FILE *open_memstream(char **ptr, size_t *sizeloc) {
if (ptr && sizeloc) {
struct memstream *ms = calloc(1, sizeof(struct memstream));
FILE *fp = 0;
if (!ms)
return 0; /* errno == ENOMEM */
ms->position = ms->size = 0;
ms->capacity = 4096;
ms->contents = calloc(ms->capacity, 1);
if (!ms->contents) {
free(ms);
return 0;
} /* errno == ENOMEM */
ms->ptr = ptr;
ms->sizeloc = sizeloc;
memstream_print(ms);
fp = funopen(ms, memstream_read, memstream_write, memstream_seek,
memstream_close);
if (!fp) {
free(ms->contents);
free(ms);
return 0; /* errno set by funopen */
}
*ptr = ms->contents;
*sizeloc = ms->size;
return fp;
}
errno = EINVAL;
return 0;
}
static fpos_t memstream_seek(void *cookie, fpos_t offset, int whence) {
struct memstream *ms = (struct memstream *)cookie;
fpos_t pos = 0;
memstream_check(ms);
memstream_info(("memstream_seek %p %i %i\n", ms, (int)offset, whence));
switch (whence) {
case SEEK_SET:
pos = offset;
break;
case SEEK_CUR:
pos = ms->position + offset;
break;
case SEEK_END:
pos = ms->size + offset;
break;
default:
errno = EINVAL;
return -1;
}
if (pos >= ms->capacity)
memstream_grow(ms, pos);
ms->position = pos;
if (ms->size < ms->position)
*ms->sizeloc = ms->size = ms->position;
memstream_print(ms);
memstream_info(("=> %i\n", (int)pos));
assert(ms->size < ms->capacity && ms->contents[ms->size] == 0);
return pos;
}
static int memstream_read(void *cookie, char *buf, int count)
{
struct memstream *ms= (struct memstream *)cookie; memstream_check(ms);
int n= min(ms->size - ms->position, count); memstream_info(("memstream_read %p %i\n", ms, count));
if (n < 1) return 0;
memcpy(buf, ms->contents, n);
ms->position += n; memstream_print(ms);
return n;
}
static int memstream_write(void *cookie, const char *buf, int count)
{
struct memstream *ms= (struct memstream *)cookie; memstream_check(ms);
if (ms->capacity <= ms->position + count)
if (memstream_grow(ms, ms->position + count) < 0) /* errno == ENOMEM */
return -1;
memcpy(ms->contents + ms->position, buf, count); memstream_info(("memstream_write %p %i\n", ms, count));
ms->position += count;
if (ms->size < ms->position) *ms->sizeloc= ms->size= ms->position; memstream_print(ms);
assert(ms->size < ms->capacity);
assert(ms->contents[ms->size] == 0);
return count;
}
