media/ffvpx/libavutil/bprint.h

   1 /*
   2  * Copyright (c) 2012 Nicolas George
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 /**
  22  * @file
  23  * @ingroup lavu_avbprint
  24  * AVBPrint public header
  25  */
  26
  27 #ifndef AVUTIL_BPRINT_H
  28 #define AVUTIL_BPRINT_H
  29
  30 #include <stdarg.h>
  31
  32 #include "attributes.h"
  33 #include "avstring.h"
  34
  35 /**
  36  * @defgroup lavu_avbprint AVBPrint
  37  * @ingroup lavu_data
  38  *
  39  * A buffer to print data progressively
  40  * @{
  41  */
  42
  43 /**
  44  * Define a structure with extra padding to a fixed size
  45  * This helps ensuring binary compatibility with future versions.
  46  */
  47
  48 #define FF_PAD_STRUCTURE(name, size, ...) \
  49 struct ff_pad_helper_##name { __VA_ARGS__ }; \
  50 typedef struct name { \
  51     __VA_ARGS__ \
  52     char reserved_padding[size - sizeof(struct ff_pad_helper_##name)]; \
  53 } name;
  54
  55 /**
  56  * Buffer to print data progressively
  57  *
  58  * The string buffer grows as necessary and is always 0-terminated.
  59  * The content of the string is never accessed, and thus is
  60  * encoding-agnostic and can even hold binary data.
  61  *
  62  * Small buffers are kept in the structure itself, and thus require no
  63  * memory allocation at all (unless the contents of the buffer is needed
  64  * after the structure goes out of scope). This is almost as lightweight as
  65  * declaring a local `char buf[512]`.
  66  *
  67  * The length of the string can go beyond the allocated size: the buffer is
  68  * then truncated, but the functions still keep account of the actual total
  69  * length.
  70  *
  71  * In other words, AVBPrint.len can be greater than AVBPrint.size and records
  72  * the total length of what would have been to the buffer if there had been
  73  * enough memory.
  74  *
  75  * Append operations do not need to be tested for failure: if a memory
  76  * allocation fails, data stop being appended to the buffer, but the length
  77  * is still updated. This situation can be tested with
  78  * av_bprint_is_complete().
  79  *
  80  * The AVBPrint.size_max field determines several possible behaviours:
  81  * - `size_max = -1` (= `UINT_MAX`) or any large value will let the buffer be
  82  *   reallocated as necessary, with an amortized linear cost.
  83  * - `size_max = 0` prevents writing anything to the buffer: only the total
  84  *   length is computed. The write operations can then possibly be repeated in
  85  *   a buffer with exactly the necessary size
  86  *   (using `size_init = size_max = len + 1`).
  87  * - `size_max = 1` is automatically replaced by the exact size available in the
  88  *   structure itself, thus ensuring no dynamic memory allocation. The
  89  *   internal buffer is large enough to hold a reasonable paragraph of text,
  90  *   such as the current paragraph.
  91  */
  92
  93 FF_PAD_STRUCTURE(AVBPrint, 1024,
  94     char *str;         /**< string so far */
  95     unsigned len;      /**< length so far */
  96     unsigned size;     /**< allocated memory */
  97     unsigned size_max; /**< maximum allocated memory */
  98     char reserved_internal_buffer[1];
  99 )
 100
 101 /**
 102  * @name Max size special values
 103  * Convenience macros for special values for av_bprint_init() size_max
 104  * parameter.
 105  * @{
 106  */
 107
 108 /**
 109  * Buffer will be reallocated as necessary, with an amortized linear cost.
 110  */
 111 #define AV_BPRINT_SIZE_UNLIMITED  ((unsigned)-1)
 112 /**
 113  * Use the exact size available in the AVBPrint structure itself.
 114  *
 115  * Thus ensuring no dynamic memory allocation. The internal buffer is large
 116  * enough to hold a reasonable paragraph of text, such as the current paragraph.
 117  */
 118 #define AV_BPRINT_SIZE_AUTOMATIC  1
 119 /**
 120  * Do not write anything to the buffer, only calculate the total length.
 121  *
 122  * The write operations can then possibly be repeated in a buffer with
 123  * exactly the necessary size (using `size_init = size_max = AVBPrint.len + 1`).
 124  */
 125 #define AV_BPRINT_SIZE_COUNT_ONLY 0
 126 /** @} */
 127
 128 /**
 129  * Init a print buffer.
 130  *
 131  * @param buf        buffer to init
 132  * @param size_init  initial size (including the final 0)
 133  * @param size_max   maximum size;
 134  *                   - `0` means do not write anything, just count the length
 135  *                   - `1` is replaced by the maximum value for automatic storage
 136  *                       any large value means that the internal buffer will be
 137  *                       reallocated as needed up to that limit
 138  *                   - `-1` is converted to `UINT_MAX`, the largest limit possible.
 139  *                   Check also `AV_BPRINT_SIZE_*` macros.
 140  */
 141 void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max);
 142
 143 /**
 144  * Init a print buffer using a pre-existing buffer.
 145  *
 146  * The buffer will not be reallocated.
 147  * In case size equals zero, the AVBPrint will be initialized to use
 148  * the internal buffer as if using AV_BPRINT_SIZE_COUNT_ONLY with
 149  * av_bprint_init().
 150  *
 151  * @param buf     buffer structure to init
 152  * @param buffer  byte buffer to use for the string data
 153  * @param size    size of buffer
 154  */
 155 void av_bprint_init_for_buffer(AVBPrint *buf, char *buffer, unsigned size);
 156
 157 /**
 158  * Append a formatted string to a print buffer.
 159  */
 160 void av_bprintf(AVBPrint *buf, const char *fmt, ...) av_printf_format(2, 3);
 161
 162 /**
 163  * Append a formatted string to a print buffer.
 164  */
 165 void av_vbprintf(AVBPrint *buf, const char *fmt, va_list vl_arg);
 166
 167 /**
 168  * Append char c n times to a print buffer.
 169  */
 170 void av_bprint_chars(AVBPrint *buf, char c, unsigned n);
 171
 172 /**
 173  * Append data to a print buffer.
 174  *
 175  * param buf  bprint buffer to use
 176  * param data pointer to data
 177  * param size size of data
 178  */
 179 void av_bprint_append_data(AVBPrint *buf, const char *data, unsigned size);
 180
 181 struct tm;
 182 /**
 183  * Append a formatted date and time to a print buffer.
 184  *
 185  * param buf  bprint buffer to use
 186  * param fmt  date and time format string, see strftime()
 187  * param tm   broken-down time structure to translate
 188  *
 189  * @note due to poor design of the standard strftime function, it may
 190  * produce poor results if the format string expands to a very long text and
 191  * the bprint buffer is near the limit stated by the size_max option.
 192  */
 193 void av_bprint_strftime(AVBPrint *buf, const char *fmt, const struct tm *tm);
 194
 195 /**
 196  * Allocate bytes in the buffer for external use.
 197  *
 198  * @param[in]  buf          buffer structure
 199  * @param[in]  size         required size
 200  * @param[out] mem          pointer to the memory area
 201  * @param[out] actual_size  size of the memory area after allocation;
 202  *                          can be larger or smaller than size
 203  */
 204 void av_bprint_get_buffer(AVBPrint *buf, unsigned size,
 205                           unsigned char **mem, unsigned *actual_size);
 206
 207 /**
 208  * Reset the string to "" but keep internal allocated data.
 209  */
 210 void av_bprint_clear(AVBPrint *buf);
 211
 212 /**
 213  * Test if the print buffer is complete (not truncated).
 214  *
 215  * It may have been truncated due to a memory allocation failure
 216  * or the size_max limit (compare size and size_max if necessary).
 217  */
 218 static inline int av_bprint_is_complete(const AVBPrint *buf)
 219 {
 220     return buf->len < buf->size;
 221 }
 222
 223 /**
 224  * Finalize a print buffer.
 225  *
 226  * The print buffer can no longer be used afterwards,
 227  * but the len and size fields are still valid.
 228  *
 229  * @arg[out] ret_str  if not NULL, used to return a permanent copy of the
 230  *                    buffer contents, or NULL if memory allocation fails;
 231  *                    if NULL, the buffer is discarded and freed
 232  * @return  0 for success or error code (probably AVERROR(ENOMEM))
 233  */
 234 int av_bprint_finalize(AVBPrint *buf, char **ret_str);
 235
 236 /**
 237  * Escape the content in src and append it to dstbuf.
 238  *
 239  * @param dstbuf        already inited destination bprint buffer
 240  * @param src           string containing the text to escape
 241  * @param special_chars string containing the special characters which
 242  *                      need to be escaped, can be NULL
 243  * @param mode          escape mode to employ, see AV_ESCAPE_MODE_* macros.
 244  *                      Any unknown value for mode will be considered equivalent to
 245  *                      AV_ESCAPE_MODE_BACKSLASH, but this behaviour can change without
 246  *                      notice.
 247  * @param flags         flags which control how to escape, see AV_ESCAPE_FLAG_* macros
 248  */
 249 void av_bprint_escape(AVBPrint *dstbuf, const char *src, const char *special_chars,
 250                       enum AVEscapeMode mode, int flags);
 251
 252 /** @} */
 253
 254 #endif /* AVUTIL_BPRINT_H */