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The gory details are explained in strbuf.h. The change of semantics this patch enforces is that the embeded buffer has always a '\0' character after its last byte, to always make it a C-string. The offs-by-one changes are all related to that very change. A strbuf can be used to store byte arrays, or as an extended string library. The `buf' member can be passed to any C legacy string function, because strbuf operations always ensure there is a terminating \0 at the end of the buffer, not accounted in the `len' field of the structure. A strbuf can be used to generate a string/buffer whose final size is not really known, and then "strbuf_detach" can be used to get the built buffer, and keep the wrapping "strbuf" structure usable for further work again. Other interesting feature: strbuf_grow(sb, size) ensure that there is enough allocated space in `sb' to put `size' new octets of data in the buffer. It helps avoiding reallocating data for nothing when the problem the strbuf helps to solve has a known typical size. Signed-off-by: Pierre Habouzit <madcoder@debian.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
96 lines
3.1 KiB
C
96 lines
3.1 KiB
C
#ifndef STRBUF_H
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#define STRBUF_H
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/*
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* Strbuf's can be use in many ways: as a byte array, or to store arbitrary
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* long, overflow safe strings.
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*
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* Strbufs has some invariants that are very important to keep in mind:
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*
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* 1. the ->buf member is always malloc-ed, hence strbuf's can be used to
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* build complex strings/buffers whose final size isn't easily known.
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*
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* It is legal to copy the ->buf pointer away. Though if you want to reuse
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* the strbuf after that, setting ->buf to NULL isn't legal.
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* `strbuf_detach' is the operation that detachs a buffer from its shell
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* while keeping the shell valid wrt its invariants.
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*
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* 2. the ->buf member is a byte array that has at least ->len + 1 bytes
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* allocated. The extra byte is used to store a '\0', allowing the ->buf
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* member to be a valid C-string. Every strbuf function ensure this
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* invariant is preserved.
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*
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* Note that it is OK to "play" with the buffer directly if you work it
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* that way:
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*
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* strbuf_grow(sb, SOME_SIZE);
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* // ... here the memory areay starting at sb->buf, and of length
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* // sb_avail(sb) is all yours, and you are sure that sb_avail(sb) is at
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* // least SOME_SIZE
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* strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE);
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*
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* Of course, SOME_OTHER_SIZE must be smaller or equal to sb_avail(sb).
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*
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* Doing so is safe, though if it has to be done in many places, adding the
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* missing API to the strbuf module is the way to go.
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*
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* XXX: do _not_ assume that the area that is yours is of size ->alloc - 1
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* even if it's true in the current implementation. Alloc is somehow a
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* "private" member that should not be messed with.
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*/
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#include <assert.h>
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struct strbuf {
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size_t alloc;
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size_t len;
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int eof;
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char *buf;
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};
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#define STRBUF_INIT { 0, 0, 0, NULL }
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/*----- strbuf life cycle -----*/
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extern void strbuf_init(struct strbuf *);
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extern void strbuf_release(struct strbuf *);
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extern void strbuf_reset(struct strbuf *);
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extern char *strbuf_detach(struct strbuf *);
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/*----- strbuf size related -----*/
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static inline size_t strbuf_avail(struct strbuf *sb) {
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return sb->alloc ? sb->alloc - sb->len - 1 : 0;
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}
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static inline void strbuf_setlen(struct strbuf *sb, size_t len) {
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assert (len < sb->alloc);
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sb->len = len;
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sb->buf[len] = '\0';
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}
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extern void strbuf_grow(struct strbuf *, size_t);
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/*----- add data in your buffer -----*/
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static inline void strbuf_addch(struct strbuf *sb, int c) {
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strbuf_grow(sb, 1);
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sb->buf[sb->len++] = c;
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sb->buf[sb->len] = '\0';
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}
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extern void strbuf_add(struct strbuf *, const void *, size_t);
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static inline void strbuf_addstr(struct strbuf *sb, const char *s) {
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strbuf_add(sb, s, strlen(s));
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}
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static inline void strbuf_addbuf(struct strbuf *sb, struct strbuf *sb2) {
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strbuf_add(sb, sb2->buf, sb2->len);
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}
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__attribute__((format(printf,2,3)))
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extern void strbuf_addf(struct strbuf *sb, const char *fmt, ...);
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extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);
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/* XXX: if read fails, any partial read is undone */
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extern ssize_t strbuf_read(struct strbuf *, int fd);
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extern void read_line(struct strbuf *, FILE *, int);
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#endif /* STRBUF_H */
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