mirror of https://git.ffmpeg.org/ffmpeg.git
255 lines
8.6 KiB
C
255 lines
8.6 KiB
C
/*
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* Copyright (c) 2012 Nicolas George
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* @ingroup lavu_avbprint
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* AVBPrint public header
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*/
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#ifndef AVUTIL_BPRINT_H
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#define AVUTIL_BPRINT_H
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#include <stdarg.h>
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#include "attributes.h"
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#include "avstring.h"
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/**
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* @defgroup lavu_avbprint AVBPrint
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* @ingroup lavu_data
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*
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* A buffer to print data progressively
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* @{
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*/
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/**
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* Define a structure with extra padding to a fixed size
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* This helps ensuring binary compatibility with future versions.
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*/
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#define FF_PAD_STRUCTURE(name, size, ...) \
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struct ff_pad_helper_##name { __VA_ARGS__ }; \
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typedef struct name { \
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__VA_ARGS__ \
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char reserved_padding[size - sizeof(struct ff_pad_helper_##name)]; \
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} name;
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/**
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* Buffer to print data progressively
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*
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* The string buffer grows as necessary and is always 0-terminated.
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* The content of the string is never accessed, and thus is
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* encoding-agnostic and can even hold binary data.
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*
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* Small buffers are kept in the structure itself, and thus require no
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* memory allocation at all (unless the contents of the buffer is needed
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* after the structure goes out of scope). This is almost as lightweight as
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* declaring a local `char buf[512]`.
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*
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* The length of the string can go beyond the allocated size: the buffer is
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* then truncated, but the functions still keep account of the actual total
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* length.
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*
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* In other words, AVBPrint.len can be greater than AVBPrint.size and records
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* the total length of what would have been to the buffer if there had been
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* enough memory.
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*
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* Append operations do not need to be tested for failure: if a memory
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* allocation fails, data stop being appended to the buffer, but the length
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* is still updated. This situation can be tested with
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* av_bprint_is_complete().
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*
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* The AVBPrint.size_max field determines several possible behaviours:
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* - `size_max = -1` (= `UINT_MAX`) or any large value will let the buffer be
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* reallocated as necessary, with an amortized linear cost.
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* - `size_max = 0` prevents writing anything to the buffer: only the total
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* length is computed. The write operations can then possibly be repeated in
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* a buffer with exactly the necessary size
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* (using `size_init = size_max = len + 1`).
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* - `size_max = 1` is automatically replaced by the exact size available in the
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* structure itself, thus ensuring no dynamic memory allocation. The
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* internal buffer is large enough to hold a reasonable paragraph of text,
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* such as the current paragraph.
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*/
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FF_PAD_STRUCTURE(AVBPrint, 1024,
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char *str; /**< string so far */
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unsigned len; /**< length so far */
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unsigned size; /**< allocated memory */
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unsigned size_max; /**< maximum allocated memory */
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char reserved_internal_buffer[1];
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)
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/**
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* @name Max size special values
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* Convenience macros for special values for av_bprint_init() size_max
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* parameter.
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* @{
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*/
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/**
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* Buffer will be reallocated as necessary, with an amortized linear cost.
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*/
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#define AV_BPRINT_SIZE_UNLIMITED ((unsigned)-1)
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/**
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* Use the exact size available in the AVBPrint structure itself.
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*
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* Thus ensuring no dynamic memory allocation. The internal buffer is large
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* enough to hold a reasonable paragraph of text, such as the current paragraph.
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*/
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#define AV_BPRINT_SIZE_AUTOMATIC 1
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/**
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* Do not write anything to the buffer, only calculate the total length.
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*
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* The write operations can then possibly be repeated in a buffer with
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* exactly the necessary size (using `size_init = size_max = AVBPrint.len + 1`).
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*/
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#define AV_BPRINT_SIZE_COUNT_ONLY 0
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/** @} */
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/**
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* Init a print buffer.
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*
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* @param buf buffer to init
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* @param size_init initial size (including the final 0)
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* @param size_max maximum size;
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* - `0` means do not write anything, just count the length
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* - `1` is replaced by the maximum value for automatic storage
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* any large value means that the internal buffer will be
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* reallocated as needed up to that limit
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* - `-1` is converted to `UINT_MAX`, the largest limit possible.
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* Check also `AV_BPRINT_SIZE_*` macros.
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*/
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void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max);
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/**
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* Init a print buffer using a pre-existing buffer.
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*
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* The buffer will not be reallocated.
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* In case size equals zero, the AVBPrint will be initialized to use
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* the internal buffer as if using AV_BPRINT_SIZE_COUNT_ONLY with
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* av_bprint_init().
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*
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* @param buf buffer structure to init
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* @param buffer byte buffer to use for the string data
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* @param size size of buffer
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*/
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void av_bprint_init_for_buffer(AVBPrint *buf, char *buffer, unsigned size);
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/**
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* Append a formatted string to a print buffer.
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*/
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void av_bprintf(AVBPrint *buf, const char *fmt, ...) av_printf_format(2, 3);
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/**
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* Append a formatted string to a print buffer.
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*/
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void av_vbprintf(AVBPrint *buf, const char *fmt, va_list vl_arg);
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/**
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* Append char c n times to a print buffer.
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*/
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void av_bprint_chars(AVBPrint *buf, char c, unsigned n);
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/**
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* Append data to a print buffer.
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*
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* @param buf bprint buffer to use
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* @param data pointer to data
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* @param size size of data
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*/
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void av_bprint_append_data(AVBPrint *buf, const char *data, unsigned size);
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struct tm;
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/**
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* Append a formatted date and time to a print buffer.
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*
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* @param buf bprint buffer to use
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* @param fmt date and time format string, see strftime()
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* @param tm broken-down time structure to translate
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*
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* @note due to poor design of the standard strftime function, it may
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* produce poor results if the format string expands to a very long text and
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* the bprint buffer is near the limit stated by the size_max option.
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*/
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void av_bprint_strftime(AVBPrint *buf, const char *fmt, const struct tm *tm);
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/**
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* Allocate bytes in the buffer for external use.
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*
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* @param[in] buf buffer structure
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* @param[in] size required size
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* @param[out] mem pointer to the memory area
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* @param[out] actual_size size of the memory area after allocation;
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* can be larger or smaller than size
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*/
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void av_bprint_get_buffer(AVBPrint *buf, unsigned size,
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unsigned char **mem, unsigned *actual_size);
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/**
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* Reset the string to "" but keep internal allocated data.
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*/
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void av_bprint_clear(AVBPrint *buf);
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/**
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* Test if the print buffer is complete (not truncated).
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*
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* It may have been truncated due to a memory allocation failure
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* or the size_max limit (compare size and size_max if necessary).
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*/
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static inline int av_bprint_is_complete(const AVBPrint *buf)
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{
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return buf->len < buf->size;
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}
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/**
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* Finalize a print buffer.
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*
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* The print buffer can no longer be used afterwards,
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* but the len and size fields are still valid.
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*
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* @arg[out] ret_str if not NULL, used to return a permanent copy of the
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* buffer contents, or NULL if memory allocation fails;
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* if NULL, the buffer is discarded and freed
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* @return 0 for success or error code (probably AVERROR(ENOMEM))
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*/
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int av_bprint_finalize(AVBPrint *buf, char **ret_str);
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/**
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* Escape the content in src and append it to dstbuf.
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*
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* @param dstbuf already inited destination bprint buffer
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* @param src string containing the text to escape
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* @param special_chars string containing the special characters which
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* need to be escaped, can be NULL
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* @param mode escape mode to employ, see AV_ESCAPE_MODE_* macros.
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* Any unknown value for mode will be considered equivalent to
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* AV_ESCAPE_MODE_BACKSLASH, but this behaviour can change without
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* notice.
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* @param flags flags which control how to escape, see AV_ESCAPE_FLAG_* macros
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*/
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void av_bprint_escape(AVBPrint *dstbuf, const char *src, const char *special_chars,
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enum AVEscapeMode mode, int flags);
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/** @} */
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#endif /* AVUTIL_BPRINT_H */
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