libstdc++/2071

	* porting.texi: Add documentation about libstdc++-v3-specific
	macros that are currently included in os_defines.h files.

	* config/basic_file_stdio.h (sys_getc): New method.
	(sys_ungetc): New method.
	* include/bits/basic_file.h: (sys_getc): New method signature.
	(sys_ungetc): New method signature.

	* include/bits/fstream.tcc (underflow): Add conditional code
	paths which avoid using short seeks on streams (especially
	useful when the stream might be interactive or a pipe).  At
	the moment, this alternate path only avoids seeking when the
	``buffer size'' of underflow() is 1 since the C standard only
	guarantees buffer space for one ungetc (this technique could
	be extended since *-*-solaris* supports buffering for 4 calls
	to ungetc and *-*-*bsd* supports buffering limited only by
	memory resources).  Also, _GLIBCPP_AVOID_FSEEK must be defined
	in a port's os_defines.h file for this alternate path to even
	be considered.  As a bonus, the idiom of using getc/ungetc
	requires no system calls whereas fseek maps to one or two
	system call(s) on many platforms.

	* config/os/bsd/freebsd/bits/os_defines.h (_GLIBCPP_AVOID_FSEEK):
	Define it.
	* config/os/solaris/solaris2.5/bits/os_defines.h
	(_GLIBCPP_AVOID_FSEEK): Likewise.
	* config/os/solaris/solaris2.6/bits/os_defines.h
	(_GLIBCPP_AVOID_FSEEK): Likewise.
	* config/os/solaris/solaris2.7/bits/os_defines.h
	(_GLIBCPP_AVOID_FSEEK): Likewise.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@43278 138bc75d-0d04-0410-961f-82ee72b054a4

5 files changed, 27 insertions, 7 deletions

diff --git a/libstdc++-v3/config/basic_file_stdio.h b/libstdc++-v3/config/basic_file_stdio.h
index 565bfea4d40..edf4d98baa9 100644
--- a/libstdc++-v3/config/basic_file_stdio.h
+++ b/libstdc++-v3/config/basic_file_stdio.h
@@ -91,6 +91,20 @@ namespace std
 
       return __ret;
     }
+
+  template<typename _CharT>
+    _CharT
+    __basic_file<_CharT>::sys_getc()
+    {
+      return getc (_M_cfile);
+    }
+
+  template<typename _CharT>
+    _CharT
+    __basic_file<_CharT>::sys_ungetc(_CharT __s)
+    {
+      return ungetc (__s, _M_cfile);
+    }
   
   template<typename _CharT>
     __basic_file<_CharT>* 
diff --git a/libstdc++-v3/config/os/bsd/freebsd/bits/os_defines.h b/libstdc++-v3/config/os/bsd/freebsd/bits/os_defines.h
index 1cb71d149ec..3a6803f8f3d 100644
--- a/libstdc++-v3/config/os/bsd/freebsd/bits/os_defines.h
+++ b/libstdc++-v3/config/os/bsd/freebsd/bits/os_defines.h
@@ -35,6 +35,7 @@
 /* System-specific #define, typedefs, corrections, etc, go here.  This
    file will come before all others. */
 
+#define _GLIBCPP_AVOID_FSEEK 1
 
 #endif
 
diff --git a/libstdc++-v3/config/os/solaris/solaris2.5/bits/os_defines.h b/libstdc++-v3/config/os/solaris/solaris2.5/bits/os_defines.h
index 4dd1fa21c46..5a756b4210d 100644
--- a/libstdc++-v3/config/os/solaris/solaris2.5/bits/os_defines.h
+++ b/libstdc++-v3/config/os/solaris/solaris2.5/bits/os_defines.h
@@ -1,4 +1,4 @@
-// Specific definitions for Solaris 2.6  -*- C++ -*-
+// Specific definitions for Solaris 2.5  -*- C++ -*-
 
 // Copyright (C) 2000 Free Software Foundation, Inc.
 //
@@ -33,6 +33,9 @@
 
 /* System-specific #define, typedefs, corrections, etc, go here.  This
    file will come before all others. */
+
+#define _GLIBCPP_AVOID_FSEEK 1
+
 // These are typedefs which libio assumes are already in place (because
 // they really are, under Linux).
 #define __off_t     off_t
@@ -43,5 +46,3 @@
 #define _G_USING_THUNKS 0
 
 #endif
-
-
diff --git a/libstdc++-v3/config/os/solaris/solaris2.6/bits/os_defines.h b/libstdc++-v3/config/os/solaris/solaris2.6/bits/os_defines.h
index 4dd1fa21c46..961e29d55d0 100644
--- a/libstdc++-v3/config/os/solaris/solaris2.6/bits/os_defines.h
+++ b/libstdc++-v3/config/os/solaris/solaris2.6/bits/os_defines.h
@@ -33,6 +33,9 @@
 
 /* System-specific #define, typedefs, corrections, etc, go here.  This
    file will come before all others. */
+
+#define _GLIBCPP_AVOID_FSEEK 1
+
 // These are typedefs which libio assumes are already in place (because
 // they really are, under Linux).
 #define __off_t     off_t
@@ -43,5 +46,3 @@
 #define _G_USING_THUNKS 0
 
 #endif
-
-
diff --git a/libstdc++-v3/config/os/solaris/solaris2.7/bits/os_defines.h b/libstdc++-v3/config/os/solaris/solaris2.7/bits/os_defines.h
index cb0afed3259..8ed386765f6 100644
--- a/libstdc++-v3/config/os/solaris/solaris2.7/bits/os_defines.h
+++ b/libstdc++-v3/config/os/solaris/solaris2.7/bits/os_defines.h
@@ -31,6 +31,11 @@
 #ifndef _GLIBCPP_OS_DEFINES
 #  define _GLIBCPP_OS_DEFINES
 
+/* System-specific #define, typedefs, corrections, etc, go here.  This
+   file will come before all others. */
+
+#define _GLIBCPP_AVOID_FSEEK 1
+
 // These are typedefs which libio assumes are already in place (because
 // they really are, under Linux).
 #define __off_t     off_t
@@ -40,6 +45,4 @@
 // Without this all the libio vtbls are offset wrongly.
 #define _G_USING_THUNKS 0
 
-
 #endif
-