bprint.h

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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 <stdarg.h>

#include "attributes.h"
#include "avstring.h"

/**
 * Define a structure with extra padding to a fixed size
 * This helps ensuring binary compatibility with future versions.
 */

#define FF_PAD_STRUCTURE(name, size, ...) \
struct ff_pad_helper_##name { __VA_ARGS__ }; \
typedef struct name { \
    __VA_ARGS__ \
    char reserved_padding[size - sizeof(struct ff_pad_helper_##name)]; \
} name;

/**
 * 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