LXR linux/tools/perf/util/strbuf.h

   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