1 files changed, 58 insertions, 0 deletions
diff --git a/go/zopfli/zopfli.go b/go/zopfli/zopfli.go
new file mode 100644
index 0000000..0cb78aa
--- /dev/null
+++ b/go/zopfli/zopfli.go
@@ -0,0 +1,58 @@
+// Copyright 2019 Google LLC
+//
+// 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
+//
+//     https://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.
+
+// Package zopfli provides a simple Go interface for Zopfli compression.
+package zopfli
+
+/*
+#cgo LDFLAGS: -lzopfli -lm
+#include <limits.h> // for INT_MAX
+#include <stdlib.h> // for free()
+#include <string.h> // for memmove()
+#include "zopfli.h"
+*/
+import "C"
+import "unsafe"
+
+// Zopfli can't handle empty input, so we use a static result.
+const emptyGzip = "\x1f\x8b\x08\x00\x00\x00\x00\x00\x00\xff\x03\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+
+// Gzip compresses data with Zopfli using default settings and gzip format.
+// The Zopfli library does not return errors, and there are no (detectable)
+// failure cases, hence no error return.
+func Gzip(inputSlice []byte) []byte {
+	var options C.struct_ZopfliOptions
+	C.ZopfliInitOptions(&options)
+
+	inputSize := (C.size_t)(len(inputSlice))
+	if inputSize == 0 {
+		return []byte(emptyGzip)
+	}
+	input := (*C.uchar)(unsafe.Pointer(&inputSlice[0]))
+	var compressed *C.uchar
+	var compressedLength C.size_t
+
+	C.ZopfliCompress(&options, C.ZOPFLI_FORMAT_GZIP,
+		input, inputSize,
+		&compressed, &compressedLength)
+	defer C.free(unsafe.Pointer(compressed))
+
+	// GoBytes only accepts int, not C.size_t. The code below does the same minus
+	// protection against zero-length values, but compressedLength is never 0 due
+	// to headers.
+	result := make([]byte, compressedLength)
+	C.memmove(unsafe.Pointer(&result[0]), unsafe.Pointer(compressed),
+		compressedLength)
+	return result
+}