windows: support for large files

note that this change will break binary compatibility with the
default 5.8.0 build options; nevertheless I think it is worth
having in 5.8.1 (people who want the compatibility can disable
the option in the makefile)

p4raw-id: //depot/perl@18327

1 files changed, 49 insertions, 0 deletions

diff --git a/win32/win32.c b/win32/win32.c
index 633dbbdbcc..556d62145c 100644
--- a/win32/win32.c
+++ b/win32/win32.c
@@ -3073,6 +3073,55 @@ win32_setmode(int fd, int mode)
     return setmode(fd, mode);
 }
 
+DllExport int
+win32_chsize(int fd, Off_t size)
+{
+#if defined(WIN64) || defined(USE_LARGE_FILES)
+    int retval = 0;
+    Off_t cur, end, extend;
+
+    cur = win32_tell(fd);
+    if (cur < 0)
+	return -1;
+    end = win32_lseek(fd, 0, SEEK_END);
+    if (end < 0)
+	return -1;
+    extend = size - end;
+    if (extend == 0) {
+	/* do nothing */
+    }
+    else if (extend > 0) {
+	/* must grow the file, padding with nulls */
+	char b[4096];
+	int oldmode = win32_setmode(fd, O_BINARY);
+	size_t count;
+	memset(b, '\0', sizeof(b));
+	do {
+	    count = extend >= sizeof(b) ? sizeof(b) : (size_t)extend;
+	    count = win32_write(fd, b, count);
+	    if (count < 0) {
+		retval = -1;
+		break;
+	    }
+	} while ((extend -= count) > 0);
+	win32_setmode(fd, oldmode);
+    }
+    else {
+	/* shrink the file */
+	win32_lseek(fd, size, SEEK_SET);
+	if (!SetEndOfFile((HANDLE)_get_osfhandle(fd))) {
+	    errno = EACCES;
+	    retval = -1;
+	}
+    }
+finish:
+    win32_lseek(fd, cur, SEEK_SET);
+    return retval;
+#else
+    return chsize(fd, size);
+#endif
+}
+
 DllExport Off_t
 win32_lseek(int fd, Off_t offset, int origin)
 {