tools/perf/util/strbuf.h

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