open_memstream.c 1.8 KB

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  1. #include "stdio_impl.h"
  2. #include <errno.h>
  3. #include <limits.h>
  4. #include <string.h>
  5. struct cookie {
  6. char **bufp;
  7. size_t *sizep;
  8. size_t pos;
  9. char *buf;
  10. size_t len;
  11. size_t space;
  12. };
  13. struct ms_FILE {
  14. FILE f;
  15. struct cookie c;
  16. unsigned char buf[BUFSIZ];
  17. };
  18. static off_t ms_seek(FILE *f, off_t off, int whence)
  19. {
  20. ssize_t base;
  21. struct cookie *c = f->cookie;
  22. if (whence>2U) {
  23. fail:
  24. errno = EINVAL;
  25. return -1;
  26. }
  27. base = (size_t [3]){0, c->pos, c->len}[whence];
  28. if (off < -base || off > SSIZE_MAX-base) goto fail;
  29. return c->pos = base+off;
  30. }
  31. static size_t ms_write(FILE *f, const unsigned char *buf, size_t len)
  32. {
  33. struct cookie *c = f->cookie;
  34. size_t len2 = f->wpos - f->wbase;
  35. char *newbuf;
  36. if (len2) {
  37. f->wpos = f->wbase;
  38. if (ms_write(f, f->wbase, len2) < len2) return 0;
  39. }
  40. if (len + c->pos >= c->space) {
  41. len2 = 2*c->space+1 | c->pos+len+1;
  42. newbuf = realloc(c->buf, len2);
  43. if (!newbuf) return 0;
  44. *c->bufp = c->buf = newbuf;
  45. memset(c->buf + c->space, 0, len2 - c->space);
  46. c->space = len2;
  47. }
  48. memcpy(c->buf+c->pos, buf, len);
  49. c->pos += len;
  50. if (c->pos >= c->len) c->len = c->pos;
  51. *c->sizep = c->pos;
  52. return len;
  53. }
  54. static int ms_close(FILE *f)
  55. {
  56. return 0;
  57. }
  58. FILE *open_memstream(char **bufp, size_t *sizep)
  59. {
  60. struct ms_FILE *f;
  61. char *buf;
  62. if (!(f=malloc(sizeof *f))) return 0;
  63. if (!(buf=malloc(sizeof *buf))) {
  64. free(f);
  65. return 0;
  66. }
  67. memset(&f->f, 0, sizeof f->f);
  68. memset(&f->c, 0, sizeof f->c);
  69. f->f.cookie = &f->c;
  70. f->c.bufp = bufp;
  71. f->c.sizep = sizep;
  72. f->c.pos = f->c.len = f->c.space = *sizep = 0;
  73. f->c.buf = *bufp = buf;
  74. *buf = 0;
  75. f->f.flags = F_NORD;
  76. f->f.fd = -1;
  77. f->f.buf = f->buf;
  78. f->f.buf_size = sizeof f->buf;
  79. f->f.lbf = EOF;
  80. f->f.write = ms_write;
  81. f->f.seek = ms_seek;
  82. f->f.close = ms_close;
  83. if (!libc.threaded) f->f.lock = -1;
  84. return __ofl_add(&f->f);
  85. }