strbuf.h 2.9 KB

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  1. /* SPDX-License-Identifier: GPL-2.0 */
  2. #ifndef __PERF_STRBUF_H
  3. #define __PERF_STRBUF_H
  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. #include <assert.h>
  41. #include <stdarg.h>
  42. #include <stddef.h>
  43. #include <string.h>
  44. #include <linux/compiler.h>
  45. #include <sys/types.h>
  46. extern char strbuf_slopbuf[];
  47. struct strbuf {
  48. size_t alloc;
  49. size_t len;
  50. char *buf;
  51. };
  52. #define STRBUF_INIT { 0, 0, strbuf_slopbuf }
  53. /*----- strbuf life cycle -----*/
  54. int 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. /*----- strbuf size related -----*/
  58. static inline ssize_t strbuf_avail(const struct strbuf *sb) {
  59. return sb->alloc ? sb->alloc - sb->len - 1 : 0;
  60. }
  61. int strbuf_grow(struct strbuf *buf, size_t);
  62. static inline int strbuf_setlen(struct strbuf *sb, size_t len) {
  63. if (!sb->alloc) {
  64. int ret = strbuf_grow(sb, 0);
  65. if (ret)
  66. return ret;
  67. }
  68. assert(len < sb->alloc);
  69. sb->len = len;
  70. sb->buf[len] = '\0';
  71. return 0;
  72. }
  73. /*----- add data in your buffer -----*/
  74. int strbuf_addch(struct strbuf *sb, int c);
  75. int strbuf_add(struct strbuf *buf, const void *, size_t);
  76. static inline int strbuf_addstr(struct strbuf *sb, const char *s) {
  77. return strbuf_add(sb, s, strlen(s));
  78. }
  79. int strbuf_addf(struct strbuf *sb, const char *fmt, ...) __printf(2, 3);
  80. /* XXX: if read fails, any partial read is undone */
  81. ssize_t strbuf_read(struct strbuf *, int fd, ssize_t hint);
  82. #endif /* __PERF_STRBUF_H */