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 detaches 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
49extern char strbuf_slopbuf[];
50struct 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 -----*/
59int strbuf_init(struct strbuf *buf, ssize_t hint);
60void strbuf_release(struct strbuf *buf);
61char *strbuf_detach(struct strbuf *buf, size_t *);
62
63/*----- strbuf size related -----*/
64static inline ssize_t strbuf_avail(const struct strbuf *sb) {
65	return sb->alloc ? sb->alloc - sb->len - 1 : 0;
66}
67
68int strbuf_grow(struct strbuf *buf, size_t);
69
70static 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 -----*/
83int strbuf_addch(struct strbuf *sb, int c);
84
85int strbuf_add(struct strbuf *buf, const void *, size_t);
86static inline int strbuf_addstr(struct strbuf *sb, const char *s) {
87	return strbuf_add(sb, s, strlen(s));
88}
89
90int strbuf_addf(struct strbuf *sb, const char *fmt, ...) __printf(2, 3);
91
92/* XXX: if read fails, any partial read is undone */
93ssize_t strbuf_read(struct strbuf *, int fd, ssize_t hint);
94
95#endif /* __PERF_STRBUF_H */
96