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 #include <stddef.h>
  44 #include <string.h>
  45 #include <sys/types.h>
  46
  47 extern char strbuf_slopbuf[];
  48 struct strbuf {
  49         size_t alloc;
  50         size_t len;
  51         char *buf;
  52 };
  53
  54 #define STRBUF_INIT  { 0, 0, strbuf_slopbuf }
  55
  56 /*----- strbuf life cycle -----*/
  57 int strbuf_init(struct strbuf *buf, ssize_t hint);
  58 void strbuf_release(struct strbuf *buf);
  59 char *strbuf_detach(struct strbuf *buf, size_t *);
  60
  61 /*----- strbuf size related -----*/
  62 static inline ssize_t strbuf_avail(const struct strbuf *sb) {
  63         return sb->alloc ? sb->alloc - sb->len - 1 : 0;
  64 }
  65
  66 int strbuf_grow(struct strbuf *buf, size_t);
  67
  68 static inline int strbuf_setlen(struct strbuf *sb, size_t len) {
  69         if (!sb->alloc) {
  70                 int ret = strbuf_grow(sb, 0);
  71                 if (ret)
  72                         return ret;
  73         }
  74         assert(len < sb->alloc);
  75         sb->len = len;
  76         sb->buf[len] = '\0';
  77         return 0;
  78 }
  79
  80 /*----- add data in your buffer -----*/
  81 int strbuf_addch(struct strbuf *sb, int c);
  82
  83 int strbuf_add(struct strbuf *buf, const void *, size_t);
  84 static inline int strbuf_addstr(struct strbuf *sb, const char *s) {
  85         return strbuf_add(sb, s, strlen(s));
  86 }
  87
  88 __attribute__((format(printf,2,3)))
  89 int strbuf_addf(struct strbuf *sb, const char *fmt, ...);
  90
  91 /* XXX: if read fails, any partial read is undone */
  92 ssize_t strbuf_read(struct strbuf *, int fd, ssize_t hint);
  93
  94 #endif /* __PERF_STRBUF_H */