| // 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 |
| } |