Implement crc32c for Darwin, update documentation

pkg/utils/checksum/crc32c/crc32c_linux.go

@@ -0,0 +1,40 @@
+/*
+ * Mini Object Storage, (C) 2014 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// +build amd64
+
+package crc32c
+
+// #include <stdint.h>
+// uint32_t crc32c_pcl(uint8_t *buf, int32_t len, uint32_t prev_crc);
+import "C"
+import (
+	"errors"
+	"unsafe"
+)
+
+func Crc32c(buffer []byte) (uint32, error) {
+	var length = len(buffer)
+	if length == 0 {
+		return 0, errors.New("Invalid input")
+	}
+
+	var cbuf *C.uint8_t
+	cbuf = (*C.uint8_t)(unsafe.Pointer(&buffer[0]))
+	crc := C.crc32c_pcl(cbuf, C.int32_t(length), C.uint32_t(0))
+
+	return uint32(crc), nil
+}