From: "Mark E." <snowball3 AT bigfoot DOT com>
To: djgpp-workers AT delorie DOT com
Date: Sun, 11 Mar 2001 00:22:41 -0500
MIME-Version: 1.0
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Subject: zero fill EOF gap patch
Message-ID: <3AAAC551.12083.441287@localhost>
X-mailer: Pegasus Mail for Win32 (v3.12c)
Reply-To: djgpp-workers AT delorie DOT com

Hello again,

This is my first draft of a patch that zero fills the space between EOF and 
the current file pointer when the current file pointer > EOF. I left out the 
patch for llseek since it's just like the one for lseek.

*** fd_props.h.orig	Tue Mar  6 13:43:54 2001
--- fd_props.h	Sat Mar 10 18:05:44 2001
*************** extern "C" {
*** 15,20 ****
--- 15,24 ----
  /* Delete file when the last descriptor referencing it is closed.  */
  #define FILE_DESC_TEMPORARY 0x01
  
+ /* Tell write and _write to test for file offset greater than EOF.  If so,
+    they will fill the gap with zeroes.  */
+ #define FILE_DESC_FILL_TEST 0x02
+ 
  typedef struct fd_properties fd_properties;
  
  struct fd_properties
*************** static __inline__ int __has_fd_propertie
*** 37,42 ****
--- 41,56 ----
    return __fd_properties && __fd_properties[_fd];
  }
  
+ static __inline__ void __set_fd_flags(int _fd, unsigned long _flags)
+ {
+   __fd_properties[_fd]->flags |= _flags;  
+ }
+ 
+ static __inline__ void __clear_fd_flags(int _fd, unsigned long _flags)
+ {
+   __fd_properties[_fd]->flags &= ~_flags;
+ }
+ 
  #endif /* !_POSIX_SOURCE */
  #endif /* !__STRICT_ANSI__ */
  #endif /* !__dj_ENFORCE_ANSI_FREESTANDING */
*** lseek.c.orig	Sun Jun 28 13:29:36 1998
--- lseek.c	Fri Mar  9 17:40:06 2001
***************
*** 1,3 ****
--- 1,4 ----
+ /* Copyright (C) 2001 DJ Delorie, see COPYING.DJ for details */
  /* Copyright (C) 1998 DJ Delorie, see COPYING.DJ for details */
  /* Copyright (C) 1995 DJ Delorie, see COPYING.DJ for details */
  #include <libc/stubs.h>
***************
*** 7,12 ****
--- 8,14 ----
  #include <dpmi.h>
  #include <sys/fsext.h>
  #include <libc/dosio.h>
+ #include <libc/fd_props.h>
  
  off_t
  lseek(int handle, off_t offset, int whence)
*************** lseek(int handle, off_t offset, int when
*** 31,35 ****
--- 33,48 ----
      errno = __doserr_to_errno(r.x.ax);
      return -1;
    }
+ 
+   if (__has_fd_properties(handle))
+   {
+     /* When seeking forward, set the EOF fill test flag.
+        When seeking to the start of file, clear the fill test flag.  */
+     if (offset > 0)
+       __set_fd_flags(handle, FILE_DESC_FILL_TEST);
+     else if (whence == SEEK_SET || whence == SEEK_END)
+       __clear_fd_flags(handle, FILE_DESC_FILL_TEST);
+   }
+     
    return (r.x.dx << 16) + r.x.ax;
  }
*** _write.c.orig	Fri Mar  2 11:41:54 2001
--- _write.c	Sat Mar 10 18:13:36 2001
***************
*** 10,15 ****
--- 10,18 ----
  #include <sys/fsext.h>
  
  #include <libc/dosio.h>
+ #include <libc/fd_props.h>
+ 
+ int _write_fill_seek_area(int fd);
  
  int
  _write(int handle, const void* buffer, size_t count)
*************** _write(int handle, const void* buffer, s
*** 27,32 ****
--- 30,42 ----
        return rv;
    }
  
+   if (__has_fd_properties(handle)
+       && (__fd_properties[handle]->flags & FILE_DESC_FILL_TEST))
+   {
+     if (_write_fill_seek_area(handle) < 0)
+       return -1;
+   }
+       
    tbsize = _go32_info_block.size_of_transfer_buffer;
    nput = 0;
    do {
*************** _write(int handle, const void* buffer, s
*** 58,60 ****
--- 68,144 ----
  
    return nput;
  }
+ 
+ int
+ _write_fill_seek_area(int fd)
+ {
+   offset_t eof_off, cur_off, fill_count;
+   unsigned long tbsize, buf_size;
+   unsigned long i, write_size, out_count;
+   char *buffer;
+   __dpmi_regs r;
+ 
+   __clear_fd_flags(fd, FILE_DESC_FILL_TEST);
+   
+   if (isatty(fd))
+     return -1;
+       
+   eof_off = lfilelength (fd);
+   if (eof_off < 0)
+     return -1;
+   
+   cur_off = llseek (fd, 0, SEEK_CUR);
+   if (cur_off < 0)
+     return -1;
+ 
+   if (cur_off <= eof_off)
+     return 0;
+     
+   /* Also quit when unable to seek to EOF.  */
+   if (llseek (fd, eof_off, SEEK_SET) == -1)
+     return -1;
+ 
+   /* Clear once again because the llseek call above will
+      set the fill test flag.  */
+   __clear_fd_flags(fd, FILE_DESC_FILL_TEST);
+   
+   /* Fill the space.  */
+   tbsize = _go32_info_block.size_of_transfer_buffer;
+   fill_count = cur_off - eof_off;
+ 
+   buf_size = (fill_count > tbsize) ? tbsize : fill_count;
+ 
+   i = 0;
+   _farsetsel(_dos_ds);
+   while (i < buf_size)
+   {
+     _farnspokel(__tb + i, 0);
+     i += 4;
+   }
+ 
+   out_count = 0;
+   do
+   {
+     r.x.ax = 0x4000;
+     r.x.bx = fd;
+     write_size = (fill_count > buf_size) ? buf_size : fill_count;
+     r.x.cx = write_size;
+     r.x.dx = __tb & 15;
+     r.x.ds = __tb / 16;
+     __dpmi_int (0x21, &r);
+     if (r.x.flags & 1)
+     {
+       errno =__doserr_to_errno (r.x.ax);
+       return -1;
+     }
+     fill_count -= r.x.ax;
+     out_count += r.x.ax;
+   } while (fill_count && (write_size == r.x.ax));
+ 
+   if (fill_count && out_count == 0)
+   {
+     errno = ENOSPC;
+     return -1;
+   }
+ }
+