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 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 */