4 strbuf's are meant to be used with all the usual C string and memory
5 APIs. Given that the length of the buffer is known, it's often better to
6 use the mem* functions than a str* one (memchr vs. strchr e.g.).
7 Though, one has to be careful about the fact that str* functions often
8 stop on NULs and that strbufs may have embedded NULs.
10 An strbuf is NUL terminated for convenience, but no function in the
11 strbuf API actually relies on the string being free of NULs.
13 strbufs has some invariants that are very important to keep in mind:
15 . The `buf` member is never NULL, so it can be used in any usual C
16 string operations safely. strbuf's _have_ to be initialized either by
17 `strbuf_init()` or by `= STRBUF_INIT` before the invariants, though.
19 Do *not* assume anything on what `buf` really is (e.g. if it is
20 allocated memory or not), use `strbuf_detach()` to unwrap a memory
21 buffer from its strbuf shell in a safe way. That is the sole supported
22 way. This will give you a malloced buffer that you can later `free()`.
24 However, it is totally safe to modify anything in the string pointed by
25 the `buf` member, between the indices `0` and `len-1` (inclusive).
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.
32 NOTE: It is OK to "play" with the buffer directly if you work it this
36 strbuf_grow(sb, SOME_SIZE); <1>
37 strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE);
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`.
43 NOTE: `SOME_OTHER_SIZE` must be smaller or equal to `strbuf_avail(sb)`.
45 Doing so is safe, though if it has to be done in many places, adding the
46 missing API to the strbuf module is the way to go.
48 WARNING: 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()`
58 This is the string buffer structure. The `len` member can be used to
59 determine the current length of the string, and `buf` member provides access to
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.
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.
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.
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.
94 Swap the contents of two string buffers.
96 * Related to the size of the buffer
100 Determine the amount of allocated but unused memory.
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
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
120 Empty the buffer by setting the size of it to zero.
122 * Related to the contents of the buffer
126 Strip whitespace from the end of a string.
130 Compare two buffers. Returns an integer less than, equal to, or greater
131 than zero if the first buffer is found, respectively, to be less than,
132 to match, or be greater than the second buffer.
134 * Adding data to the buffer
136 NOTE: All of the functions in this section will grow the buffer as necessary.
137 If they fail for some reason other than memory shortage and the buffer hadn't
138 been allocated before (i.e. the `struct strbuf` was set to `STRBUF_INIT`),
139 then they will free() it.
143 Add a single character to the buffer.
147 Add a character the specified number of times to the buffer.
151 Insert data to the given position of the buffer. The remaining contents
152 will be shifted, not overwritten.
156 Remove given amount of data from a given position of the buffer.
160 Remove the bytes between `pos..pos+len` and replace it with the given
163 `strbuf_add_commented_lines`::
165 Add a NUL-terminated string to the buffer. Each line will be prepended
166 by a comment character and a blank.
170 Add data of given length to the buffer.
174 Add a NUL-terminated string to the buffer.
176 NOTE: This function will *always* be implemented as an inline or a macro
180 strbuf_add(..., s, strlen(s));
183 Meaning that this is efficient to write things like:
186 strbuf_addstr(sb, "immediate string");
191 Copy the contents of an other buffer at the end of the current one.
195 Copy part of the buffer from a given position till a given length to the
200 This function can be used to expand a format string containing
201 placeholders. To that end, it parses the string and calls the specified
202 function for every percent sign found.
204 The callback function is given a pointer to the character after the `%`
205 and a pointer to the struct strbuf. It is expected to add the expanded
206 version of the placeholder to the strbuf, e.g. to add a newline
207 character if the letter `n` appears after a `%`. The function returns
208 the length of the placeholder recognized and `strbuf_expand()` skips
211 The format `%%` is automatically expanded to a single `%` as a quoting
212 mechanism; callers do not need to handle the `%` placeholder themselves,
213 and the callback function will not be invoked for this placeholder.
215 All other characters (non-percent and not skipped ones) are copied
216 verbatim to the strbuf. If the callback returned zero, meaning that the
217 placeholder is unknown, then the percent sign is copied, too.
219 In order to facilitate caching and to make it possible to give
220 parameters to the callback, `strbuf_expand()` passes a context pointer,
221 which can be used by the programmer of the callback as she sees fit.
223 `strbuf_expand_dict_cb`::
225 Used as callback for `strbuf_expand()`, expects an array of
226 struct strbuf_expand_dict_entry as context, i.e. pairs of
227 placeholder and replacement string. The array needs to be
228 terminated by an entry with placeholder set to NULL.
230 `strbuf_addbuf_percentquote`::
232 Append the contents of one strbuf to another, quoting any
233 percent signs ("%") into double-percents ("%%") in the
234 destination. This is useful for literal data to be fed to either
235 strbuf_expand or to the *printf family of functions.
237 `strbuf_humanise_bytes`::
239 Append the given byte size as a human-readable string (i.e. 12.23 KiB,
244 Add a formatted string to the buffer.
246 `strbuf_commented_addf`::
248 Add a formatted string prepended by a comment character and a
253 Read a given size of data from a FILE* pointer to the buffer.
255 NOTE: The buffer is rewound if the read fails. If -1 is returned,
256 `errno` must be consulted, like you would do for `read(3)`.
257 `strbuf_read()`, `strbuf_read_file()` and `strbuf_getline()` has the
258 same behaviour as well.
262 Read the contents of a given file descriptor. The third argument can be
263 used to give a hint about the file size, to avoid reallocs.
267 Read the contents of a file, specified by its path. The third argument
268 can be used to give a hint about the file size, to avoid reallocs.
272 Read the target of a symbolic link, specified by its path. The third
273 argument can be used to give a hint about the size, to avoid reallocs.
277 Read a line from a FILE *, overwriting the existing contents
278 of the strbuf. The second argument specifies the line
279 terminator character, typically `'\n'`.
280 Reading stops after the terminator or at EOF. The terminator
281 is removed from the buffer before returning. Returns 0 unless
282 there was nothing left before EOF, in which case it returns `EOF`.
284 `strbuf_getwholeline`::
286 Like `strbuf_getline`, but keeps the trailing terminator (if
289 `strbuf_getwholeline_fd`::
291 Like `strbuf_getwholeline`, but operates on a file descriptor.
292 It reads one character at a time, so it is very slow. Do not
293 use it unless you need the correct position in the file
298 Strip whitespace from a buffer. The second parameter controls if
299 comments are considered contents to be removed or not.
306 Split a string or strbuf into a list of strbufs at a specified
307 terminator character. The returned substrings include the
308 terminator characters. Some of these functions take a `max`
309 parameter, which, if positive, limits the output to that
310 number of substrings.
314 Free a list of strbufs (for example, the return values of the
315 `strbuf_split()` functions).
319 Launch the user preferred editor to edit a file and fill the buffer
320 with the file's contents upon the user completing their editing. The
321 third argument can be used to set the environment which the editor is
322 run in. If the buffer is NULL the editor is launched as usual but the
323 file's contents are not read into the buffer upon completion.