source: asp3_tinet_ecnl_arm/trunk/musl-1.1.18/src/stdio/open_memstream.c@ 352

#include "stdio_impl.h"
#include <errno.h>
#include <limits.h>
#include <string.h>

struct cookie {
        char **bufp;
        size_t *sizep;
        size_t pos;
        char *buf;
        size_t len;
        size_t space;
};

static off_t ms_seek(FILE *f, off_t off, int whence)
{
        ssize_t base;
        struct cookie *c = f->cookie;
        if (whence>2U) {
fail:
                errno = EINVAL;
                return -1;
        }
        base = (size_t [3]){0, c->pos, c->len}[whence];
        if (off < -base || off > SSIZE_MAX-base) goto fail;
        return c->pos = base+off;
}

static size_t ms_write(FILE *f, const unsigned char *buf, size_t len)
{
        struct cookie *c = f->cookie;
        size_t len2 = f->wpos - f->wbase;
        char *newbuf;
        if (len2) {
                f->wpos = f->wbase;
                if (ms_write(f, f->wbase, len2) < len2) return 0;
        }
        if (len + c->pos >= c->space) {
                len2 = 2*c->space+1 | c->pos+len+1;
                newbuf = realloc(c->buf, len2);
                if (!newbuf) return 0;
                *c->bufp = c->buf = newbuf;
                memset(c->buf + c->space, 0, len2 - c->space);
                c->space = len2;
        }
        memcpy(c->buf+c->pos, buf, len);
        c->pos += len;
        if (c->pos >= c->len) c->len = c->pos;
        *c->sizep = c->pos;
        return len;
}

static int ms_close(FILE *f)
{
        return 0;
}

FILE *open_memstream(char **bufp, size_t *sizep)
{
        FILE *f;
        struct cookie *c;
        char *buf;

        if (!(f=malloc(sizeof *f + sizeof *c + BUFSIZ))) return 0;
        if (!(buf=malloc(sizeof *buf))) {
                free(f);
                return 0;
        }
        memset(f, 0, sizeof *f + sizeof *c);
        f->cookie = c = (void *)(f+1);

        c->bufp = bufp;
        c->sizep = sizep;
        c->pos = c->len = c->space = *sizep = 0;
        c->buf = *bufp = buf;
        *buf = 0;

        f->flags = F_NORD;
        f->fd = -1;
        f->buf = (void *)(c+1);
        f->buf_size = BUFSIZ;
        f->lbf = EOF;
        f->write = ms_write;
        f->seek = ms_seek;
        f->close = ms_close;

        if (!libc.threaded) f->lock = -1;

        return __ofl_add(f);
}