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authorPierre Habouzit <madcoder@debian.org>2007-09-06 11:20:05 (GMT)
committerJunio C Hamano <gitster@pobox.com>2007-09-07 06:57:44 (GMT)
commitb449f4cfc972929b638b90d375b8960c37790618 (patch)
tree4cc9b5425447e4b34966b033a6326ebb50b1e635 /strbuf.h
parentb5ef6ac978012475660a36583b2174e9bd8188a5 (diff)
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Rework strbuf API and semantics.
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>
Diffstat (limited to 'strbuf.h')
-rw-r--r--strbuf.h86
1 files changed, 84 insertions, 2 deletions
diff --git a/strbuf.h b/strbuf.h
index 74cc012..b40dc99 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -1,13 +1,95 @@
#ifndef STRBUF_H
#define STRBUF_H
+
+/*
+ * Strbuf's can be use in many ways: as a byte array, or to store arbitrary
+ * long, overflow safe strings.
+ *
+ * Strbufs has some invariants that are very important to keep in mind:
+ *
+ * 1. the ->buf member is always malloc-ed, hence strbuf's can be used to
+ * build complex strings/buffers whose final size isn't easily known.
+ *
+ * It is legal to copy the ->buf pointer away. Though if you want to reuse
+ * the strbuf after that, setting ->buf to NULL isn't legal.
+ * `strbuf_detach' is the operation that detachs a buffer from its shell
+ * while keeping the shell valid wrt its invariants.
+ *
+ * 2. 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 that it is OK to "play" with the buffer directly if you work it
+ * that way:
+ *
+ * strbuf_grow(sb, SOME_SIZE);
+ * // ... here the memory areay starting at sb->buf, and of length
+ * // sb_avail(sb) is all yours, and you are sure that sb_avail(sb) is at
+ * // least SOME_SIZE
+ * strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE);
+ *
+ * Of course, SOME_OTHER_SIZE must be smaller or equal to sb_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.
+ *
+ * XXX: 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.
+ */
+
+#include <assert.h>
+
struct strbuf {
- int alloc;
- int len;
+ size_t alloc;
+ size_t len;
int eof;
char *buf;
};
+#define STRBUF_INIT { 0, 0, 0, NULL }
+
+/*----- strbuf life cycle -----*/
extern void strbuf_init(struct strbuf *);
+extern void strbuf_release(struct strbuf *);
+extern void strbuf_reset(struct strbuf *);
+extern char *strbuf_detach(struct strbuf *);
+
+/*----- strbuf size related -----*/
+static inline size_t strbuf_avail(struct strbuf *sb) {
+ return sb->alloc ? sb->alloc - sb->len - 1 : 0;
+}
+static inline void strbuf_setlen(struct strbuf *sb, size_t len) {
+ assert (len < sb->alloc);
+ sb->len = len;
+ sb->buf[len] = '\0';
+}
+
+extern void strbuf_grow(struct strbuf *, size_t);
+
+/*----- add data in your buffer -----*/
+static inline void strbuf_addch(struct strbuf *sb, int c) {
+ strbuf_grow(sb, 1);
+ sb->buf[sb->len++] = c;
+ sb->buf[sb->len] = '\0';
+}
+
+extern void strbuf_add(struct strbuf *, const void *, size_t);
+static inline void strbuf_addstr(struct strbuf *sb, const char *s) {
+ strbuf_add(sb, s, strlen(s));
+}
+static inline void strbuf_addbuf(struct strbuf *sb, struct strbuf *sb2) {
+ strbuf_add(sb, sb2->buf, sb2->len);
+}
+
+__attribute__((format(printf,2,3)))
+extern void strbuf_addf(struct strbuf *sb, const char *fmt, ...);
+
+extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);
+/* XXX: if read fails, any partial read is undone */
+extern ssize_t strbuf_read(struct strbuf *, int fd);
+
extern void read_line(struct strbuf *, FILE *, int);
#endif /* STRBUF_H */