Advanced Programming in the UNIX® Environment

ptg10805159

Appendix C Chapter 5 Solutions 917

if (ms->curpos > ms->vsize) {

ms->vsize = ms->curpos;

if (((ms->flags & (MS_READ|MS_WRITE)) ==

(MS_READ|MS_WRITE)) && (ms->vsize < ms->rsize))

*(ms->buf + ms->vsize) = 0;

}

if ((ms->flags & (MS_WRITE|MS_APPEND)) &&

!(ms->flags & MS_READ)) {

if (ms->curpos < ms->rsize)

*(ms->buf + ms->curpos) = 0;

else

*(ms->buf + ms->rsize - 1) = 0;

}

return(nw);

}

static fpos_t

mstream_seek(void *cookie, fpos_t pos, int whence)

{

int off;

struct memstream *ms = cookie;

switch (whence) {

case SEEK_SET:

off = pos;

break;

case SEEK_END:

off = ms->vsize + pos;

break;

case SEEK_CUR:

off = ms->curpos + pos;

break;

}

if (off < 0 || off > ms->vsize) {

errno = EINVAL;

return -1;

}

ms->curpos = off;

return(off);

}

static int

mstream_close(void *cookie)

{

struct memstream *ms = cookie;

if (ms->flags & MS_MYBUF)

free(ms->buf);

free(ms);

return(0);

}

Figure C.4 Implementation offmemopenfor BSD systems