github.com/afumu/libc@v0.0.6/musl/src/stdio/open_memstream.c (about)

     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  }