libio/stdiostream.cc

   1 /* This is part of libio/iostream, providing -*- C++ -*- input/output.
   2 Copyright (C) 1993 Free Software Foundation
   3
   4 This file is part of the GNU IO Library.  This library is free
   5 software; you can redistribute it and/or modify it under the
   6 terms of the GNU General Public License as published by the
   7 Free Software Foundation; either version 2, or (at your option)
   8 any later version.
   9
  10 This library is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this library; see the file COPYING.  If not, write to the Free
  17 Software Foundation, 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  18
  19 As a special exception, if you link this library with files
  20 compiled with a GNU compiler to produce an executable, this does not cause
  21 the resulting executable to be covered by the GNU General Public License.
  22 This exception does not however invalidate any other reasons why
  23 the executable file might be covered by the GNU General Public License. */
  24
  25 /* Written by Per Bothner (bothner@cygnus.com). */
  26
  27 #ifdef __GNUG__
  28 #pragma implementation
  29 #endif
  30
  31 #include <stdiostream.h>
  32 #include "libioP.h"
  33
  34 // A stdiobuf is "tied" to a FILE object (as used by the stdio package).
  35 // Thus a stdiobuf is always synchronized with the corresponding FILE,
  36 // though at the cost of some overhead.  (If you use the implementation
  37 // of stdio supplied with this library, you don't need stdiobufs.)
  38 // This implementation inherits from filebuf, but implement the virtual
  39 // functions sys_read/..., using the stdio functions fread/... instead
  40 // of the low-level read/... system calls.  This has the advantage that
  41 // we get all of the nice filebuf semantics automatically, though
  42 // with some overhead.
  43
  44
  45 #ifndef SEEK_SET
  46 #define SEEK_SET 0
  47 #endif
  48 #ifndef SEEK_CUR
  49 #define SEEK_CUR 1
  50 #endif
  51 #ifndef SEEK_END
  52 #define SEEK_END 2
  53 #endif
  54
  55 stdiobuf::stdiobuf(FILE *f) : filebuf(fileno(f))
  56 {
  57     _file = f;
  58     // Turn off buffer in stdiobuf.  Instead, rely on buffering in (FILE).
  59     // Thus the stdiobuf will be synchronized with the FILE.
  60     setbuf(NULL, 0);
  61 }
  62
  63 stdiobuf::~stdiobuf()
  64 {
  65   /* Only needed if we're buffered.  Not buffered is the default. */
  66   _IO_do_flush((_IO_FILE*)this);
  67 }
  68
  69 streamsize stdiobuf::sys_read(char* buf, streamsize size)
  70 {
  71   // A minor optimization, but it makes a noticable difference.
  72   // A bigger optimization would be to write stdiobuf::underflow,
  73   // but that has some modularity disadvantages.  Re-evaluate that
  74   // after we have gotten rid of the double indirection.  FIXME
  75   if (size == 1)
  76     {
  77       register ch = getc(_file);
  78       if (ch == EOF)
  79         return 0;
  80       *buf = (char)ch;
  81       return 1;
  82     }
  83   else
  84     return fread(buf, 1, size, _file);
  85 }
  86
  87 streamsize stdiobuf::sys_write(const char *buf, streamsize n)
  88 {
  89     _IO_ssize_t count = fwrite(buf, 1, n, _file);
  90     if (_offset >= 0)
  91         _offset += n;
  92     return count;
  93 }
  94
  95 streampos stdiobuf::sys_seek(streamoff offset, _seek_dir dir)
  96 {
  97     // Normally, equivalent to: fdir=dir
  98     int fdir =
  99         (dir == ios::beg) ? SEEK_SET :
 100         (dir == ios::cur) ? SEEK_CUR :
 101         (dir == ios::end) ? SEEK_END :
 102         dir;
 103     return fseek(_file, offset, fdir);
 104 }
 105
 106 int stdiobuf::sys_close()
 107 {
 108     int status = fclose(_file);
 109     _file = NULL;
 110     return status;
 111 }
 112
 113 int stdiobuf::sync()
 114 {
 115   if (_IO_do_flush((_IO_FILE*)this))
 116     return EOF;
 117   if (!(xflags() & _IO_NO_WRITES))
 118     if (fflush(_file))
 119       return EOF;
 120   return 0;
 121 }
 122
 123 int stdiobuf::overflow(int c /* = EOF*/)
 124 {
 125     if (filebuf::overflow(c) == EOF)
 126         return EOF;
 127     if (c != EOF)
 128         return c;
 129     return fflush(_file);
 130 }
 131
 132 streamsize stdiobuf::xsputn(const char* s, streamsize n)
 133 {
 134   if (buffered ())
 135     {
 136       // The filebuf implementation of sputn loses.
 137       return streambuf::xsputn(s, n);
 138     }
 139   else
 140     return fwrite (s, 1, n, _file);
 141 }
 142
 143 void stdiobuf::buffered (int b)
 144 {
 145   if (b)
 146     {
 147       if (_flags & _IO_UNBUFFERED)
 148         { /* Was unbuffered, make it buffered. */
 149           _flags &= ~_IO_UNBUFFERED;
 150         }
 151     }
 152   else
 153     {
 154       if (!(_flags & _IO_UNBUFFERED))
 155         { /* Was buffered, make it unbuffered. */
 156           setbuf(NULL, 0);
 157         }
 158     }
 159 }