src/stdio/fmemopen.c

   1 #include "stdio_impl.h"
   2 #include <errno.h>
   3 #include <string.h>
   4 #include <stdlib.h>
   5 #include <stddef.h>
   6 #include <inttypes.h>
   7 #include "libc.h"
   8
   9 struct cookie {
  10         size_t pos, len, size;
  11         unsigned char *buf;
  12         int mode;
  13 };
  14
  15 struct mem_FILE {
  16         FILE f;
  17         struct cookie c;
  18         unsigned char buf[UNGET+BUFSIZ], buf2[];
  19 };
  20
  21 static off_t mseek(FILE *f, off_t off, int whence)
  22 {
  23         ssize_t base;
  24         struct cookie *c = f->cookie;
  25         if (whence>2U) {
  26 fail:
  27                 errno = EINVAL;
  28                 return -1;
  29         }
  30         base = (size_t [3]){0, c->pos, c->len}[whence];
  31         if (off < -base || off > (ssize_t)c->size-base) goto fail;
  32         return c->pos = base+off;
  33 }
  34
  35 static size_t mread(FILE *f, unsigned char *buf, size_t len)
  36 {
  37         struct cookie *c = f->cookie;
  38         size_t rem = c->len - c->pos;
  39         if (c->pos > c->len) rem = 0;
  40         if (len > rem) {
  41                 len = rem;
  42                 f->flags |= F_EOF;
  43         }
  44         memcpy(buf, c->buf+c->pos, len);
  45         c->pos += len;
  46         rem -= len;
  47         if (rem > f->buf_size) rem = f->buf_size;
  48         f->rpos = f->buf;
  49         f->rend = f->buf + rem;
  50         memcpy(f->rpos, c->buf+c->pos, rem);
  51         c->pos += rem;
  52         return len;
  53 }
  54
  55 static size_t mwrite(FILE *f, const unsigned char *buf, size_t len)
  56 {
  57         struct cookie *c = f->cookie;
  58         size_t rem;
  59         size_t len2 = f->wpos - f->wbase;
  60         if (len2) {
  61                 f->wpos = f->wbase;
  62                 if (mwrite(f, f->wpos, len2) < len2) return 0;
  63         }
  64         if (c->mode == 'a') c->pos = c->len;
  65         rem = c->size - c->pos;
  66         if (len > rem) len = rem;
  67         memcpy(c->buf+c->pos, buf, len);
  68         c->pos += len;
  69         if (c->pos > c->len) {
  70                 c->len = c->pos;
  71                 if (c->len < c->size) c->buf[c->len] = 0;
  72                 else if ((f->flags&F_NORD) && c->size) c->buf[c->size-1] = 0;
  73         }
  74         return len;
  75 }
  76
  77 static int mclose(FILE *m)
  78 {
  79         return 0;
  80 }
  81
  82 FILE *fmemopen(void *restrict buf, size_t size, const char *restrict mode)
  83 {
  84         struct mem_FILE *f;
  85         int plus = !!strchr(mode, '+');
  86
  87         if (!strchr("rwa", *mode)) {
  88                 errno = EINVAL;
  89                 return 0;
  90         }
  91
  92         if (!buf && size > PTRDIFF_MAX) {
  93                 errno = ENOMEM;
  94                 return 0;
  95         }
  96
  97         f = malloc(sizeof *f + (buf?0:size));
  98         if (!f) return 0;
  99         memset(f, 0, offsetof(struct mem_FILE, buf));
 100         f->f.cookie = &f->c;
 101         f->f.fd = -1;
 102         f->f.lbf = EOF;
 103         f->f.buf = f->buf + UNGET;
 104         f->f.buf_size = sizeof f->buf - UNGET;
 105         if (!buf) {
 106                 buf = f->buf2;
 107                 memset(buf, 0, size);
 108         }
 109
 110         f->c.buf = buf;
 111         f->c.size = size;
 112         f->c.mode = *mode;
 113
 114         if (!plus) f->f.flags = (*mode == 'r') ? F_NOWR : F_NORD;
 115         if (*mode == 'r') f->c.len = size;
 116         else if (*mode == 'a') f->c.len = f->c.pos = strnlen(buf, size);
 117         else if (plus) *f->c.buf = 0;
 118
 119         f->f.read = mread;
 120         f->f.write = mwrite;
 121         f->f.seek = mseek;
 122         f->f.close = mclose;
 123
 124         if (!libc.threaded) f->f.lock = -1;
 125
 126         return __ofl_add(&f->f);
 127 }