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Diffstat (limited to 'Documentation/technical/api-strbuf.txt')
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diff --git a/Documentation/technical/api-strbuf.txt b/Documentation/technical/api-strbuf.txt deleted file mode 100644 index afe2759951..0000000000 --- a/Documentation/technical/api-strbuf.txt +++ /dev/null @@ -1,272 +0,0 @@ -strbuf API -========== - -strbuf's are meant to be used with all the usual C string and memory -APIs. Given that the length of the buffer is known, it's often better to -use the mem* functions than a str* one (memchr vs. strchr e.g.). -Though, one has to be careful about the fact that str* functions often -stop on NULs and that strbufs may have embedded NULs. - -An strbuf is NUL terminated for convenience, but no function in the -strbuf API actually relies on the string being free of NULs. - -strbufs has some invariants that are very important to keep in mind: - -. The `buf` member is never NULL, so it can be used in any usual C -string operations safely. strbuf's _have_ to be initialized either by -`strbuf_init()` or by `= STRBUF_INIT` before the invariants, though. -+ -Do *not* assume anything on what `buf` really is (e.g. if it is -allocated memory or not), use `strbuf_detach()` to unwrap a memory -buffer from its strbuf shell in a safe way. That is the sole supported -way. This will give you a malloced buffer that you can later `free()`. -+ -However, it is totally safe to modify anything in the string pointed by -the `buf` member, between the indices `0` and `len-1` (inclusive). - -. The `buf` member is a byte array that has at least `len + 1` bytes - allocated. The extra byte is used to store a `'\0'`, allowing the - `buf` member to be a valid C-string. Every strbuf function ensure this - invariant is preserved. -+ -NOTE: It is OK to "play" with the buffer directly if you work it this - way: -+ ----- -strbuf_grow(sb, SOME_SIZE); <1> -strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE); ----- -<1> Here, the memory array starting at `sb->buf`, and of length -`strbuf_avail(sb)` is all yours, and you can be sure that -`strbuf_avail(sb)` is at least `SOME_SIZE`. -+ -NOTE: `SOME_OTHER_SIZE` must be smaller or equal to `strbuf_avail(sb)`. -+ -Doing so is safe, though if it has to be done in many places, adding the -missing API to the strbuf module is the way to go. -+ -WARNING: Do _not_ assume that the area that is yours is of size `alloc -- 1` even if it's true in the current implementation. Alloc is somehow a -"private" member that should not be messed with. Use `strbuf_avail()` -instead. - -Data structures ---------------- - -* `struct strbuf` - -This is the string buffer structure. The `len` member can be used to -determine the current length of the string, and `buf` member provides access to -the string itself. - -Functions ---------- - -* Life cycle - -`strbuf_init`:: - - Initialize the structure. The second parameter can be zero or a bigger - number to allocate memory, in case you want to prevent further reallocs. - -`strbuf_release`:: - - Release a string buffer and the memory it used. You should not use the - string buffer after using this function, unless you initialize it again. - -`strbuf_detach`:: - - Detach the string from the strbuf and returns it; you now own the - storage the string occupies and it is your responsibility from then on - to release it with `free(3)` when you are done with it. - -`strbuf_attach`:: - - Attach a string to a buffer. You should specify the string to attach, - the current length of the string and the amount of allocated memory. - The amount must be larger than the string length, because the string you - pass is supposed to be a NUL-terminated string. This string _must_ be - malloc()ed, and after attaching, the pointer cannot be relied upon - anymore, and neither be free()d directly. - -`strbuf_swap`:: - - Swap the contents of two string buffers. - -* Related to the size of the buffer - -`strbuf_avail`:: - - Determine the amount of allocated but unused memory. - -`strbuf_grow`:: - - Ensure that at least this amount of unused memory is available after - `len`. This is used when you know a typical size for what you will add - and want to avoid repetitive automatic resizing of the underlying buffer. - This is never a needed operation, but can be critical for performance in - some cases. - -`strbuf_setlen`:: - - Set the length of the buffer to a given value. This function does *not* - allocate new memory, so you should not perform a `strbuf_setlen()` to a - length that is larger than `len + strbuf_avail()`. `strbuf_setlen()` is - just meant as a 'please fix invariants from this strbuf I just messed - with'. - -`strbuf_reset`:: - - Empty the buffer by setting the size of it to zero. - -* Related to the contents of the buffer - -`strbuf_rtrim`:: - - Strip whitespace from the end of a string. - -`strbuf_cmp`:: - - Compare two buffers. Returns an integer less than, equal to, or greater - than zero if the first buffer is found, respectively, to be less than, - to match, or be greater than the second buffer. - -* Adding data to the buffer - -NOTE: All of the functions in this section will grow the buffer as necessary. -If they fail for some reason other than memory shortage and the buffer hadn't -been allocated before (i.e. the `struct strbuf` was set to `STRBUF_INIT`), -then they will free() it. - -`strbuf_addch`:: - - Add a single character to the buffer. - -`strbuf_insert`:: - - Insert data to the given position of the buffer. The remaining contents - will be shifted, not overwritten. - -`strbuf_remove`:: - - Remove given amount of data from a given position of the buffer. - -`strbuf_splice`:: - - Remove the bytes between `pos..pos+len` and replace it with the given - data. - -`strbuf_add`:: - - Add data of given length to the buffer. - -`strbuf_addstr`:: - -Add a NUL-terminated string to the buffer. -+ -NOTE: This function will *always* be implemented as an inline or a macro -that expands to: -+ ----- -strbuf_add(..., s, strlen(s)); ----- -+ -Meaning that this is efficient to write things like: -+ ----- -strbuf_addstr(sb, "immediate string"); ----- - -`strbuf_addbuf`:: - - Copy the contents of an other buffer at the end of the current one. - -`strbuf_adddup`:: - - Copy part of the buffer from a given position till a given length to the - end of the buffer. - -`strbuf_expand`:: - - This function can be used to expand a format string containing - placeholders. To that end, it parses the string and calls the specified - function for every percent sign found. -+ -The callback function is given a pointer to the character after the `%` -and a pointer to the struct strbuf. It is expected to add the expanded -version of the placeholder to the strbuf, e.g. to add a newline -character if the letter `n` appears after a `%`. The function returns -the length of the placeholder recognized and `strbuf_expand()` skips -over it. -+ -The format `%%` is automatically expanded to a single `%` as a quoting -mechanism; callers do not need to handle the `%` placeholder themselves, -and the callback function will not be invoked for this placeholder. -+ -All other characters (non-percent and not skipped ones) are copied -verbatim to the strbuf. If the callback returned zero, meaning that the -placeholder is unknown, then the percent sign is copied, too. -+ -In order to facilitate caching and to make it possible to give -parameters to the callback, `strbuf_expand()` passes a context pointer, -which can be used by the programmer of the callback as she sees fit. - -`strbuf_expand_dict_cb`:: - - Used as callback for `strbuf_expand()`, expects an array of - struct strbuf_expand_dict_entry as context, i.e. pairs of - placeholder and replacement string. The array needs to be - terminated by an entry with placeholder set to NULL. - -`strbuf_addbuf_percentquote`:: - - Append the contents of one strbuf to another, quoting any - percent signs ("%") into double-percents ("%%") in the - destination. This is useful for literal data to be fed to either - strbuf_expand or to the *printf family of functions. - -`strbuf_addf`:: - - Add a formatted string to the buffer. - -`strbuf_fread`:: - - Read a given size of data from a FILE* pointer to the buffer. -+ -NOTE: The buffer is rewound if the read fails. If -1 is returned, -`errno` must be consulted, like you would do for `read(3)`. -`strbuf_read()`, `strbuf_read_file()` and `strbuf_getline()` has the -same behaviour as well. - -`strbuf_read`:: - - Read the contents of a given file descriptor. The third argument can be - used to give a hint about the file size, to avoid reallocs. - -`strbuf_read_file`:: - - Read the contents of a file, specified by its path. The third argument - can be used to give a hint about the file size, to avoid reallocs. - -`strbuf_readlink`:: - - Read the target of a symbolic link, specified by its path. The third - argument can be used to give a hint about the size, to avoid reallocs. - -`strbuf_getline`:: - - Read a line from a FILE* pointer. The second argument specifies the line - terminator character, typically `'\n'`. - -`stripspace`:: - - Strip whitespace from a buffer. The second parameter controls if - comments are considered contents to be removed or not. - -`launch_editor`:: - - Launch the user preferred editor to edit a file and fill the buffer - with the file's contents upon the user completing their editing. The - third argument can be used to set the environment which the editor is - run in. If the buffer is NULL the editor is launched as usual but the - file's contents are not read into the buffer upon completion. |