open_memstream.c raw

   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  }
 100