newlib-cygwin/winsup/mingw/mingwex/mingw-fseek.c

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/*
* Workaround for limitations on win9x where a file contents are
* not zero'd out if you seek past the end and then write.
* Copied from ming local-patch to binutils/bfd/libbfd.c written by
* Mumit Khan <khan@xraylith.wisc.edu>
*/
#include <windows.h>
#include <stdio.h>
#include <io.h>
#include <stdlib.h>
#define ZEROBLOCKSIZE 512
static int __mingw_fseek_called;
/* The fseek in Win9x runtime does not zero out the file if seeking past
the end; if you don't want random stuff from your disk included in your
output DLL/executable, use this version instead. On WinNT/Win2k, it
just calls runtime fseek().
CHECK/FIXME: Does this work for both text and binary modes?? */
int
__mingw_fseek (FILE *fp, long offset, int whence)
{
# undef fseek
__mingw_fseek_called = 1;
return fseek (fp, offset, whence);
}
int
__mingw_fwrite (const void *buffer, size_t size, size_t count, FILE *fp)
{
# undef fwrite
if ((_osver & 0x8000) && __mingw_fseek_called)
{
DWORD actual_length, current_position;
__mingw_fseek_called = 0;
fflush (fp);
actual_length = GetFileSize ((HANDLE) _get_osfhandle (fileno (fp)),
NULL);
current_position = SetFilePointer ((HANDLE) _get_osfhandle (fileno (fp)),
0, 0, FILE_CURRENT);
#ifdef DEBUG
printf ("__mingw_fwrite: current %ld, actual %ld\n",
current_position, actual_length);
#endif /* DEBUG */
if (current_position > actual_length)
{
static char __mingw_zeros[ZEROBLOCKSIZE];
long numleft;
SetFilePointer ((HANDLE) _get_osfhandle (fileno (fp)),
0, 0, FILE_END);
numleft = current_position - actual_length;
#ifdef DEBUG
printf ("__mingw_fwrite: Seeking %ld bytes past end\n", numleft);
#endif /* DEBUG */
while (numleft > 0)
{
DWORD nzeros = (numleft > ZEROBLOCKSIZE)
? ZEROBLOCKSIZE : numleft;
DWORD written;
if (! WriteFile ((HANDLE) _get_osfhandle (fileno (fp)),
__mingw_zeros, nzeros, &written, NULL))
{
/* Best we can hope for, or at least DJ says so. */
SetFilePointer ((HANDLE) _get_osfhandle (fileno (fp)),
0, 0, FILE_BEGIN);
return -1;
}
if (written < nzeros)
{
/* Likewise. */
SetFilePointer ((HANDLE) _get_osfhandle (fileno (fp)),
0, 0, FILE_BEGIN);
return -1;
}
numleft -= written;
}
FlushFileBuffers ((HANDLE) _get_osfhandle (fileno (fp)));
}
}
return fwrite (buffer, size, count, fp);
}