src/stdio/open_memstream.c

   1 #include "stdio_impl.h"
   2 #include <errno.h>
   3 #include <limits.h>
   4 #include <string.h>
   5 #include <stdlib.h>
   6 #include "libc.h"
   7
   8 struct cookie {
   9         char **bufp;
  10         size_t *sizep;
  11         size_t pos;
  12         char *buf;
  13         size_t len;
  14         size_t space;
  15 };
  16
  17 struct ms_FILE {
  18         FILE f;
  19         struct cookie c;
  20         unsigned char buf[BUFSIZ];
  21 };
  22
  23 static off_t ms_seek(FILE *f, off_t off, int whence)
  24 {
  25         ssize_t base;
  26         struct cookie *c = f->cookie;
  27         if (whence>2U) {
  28 fail:
  29                 errno = EINVAL;
  30                 return -1;
  31         }
  32         base = (size_t [3]){0, c->pos, c->len}[whence];
  33         if (off < -base || off > SSIZE_MAX-base) goto fail;
  34         return c->pos = base+off;
  35 }
  36
  37 static size_t ms_write(FILE *f, const unsigned char *buf, size_t len)
  38 {
  39         struct cookie *c = f->cookie;
  40         size_t len2 = f->wpos - f->wbase;
  41         char *newbuf;
  42         if (len2) {
  43                 f->wpos = f->wbase;
  44                 if (ms_write(f, f->wbase, len2) < len2) return 0;
  45         }
  46         if (len + c->pos >= c->space) {
  47                 len2 = 2*c->space+1 | c->pos+len+1;
  48                 newbuf = realloc(c->buf, len2);
  49                 if (!newbuf) return 0;
  50                 *c->bufp = c->buf = newbuf;
  51                 memset(c->buf + c->space, 0, len2 - c->space);
  52                 c->space = len2;
  53         }
  54         memcpy(c->buf+c->pos, buf, len);
  55         c->pos += len;
  56         if (c->pos >= c->len) c->len = c->pos;
  57         *c->sizep = c->pos;
  58         return len;
  59 }
  60
  61 static int ms_close(FILE *f)
  62 {
  63         return 0;
  64 }
  65
  66 FILE *open_memstream(char **bufp, size_t *sizep)
  67 {
  68         struct ms_FILE *f;
  69         char *buf;
  70
  71         if (!(f=malloc(sizeof *f))) return 0;
  72         if (!(buf=malloc(sizeof *buf))) {
  73                 free(f);
  74                 return 0;
  75         }
  76         memset(&f->f, 0, sizeof f->f);
  77         memset(&f->c, 0, sizeof f->c);
  78         f->f.cookie = &f->c;
  79
  80         f->c.bufp = bufp;
  81         f->c.sizep = sizep;
  82         f->c.pos = f->c.len = f->c.space = *sizep = 0;
  83         f->c.buf = *bufp = buf;
  84         *buf = 0;
  85
  86         f->f.flags = F_NORD;
  87         f->f.fd = -1;
  88         f->f.buf = f->buf;
  89         f->f.buf_size = sizeof f->buf;
  90         f->f.lbf = EOF;
  91         f->f.write = ms_write;
  92         f->f.seek = ms_seek;
  93         f->f.close = ms_close;
  94         f->f.mode = -1;
  95
  96         if (!libc.threaded) f->f.lock = -1;
  97
  98         return __ofl_add(&f->f);
  99 }