8 <<fmemopen>>---open a stream around a fixed-length string
19 <<fmemopen>> creates a seekable <<FILE>> stream that wraps a
20 fixed-length buffer of <[size]> bytes starting at <[buf]>.  The stream
27 The stream maintains a current position, which moves according to
29 The stream also maintains a current file size, which is never greater
34 <[mode]> starts with <<a>>, the position and file size start at the
42 buffer).  When the stream is flushed or closed after a write that
43 changed the file size, a NUL byte is written at the current position
44 if there is still room; if the stream is not also open for reading, a
46 stream has exceeded <[size]>, so that a write-only <[buf]> is always
47 NUL-terminated when the stream is flushed or closed (and the initial
49 outside the bounds of <[size]>.  A NUL byte written during a flush is
80   char writeonly; /* 1 if write-only */
81   char saved; /* saved character that lived at pos before write-only NUL */
84 /* Read up to non-zero N bytes into BUF from stream described by
94   if (c->pos > c->eof)  in fmemreader()
96   if (n >= c->eof - c->pos)  in fmemreader()
97     n = c->eof - c->pos;  in fmemreader()
98   memcpy (buf, c->buf + c->pos, n);  in fmemreader()
99   c->pos += n;  in fmemreader()
103 /* Write up to non-zero N bytes of BUF into the stream described by COOKIE,
115      a seek beyond eof, ensure all intermediate bytes are NUL.  */  in fmemwriter()
116   if (c->append)  in fmemwriter()
117     c->pos = c->eof;  in fmemwriter()
118   else if (c->pos > c->eof)  in fmemwriter()
119     memset (c->buf + c->eof, '\0', c->pos - c->eof);  in fmemwriter()
120   /* Do not write beyond EOF; saving room for NUL on write-only stream.  */  in fmemwriter()
121   if (c->pos + n > c->max - c->writeonly)  in fmemwriter()
123       adjust = c->writeonly;  in fmemwriter()
124       n = c->max - c->pos;  in fmemwriter()
127      the last byte is NUL instead of from buf.  Write a NUL if  in fmemwriter()
128      write-only; or if read-write, eof changed, and there is still  in fmemwriter()
131   if (c->pos + n > c->eof)  in fmemwriter()
133       c->eof = c->pos + n;  in fmemwriter()
134       if (c->eof - adjust < c->max)  in fmemwriter()
135 	c->saved = c->buf[c->eof - adjust] = '\0';  in fmemwriter()
137   else if (c->writeonly)  in fmemwriter()
141 	  c->saved = c->buf[c->pos + n - adjust];  in fmemwriter()
142 	  c->buf[c->pos + n - adjust] = '\0';  in fmemwriter()
147   c->pos += n;  in fmemwriter()
148   if (n - adjust)  in fmemwriter()
149     memcpy (c->buf + c->pos - n, buf, n - adjust);  in fmemwriter()
174     offset += c->pos;  in fmemseeker()
176     offset += c->eof;  in fmemseeker()
180       offset = -1;  in fmemseeker()
182   else if (offset > (off_t) c->max)  in fmemseeker()
185       offset = -1;  in fmemseeker()
191       offset = -1;  in fmemseeker()
196       if (c->writeonly && c->pos < c->eof)  in fmemseeker()
198 	  c->buf[c->pos] = c->saved;  in fmemseeker()
199 	  c->saved = '\0';  in fmemseeker()
201       c->pos = offset;  in fmemseeker()
202       if (c->writeonly && c->pos < c->eof)  in fmemseeker()
204 	  c->saved = c->buf[c->pos];  in fmemseeker()
205 	  c->buf[c->pos] = '\0';  in fmemseeker()
223     offset += c->pos;  in fmemseeker64()
225     offset += c->eof;  in fmemseeker64()
229       offset = -1;  in fmemseeker64()
231   else if (offset > (_off64_t) c->max)  in fmemseeker64()
234       offset = -1;  in fmemseeker64()
238       if (c->writeonly && c->pos < c->eof)  in fmemseeker64()
240 	  c->buf[c->pos] = c->saved;  in fmemseeker64()
241 	  c->saved = '\0';  in fmemseeker64()
243       c->pos = offset;  in fmemseeker64()
244       if (c->writeonly && c->pos < c->eof)  in fmemseeker64()
246 	  c->saved = c->buf[c->pos];  in fmemseeker64()
247 	  c->buf[c->pos] = '\0';  in fmemseeker64()
260   free (c->storage);  in fmemcloser()
264 /* Open a memstream around buffer BUF of SIZE bytes, using MODE.
290       fp->_flags = 0;		/* release */  in fmemopen()
292       __lock_close_recursive (fp->_lock);  in fmemopen()
298   c->storage = c;  in fmemopen()
299   c->max = size;  in fmemopen()
301   /* w/a, buf or no buf: Guarantee a NUL after any file writes.  */  in fmemopen()
302   c->writeonly = (flags & __SWR) != 0;  in fmemopen()
303   c->saved = '\0';  in fmemopen()
306       /* r+/w+/a+, and no buf: file starts empty.  */  in fmemopen()
307       c->buf = (char *) (c + 1);  in fmemopen()
308       c->buf[0] = '\0';  in fmemopen()
309       c->pos = c->eof = 0;  in fmemopen()
310       c->append = (flags & __SAPP) != 0;  in fmemopen()
314       c->buf = (char *) buf;  in fmemopen()
317 	case 'a':  in fmemopen()
318 	  /* a/a+ and buf: position and size at first NUL.  */  in fmemopen()
319 	  buf = memchr (c->buf, '\0', size);  in fmemopen()
320 	  c->eof = c->pos = buf ? (size_t) ((char *) buf - c->buf) : size;  in fmemopen()
321 	  if (!buf && c->writeonly)  in fmemopen()
322 	    /* a: guarantee a NUL within size even if no writes.  */  in fmemopen()
323 	    c->buf[size - 1] = '\0';  in fmemopen()
324 	  c->append = 1;  in fmemopen()
328 	  c->pos = c->append = 0;  in fmemopen()
329 	  c->eof = size;  in fmemopen()
333 	  c->pos = c->append = c->eof = 0;  in fmemopen()
334 	  *c->buf = '\0';  in fmemopen()
342   fp->_file = -1;  in fmemopen()
343   fp->_flags = flags;  in fmemopen()
344   fp->_cookie = c;  in fmemopen()
345   fp->_read = flags & (__SRD | __SRW) ? fmemreader : NULL;  in fmemopen()
346   fp->_write = flags & (__SWR | __SRW) ? fmemwriter : NULL;  in fmemopen()
347   fp->_seek = fmemseeker;  in fmemopen()
349   fp->_seek64 = fmemseeker64;  in fmemopen()
350   fp->_flags |= __SL64;  in fmemopen()
352   fp->_close = fmemcloser;  in fmemopen()