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