src/stdio/fmemopen.c

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