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/* bytes to hex implementation */

#include "Python.h"

#include "pystrhex.h" 
 
static PyObject *_Py_strhex_impl(const char* argbuf, const Py_ssize_t arglen,
                                 const PyObject* sep, int bytes_per_sep_group, 
                                 const int return_bytes) 
{
    assert(arglen >= 0); 
 
    Py_UCS1 sep_char = 0; 
    if (sep) { 
        Py_ssize_t seplen = PyObject_Length((PyObject*)sep); 
        if (seplen < 0) { 
            return NULL; 
        } 
        if (seplen != 1) { 
            PyErr_SetString(PyExc_ValueError, "sep must be length 1."); 
            return NULL; 
        } 
        if (PyUnicode_Check(sep)) { 
            if (PyUnicode_READY(sep)) 
                return NULL; 
            if (PyUnicode_KIND(sep) != PyUnicode_1BYTE_KIND) { 
                PyErr_SetString(PyExc_ValueError, "sep must be ASCII."); 
                return NULL; 
            } 
            sep_char = PyUnicode_READ_CHAR(sep, 0); 
        } 
        else if (PyBytes_Check(sep)) { 
            sep_char = PyBytes_AS_STRING(sep)[0]; 
        } 
        else { 
            PyErr_SetString(PyExc_TypeError, "sep must be str or bytes."); 
            return NULL; 
        } 
        if (sep_char > 127 && !return_bytes) { 
            PyErr_SetString(PyExc_ValueError, "sep must be ASCII."); 
            return NULL; 
        } 
    } 
    else { 
        bytes_per_sep_group = 0; 
    } 
 
    unsigned int abs_bytes_per_sep = abs(bytes_per_sep_group); 
    Py_ssize_t resultlen = 0; 
    if (bytes_per_sep_group && arglen > 0) { 
        /* How many sep characters we'll be inserting. */ 
        resultlen = (arglen - 1) / abs_bytes_per_sep; 
    } 
    /* Bounds checking for our Py_ssize_t indices. */ 
    if (arglen >= PY_SSIZE_T_MAX / 2 - resultlen) { 
        return PyErr_NoMemory();
    } 
    resultlen += arglen * 2; 

    if ((size_t)abs_bytes_per_sep >= (size_t)arglen) { 
        bytes_per_sep_group = 0; 
        abs_bytes_per_sep = 0; 
    } 
 
    PyObject *retval; 
    Py_UCS1 *retbuf; 
    if (return_bytes) {
        /* If _PyBytes_FromSize() were public we could avoid malloc+copy. */
        retval = PyBytes_FromStringAndSize(NULL, resultlen); 
        if (!retval) { 
            return NULL; 
        } 
        retbuf = (Py_UCS1 *)PyBytes_AS_STRING(retval); 
    } 
    else { 
        retval = PyUnicode_New(resultlen, 127); 
        if (!retval) { 
            return NULL;
        } 
        retbuf = PyUnicode_1BYTE_DATA(retval);
    }

    /* Hexlify */ 
    Py_ssize_t i, j; 
    unsigned char c; 
 
    if (bytes_per_sep_group == 0) { 
        for (i = j = 0; i < arglen; ++i) { 
            assert((j + 1) < resultlen); 
            c = argbuf[i]; 
            retbuf[j++] = Py_hexdigits[c >> 4]; 
            retbuf[j++] = Py_hexdigits[c & 0x0f]; 
        } 
        assert(j == resultlen); 
    } 
    else { 
        /* The number of complete chunk+sep periods */ 
        Py_ssize_t chunks = (arglen - 1) / abs_bytes_per_sep; 
        Py_ssize_t chunk; 
        unsigned int k; 
 
        if (bytes_per_sep_group < 0) { 
            i = j = 0; 
            for (chunk = 0; chunk < chunks; chunk++) { 
                for (k = 0; k < abs_bytes_per_sep; k++) { 
                    c = argbuf[i++]; 
                    retbuf[j++] = Py_hexdigits[c >> 4]; 
                    retbuf[j++] = Py_hexdigits[c & 0x0f]; 
                } 
                retbuf[j++] = sep_char; 
            } 
            while (i < arglen) { 
                c = argbuf[i++]; 
                retbuf[j++] = Py_hexdigits[c >> 4]; 
                retbuf[j++] = Py_hexdigits[c & 0x0f]; 
            } 
            assert(j == resultlen); 
        } 
        else { 
            i = arglen - 1; 
            j = resultlen - 1; 
            for (chunk = 0; chunk < chunks; chunk++) { 
                for (k = 0; k < abs_bytes_per_sep; k++) { 
                    c = argbuf[i--]; 
                    retbuf[j--] = Py_hexdigits[c & 0x0f]; 
                    retbuf[j--] = Py_hexdigits[c >> 4]; 
                } 
                retbuf[j--] = sep_char; 
            } 
            while (i >= 0) { 
                c = argbuf[i--]; 
                retbuf[j--] = Py_hexdigits[c & 0x0f]; 
                retbuf[j--] = Py_hexdigits[c >> 4]; 
            } 
            assert(j == -1); 
        } 
    }

#ifdef Py_DEBUG
    if (!return_bytes) { 
        assert(_PyUnicode_CheckConsistency(retval, 1));
    }
#endif

    return retval;
}

PyObject * _Py_strhex(const char* argbuf, const Py_ssize_t arglen) 
{
    return _Py_strhex_impl(argbuf, arglen, NULL, 0, 0); 
}

/* Same as above but returns a bytes() instead of str() to avoid the
 * need to decode the str() when bytes are needed. */
PyObject * _Py_strhex_bytes(const char* argbuf, const Py_ssize_t arglen) 
{
    return _Py_strhex_impl(argbuf, arglen, NULL, 0, 1); 
}
 
/* These variants include support for a separator between every N bytes: */ 
 
PyObject * _Py_strhex_with_sep(const char* argbuf, const Py_ssize_t arglen, const PyObject* sep, const int bytes_per_group) 
{ 
    return _Py_strhex_impl(argbuf, arglen, sep, bytes_per_group, 0); 
} 
 
/* Same as above but returns a bytes() instead of str() to avoid the 
 * need to decode the str() when bytes are needed. */ 
PyObject * _Py_strhex_bytes_with_sep(const char* argbuf, const Py_ssize_t arglen, const PyObject* sep, const int bytes_per_group) 
{ 
    return _Py_strhex_impl(argbuf, arglen, sep, bytes_per_group, 1); 
}