object, buffer);
+}
+
+static struct PyMethodDef module_functions[] = {
+    _CLEARCACHE_METHODDEF
+    CALCSIZE_METHODDEF
+    ITER_UNPACK_METHODDEF
+    {"pack",            _PyCFunction_CAST(pack), METH_FASTCALL,   pack_doc},
+    {"pack_into",       _PyCFunction_CAST(pack_into), METH_FASTCALL,   pack_into_doc},
+    UNPACK_METHODDEF
+    UNPACK_FROM_METHODDEF
+    {NULL,       NULL}          /* sentinel */
+};
+
+
+/* Module initialization */
+
+PyDoc_STRVAR(module_doc,
+"Functions to convert between Python values and C structs.\n\
+Python bytes objects are used to hold the data representing the C struct\n\
+and also as format strings (explained below) to describe the layout of data\n\
+in the C struct.\n\
+\n\
+The optional first format char indicates byte order, size and alignment:\n\
+  @: native order, size & alignment (default)\n\
+  =: native order, std. size & alignment\n\
+  <: little-endian, std. size & alignment\n\
+  >: big-endian, std. size & alignment\n\
+  !: same as >\n\
+\n\
+The remaining chars indicate types of args and must match exactly;\n\
+these can be preceded by a decimal repeat count:\n\
+  x: pad byte (no data); c:char; b:signed byte; B:unsigned byte;\n\
+  ?: _Bool (requires C99; if not available, char is used instead)\n\
+  h:short; H:unsigned short; i:int; I:unsigned int;\n\
+  l:long; L:unsigned long; f:float; d:double; e:half-float.\n\
+Special cases (preceding decimal count indicates length):\n\
+  s:string (array of char); p: pascal string (with count byte).\n\
+Special cases (only available in native format):\n\
+  n:ssize_t; N:size_t;\n\
+  P:an integer type that is wide enough to hold a pointer.\n\
+Special case (not in native mode unless 'long long' in platform C):\n\
+  q:long long; Q:unsigned long long\n\
+Whitespace between formats is ignored.\n\
+\n\
+The variable struct.error is an exception raised on errors.\n");
+
+
+static int
+_structmodule_traverse(PyObject *module, visitproc visit, void *arg)
+{
+    _structmodulestate *state = get_struct_state(module);
+    if (state) {
+        Py_VISIT(state->cache);
+        Py_VISIT(state->PyStructType);
+        Py_VISIT(state->unpackiter_type);
+        Py_VISIT(state->StructError);
+    }
+    return 0;
+}
+
+static int
+_structmodule_clear(PyObject *module)
+{
+    _structmodulestate *state = get_struct_state(module);
+    if (state) {
+        Py_CLEAR(state->cache);
+        Py_CLEAR(state->PyStructType);
+        Py_CLEAR(state->unpackiter_type);
+        Py_CLEAR(state->StructError);
+    }
+    return 0;
+}
+
+static void
+_structmodule_free(void *module)
+{
+    _structmodule_clear((PyObject *)module);
+}
+
+static int
+_structmodule_exec(PyObject *m)
+{
+    _structmodulestate *state = get_struct_state(m);
+
+    state->PyStructType = PyType_FromModuleAndSpec(
+        m, &PyStructType_spec, NULL);
+    if (state->PyStructType == NULL) {
+        return -1;
+    }
+    if (PyModule_AddType(m, (PyTypeObject *)state->PyStructType) < 0) {
+        return -1;
+    }
+
+    state->unpackiter_type = PyType_FromModuleAndSpec(
+        m, &unpackiter_type_spec, NULL);
+    if (state->unpackiter_type == NULL) {
+        return -1;
+    }
+
+    /* Check endian and swap in faster functions */
+    {
+        const formatdef *native = native_table;
+        formatdef *other, *ptr;
+#if PY_LITTLE_ENDIAN
+        other = lilendian_table;
+#else
+        other = bigendian_table;
+#endif
+        /* Scan through the native table, find a matching
+           entry in the endian table and swap in the
+           native implementations whenever possible
+           (64-bit platforms may not have "standard" sizes) */
+        while (native->format != '\0' && other->format != '\0') {
+            ptr = other;
+            while (ptr->format != '\0') {
+                if (ptr->format == native->format) {
+                    /* Match faster when formats are
+                       listed in the same order */
+                    if (ptr == other)
+                        other++;
+                    /* Only use the trick if the
+                       size matches */
+                    if (ptr->size != native->size)
+                        break;
+                    /* Skip float and double, could be
+                       "unknown" float format */
+                    if (ptr->format == 'd' || ptr->format == 'f')
+                        break;
+                    /* Skip _Bool, semantics are different for standard size */
+                    if (ptr->format == '?')
+                        break;
+                    ptr->pack = native->pack;
+                    ptr->unpack = native->unpack;
+                    break;
+                }
+                ptr++;
+            }
+            native++;
+        }
+    }
+
+    /* Add some symbolic constants to the module */
+    state->StructError = PyErr_NewException("struct.error", NULL, NULL);
+    if (state->StructError == NULL) {
+        return -1;
+    }
+    if (PyModule_AddObjectRef(m, "error", state->StructError) < 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static PyModuleDef_Slot _structmodule_slots[] = {
+    {Py_mod_exec, _structmodule_exec},
+    {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},
+    {0, NULL}
+};
+
+static struct PyModuleDef _structmodule = {
+    PyModuleDef_HEAD_INIT,
+    .m_name = "_struct",
+    .m_doc = module_doc,
+    .m_size = sizeof(_structmodulestate),
+    .m_methods = module_functions,
+    .m_slots = _structmodule_slots,
+    .m_traverse = _structmodule_traverse,
+    .m_clear = _structmodule_clear,
+    .m_free = _structmodule_free,
+};
+
+PyMODINIT_FUNC
+PyInit__struct(void)
+{
+    return PyModuleDef_Init(&_structmodule);
+}