intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 210 insertions, 0 deletions

diff --git a/contrib/tools/python3/src/Python/pyarena.c b/contrib/tools/python3/src/Python/pyarena.c
new file mode 100644
index 0000000000..aefb787e55
--- /dev/null
+++ b/contrib/tools/python3/src/Python/pyarena.c
@@ -0,0 +1,210 @@
+#include "Python.h"
+
+/* A simple arena block structure.
+
+   Measurements with standard library modules suggest the average
+   allocation is about 20 bytes and that most compiles use a single
+   block.
+
+   TODO(jhylton): Think about a realloc API, maybe just for the last
+   allocation?
+*/
+
+#define DEFAULT_BLOCK_SIZE 8192
+#define ALIGNMENT               8
+
+typedef struct _block {
+    /* Total number of bytes owned by this block available to pass out.
+     * Read-only after initialization.  The first such byte starts at
+     * ab_mem.
+     */
+    size_t ab_size;
+
+    /* Total number of bytes already passed out.  The next byte available
+     * to pass out starts at ab_mem + ab_offset.
+     */
+    size_t ab_offset;
+
+    /* An arena maintains a singly-linked, NULL-terminated list of
+     * all blocks owned by the arena.  These are linked via the
+     * ab_next member.
+     */
+    struct _block *ab_next;
+
+    /* Pointer to the first allocatable byte owned by this block.  Read-
+     * only after initialization.
+     */
+    void *ab_mem;
+} block;
+
+/* The arena manages two kinds of memory, blocks of raw memory
+   and a list of PyObject* pointers.  PyObjects are decrefed
+   when the arena is freed.
+*/
+
+struct _arena {
+    /* Pointer to the first block allocated for the arena, never NULL.
+       It is used only to find the first block when the arena is
+       being freed.
+     */
+    block *a_head;
+
+    /* Pointer to the block currently used for allocation.  Its
+       ab_next field should be NULL.  If it is not-null after a
+       call to block_alloc(), it means a new block has been allocated
+       and a_cur should be reset to point it.
+     */
+    block *a_cur;
+
+    /* A Python list object containing references to all the PyObject
+       pointers associated with this arena.  They will be DECREFed
+       when the arena is freed.
+    */
+    PyObject *a_objects;
+
+#if defined(Py_DEBUG)
+    /* Debug output */
+    size_t total_allocs;
+    size_t total_size;
+    size_t total_blocks;
+    size_t total_block_size;
+    size_t total_big_blocks;
+#endif
+};
+
+static block *
+block_new(size_t size)
+{
+    /* Allocate header and block as one unit.
+       ab_mem points just past header. */
+    block *b = (block *)PyMem_Malloc(sizeof(block) + size);
+    if (!b)
+        return NULL;
+    b->ab_size = size;
+    b->ab_mem = (void *)(b + 1);
+    b->ab_next = NULL;
+    b->ab_offset = (char *)_Py_ALIGN_UP(b->ab_mem, ALIGNMENT) -
+            (char *)(b->ab_mem);
+    return b;
+}
+
+static void
+block_free(block *b) {
+    while (b) {
+        block *next = b->ab_next;
+        PyMem_Free(b);
+        b = next;
+    }
+}
+
+static void *
+block_alloc(block *b, size_t size)
+{
+    void *p;
+    assert(b);
+    size = _Py_SIZE_ROUND_UP(size, ALIGNMENT);
+    if (b->ab_offset + size > b->ab_size) {
+        /* If we need to allocate more memory than will fit in
+           the default block, allocate a one-off block that is
+           exactly the right size. */
+        /* TODO(jhylton): Think about space waste at end of block */
+        block *newbl = block_new(
+                        size < DEFAULT_BLOCK_SIZE ?
+                        DEFAULT_BLOCK_SIZE : size);
+        if (!newbl)
+            return NULL;
+        assert(!b->ab_next);
+        b->ab_next = newbl;
+        b = newbl;
+    }
+
+    assert(b->ab_offset + size <= b->ab_size);
+    p = (void *)(((char *)b->ab_mem) + b->ab_offset);
+    b->ab_offset += size;
+    return p;
+}
+
+PyArena *
+PyArena_New()
+{
+    PyArena* arena = (PyArena *)PyMem_Malloc(sizeof(PyArena));
+    if (!arena)
+        return (PyArena*)PyErr_NoMemory();
+
+    arena->a_head = block_new(DEFAULT_BLOCK_SIZE);
+    arena->a_cur = arena->a_head;
+    if (!arena->a_head) {
+        PyMem_Free((void *)arena);
+        return (PyArena*)PyErr_NoMemory();
+    }
+    arena->a_objects = PyList_New(0);
+    if (!arena->a_objects) {
+        block_free(arena->a_head);
+        PyMem_Free((void *)arena);
+        return (PyArena*)PyErr_NoMemory();
+    }
+#if defined(Py_DEBUG)
+    arena->total_allocs = 0;
+    arena->total_size = 0;
+    arena->total_blocks = 1;
+    arena->total_block_size = DEFAULT_BLOCK_SIZE;
+    arena->total_big_blocks = 0;
+#endif
+    return arena;
+}
+
+void
+PyArena_Free(PyArena *arena)
+{
+    assert(arena);
+#if defined(Py_DEBUG)
+    /*
+    fprintf(stderr,
+        "alloc=%zu size=%zu blocks=%zu block_size=%zu big=%zu objects=%zu\n",
+        arena->total_allocs, arena->total_size, arena->total_blocks,
+        arena->total_block_size, arena->total_big_blocks,
+        PyList_Size(arena->a_objects));
+    */
+#endif
+    block_free(arena->a_head);
+    /* This property normally holds, except when the code being compiled
+       is sys.getobjects(0), in which case there will be two references.
+    assert(arena->a_objects->ob_refcnt == 1);
+    */
+
+    Py_DECREF(arena->a_objects);
+    PyMem_Free(arena);
+}
+
+void *
+PyArena_Malloc(PyArena *arena, size_t size)
+{
+    void *p = block_alloc(arena->a_cur, size);
+    if (!p)
+        return PyErr_NoMemory();
+#if defined(Py_DEBUG)
+    arena->total_allocs++;
+    arena->total_size += size;
+#endif
+    /* Reset cur if we allocated a new block. */
+    if (arena->a_cur->ab_next) {
+        arena->a_cur = arena->a_cur->ab_next;
+#if defined(Py_DEBUG)
+        arena->total_blocks++;
+        arena->total_block_size += arena->a_cur->ab_size;
+        if (arena->a_cur->ab_size > DEFAULT_BLOCK_SIZE)
+            ++arena->total_big_blocks;
+#endif
+    }
+    return p;
+}
+
+int
+PyArena_AddPyObject(PyArena *arena, PyObject *obj)
+{
+    int r = PyList_Append(arena->a_objects, obj);
+    if (r >= 0) {
+        Py_DECREF(obj);
+    }
+    return r;
+}