perf/util/strbuf.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #ifndef __PERF_STRBUF_H
0003 #define __PERF_STRBUF_H
0004
0005 /*
0006  * Strbuf's can be use in many ways: as a byte array, or to store arbitrary
0007  * long, overflow safe strings.
0008  *
0009  * Strbufs has some invariants that are very important to keep in mind:
0010  *
0011  * 1. the ->buf member is always malloc-ed, hence strbuf's can be used to
0012  *    build complex strings/buffers whose final size isn't easily known.
0013  *
0014  *    It is NOT legal to copy the ->buf pointer away.
0015  *    `strbuf_detach' is the operation that detaches a buffer from its shell
0016  *    while keeping the shell valid wrt its invariants.
0017  *
0018  * 2. the ->buf member is a byte array that has at least ->len + 1 bytes
0019  *    allocated. The extra byte is used to store a '\0', allowing the ->buf
0020  *    member to be a valid C-string. Every strbuf function ensure this
0021  *    invariant is preserved.
0022  *
0023  *    Note that it is OK to "play" with the buffer directly if you work it
0024  *    that way:
0025  *
0026  *    strbuf_grow(sb, SOME_SIZE);
0027  *       ... Here, the memory array starting at sb->buf, and of length
0028  *       ... strbuf_avail(sb) is all yours, and you are sure that
0029  *       ... strbuf_avail(sb) is at least SOME_SIZE.
0030  *    strbuf_setlen(sb, sb->len + SOME_OTHER_SIZE);
0031  *
0032  *    Of course, SOME_OTHER_SIZE must be smaller or equal to strbuf_avail(sb).
0033  *
0034  *    Doing so is safe, though if it has to be done in many places, adding the
0035  *    missing API to the strbuf module is the way to go.
0036  *
0037  *    XXX: do _not_ assume that the area that is yours is of size ->alloc - 1
0038  *         even if it's true in the current implementation. Alloc is somehow a
0039  *         "private" member that should not be messed with.
0040  */
0041
0042 #include <assert.h>
0043 #include <stdarg.h>
0044 #include <stddef.h>
0045 #include <string.h>
0046 #include <linux/compiler.h>
0047 #include <sys/types.h>
0048
0049 extern char strbuf_slopbuf[];
0050 struct strbuf {
0051     size_t alloc;
0052     size_t len;
0053     char *buf;
0054 };
0055
0056 #define STRBUF_INIT  { 0, 0, strbuf_slopbuf }
0057
0058 /*----- strbuf life cycle -----*/
0059 int strbuf_init(struct strbuf *buf, ssize_t hint);
0060 void strbuf_release(struct strbuf *buf);
0061 char *strbuf_detach(struct strbuf *buf, size_t *);
0062
0063 /*----- strbuf size related -----*/
0064 static inline ssize_t strbuf_avail(const struct strbuf *sb) {
0065     return sb->alloc ? sb->alloc - sb->len - 1 : 0;
0066 }
0067
0068 int strbuf_grow(struct strbuf *buf, size_t);
0069
0070 static inline int strbuf_setlen(struct strbuf *sb, size_t len) {
0071     if (!sb->alloc) {
0072         int ret = strbuf_grow(sb, 0);
0073         if (ret)
0074             return ret;
0075     }
0076     assert(len < sb->alloc);
0077     sb->len = len;
0078     sb->buf[len] = '\0';
0079     return 0;
0080 }
0081
0082 /*----- add data in your buffer -----*/
0083 int strbuf_addch(struct strbuf *sb, int c);
0084
0085 int strbuf_add(struct strbuf *buf, const void *, size_t);
0086 static inline int strbuf_addstr(struct strbuf *sb, const char *s) {
0087     return strbuf_add(sb, s, strlen(s));
0088 }
0089
0090 int strbuf_addf(struct strbuf *sb, const char *fmt, ...) __printf(2, 3);
0091
0092 /* XXX: if read fails, any partial read is undone */
0093 ssize_t strbuf_read(struct strbuf *, int fd, ssize_t hint);
0094
0095 #endif /* __PERF_STRBUF_H */