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/*
* Copyright (c) 2012 Nicolas George
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVUTIL_BPRINT_H
#define AVUTIL_BPRINT_H
#include "attributes.h"
/**
* Define a structure with extra padding to a fixed size
* This helps ensuring binary compatibility with future versions.
*/
#define FF_PAD_STRUCTURE(size, ...) \
__VA_ARGS__ \
char reserved_padding[size - sizeof(struct { __VA_ARGS__ })];
/**
* Buffer to print data progressively
*
* The string buffer grows as necessary and is always 0-terminated.
* The content of the string is never accessed, and thus is
* encoding-agnostic and can even hold binary data.
*
* Small buffers are kept in the structure itself, and thus require no
* memory allocation at all (unless the contents of the buffer is needed
* after the structure goes out of scope). This is almost as lightweight as
* declaring a local "char buf[512]".
*
* The length of the string can go beyond the allocated size: the buffer is
* then truncated, but the functions still keep account of the actual total
* length.
*
* In other words, buf->len can be greater than buf->size and records the
* total length of what would have been to the buffer if there had been
* enough memory.
*
* Append operations do not need to be tested for failure: if a memory
* allocation fails, data stop being appended to the buffer, but the length
* is still updated. This situation can be tested with
* av_bprint_is_complete().
*
* The size_max field determines several possible behaviours:
*
* size_max = -1 (= UINT_MAX) or any large value will let the buffer be
* reallocated as necessary, with an amortized linear cost.
*
* size_max = 0 prevents writing anything to the buffer: only the total
* length is computed. The write operations can then possibly be repeated in
* a buffer with exactly the necessary size
* (using size_init = size_max = len + 1).
*
* size_max = 1 is automatically replaced by the exact size available in the
* structure itself, thus ensuring no dynamic memory allocation. The
* internal buffer is large enough to hold a reasonable paragraph of text,
* such as the current paragraph.
*/
typedef struct AVBPrint {
FF_PAD_STRUCTURE(1024,
char *str; /** string so far */
unsigned len; /** length so far */
unsigned size; /** allocated memory */
unsigned size_max; /** maximum allocated memory */
char reserved_internal_buffer[1];
)
} AVBPrint;
/**
* Init a print buffer.
*
* @param buf buffer to init
* @param size_init initial size (including the final 0)
* @param size_max maximum size;
* 0 means do not write anything, just count the length;
* 1 is replaced by the maximum value for automatic storage
*/
void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max);
/**
* Convenience macros for special values for size_max.
*/
#define AV_BPRINT_SIZE_UNLIMITED ((unsigned)-1)
#define AV_BPRINT_SIZE_AUTOMATIC 1
#define AV_BPRINT_SIZE_COUNT_ONLY 0
/**
* Init a print buffer using a pre-existing buffer.
*
* The buffer will not be reallocated.
*
* @param buf buffer structure to init
* @param buffer byte buffer to use for the string data
* @param size size of buffer
*/
void av_bprint_init_for_buffer(AVBPrint *buf, char *buffer, unsigned size);
/**
* Append a formated string to a print buffer.
*/
void av_bprintf(AVBPrint *buf, const char *fmt, ...) av_printf_format(2, 3);
/**
* Append char c n times to a print buffer.
*/
void av_bprint_chars(AVBPrint *buf, char c, unsigned n);
/**
* Reset the string to "" but keep internal allocated data.
*/
void av_bprint_clear(AVBPrint *buf);
/**
* Test if the print buffer is complete (not truncated).
*
* It may have been truncated due to a memory allocation failure
* or the size_max limit (compare size and size_max if necessary).
*/
static inline int av_bprint_is_complete(AVBPrint *buf)
{
return buf->len < buf->size;
}
/**
* Finalize a print buffer.
*
* The print buffer can no longer be used afterwards,
* but the len and size fields are still valid.
*
* @arg[out] ret_str if not NULL, used to return a permanent copy of the
* buffer contents, or NULL if memory allocation fails;
* if NULL, the buffer is discarded and freed
* @return 0 for success or error code (probably AVERROR(ENOMEM))
*/
int av_bprint_finalize(AVBPrint *buf, char **ret_str);
#endif /* AVUTIL_BPRINT_H */
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