--- /dev/null
+/* Fmemopen implementation.
+ Copyright (C) 2000 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Hanno Mueller, kontakt@hanno.de, 2000.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Library General Public License as
+ published by the Free Software Foundation; either version 2 of the
+ License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Library General Public License for more details.
+
+ You should have received a copy of the GNU Library General Public
+ License along with the GNU C Library; see the file COPYING.LIB. If not,
+ write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA. */
+
+/*
+ * fmemopen() - "my" version of a string stream
+ * Hanno Mueller, kontakt@hanno.de
+ *
+ *
+ * I needed fmemopen() for an application that I currently work on,
+ * but couldn't find it in libio. The following snippet of code is an
+ * attempt to implement what glibc's documentation describes.
+ *
+ * No, it isn't really tested yet. :-)
+ *
+ *
+ *
+ * I already see some potential problems:
+ *
+ * - I never used the "original" fmemopen(). I am sure that "my"
+ * fmemopen() behaves differently than the original version.
+ *
+ * - The documentation doesn't say wether a string stream allows
+ * seeks. I checked the old fmemopen implementation in glibc's stdio
+ * directory, wasn't quite able to see what is going on in that
+ * source, but as far as I understand there was no seek there. For
+ * my application, I needed fseek() and ftell(), so it's here.
+ *
+ * - "append" mode and fseek(p, SEEK_END) have two different ideas
+ * about the "end" of the stream.
+ *
+ * As described in the documentation, when opening the file in
+ * "append" mode, the position pointer will be set to the first null
+ * character of the string buffer (yet the buffer may already
+ * contain more data). For fseek(), the last byte of the buffer is
+ * used as the end of the stream.
+ *
+ * - It is unclear to me what the documentation tries to say when it
+ * explains what happens when you use fmemopen with a NULL
+ * buffer.
+ *
+ * Quote: "fmemopen [then] allocates an array SIZE bytes long. This
+ * is really only useful if you are going to write things to the
+ * buffer and then read them back in again."
+ *
+ * What does that mean if the original fmemopen() did not allow
+ * seeking? How do you read what you just wrote without seeking back
+ * to the beginning of the stream?
+ *
+ * - I think there should be a second version of fmemopen() that does
+ * not add null characters for each write. (At least in my
+ * application, I am not actually using strings but binary data and
+ * so I don't need the stream to add null characters on its own.)
+ */
+
+#include <libio.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+
+typedef struct fmemopen_cookie_struct fmemopen_cookie_t;
+struct fmemopen_cookie_struct
+{
+ char *buffer;
+ int mybuffer;
+ size_t size;
+ _IO_off64_t pos;
+ size_t maxpos;
+};
+
+
+ssize_t
+fmemopen_read (void *cookie, char *b, size_t s)
+{
+ fmemopen_cookie_t *c;
+
+ c = (fmemopen_cookie_t *) cookie;
+
+ if ((c->pos + s) > c->size)
+ {
+ if (c->pos == c->size)
+ return -1;
+ s = c->size - c->pos;
+ }
+
+ memcpy (b, &(c->buffer[c->pos]), s);
+
+ c->pos += s;
+ if (c->pos > c->maxpos)
+ c->maxpos = c->pos;
+
+ return s;
+}
+
+
+ssize_t
+fmemopen_write (void *cookie, const char *b, size_t s)
+{
+ fmemopen_cookie_t *c;
+ int addnullc;
+
+ c = (fmemopen_cookie_t *) cookie;
+
+ addnullc = ((s == 0) || (b[s - 1] != '\0')) ? 1 : 0;
+
+ if ((c->pos + s + addnullc) > c->size)
+ {
+ if ((c->pos + addnullc) == c->size)
+ return -1;
+ s = c->size - c->pos - addnullc;
+ }
+
+ memcpy (&(c->buffer[c->pos]), b, s);
+
+ c->pos += s;
+ if (c->pos > c->maxpos)
+ {
+ c->maxpos = c->pos;
+ if (addnullc)
+ c->buffer[c->maxpos] = '\0';
+ }
+
+ return s;
+}
+
+
+int
+fmemopen_seek (void *cookie, _IO_off64_t * p, int w)
+{
+ _IO_off64_t np;
+ fmemopen_cookie_t *c;
+
+ c = (fmemopen_cookie_t *) cookie;
+
+ switch (w)
+ {
+
+ case SEEK_SET:
+ np = *p;
+ break;
+
+ case SEEK_CUR:
+ np = c->pos + *p;
+ break;
+
+ case SEEK_END:
+ np = c->size - *p;
+ break;
+
+ }
+
+ if ((np < 0) || (np > c->size))
+ return -1;
+
+ c->pos = np;
+
+ return np;
+}
+
+
+int
+fmemopen_close (void *cookie)
+{
+ fmemopen_cookie_t *c;
+
+ c = (fmemopen_cookie_t *) cookie;
+
+ if (c->mybuffer)
+ free (c->buffer);
+ free (c);
+
+ return 0;
+}
+
+
+FILE *
+fmemopen (void *buf, size_t len, const char *mode)
+{
+ cookie_io_functions_t iof;
+ fmemopen_cookie_t *c;
+
+ c = (fmemopen_cookie_t *) malloc (sizeof (fmemopen_cookie_t));
+ if (c == NULL)
+ return NULL;
+
+ c->mybuffer = (buf == NULL);
+
+ if (c->mybuffer)
+ {
+ c->buffer = (char *) malloc (len);
+ if (c->buffer == NULL)
+ {
+ free (c);
+ return NULL;
+ }
+ c->buffer[0] = '\0';
+ }
+ else
+ {
+ c->buffer = buf;
+ }
+
+ c->size = len;
+
+ if (mode[0] == 'w')
+ c->buffer[0] = '\0';
+
+ c->maxpos = strlen (c->buffer);
+
+ if (mode[0] == 'a')
+ {
+ c->pos = c->maxpos;
+ }
+ else
+ {
+ c->pos = 0;
+ }
+
+ iof.read = fmemopen_read;
+ iof.write = fmemopen_write;
+ iof.seek = fmemopen_seek;
+ iof.close = fmemopen_close;
+
+ return fopencookie (c, mode, iof);
+}
--- /dev/null
+/* Test for fmemopen implementation.
+ Copyright (C) 2000 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Hanno Mueller, kontakt@hanno.de, 2000.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Library General Public License as
+ published by the Free Software Foundation; either version 2 of the
+ License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Library General Public License for more details.
+
+ You should have received a copy of the GNU Library General Public
+ License along with the GNU C Library; see the file COPYING.LIB. If not,
+ write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ Boston, MA 02111-1307, USA. */
+
+static char buffer[] = "foobar";
+
+#include <stdio.h>
+#include <string.h>
+
+int
+main (void)
+{
+ int ch;
+ FILE *stream;
+
+ stream = fmemopen (buffer, strlen (buffer), "r");
+
+ while ((ch = fgetc (stream)) != EOF)
+ printf ("Got %c\n", ch);
+
+ fclose (stream);
+
+ return 0;
+}