bprint.h (8818B)
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 */