EIC code displayed by LXR master/​include/​python3.13/​internal/​pycore_blocks_output_buffer.h	Source navigation Diff markup Identifier search General search
	Version: master test Revert   Change

File indexing completed on 2025-11-19 09:50:45

 /*
    _BlocksOutputBuffer is used to maintain an output buffer
    that has unpredictable size. Suitable for compression/decompression
    API (bz2/lzma/zlib) that has stream->next_out and stream->avail_out:
 
         stream->next_out:  point to the next output position.
         stream->avail_out: the number of available bytes left in the buffer.
 
    It maintains a list of bytes object, so there is no overhead of resizing
    the buffer.
 
    Usage:
 
    1, Initialize the struct instance like this:
         _BlocksOutputBuffer buffer = {.list = NULL};
       Set .list to NULL for _BlocksOutputBuffer_OnError()
 
    2, Initialize the buffer use one of these functions:
         _BlocksOutputBuffer_InitAndGrow()
         _BlocksOutputBuffer_InitWithSize()
 
    3, If (avail_out == 0), grow the buffer:
         _BlocksOutputBuffer_Grow()
 
    4, Get the current outputted data size:
         _BlocksOutputBuffer_GetDataSize()
 
    5, Finish the buffer, and return a bytes object:
         _BlocksOutputBuffer_Finish()
 
    6, Clean up the buffer when an error occurred:
         _BlocksOutputBuffer_OnError()
 */
 
 #ifndef Py_INTERNAL_BLOCKS_OUTPUT_BUFFER_H
 #define Py_INTERNAL_BLOCKS_OUTPUT_BUFFER_H
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 #include "Python.h"
 
 #ifndef Py_BUILD_CORE
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
 typedef struct {
     // List of bytes objects
     PyObject *list;
     // Number of whole allocated size
     Py_ssize_t allocated;
     // Max length of the buffer, negative number means unlimited length.
     Py_ssize_t max_length;
 } _BlocksOutputBuffer;
 
 static const char unable_allocate_msg[] = "Unable to allocate output buffer.";
 
 /* In 32-bit build, the max block size should <= INT32_MAX. */
 #define OUTPUT_BUFFER_MAX_BLOCK_SIZE (256*1024*1024)
 
 /* Block size sequence */
 #define KB (1024)
 #define MB (1024*1024)
 static const Py_ssize_t BUFFER_BLOCK_SIZE[] =
     { 32*KB, 64*KB, 256*KB, 1*MB, 4*MB, 8*MB, 16*MB, 16*MB,
       32*MB, 32*MB, 32*MB, 32*MB, 64*MB, 64*MB, 128*MB, 128*MB,
       OUTPUT_BUFFER_MAX_BLOCK_SIZE };
 #undef KB
 #undef MB
 
 /* According to the block sizes defined by BUFFER_BLOCK_SIZE, the whole
    allocated size growth step is:
     1   32 KB       +32 KB
     2   96 KB       +64 KB
     3   352 KB      +256 KB
     4   1.34 MB     +1 MB
     5   5.34 MB     +4 MB
     6   13.34 MB    +8 MB
     7   29.34 MB    +16 MB
     8   45.34 MB    +16 MB
     9   77.34 MB    +32 MB
     10  109.34 MB   +32 MB
     11  141.34 MB   +32 MB
     12  173.34 MB   +32 MB
     13  237.34 MB   +64 MB
     14  301.34 MB   +64 MB
     15  429.34 MB   +128 MB
     16  557.34 MB   +128 MB
     17  813.34 MB   +256 MB
     18  1069.34 MB  +256 MB
     19  1325.34 MB  +256 MB
     20  1581.34 MB  +256 MB
     21  1837.34 MB  +256 MB
     22  2093.34 MB  +256 MB
     ...
 */
 
 /* Initialize the buffer, and grow the buffer.
 
    max_length: Max length of the buffer, -1 for unlimited length.
 
    On success, return allocated size (>=0)
    On failure, return -1
 */
 static inline Py_ssize_t
 _BlocksOutputBuffer_InitAndGrow(_BlocksOutputBuffer *buffer,
                                 const Py_ssize_t max_length,
                                 void **next_out)
 {
     PyObject *b;
     Py_ssize_t block_size;
 
     // ensure .list was set to NULL
     assert(buffer->list == NULL);
 
     // get block size
     if (0 <= max_length && max_length < BUFFER_BLOCK_SIZE[0]) {
         block_size = max_length;
     } else {
         block_size = BUFFER_BLOCK_SIZE[0];
     }
 
     // the first block
     b = PyBytes_FromStringAndSize(NULL, block_size);
     if (b == NULL) {
         return -1;
     }
 
     // create the list
     buffer->list = PyList_New(1);
     if (buffer->list == NULL) {
         Py_DECREF(b);
         return -1;
     }
     PyList_SET_ITEM(buffer->list, 0, b);
 
     // set variables
     buffer->allocated = block_size;
     buffer->max_length = max_length;
 
     *next_out = PyBytes_AS_STRING(b);
     return block_size;
 }
 
 /* Initialize the buffer, with an initial size.
 
    Check block size limit in the outer wrapper function. For example, some libs
    accept UINT32_MAX as the maximum block size, then init_size should <= it.
 
    On success, return allocated size (>=0)
    On failure, return -1
 */
 static inline Py_ssize_t
 _BlocksOutputBuffer_InitWithSize(_BlocksOutputBuffer *buffer,
                                  const Py_ssize_t init_size,
                                  void **next_out)
 {
     PyObject *b;
 
     // ensure .list was set to NULL
     assert(buffer->list == NULL);
 
     // the first block
     b = PyBytes_FromStringAndSize(NULL, init_size);
     if (b == NULL) {
         PyErr_SetString(PyExc_MemoryError, unable_allocate_msg);
         return -1;
     }
 
     // create the list
     buffer->list = PyList_New(1);
     if (buffer->list == NULL) {
         Py_DECREF(b);
         return -1;
     }
     PyList_SET_ITEM(buffer->list, 0, b);
 
     // set variables
     buffer->allocated = init_size;
     buffer->max_length = -1;
 
     *next_out = PyBytes_AS_STRING(b);
     return init_size;
 }
 
 /* Grow the buffer. The avail_out must be 0, please check it before calling.
 
    On success, return allocated size (>=0)
    On failure, return -1
 */
 static inline Py_ssize_t
 _BlocksOutputBuffer_Grow(_BlocksOutputBuffer *buffer,
                          void **next_out,
                          const Py_ssize_t avail_out)
 {
     PyObject *b;
     const Py_ssize_t list_len = Py_SIZE(buffer->list);
     Py_ssize_t block_size;
 
     // ensure no gaps in the data
     if (avail_out != 0) {
         PyErr_SetString(PyExc_SystemError,
                         "avail_out is non-zero in _BlocksOutputBuffer_Grow().");
         return -1;
     }
 
     // get block size
     if (list_len < (Py_ssize_t) Py_ARRAY_LENGTH(BUFFER_BLOCK_SIZE)) {
         block_size = BUFFER_BLOCK_SIZE[list_len];
     } else {
         block_size = BUFFER_BLOCK_SIZE[Py_ARRAY_LENGTH(BUFFER_BLOCK_SIZE) - 1];
     }
 
     // check max_length
     if (buffer->max_length >= 0) {
         // if (rest == 0), should not grow the buffer.
         Py_ssize_t rest = buffer->max_length - buffer->allocated;
         assert(rest > 0);
 
         // block_size of the last block
         if (block_size > rest) {
             block_size = rest;
         }
     }
 
     // check buffer->allocated overflow
     if (block_size > PY_SSIZE_T_MAX - buffer->allocated) {
         PyErr_SetString(PyExc_MemoryError, unable_allocate_msg);
         return -1;
     }
 
     // create the block
     b = PyBytes_FromStringAndSize(NULL, block_size);
     if (b == NULL) {
         PyErr_SetString(PyExc_MemoryError, unable_allocate_msg);
         return -1;
     }
     if (PyList_Append(buffer->list, b) < 0) {
         Py_DECREF(b);
         return -1;
     }
     Py_DECREF(b);
 
     // set variables
     buffer->allocated += block_size;
 
     *next_out = PyBytes_AS_STRING(b);
     return block_size;
 }
 
 /* Return the current outputted data size. */
 static inline Py_ssize_t
 _BlocksOutputBuffer_GetDataSize(_BlocksOutputBuffer *buffer,
                                 const Py_ssize_t avail_out)
 {
     return buffer->allocated - avail_out;
 }
 
 /* Finish the buffer.
 
    Return a bytes object on success
    Return NULL on failure
 */
 static inline PyObject *
 _BlocksOutputBuffer_Finish(_BlocksOutputBuffer *buffer,
                            const Py_ssize_t avail_out)
 {
     PyObject *result, *block;
     const Py_ssize_t list_len = Py_SIZE(buffer->list);
 
     // fast path for single block
     if ((list_len == 1 && avail_out == 0) ||
         (list_len == 2 && Py_SIZE(PyList_GET_ITEM(buffer->list, 1)) == avail_out))
     {
         block = PyList_GET_ITEM(buffer->list, 0);
         Py_INCREF(block);
 
         Py_CLEAR(buffer->list);
         return block;
     }
 
     // final bytes object
     result = PyBytes_FromStringAndSize(NULL, buffer->allocated - avail_out);
     if (result == NULL) {
         PyErr_SetString(PyExc_MemoryError, unable_allocate_msg);
         return NULL;
     }
 
     // memory copy
     if (list_len > 0) {
         char *posi = PyBytes_AS_STRING(result);
 
         // blocks except the last one
         Py_ssize_t i = 0;
         for (; i < list_len-1; i++) {
             block = PyList_GET_ITEM(buffer->list, i);
             memcpy(posi, PyBytes_AS_STRING(block), Py_SIZE(block));
             posi += Py_SIZE(block);
         }
         // the last block
         block = PyList_GET_ITEM(buffer->list, i);
         memcpy(posi, PyBytes_AS_STRING(block), Py_SIZE(block) - avail_out);
     } else {
         assert(Py_SIZE(result) == 0);
     }
 
     Py_CLEAR(buffer->list);
     return result;
 }
 
 /* Clean up the buffer when an error occurred. */
 static inline void
 _BlocksOutputBuffer_OnError(_BlocksOutputBuffer *buffer)
 {
     Py_CLEAR(buffer->list);
 }
 
 #ifdef __cplusplus
 }
 #endif
 #endif /* Py_INTERNAL_BLOCKS_OUTPUT_BUFFER_H */

This page was automatically generated by the 2.3.7 LXR engine. The LXR team