func ExampleWriter_RegisterCompressor() {
// Override the default Deflate compressor with a higher compression
// level.
// Create a buffer to write our archive to.
buf := new(bytes.Buffer)
// Create a new zip archive.
w := zip.NewWriter(buf)
var fw *flate.Writer
// Register the deflator.
w.RegisterCompressor(zip.Deflate, func(out io.Writer) (io.WriteCloser, error) {
var err error
if fw == nil {
// Creating a flate compressor for every file is
// expensive, create one and reuse it.
fw, err = flate.NewWriter(out, flate.BestCompression)
} else {
fw.Reset(out)
}
return fw, err
})
// Proceed to add files to w.
}
// Step 1: compresses buffer to buffer
// Step 2: send writer to channel
// Step 3: Close result channel to indicate we are done
func compressBlock(p, prevTail []byte, z Writer, r result) {
defer close(r.result)
buf := make([]byte, 0, len(p))
dest := bytes.NewBuffer(buf)
var compressor *flate.Writer
var err error
if len(prevTail) > 0 {
compressor, err = flate.NewWriterDict(dest, z.level, prevTail)
} else {
compressor, err = flate.NewWriter(dest, z.level)
}
if err != nil {
z.pushError(err)
return
}
compressor.Write(p)
err = compressor.Flush()
if err != nil {
z.pushError(err)
return
}
if z.closed {
err = compressor.Close()
if err != nil {
z.pushError(err)
return
}
}
// Read back buffer
buf = dest.Bytes()
r.result <- buf
}