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2134
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1 /*
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2 * Copyright (c) 2012 Nicolas George
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3 *
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4 * This file is part of FFmpeg.
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5 *
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6 * FFmpeg is free software; you can redistribute it and/or
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7 * modify it under the terms of the GNU Lesser General Public
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8 * License as published by the Free Software Foundation; either
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9 * version 2.1 of the License, or (at your option) any later version.
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10 *
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11 * FFmpeg is distributed in the hope that it will be useful,
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12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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14 * Lesser General Public License for more details.
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15 *
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16 * You should have received a copy of the GNU Lesser General Public
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17 * License along with FFmpeg; if not, write to the Free Software
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18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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19 */
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20
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21 #ifndef AVUTIL_BPRINT_H
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22 #define AVUTIL_BPRINT_H
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23
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24 #include "attributes.h"
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25 #include "avstring.h"
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26
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27 /**
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28 * Define a structure with extra padding to a fixed size
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29 * This helps ensuring binary compatibility with future versions.
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30 */
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31 #define FF_PAD_STRUCTURE(size, ...) \
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32 __VA_ARGS__ \
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33 char reserved_padding[size - sizeof(struct { __VA_ARGS__ })];
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34
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35 /**
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36 * Buffer to print data progressively
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37 *
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38 * The string buffer grows as necessary and is always 0-terminated.
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39 * The content of the string is never accessed, and thus is
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40 * encoding-agnostic and can even hold binary data.
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41 *
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42 * Small buffers are kept in the structure itself, and thus require no
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43 * memory allocation at all (unless the contents of the buffer is needed
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44 * after the structure goes out of scope). This is almost as lightweight as
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45 * declaring a local "char buf[512]".
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46 *
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47 * The length of the string can go beyond the allocated size: the buffer is
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48 * then truncated, but the functions still keep account of the actual total
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49 * length.
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50 *
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51 * In other words, buf->len can be greater than buf->size and records the
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52 * total length of what would have been to the buffer if there had been
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53 * enough memory.
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54 *
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55 * Append operations do not need to be tested for failure: if a memory
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56 * allocation fails, data stop being appended to the buffer, but the length
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57 * is still updated. This situation can be tested with
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58 * av_bprint_is_complete().
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59 *
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60 * The size_max field determines several possible behaviours:
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61 *
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62 * size_max = -1 (= UINT_MAX) or any large value will let the buffer be
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63 * reallocated as necessary, with an amortized linear cost.
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64 *
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65 * size_max = 0 prevents writing anything to the buffer: only the total
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66 * length is computed. The write operations can then possibly be repeated in
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67 * a buffer with exactly the necessary size
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68 * (using size_init = size_max = len + 1).
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69 *
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70 * size_max = 1 is automatically replaced by the exact size available in the
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71 * structure itself, thus ensuring no dynamic memory allocation. The
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72 * internal buffer is large enough to hold a reasonable paragraph of text,
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73 * such as the current paragraph.
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74 */
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75 typedef struct AVBPrint {
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76 FF_PAD_STRUCTURE(1024,
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77 char *str; /** string so far */
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78 unsigned len; /** length so far */
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79 unsigned size; /** allocated memory */
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80 unsigned size_max; /** maximum allocated memory */
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81 char reserved_internal_buffer[1];
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82 )
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83 } AVBPrint;
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84
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85 /**
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86 * Convenience macros for special values for av_bprint_init() size_max
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87 * parameter.
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88 */
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89 #define AV_BPRINT_SIZE_UNLIMITED ((unsigned)-1)
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90 #define AV_BPRINT_SIZE_AUTOMATIC 1
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91 #define AV_BPRINT_SIZE_COUNT_ONLY 0
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92
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93 /**
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94 * Init a print buffer.
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95 *
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96 * @param buf buffer to init
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97 * @param size_init initial size (including the final 0)
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98 * @param size_max maximum size;
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99 * 0 means do not write anything, just count the length;
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100 * 1 is replaced by the maximum value for automatic storage;
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101 * any large value means that the internal buffer will be
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102 * reallocated as needed up to that limit; -1 is converted to
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103 * UINT_MAX, the largest limit possible.
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104 * Check also AV_BPRINT_SIZE_* macros.
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105 */
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106 void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max);
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107
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108 /**
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109 * Init a print buffer using a pre-existing buffer.
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110 *
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111 * The buffer will not be reallocated.
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112 *
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113 * @param buf buffer structure to init
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114 * @param buffer byte buffer to use for the string data
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115 * @param size size of buffer
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116 */
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117 void av_bprint_init_for_buffer(AVBPrint *buf, char *buffer, unsigned size);
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118
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119 /**
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120 * Append a formatted string to a print buffer.
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121 */
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122 void av_bprintf(AVBPrint *buf, const char *fmt, ...) av_printf_format(2, 3);
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123
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124 /**
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125 * Append char c n times to a print buffer.
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126 */
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127 void av_bprint_chars(AVBPrint *buf, char c, unsigned n);
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128
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129 struct tm;
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130 /**
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131 * Append a formatted date and time to a print buffer.
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132 *
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133 * param buf bprint buffer to use
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134 * param fmt date and time format string, see strftime()
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135 * param tm broken-down time structure to translate
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136 *
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137 * @note due to poor design of the standard strftime function, it may
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138 * produce poor results if the format string expands to a very long text and
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139 * the bprint buffer is near the limit stated by the size_max option.
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140 */
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141 void av_bprint_strftime(AVBPrint *buf, const char *fmt, const struct tm *tm);
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142
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143 /**
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144 * Allocate bytes in the buffer for external use.
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145 *
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146 * @param[in] buf buffer structure
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147 * @param[in] size required size
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148 * @param[out] mem pointer to the memory area
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149 * @param[out] actual_size size of the memory area after allocation;
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150 * can be larger or smaller than size
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151 */
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152 void av_bprint_get_buffer(AVBPrint *buf, unsigned size,
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153 unsigned char **mem, unsigned *actual_size);
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154
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155 /**
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156 * Reset the string to "" but keep internal allocated data.
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157 */
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158 void av_bprint_clear(AVBPrint *buf);
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159
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160 /**
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161 * Test if the print buffer is complete (not truncated).
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162 *
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163 * It may have been truncated due to a memory allocation failure
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164 * or the size_max limit (compare size and size_max if necessary).
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165 */
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166 static inline int av_bprint_is_complete(AVBPrint *buf)
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167 {
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168 return buf->len < buf->size;
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169 }
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170
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171 /**
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172 * Finalize a print buffer.
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173 *
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174 * The print buffer can no longer be used afterwards,
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175 * but the len and size fields are still valid.
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176 *
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177 * @arg[out] ret_str if not NULL, used to return a permanent copy of the
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178 * buffer contents, or NULL if memory allocation fails;
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179 * if NULL, the buffer is discarded and freed
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180 * @return 0 for success or error code (probably AVERROR(ENOMEM))
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181 */
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182 int av_bprint_finalize(AVBPrint *buf, char **ret_str);
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183
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184 /**
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185 * Escape the content in src and append it to dstbuf.
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186 *
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187 * @param dstbuf already inited destination bprint buffer
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188 * @param src string containing the text to escape
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189 * @param special_chars string containing the special characters which
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190 * need to be escaped, can be NULL
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191 * @param mode escape mode to employ, see AV_ESCAPE_MODE_* macros.
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192 * Any unknown value for mode will be considered equivalent to
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193 * AV_ESCAPE_MODE_BACKSLASH, but this behaviour can change without
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194 * notice.
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195 * @param flags flags which control how to escape, see AV_ESCAPE_FLAG_* macros
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196 */
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197 void av_bprint_escape(AVBPrint *dstbuf, const char *src, const char *special_chars,
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198 enum AVEscapeMode mode, int flags);
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199
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200 #endif /* AVUTIL_BPRINT_H */
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