[PATCH 2/6] Add fmemopen compatibility version.

[Ondrej Bilka <neleai at seznam dot cz>]

We change behaviour to fmemopen to be more consistent with streams 
returned by fopen. However some apps can depend on existing behaviour so this
adds compatibility symbol.
Also patch 6/6 needs additional field in fmemopen_cookie_struct

	* libio/Makefile (routines): Add oldfmemopen.
	* libio/Versions (libc): Add compatibility symbol.
	* libio/oldfmemopen.c: New file.

---
 libio/Makefile      |    2 +-
 libio/Versions      |    3 +
 libio/oldfmemopen.c |  268 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 272 insertions(+), 1 deletion(-)
 create mode 100644 libio/oldfmemopen.c

diff --git a/libio/Makefile b/libio/Makefile
index e15cd40..1e3e67f 100644
--- a/libio/Makefile
+++ b/libio/Makefile
@@ -44,7 +44,7 @@ routines	:=							      \
 	__fbufsize __freading __fwriting __freadable __fwritable __flbf	      \
 	__fpurge __fpending __fsetlocking				      \
 									      \
-	libc_fatal fmemopen
+	libc_fatal oldfmemopen fmemopen
 
 include ../Makeconfig
 
diff --git a/libio/Versions b/libio/Versions
index 8df89d2..d1390ee 100644
--- a/libio/Versions
+++ b/libio/Versions
@@ -148,6 +148,9 @@ libc {
   GLIBC_2.4 {
     open_wmemstream;
   }
+  GLIBC_2.17 {
+    fmemopen;
+  }
   GLIBC_PRIVATE {
     # Used by NPTL and librt
     __libc_fatal;
diff --git a/libio/oldfmemopen.c b/libio/oldfmemopen.c
new file mode 100644
index 0000000..96dcd0f
--- /dev/null
+++ b/libio/oldfmemopen.c
@@ -0,0 +1,268 @@
+/* Fmemopen implementation.
+   Copyright (C) 2000-2013 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 Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/*
+ * 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.
+ *
+ *
+ *
+ * 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 <shlib-compat.h>
+#if SHLIB_COMPAT (libc, GLIBC_2_17, GLIBC_2_18)
+
+
+# include <errno.h>
+# include <libio.h>
+# include <stdio.h>
+# include <stdlib.h>
+# include <stdint.h>
+# include <string.h>
+# include <sys/types.h>
+# include "libioP.h"
+
+
+typedef struct oldfmemopen_cookie_struct oldfmemopen_cookie_t;
+struct oldfmemopen_cookie_struct
+{
+  char *buffer;
+  int mybuffer;
+  int binmode;
+  size_t size;
+  _IO_off64_t pos;
+  size_t maxpos;
+};
+
+
+static ssize_t
+oldfmemopen_read (void *cookie, char *b, size_t s)
+{
+  oldfmemopen_cookie_t *c;
+
+  c = (oldfmemopen_cookie_t *) cookie;
+
+  if (c->pos + s > c->size)
+    {
+      if ((size_t) c->pos == c->size)
+        return 0;
+      s = c->size - c->pos;
+    }
+
+  memcpy (b, &(c->buffer[c->pos]), s);
+
+  c->pos += s;
+  if ((size_t) c->pos > c->maxpos)
+    c->maxpos = c->pos;
+
+  return s;
+}
+
+
+static ssize_t
+oldfmemopen_write (void *cookie, const char *b, size_t s)
+{
+  oldfmemopen_cookie_t *c;
+  int addnullc;
+
+  c = (oldfmemopen_cookie_t *) cookie;
+
+  addnullc = c->binmode == 0 && (s == 0 || b[s - 1] != '\0');
+
+  if (c->pos + s + addnullc > c->size)
+    {
+      if ((size_t) (c->pos + addnullc) == c->size)
+        {
+          __set_errno (ENOSPC);
+          return 0;
+        }
+      s = c->size - c->pos - addnullc;
+    }
+
+  memcpy (&(c->buffer[c->pos]), b, s);
+
+  c->pos += s;
+  if ((size_t) c->pos > c->maxpos)
+    {
+      c->maxpos = c->pos;
+      if (addnullc)
+        c->buffer[c->maxpos] = '\0';
+    }
+
+  return s;
+}
+
+
+static int
+oldfmemopen_seek (void *cookie, _IO_off64_t *p, int w)
+{
+  _IO_off64_t np;
+  oldfmemopen_cookie_t *c;
+
+  c = (oldfmemopen_cookie_t *) cookie;
+
+  switch (w)
+    {
+    case SEEK_SET:
+      np = *p;
+      break;
+
+    case SEEK_CUR:
+      np = c->pos + *p;
+      break;
+
+    case SEEK_END:
+      np = (c->binmode ? c->size : c->maxpos) - *p;
+      break;
+
+    default:
+      return -1;
+    }
+
+  if (np < 0 || (size_t) np > c->size)
+    return -1;
+
+  *p = c->pos = np;
+
+  return 0;
+}
+
+
+static int
+oldfmemopen_close (void *cookie)
+{
+  oldfmemopen_cookie_t *c;
+
+  c = (oldfmemopen_cookie_t *) cookie;
+
+  if (c->mybuffer)
+    free (c->buffer);
+  free (c);
+
+  return 0;
+}
+
+
+FILE *
+attribute_compat_text_section
+oldfmemopen (void *buf, size_t len, const char *mode)
+{
+  cookie_io_functions_t iof;
+  oldfmemopen_cookie_t *c;
+
+  if (__builtin_expect (len == 0, 0))
+    {
+einval:
+      __set_errno (EINVAL);
+      return NULL;
+    }
+
+  c = (oldfmemopen_cookie_t *) malloc (sizeof (oldfmemopen_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';
+      c->maxpos = 0;
+    }
+  else
+    {
+      if (__builtin_expect ((uintptr_t) len > -(uintptr_t) buf, 0))
+        {
+          free (c);
+          goto einval;
+        }
+
+      c->buffer = buf;
+
+      if (mode[0] == 'w')
+        c->buffer[0] = '\0';
+
+      c->maxpos = strnlen (c->buffer, len);
+    }
+
+  c->size = len;
+
+  if (mode[0] == 'a')
+    c->pos = c->maxpos;
+  else
+    c->pos = 0;
+
+  c->binmode = mode[0] != '\0' && mode[1] == 'b';
+
+  iof.read = oldfmemopen_read;
+  iof.write = oldfmemopen_write;
+  iof.seek = oldfmemopen_seek;
+  iof.close = oldfmemopen_close;
+
+  return _IO_fopencookie (c, mode, iof);
+}
+
+compat_symbol (libc, oldfmemopen, fmemopen, GLIBC_2_17);
+#endif
-- 
1.7.10.4