lz4/options.go

package lz4

import (
	"fmt"
	"runtime"
	"sync"
)

//go:generate go run golang.org/x/tools/cmd/stringer -type=BlockSize,CompressionLevel -output options_gen.go

// Option defines the parameters to setup an LZ4 Writer or Reader.
type Option func(*_Writer) error

// Default options.
var (
	defaultBlockSizeOption = BlockSizeOption(Block4Mb)
	defaultChecksumOption  = ChecksumOption(true)
	defaultConcurrency     = ConcurrencyOption(1)
)

const (
	Block64Kb BlockSize = 1 << (16 + iota*2)
	Block256Kb
	Block1Mb
	Block4Mb
)

var (
	blockPool64K  = sync.Pool{New: func() interface{} { return make([]byte, Block64Kb) }}
	blockPool256K = sync.Pool{New: func() interface{} { return make([]byte, Block256Kb) }}
	blockPool1M   = sync.Pool{New: func() interface{} { return make([]byte, Block1Mb) }}
	blockPool4M   = sync.Pool{New: func() interface{} { return make([]byte, Block4Mb) }}
)

// BlockSizeIndex defines the size of the blocks to be compressed.
type BlockSize uint32

func (b BlockSize) isValid() bool {
	return b.index() > 0
}

func (b BlockSize) index() BlockSizeIndex {
	switch b {
	case Block64Kb:
		return 4
	case Block256Kb:
		return 5
	case Block1Mb:
		return 6
	case Block4Mb:
		return 7
	}
	return 0
}

type BlockSizeIndex uint8

func (b BlockSizeIndex) get() []byte {
	var buf interface{}
	switch b {
	case 4:
		buf = blockPool64K.Get()
	case 5:
		buf = blockPool256K.Get()
	case 6:
		buf = blockPool1M.Get()
	case 7:
		buf = blockPool4M.Get()
	}
	return buf.([]byte)
}

func (b BlockSizeIndex) put(buf []byte) {
	switch b {
	case 4:
		blockPool64K.Put(buf)
	case 5:
		blockPool256K.Put(buf)
	case 6:
		blockPool1M.Put(buf)
	case 7:
		blockPool4M.Put(buf)
	}
}

// BlockSizeOption defines the maximum size of compressed blocks (default=Block4Mb).
func BlockSizeOption(size BlockSize) Option {
	return func(w *_Writer) error {
		if !size.isValid() {
			return fmt.Errorf("lz4: invalid block size %d", size)
		}
		w.frame.Descriptor.Flags.BlockSizeIndexSet(size.index())
		return nil
	}
}

// BlockChecksumOption enables or disables block checksum (default=false).
func BlockChecksumOption(flag bool) Option {
	return func(w *_Writer) error {
		w.frame.Descriptor.Flags.BlockChecksumSet(flag)
		return nil
	}
}

// ChecksumOption enables/disables all blocks checksum (default=true).
func ChecksumOption(flag bool) Option {
	return func(w *_Writer) error {
		w.frame.Descriptor.Flags.ContentChecksumSet(flag)
		return nil
	}
}

// SizeOption sets the size of the original uncompressed data (default=0).
func SizeOption(size uint64) Option {
	return func(w *_Writer) error {
		w.frame.Descriptor.Flags.SizeSet(size > 0)
		w.frame.Descriptor.ContentSize = size
		return nil
	}
}

// ConcurrencyOption sets the number of go routines used for compression.
// If n<0, then the output of runtime.GOMAXPROCS(0) is used.
func ConcurrencyOption(n int) Option {
	return func(w *_Writer) error {
		switch n {
		case 0, 1:
		default:
			if n < 0 {
				n = runtime.GOMAXPROCS(0)
			}
		}
		w.num = n
		return nil
	}
}

// CompressionLevel defines the level of compression to use. The higher the better, but slower, compression.
type CompressionLevel uint32

const (
	Fast   CompressionLevel = 0
	Level1 CompressionLevel = 1 << (8 + iota)
	Level2
	Level3
	Level4
	Level5
	Level6
	Level7
	Level8
	Level9
)

// CompressionLevelOption defines the compression level (default=Fast).
func CompressionLevelOption(level CompressionLevel) Option {
	return func(w *_Writer) error {
		switch level {
		case Fast, Level1, Level2, Level3, Level4, Level5, Level6, Level7, Level8, Level9:
		default:
			return fmt.Errorf("lz4: invalid compression level %d", level)
		}
		w.level = level
		return nil
	}
}