1 files changed, 71 insertions, 0 deletions
diff --git a/ext/zip/lib/zip_filerange_crc.c b/ext/zip/lib/zip_filerange_crc.c
new file mode 100644
index 000000000..4d1ad5669
--- /dev/null
+++ b/ext/zip/lib/zip_filerange_crc.c
@@ -0,0 +1,71 @@
+/*
+  zip_filerange_crc.c -- compute CRC32 for a range of a file
+  Copyright (C) 2008 Dieter Baron and Thomas Klausner
+
+  This file is part of libzip, a library to manipulate ZIP archives.
+  The authors can be contacted at <libzip@nih.at>
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions
+  are met:
+  1. Redistributions of source code must retain the above copyright
+     notice, this list of conditions and the following disclaimer.
+  2. Redistributions in binary form must reproduce the above copyright
+     notice, this list of conditions and the following disclaimer in
+     the documentation and/or other materials provided with the
+     distribution.
+  3. The names of the authors may not be used to endorse or promote
+     products derived from this software without specific prior
+     written permission.
+ 
+  THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS
+  OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
+  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
+  IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+  IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+
+
+#include <stdio.h>
+#include <errno.h>
+
+#include "zipint.h"
+
+
+
+
+int
+_zip_filerange_crc(FILE *fp, off_t start, off_t len, uLong *crcp,
+		   struct zip_error *errp)
+{
+    Bytef buf[BUFSIZE];
+    size_t n;
+
+    *crcp = crc32(0L, Z_NULL, 0);
+
+    if (fseeko(fp, start, SEEK_SET) != 0) {
+	_zip_error_set(errp, ZIP_ER_SEEK, errno);
+	return -1;
+    }
+    
+    while (len > 0) {
+	n = len > BUFSIZE ? BUFSIZE : len;
+	if ((n=fread(buf, 1, n, fp)) <= 0) {
+	    _zip_error_set(errp, ZIP_ER_READ, errno);
+	    return -1;
+	}
+
+	*crcp = crc32(*crcp, buf, n);
+
+	len-= n;
+    }
+
+    return 0;
+}