src/stdio/fmemopen.c

   1 #include "stdio_impl.h"
   2 #include <errno.h>
   3 #include <string.h>
   4 #include <inttypes.h>
   5
   6 struct cookie {
   7         size_t pos, len, size;
   8         unsigned char *buf;
   9         int mode;
  10 };
  11
  12 static off_t mseek(FILE *f, off_t off, int whence)
  13 {
  14         ssize_t base;
  15         struct cookie *c = f->cookie;
  16         if (whence>2U) {
  17 fail:
  18                 errno = EINVAL;
  19                 return -1;
  20         }
  21         base = (size_t [3]){0, c->pos, c->len}[whence];
  22         if (off < -base || off > (ssize_t)c->size-base) goto fail;
  23         return c->pos = base+off;
  24 }
  25
  26 static size_t mread(FILE *f, unsigned char *buf, size_t len)
  27 {
  28         struct cookie *c = f->cookie;
  29         size_t rem = c->len - c->pos;
  30         if (c->pos > c->len) rem = 0;
  31         if (len > rem) {
  32                 len = rem;
  33                 f->flags |= F_EOF;
  34         }
  35         memcpy(buf, c->buf+c->pos, len);
  36         c->pos += len;
  37         rem -= len;
  38         if (rem > f->buf_size) rem = f->buf_size;
  39         f->rpos = f->buf;
  40         f->rend = f->buf + rem;
  41         memcpy(f->rpos, c->buf+c->pos, rem);
  42         c->pos += rem;
  43         return len;
  44 }
  45
  46 static size_t mwrite(FILE *f, const unsigned char *buf, size_t len)
  47 {
  48         struct cookie *c = f->cookie;
  49         size_t rem;
  50         size_t len2 = f->wpos - f->wbase;
  51         if (len2) {
  52                 f->wpos = f->wbase;
  53                 if (mwrite(f, f->wpos, len2) < len2) return 0;
  54         }
  55         if (c->mode == 'a') c->pos = c->len;
  56         rem = c->size - c->pos;
  57         if (len > rem) len = rem;
  58         memcpy(c->buf+c->pos, buf, len);
  59         c->pos += len;
  60         if (c->pos > c->len) {
  61                 c->len = c->pos;
  62                 if (c->len < c->size) c->buf[c->len] = 0;
  63                 else if ((f->flags&F_NORD) && c->size) c->buf[c->size-1] = 0;
  64         }
  65         return len;
  66 }
  67
  68 static int mclose(FILE *m)
  69 {
  70         return 0;
  71 }
  72
  73 FILE *fmemopen(void *restrict buf, size_t size, const char *restrict mode)
  74 {
  75         FILE *f;
  76         struct cookie *c;
  77         int plus = !!strchr(mode, '+');
  78
  79         if (!size || !strchr("rwa", *mode)) {
  80                 errno = EINVAL;
  81                 return 0;
  82         }
  83
  84         if (!buf && size > SIZE_MAX-sizeof(FILE)-BUFSIZ-UNGET) {
  85                 errno = ENOMEM;
  86                 return 0;
  87         }
  88
  89         f = calloc(sizeof *f + sizeof *c + UNGET + BUFSIZ + (buf?0:size), 1);
  90         if (!f) return 0;
  91         f->cookie = c = (void *)(f+1);
  92         f->fd = -1;
  93         f->lbf = EOF;
  94         f->buf = (unsigned char *)(c+1) + UNGET;
  95         f->buf_size = BUFSIZ;
  96         if (!buf) buf = f->buf + BUFSIZ;
  97
  98         c->buf = buf;
  99         c->size = size;
 100         c->mode = *mode;
 101
 102         if (!plus) f->flags = (*mode == 'r') ? F_NOWR : F_NORD;
 103         if (*mode == 'r') c->len = size;
 104         else if (*mode == 'a') c->len = c->pos = strnlen(buf, size);
 105
 106         f->read = mread;
 107         f->write = mwrite;
 108         f->seek = mseek;
 109         f->close = mclose;
 110
 111         if (!libc.threaded) f->lock = -1;
 112
 113         return __ofl_add(f);
 114 }