1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __PERF_STRBUF_H
3 #define __PERF_STRBUF_H
4
5 /*
6 * Strbuf's can be use in many ways: as a byte array, or to store arbitrary
7 * long, overflow safe strings.
8 *
9 * Strbufs has some invariants that are very important to keep in mind:
10 *
11 * 1. the ->buf member is always malloc-ed, hence strbuf's can be used to
12 * build complex strings/buffers whose final size isn't easily known.
13 *
14 * It is NOT legal to copy the ->buf pointer away.
15 * `strbuf_detach' is the operation that detachs a buffer from its shell
16 * while keeping the shell valid wrt its invariants.
17 *
18 * 2. the ->buf member is a byte array that has at least ->len + 1 bytes
19 * allocated. The extra byte is used to store a '\0', allowing the ->buf
20 * member to be a valid C-string. Every strbuf function ensure this
21 * invariant is preserved.
22 *
23 * Note that it is OK to "play" with the buffer directly if you work it
24 * that way:
25 *
26 * strbuf_grow(sb, SOME_SIZE);
27 * ... Here, the memory array starting at sb->buf, and of length
28 * ... strbuf_avail(sb) is all yours, and you are sure that
29 * ... strbuf_avail(sb) is at least SOME_SIZE.
30 * strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE);
31 *
32 * Of course, SOME_OTHER_SIZE must be smaller or equal to strbuf_avail(sb).
33 *
34 * Doing so is safe, though if it has to be done in many places, adding the
35 * missing API to the strbuf module is the way to go.
36 *
37 * XXX: do _not_ assume that the area that is yours is of size ->alloc - 1
38 * even if it's true in the current implementation. Alloc is somehow a
39 * "private" member that should not be messed with.
40 */
41
42 #include <assert.h>
43 #include <stdarg.h>
44 #include <stddef.h>
45 #include <string.h>
46 #include <linux/compiler.h>
47 #include <sys/types.h>
48
49 extern char strbuf_slopbuf[];
50 struct strbuf {
51 size_t alloc;
52 size_t len;
53 char *buf;
54 };
55
56 #define STRBUF_INIT { 0, 0, strbuf_slopbuf }
57
58 /*----- strbuf life cycle -----*/
59 int strbuf_init(struct strbuf *buf, ssize_t hint);
60 void strbuf_release(struct strbuf *buf);
61 char *strbuf_detach(struct strbuf *buf, size_t *);
62
63 /*----- strbuf size related -----*/
64 static inline ssize_t strbuf_avail(const struct strbuf *sb) {
65 return sb->alloc ? sb->alloc - sb->len - 1 : 0;
66 }
67
68 int strbuf_grow(struct strbuf *buf, size_t);
69
70 static inline int strbuf_setlen(struct strbuf *sb, size_t len) {
71 if (!sb->alloc) {
72 int ret = strbuf_grow(sb, 0);
73 if (ret)
74 return ret;
75 }
76 assert(len < sb->alloc);
77 sb->len = len;
78 sb->buf[len] = '\0';
79 return 0;
80 }
81
82 /*----- add data in your buffer -----*/
83 int strbuf_addch(struct strbuf *sb, int c);
84
85 int strbuf_add(struct strbuf *buf, const void *, size_t);
86 static inline int strbuf_addstr(struct strbuf *sb, const char *s) {
87 return strbuf_add(sb, s, strlen(s));
88 }
89
90 int strbuf_addf(struct strbuf *sb, const char *fmt, ...) __printf(2, 3);
91
92 /* XXX: if read fails, any partial read is undone */
93 ssize_t strbuf_read(struct strbuf *, int fd, ssize_t hint);
94
95 #endif /* __PERF_STRBUF_H */