1strbuf API 2========== 3 4strbuf's are meant to be used with all the usual C string and memory 5APIs. Given that the length of the buffer is known, it's often better to 6use the mem* functions than a str* one (memchr vs. strchr e.g.). 7Though, one has to be careful about the fact that str* functions often 8stop on NULs and that strbufs may have embedded NULs. 9 10A strbuf is NUL terminated for convenience, but no function in the 11strbuf API actually relies on the string being free of NULs. 12 13strbufs have some invariants that are very important to keep in mind: 14 15. The `buf` member is never NULL, so it can be used in any usual C 16string operations safely. strbuf's _have_ to be initialized either by 17`strbuf_init()` or by `= STRBUF_INIT` before the invariants, though. 18+ 19Do *not* assume anything on what `buf` really is (e.g. if it is 20allocated memory or not), use `strbuf_detach()` to unwrap a memory 21buffer from its strbuf shell in a safe way. That is the sole supported 22way. This will give you a malloced buffer that you can later `free()`. 23+ 24However, it is totally safe to modify anything in the string pointed by 25the `buf` member, between the indices `0` and `len-1` (inclusive). 26 27. The `buf` member is a byte array that has at least `len + 1` bytes 28 allocated. The extra byte is used to store a `'\0'`, allowing the 29 `buf` member to be a valid C-string. Every strbuf function ensure this 30 invariant is preserved. 31+ 32NOTE: It is OK to "play" with the buffer directly if you work it this 33 way: 34+ 35---- 36strbuf_grow(sb, SOME_SIZE); <1> 37strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE); 38---- 39<1> Here, the memory array starting at `sb->buf`, and of length 40`strbuf_avail(sb)` is all yours, and you can be sure that 41`strbuf_avail(sb)` is at least `SOME_SIZE`. 42+ 43NOTE: `SOME_OTHER_SIZE` must be smaller or equal to `strbuf_avail(sb)`. 44+ 45Doing so is safe, though if it has to be done in many places, adding the 46missing API to the strbuf module is the way to go. 47+ 48WARNING: Do _not_ assume that the area that is yours is of size `alloc 49- 1` even if it's true in the current implementation. Alloc is somehow a 50"private" member that should not be messed with. Use `strbuf_avail()` 51instead. 52 53Data structures 54--------------- 55 56* `struct strbuf` 57 58This is the string buffer structure. The `len` member can be used to 59determine the current length of the string, and `buf` member provides 60access to the string itself. 61 62Functions 63--------- 64 65* Life cycle 66 67`strbuf_init`:: 68 69 Initialize the structure. The second parameter can be zero or a bigger 70 number to allocate memory, in case you want to prevent further reallocs. 71 72`strbuf_release`:: 73 74 Release a string buffer and the memory it used. You should not use the 75 string buffer after using this function, unless you initialize it again. 76 77`strbuf_detach`:: 78 79 Detach the string from the strbuf and returns it; you now own the 80 storage the string occupies and it is your responsibility from then on 81 to release it with `free(3)` when you are done with it. 82 83`strbuf_attach`:: 84 85 Attach a string to a buffer. You should specify the string to attach, 86 the current length of the string and the amount of allocated memory. 87 The amount must be larger than the string length, because the string you 88 pass is supposed to be a NUL-terminated string. This string _must_ be 89 malloc()ed, and after attaching, the pointer cannot be relied upon 90 anymore, and neither be free()d directly. 91 92`strbuf_swap`:: 93 94 Swap the contents of two string buffers. 95 96* Related to the size of the buffer 97 98`strbuf_avail`:: 99 100 Determine the amount of allocated but unused memory. 101 102`strbuf_grow`:: 103 104 Ensure that at least this amount of unused memory is available after 105 `len`. This is used when you know a typical size for what you will add 106 and want to avoid repetitive automatic resizing of the underlying buffer. 107 This is never a needed operation, but can be critical for performance in 108 some cases. 109 110`strbuf_setlen`:: 111 112 Set the length of the buffer to a given value. This function does *not* 113 allocate new memory, so you should not perform a `strbuf_setlen()` to a 114 length that is larger than `len + strbuf_avail()`. `strbuf_setlen()` is 115 just meant as a 'please fix invariants from this strbuf I just messed 116 with'. 117 118`strbuf_reset`:: 119 120 Empty the buffer by setting the size of it to zero. 121 122* Related to the contents of the buffer 123 124`strbuf_trim`:: 125 126 Strip whitespace from the beginning and end of a string. 127 Equivalent to performing `strbuf_rtrim()` followed by `strbuf_ltrim()`. 128 129`strbuf_rtrim`:: 130 131 Strip whitespace from the end of a string. 132 133`strbuf_ltrim`:: 134 135 Strip whitespace from the beginning of a string. 136 137`strbuf_reencode`:: 138 139 Replace the contents of the strbuf with a reencoded form. Returns -1 140 on error, 0 on success. 141 142`strbuf_tolower`:: 143 144 Lowercase each character in the buffer using `tolower`. 145 146`strbuf_cmp`:: 147 148 Compare two buffers. Returns an integer less than, equal to, or greater 149 than zero if the first buffer is found, respectively, to be less than, 150 to match, or be greater than the second buffer. 151 152* Adding data to the buffer 153 154NOTE: All of the functions in this section will grow the buffer as necessary. 155If they fail for some reason other than memory shortage and the buffer hadn't 156been allocated before (i.e. the `struct strbuf` was set to `STRBUF_INIT`), 157then they will free() it. 158 159`strbuf_addch`:: 160 161 Add a single character to the buffer. 162 163`strbuf_addchars`:: 164 165 Add a character the specified number of times to the buffer. 166 167`strbuf_insert`:: 168 169 Insert data to the given position of the buffer. The remaining contents 170 will be shifted, not overwritten. 171 172`strbuf_remove`:: 173 174 Remove given amount of data from a given position of the buffer. 175 176`strbuf_splice`:: 177 178 Remove the bytes between `pos..pos+len` and replace it with the given 179 data. 180 181`strbuf_add_commented_lines`:: 182 183 Add a NUL-terminated string to the buffer. Each line will be prepended 184 by a comment character and a blank. 185 186`strbuf_add`:: 187 188 Add data of given length to the buffer. 189 190`strbuf_addstr`:: 191 192Add a NUL-terminated string to the buffer. 193+ 194NOTE: This function will *always* be implemented as an inline or a macro 195that expands to: 196+ 197---- 198strbuf_add(..., s, strlen(s)); 199---- 200+ 201Meaning that this is efficient to write things like: 202+ 203---- 204strbuf_addstr(sb, "immediate string"); 205---- 206 207`strbuf_addbuf`:: 208 209 Copy the contents of another buffer at the end of the current one. 210 211`strbuf_adddup`:: 212 213 Copy part of the buffer from a given position till a given length to the 214 end of the buffer. 215 216`strbuf_expand`:: 217 218 This function can be used to expand a format string containing 219 placeholders. To that end, it parses the string and calls the specified 220 function for every percent sign found. 221+ 222The callback function is given a pointer to the character after the `%` 223and a pointer to the struct strbuf. It is expected to add the expanded 224version of the placeholder to the strbuf, e.g. to add a newline 225character if the letter `n` appears after a `%`. The function returns 226the length of the placeholder recognized and `strbuf_expand()` skips 227over it. 228+ 229The format `%%` is automatically expanded to a single `%` as a quoting 230mechanism; callers do not need to handle the `%` placeholder themselves, 231and the callback function will not be invoked for this placeholder. 232+ 233All other characters (non-percent and not skipped ones) are copied 234verbatim to the strbuf. If the callback returned zero, meaning that the 235placeholder is unknown, then the percent sign is copied, too. 236+ 237In order to facilitate caching and to make it possible to give 238parameters to the callback, `strbuf_expand()` passes a context pointer, 239which can be used by the programmer of the callback as she sees fit. 240 241`strbuf_expand_dict_cb`:: 242 243 Used as callback for `strbuf_expand()`, expects an array of 244 struct strbuf_expand_dict_entry as context, i.e. pairs of 245 placeholder and replacement string. The array needs to be 246 terminated by an entry with placeholder set to NULL. 247 248`strbuf_addbuf_percentquote`:: 249 250 Append the contents of one strbuf to another, quoting any 251 percent signs ("%") into double-percents ("%%") in the 252 destination. This is useful for literal data to be fed to either 253 strbuf_expand or to the *printf family of functions. 254 255`strbuf_humanise_bytes`:: 256 257 Append the given byte size as a human-readable string (i.e. 12.23 KiB, 258 3.50 MiB). 259 260`strbuf_addf`:: 261 262 Add a formatted string to the buffer. 263 264`strbuf_commented_addf`:: 265 266 Add a formatted string prepended by a comment character and a 267 blank to the buffer. 268 269`strbuf_fread`:: 270 271 Read a given size of data from a FILE* pointer to the buffer. 272+ 273NOTE: The buffer is rewound if the read fails. If -1 is returned, 274`errno` must be consulted, like you would do for `read(3)`. 275`strbuf_read()`, `strbuf_read_file()` and `strbuf_getline()` has the 276same behaviour as well. 277 278`strbuf_read`:: 279 280 Read the contents of a given file descriptor. The third argument can be 281 used to give a hint about the file size, to avoid reallocs. 282 283`strbuf_read_file`:: 284 285 Read the contents of a file, specified by its path. The third argument 286 can be used to give a hint about the file size, to avoid reallocs. 287 288`strbuf_readlink`:: 289 290 Read the target of a symbolic link, specified by its path. The third 291 argument can be used to give a hint about the size, to avoid reallocs. 292 293`strbuf_getline`:: 294 295 Read a line from a FILE *, overwriting the existing contents 296 of the strbuf. The second argument specifies the line 297 terminator character, typically `'\n'`. 298 Reading stops after the terminator or at EOF. The terminator 299 is removed from the buffer before returning. Returns 0 unless 300 there was nothing left before EOF, in which case it returns `EOF`. 301 302`strbuf_getwholeline`:: 303 304 Like `strbuf_getline`, but keeps the trailing terminator (if 305 any) in the buffer. 306 307`strbuf_getwholeline_fd`:: 308 309 Like `strbuf_getwholeline`, but operates on a file descriptor. 310 It reads one character at a time, so it is very slow. Do not 311 use it unless you need the correct position in the file 312 descriptor. 313 314`strbuf_getcwd`:: 315 316 Set the buffer to the path of the current working directory. 317 318`strbuf_add_absolute_path` 319 320 Add a path to a buffer, converting a relative path to an 321 absolute one in the process. Symbolic links are not 322 resolved. 323 324`stripspace`:: 325 326 Strip whitespace from a buffer. The second parameter controls if 327 comments are considered contents to be removed or not. 328 329`strbuf_split_buf`:: 330`strbuf_split_str`:: 331`strbuf_split_max`:: 332`strbuf_split`:: 333 334 Split a string or strbuf into a list of strbufs at a specified 335 terminator character. The returned substrings include the 336 terminator characters. Some of these functions take a `max` 337 parameter, which, if positive, limits the output to that 338 number of substrings. 339 340`strbuf_list_free`:: 341 342 Free a list of strbufs (for example, the return values of the 343 `strbuf_split()` functions). 344 345`launch_editor`:: 346 347 Launch the user preferred editor to edit a file and fill the buffer 348 with the file's contents upon the user completing their editing. The 349 third argument can be used to set the environment which the editor is 350 run in. If the buffer is NULL the editor is launched as usual but the 351 file's contents are not read into the buffer upon completion.