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package lz4
import (
"fmt"
"reflect"
"runtime"
"github.com/pierrec/lz4/v4/internal/lz4block"
"github.com/pierrec/lz4/v4/internal/lz4errors"
)
//go:generate go run golang.org/x/tools/cmd/stringer -type=BlockSize,CompressionLevel -output options_gen.go
type (
applier interface {
Apply(...Option) error
private()
}
// Option defines the parameters to setup an LZ4 Writer or Reader.
Option func(applier) error
)
// String returns a string representation of the option with its parameter(s).
func (o Option) String() string {
return o(nil).Error()
}
// Default options.
var (
DefaultBlockSizeOption = BlockSizeOption(Block4Mb)
DefaultChecksumOption = ChecksumOption(true)
DefaultConcurrency = ConcurrencyOption(1)
defaultOnBlockDone = OnBlockDoneOption(nil)
)
const (
Block64Kb BlockSize = 1 << (16 + iota*2)
Block256Kb
Block1Mb
Block4Mb
)
// BlockSizeIndex defines the size of the blocks to be compressed.
type BlockSize uint32
// BlockSizeOption defines the maximum size of compressed blocks (default=Block4Mb).
func BlockSizeOption(size BlockSize) Option {
return func(a applier) error {
switch w := a.(type) {
case nil:
s := fmt.Sprintf("BlockSizeOption(%s)", size)
return lz4errors.Error(s)
case *Writer:
size := uint32(size)
if !lz4block.IsValid(size) {
return fmt.Errorf("%w: %d", lz4errors.ErrOptionInvalidBlockSize, size)
}
w.frame.Descriptor.Flags.BlockSizeIndexSet(lz4block.Index(size))
return nil
}
return lz4errors.ErrOptionNotApplicable
}
}
// BlockChecksumOption enables or disables block checksum (default=false).
func BlockChecksumOption(flag bool) Option {
return func(a applier) error {
switch w := a.(type) {
case nil:
s := fmt.Sprintf("BlockChecksumOption(%v)", flag)
return lz4errors.Error(s)
case *Writer:
w.frame.Descriptor.Flags.BlockChecksumSet(flag)
return nil
}
return lz4errors.ErrOptionNotApplicable
}
}
// ChecksumOption enables/disables all blocks or content checksum (default=true).
func ChecksumOption(flag bool) Option {
return func(a applier) error {
switch w := a.(type) {
case nil:
s := fmt.Sprintf("ChecksumOption(%v)", flag)
return lz4errors.Error(s)
case *Writer:
w.frame.Descriptor.Flags.ContentChecksumSet(flag)
return nil
}
return lz4errors.ErrOptionNotApplicable
}
}
// SizeOption sets the size of the original uncompressed data (default=0). It is useful to know the size of the
// whole uncompressed data stream.
func SizeOption(size uint64) Option {
return func(a applier) error {
switch w := a.(type) {
case nil:
s := fmt.Sprintf("SizeOption(%d)", size)
return lz4errors.Error(s)
case *Writer:
w.frame.Descriptor.Flags.SizeSet(size > 0)
w.frame.Descriptor.ContentSize = size
return nil
}
return lz4errors.ErrOptionNotApplicable
}
}
// 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 {
if n <= 0 {
n = runtime.GOMAXPROCS(0)
}
return func(a applier) error {
switch rw := a.(type) {
case nil:
s := fmt.Sprintf("ConcurrencyOption(%d)", n)
return lz4errors.Error(s)
case *Writer:
rw.num = n
return nil
case *Reader:
rw.num = n
return nil
}
return lz4errors.ErrOptionNotApplicable
}
}
// 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(a applier) error {
switch w := a.(type) {
case nil:
s := fmt.Sprintf("CompressionLevelOption(%s)", level)
return lz4errors.Error(s)
case *Writer:
switch level {
case Fast, Level1, Level2, Level3, Level4, Level5, Level6, Level7, Level8, Level9:
default:
return fmt.Errorf("%w: %d", lz4errors.ErrOptionInvalidCompressionLevel, level)
}
w.level = lz4block.CompressionLevel(level)
return nil
}
return lz4errors.ErrOptionNotApplicable
}
}
func onBlockDone(int) {}
// OnBlockDoneOption is triggered when a block has been processed. For a Writer, it is when is has been compressed,
// for a Reader, it is when it has been uncompressed.
func OnBlockDoneOption(handler func(size int)) Option {
if handler == nil {
handler = onBlockDone
}
return func(a applier) error {
switch rw := a.(type) {
case nil:
s := fmt.Sprintf("OnBlockDoneOption(%s)", reflect.TypeOf(handler).String())
return lz4errors.Error(s)
case *Writer:
rw.handler = handler
return nil
case *Reader:
rw.handler = handler
return nil
}
return lz4errors.ErrOptionNotApplicable
}
}
// LegacyOption provides support for writing LZ4 frames in the legacy format.
//
// See https://github.com/lz4/lz4/blob/dev/doc/lz4_Frame_format.md#legacy-frame.
//
// NB. compressed Linux kernel images use a tweaked LZ4 legacy format where
// the compressed stream is followed by the original (uncompressed) size of
// the kernel (https://events.static.linuxfound.org/sites/events/files/lcjpcojp13_klee.pdf).
// This is also supported as a special case.
func LegacyOption(legacy bool) Option {
return func(a applier) error {
switch rw := a.(type) {
case nil:
s := fmt.Sprintf("LegacyOption(%v)", legacy)
return lz4errors.Error(s)
case *Writer:
rw.legacy = legacy
return nil
}
return lz4errors.ErrOptionNotApplicable
}
}
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