From 404aeae4545d2426c089a5f8d5e82dae56f5212b Mon Sep 17 00:00:00 2001 From: Rutger Broekhoff Date: Fri, 29 Dec 2023 21:31:53 +0100 Subject: Make Nix builds work --- vendor/github.com/klauspost/compress/s2/writer.go | 1020 +++++++++++++++++++++ 1 file changed, 1020 insertions(+) create mode 100644 vendor/github.com/klauspost/compress/s2/writer.go (limited to 'vendor/github.com/klauspost/compress/s2/writer.go') diff --git a/vendor/github.com/klauspost/compress/s2/writer.go b/vendor/github.com/klauspost/compress/s2/writer.go new file mode 100644 index 0000000..089cd36 --- /dev/null +++ b/vendor/github.com/klauspost/compress/s2/writer.go @@ -0,0 +1,1020 @@ +// Copyright 2011 The Snappy-Go Authors. All rights reserved. +// Copyright (c) 2019+ Klaus Post. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package s2 + +import ( + "crypto/rand" + "encoding/binary" + "errors" + "fmt" + "io" + "runtime" + "sync" +) + +const ( + levelUncompressed = iota + 1 + levelFast + levelBetter + levelBest +) + +// NewWriter returns a new Writer that compresses to w, using the +// framing format described at +// https://github.com/google/snappy/blob/master/framing_format.txt +// +// Users must call Close to guarantee all data has been forwarded to +// the underlying io.Writer and that resources are released. +// They may also call Flush zero or more times before calling Close. +func NewWriter(w io.Writer, opts ...WriterOption) *Writer { + w2 := Writer{ + blockSize: defaultBlockSize, + concurrency: runtime.GOMAXPROCS(0), + randSrc: rand.Reader, + level: levelFast, + } + for _, opt := range opts { + if err := opt(&w2); err != nil { + w2.errState = err + return &w2 + } + } + w2.obufLen = obufHeaderLen + MaxEncodedLen(w2.blockSize) + w2.paramsOK = true + w2.ibuf = make([]byte, 0, w2.blockSize) + w2.buffers.New = func() interface{} { + return make([]byte, w2.obufLen) + } + w2.Reset(w) + return &w2 +} + +// Writer is an io.Writer that can write Snappy-compressed bytes. +type Writer struct { + errMu sync.Mutex + errState error + + // ibuf is a buffer for the incoming (uncompressed) bytes. + ibuf []byte + + blockSize int + obufLen int + concurrency int + written int64 + uncompWritten int64 // Bytes sent to compression + output chan chan result + buffers sync.Pool + pad int + + writer io.Writer + randSrc io.Reader + writerWg sync.WaitGroup + index Index + customEnc func(dst, src []byte) int + + // wroteStreamHeader is whether we have written the stream header. + wroteStreamHeader bool + paramsOK bool + snappy bool + flushOnWrite bool + appendIndex bool + level uint8 +} + +type result struct { + b []byte + // Uncompressed start offset + startOffset int64 +} + +// err returns the previously set error. +// If no error has been set it is set to err if not nil. +func (w *Writer) err(err error) error { + w.errMu.Lock() + errSet := w.errState + if errSet == nil && err != nil { + w.errState = err + errSet = err + } + w.errMu.Unlock() + return errSet +} + +// Reset discards the writer's state and switches the Snappy writer to write to w. +// This permits reusing a Writer rather than allocating a new one. +func (w *Writer) Reset(writer io.Writer) { + if !w.paramsOK { + return + } + // Close previous writer, if any. + if w.output != nil { + close(w.output) + w.writerWg.Wait() + w.output = nil + } + w.errState = nil + w.ibuf = w.ibuf[:0] + w.wroteStreamHeader = false + w.written = 0 + w.writer = writer + w.uncompWritten = 0 + w.index.reset(w.blockSize) + + // If we didn't get a writer, stop here. + if writer == nil { + return + } + // If no concurrency requested, don't spin up writer goroutine. + if w.concurrency == 1 { + return + } + + toWrite := make(chan chan result, w.concurrency) + w.output = toWrite + w.writerWg.Add(1) + + // Start a writer goroutine that will write all output in order. + go func() { + defer w.writerWg.Done() + + // Get a queued write. + for write := range toWrite { + // Wait for the data to be available. + input := <-write + in := input.b + if len(in) > 0 { + if w.err(nil) == nil { + // Don't expose data from previous buffers. + toWrite := in[:len(in):len(in)] + // Write to output. + n, err := writer.Write(toWrite) + if err == nil && n != len(toWrite) { + err = io.ErrShortBuffer + } + _ = w.err(err) + w.err(w.index.add(w.written, input.startOffset)) + w.written += int64(n) + } + } + if cap(in) >= w.obufLen { + w.buffers.Put(in) + } + // close the incoming write request. + // This can be used for synchronizing flushes. + close(write) + } + }() +} + +// Write satisfies the io.Writer interface. +func (w *Writer) Write(p []byte) (nRet int, errRet error) { + if err := w.err(nil); err != nil { + return 0, err + } + if w.flushOnWrite { + return w.write(p) + } + // If we exceed the input buffer size, start writing + for len(p) > (cap(w.ibuf)-len(w.ibuf)) && w.err(nil) == nil { + var n int + if len(w.ibuf) == 0 { + // Large write, empty buffer. + // Write directly from p to avoid copy. + n, _ = w.write(p) + } else { + n = copy(w.ibuf[len(w.ibuf):cap(w.ibuf)], p) + w.ibuf = w.ibuf[:len(w.ibuf)+n] + w.write(w.ibuf) + w.ibuf = w.ibuf[:0] + } + nRet += n + p = p[n:] + } + if err := w.err(nil); err != nil { + return nRet, err + } + // p should always be able to fit into w.ibuf now. + n := copy(w.ibuf[len(w.ibuf):cap(w.ibuf)], p) + w.ibuf = w.ibuf[:len(w.ibuf)+n] + nRet += n + return nRet, nil +} + +// ReadFrom implements the io.ReaderFrom interface. +// Using this is typically more efficient since it avoids a memory copy. +// ReadFrom reads data from r until EOF or error. +// The return value n is the number of bytes read. +// Any error except io.EOF encountered during the read is also returned. +func (w *Writer) ReadFrom(r io.Reader) (n int64, err error) { + if err := w.err(nil); err != nil { + return 0, err + } + if len(w.ibuf) > 0 { + err := w.Flush() + if err != nil { + return 0, err + } + } + if br, ok := r.(byter); ok { + buf := br.Bytes() + if err := w.EncodeBuffer(buf); err != nil { + return 0, err + } + return int64(len(buf)), w.Flush() + } + for { + inbuf := w.buffers.Get().([]byte)[:w.blockSize+obufHeaderLen] + n2, err := io.ReadFull(r, inbuf[obufHeaderLen:]) + if err != nil { + if err == io.ErrUnexpectedEOF { + err = io.EOF + } + if err != io.EOF { + return n, w.err(err) + } + } + if n2 == 0 { + break + } + n += int64(n2) + err2 := w.writeFull(inbuf[:n2+obufHeaderLen]) + if w.err(err2) != nil { + break + } + + if err != nil { + // We got EOF and wrote everything + break + } + } + + return n, w.err(nil) +} + +// AddSkippableBlock will add a skippable block to the stream. +// The ID must be 0x80-0xfe (inclusive). +// Length of the skippable block must be <= 16777215 bytes. +func (w *Writer) AddSkippableBlock(id uint8, data []byte) (err error) { + if err := w.err(nil); err != nil { + return err + } + if len(data) == 0 { + return nil + } + if id < 0x80 || id > chunkTypePadding { + return fmt.Errorf("invalid skippable block id %x", id) + } + if len(data) > maxChunkSize { + return fmt.Errorf("skippable block excessed maximum size") + } + var header [4]byte + chunkLen := 4 + len(data) + header[0] = id + header[1] = uint8(chunkLen >> 0) + header[2] = uint8(chunkLen >> 8) + header[3] = uint8(chunkLen >> 16) + if w.concurrency == 1 { + write := func(b []byte) error { + n, err := w.writer.Write(b) + if err = w.err(err); err != nil { + return err + } + if n != len(data) { + return w.err(io.ErrShortWrite) + } + w.written += int64(n) + return w.err(nil) + } + if !w.wroteStreamHeader { + w.wroteStreamHeader = true + if w.snappy { + if err := write([]byte(magicChunkSnappy)); err != nil { + return err + } + } else { + if err := write([]byte(magicChunk)); err != nil { + return err + } + } + } + if err := write(header[:]); err != nil { + return err + } + if err := write(data); err != nil { + return err + } + } + + // Create output... + if !w.wroteStreamHeader { + w.wroteStreamHeader = true + hWriter := make(chan result) + w.output <- hWriter + if w.snappy { + hWriter <- result{startOffset: w.uncompWritten, b: []byte(magicChunkSnappy)} + } else { + hWriter <- result{startOffset: w.uncompWritten, b: []byte(magicChunk)} + } + } + + // Copy input. + inbuf := w.buffers.Get().([]byte)[:4] + copy(inbuf, header[:]) + inbuf = append(inbuf, data...) + + output := make(chan result, 1) + // Queue output. + w.output <- output + output <- result{startOffset: w.uncompWritten, b: inbuf} + + return nil +} + +// EncodeBuffer will add a buffer to the stream. +// This is the fastest way to encode a stream, +// but the input buffer cannot be written to by the caller +// until Flush or Close has been called when concurrency != 1. +// +// If you cannot control that, use the regular Write function. +// +// Note that input is not buffered. +// This means that each write will result in discrete blocks being created. +// For buffered writes, use the regular Write function. +func (w *Writer) EncodeBuffer(buf []byte) (err error) { + if err := w.err(nil); err != nil { + return err + } + + if w.flushOnWrite { + _, err := w.write(buf) + return err + } + // Flush queued data first. + if len(w.ibuf) > 0 { + err := w.Flush() + if err != nil { + return err + } + } + if w.concurrency == 1 { + _, err := w.writeSync(buf) + return err + } + + // Spawn goroutine and write block to output channel. + if !w.wroteStreamHeader { + w.wroteStreamHeader = true + hWriter := make(chan result) + w.output <- hWriter + if w.snappy { + hWriter <- result{startOffset: w.uncompWritten, b: []byte(magicChunkSnappy)} + } else { + hWriter <- result{startOffset: w.uncompWritten, b: []byte(magicChunk)} + } + } + + for len(buf) > 0 { + // Cut input. + uncompressed := buf + if len(uncompressed) > w.blockSize { + uncompressed = uncompressed[:w.blockSize] + } + buf = buf[len(uncompressed):] + // Get an output buffer. + obuf := w.buffers.Get().([]byte)[:len(uncompressed)+obufHeaderLen] + output := make(chan result) + // Queue output now, so we keep order. + w.output <- output + res := result{ + startOffset: w.uncompWritten, + } + w.uncompWritten += int64(len(uncompressed)) + go func() { + checksum := crc(uncompressed) + + // Set to uncompressed. + chunkType := uint8(chunkTypeUncompressedData) + chunkLen := 4 + len(uncompressed) + + // Attempt compressing. + n := binary.PutUvarint(obuf[obufHeaderLen:], uint64(len(uncompressed))) + n2 := w.encodeBlock(obuf[obufHeaderLen+n:], uncompressed) + + // Check if we should use this, or store as uncompressed instead. + if n2 > 0 { + chunkType = uint8(chunkTypeCompressedData) + chunkLen = 4 + n + n2 + obuf = obuf[:obufHeaderLen+n+n2] + } else { + // copy uncompressed + copy(obuf[obufHeaderLen:], uncompressed) + } + + // Fill in the per-chunk header that comes before the body. + obuf[0] = chunkType + obuf[1] = uint8(chunkLen >> 0) + obuf[2] = uint8(chunkLen >> 8) + obuf[3] = uint8(chunkLen >> 16) + obuf[4] = uint8(checksum >> 0) + obuf[5] = uint8(checksum >> 8) + obuf[6] = uint8(checksum >> 16) + obuf[7] = uint8(checksum >> 24) + + // Queue final output. + res.b = obuf + output <- res + }() + } + return nil +} + +func (w *Writer) encodeBlock(obuf, uncompressed []byte) int { + if w.customEnc != nil { + if ret := w.customEnc(obuf, uncompressed); ret >= 0 { + return ret + } + } + if w.snappy { + switch w.level { + case levelFast: + return encodeBlockSnappy(obuf, uncompressed) + case levelBetter: + return encodeBlockBetterSnappy(obuf, uncompressed) + case levelBest: + return encodeBlockBestSnappy(obuf, uncompressed) + } + return 0 + } + switch w.level { + case levelFast: + return encodeBlock(obuf, uncompressed) + case levelBetter: + return encodeBlockBetter(obuf, uncompressed) + case levelBest: + return encodeBlockBest(obuf, uncompressed, nil) + } + return 0 +} + +func (w *Writer) write(p []byte) (nRet int, errRet error) { + if err := w.err(nil); err != nil { + return 0, err + } + if w.concurrency == 1 { + return w.writeSync(p) + } + + // Spawn goroutine and write block to output channel. + for len(p) > 0 { + if !w.wroteStreamHeader { + w.wroteStreamHeader = true + hWriter := make(chan result) + w.output <- hWriter + if w.snappy { + hWriter <- result{startOffset: w.uncompWritten, b: []byte(magicChunkSnappy)} + } else { + hWriter <- result{startOffset: w.uncompWritten, b: []byte(magicChunk)} + } + } + + var uncompressed []byte + if len(p) > w.blockSize { + uncompressed, p = p[:w.blockSize], p[w.blockSize:] + } else { + uncompressed, p = p, nil + } + + // Copy input. + // If the block is incompressible, this is used for the result. + inbuf := w.buffers.Get().([]byte)[:len(uncompressed)+obufHeaderLen] + obuf := w.buffers.Get().([]byte)[:w.obufLen] + copy(inbuf[obufHeaderLen:], uncompressed) + uncompressed = inbuf[obufHeaderLen:] + + output := make(chan result) + // Queue output now, so we keep order. + w.output <- output + res := result{ + startOffset: w.uncompWritten, + } + w.uncompWritten += int64(len(uncompressed)) + + go func() { + checksum := crc(uncompressed) + + // Set to uncompressed. + chunkType := uint8(chunkTypeUncompressedData) + chunkLen := 4 + len(uncompressed) + + // Attempt compressing. + n := binary.PutUvarint(obuf[obufHeaderLen:], uint64(len(uncompressed))) + n2 := w.encodeBlock(obuf[obufHeaderLen+n:], uncompressed) + + // Check if we should use this, or store as uncompressed instead. + if n2 > 0 { + chunkType = uint8(chunkTypeCompressedData) + chunkLen = 4 + n + n2 + obuf = obuf[:obufHeaderLen+n+n2] + } else { + // Use input as output. + obuf, inbuf = inbuf, obuf + } + + // Fill in the per-chunk header that comes before the body. + obuf[0] = chunkType + obuf[1] = uint8(chunkLen >> 0) + obuf[2] = uint8(chunkLen >> 8) + obuf[3] = uint8(chunkLen >> 16) + obuf[4] = uint8(checksum >> 0) + obuf[5] = uint8(checksum >> 8) + obuf[6] = uint8(checksum >> 16) + obuf[7] = uint8(checksum >> 24) + + // Queue final output. + res.b = obuf + output <- res + + // Put unused buffer back in pool. + w.buffers.Put(inbuf) + }() + nRet += len(uncompressed) + } + return nRet, nil +} + +// writeFull is a special version of write that will always write the full buffer. +// Data to be compressed should start at offset obufHeaderLen and fill the remainder of the buffer. +// The data will be written as a single block. +// The caller is not allowed to use inbuf after this function has been called. +func (w *Writer) writeFull(inbuf []byte) (errRet error) { + if err := w.err(nil); err != nil { + return err + } + + if w.concurrency == 1 { + _, err := w.writeSync(inbuf[obufHeaderLen:]) + return err + } + + // Spawn goroutine and write block to output channel. + if !w.wroteStreamHeader { + w.wroteStreamHeader = true + hWriter := make(chan result) + w.output <- hWriter + if w.snappy { + hWriter <- result{startOffset: w.uncompWritten, b: []byte(magicChunkSnappy)} + } else { + hWriter <- result{startOffset: w.uncompWritten, b: []byte(magicChunk)} + } + } + + // Get an output buffer. + obuf := w.buffers.Get().([]byte)[:w.obufLen] + uncompressed := inbuf[obufHeaderLen:] + + output := make(chan result) + // Queue output now, so we keep order. + w.output <- output + res := result{ + startOffset: w.uncompWritten, + } + w.uncompWritten += int64(len(uncompressed)) + + go func() { + checksum := crc(uncompressed) + + // Set to uncompressed. + chunkType := uint8(chunkTypeUncompressedData) + chunkLen := 4 + len(uncompressed) + + // Attempt compressing. + n := binary.PutUvarint(obuf[obufHeaderLen:], uint64(len(uncompressed))) + n2 := w.encodeBlock(obuf[obufHeaderLen+n:], uncompressed) + + // Check if we should use this, or store as uncompressed instead. + if n2 > 0 { + chunkType = uint8(chunkTypeCompressedData) + chunkLen = 4 + n + n2 + obuf = obuf[:obufHeaderLen+n+n2] + } else { + // Use input as output. + obuf, inbuf = inbuf, obuf + } + + // Fill in the per-chunk header that comes before the body. + obuf[0] = chunkType + obuf[1] = uint8(chunkLen >> 0) + obuf[2] = uint8(chunkLen >> 8) + obuf[3] = uint8(chunkLen >> 16) + obuf[4] = uint8(checksum >> 0) + obuf[5] = uint8(checksum >> 8) + obuf[6] = uint8(checksum >> 16) + obuf[7] = uint8(checksum >> 24) + + // Queue final output. + res.b = obuf + output <- res + + // Put unused buffer back in pool. + w.buffers.Put(inbuf) + }() + return nil +} + +func (w *Writer) writeSync(p []byte) (nRet int, errRet error) { + if err := w.err(nil); err != nil { + return 0, err + } + if !w.wroteStreamHeader { + w.wroteStreamHeader = true + var n int + var err error + if w.snappy { + n, err = w.writer.Write([]byte(magicChunkSnappy)) + } else { + n, err = w.writer.Write([]byte(magicChunk)) + } + if err != nil { + return 0, w.err(err) + } + if n != len(magicChunk) { + return 0, w.err(io.ErrShortWrite) + } + w.written += int64(n) + } + + for len(p) > 0 { + var uncompressed []byte + if len(p) > w.blockSize { + uncompressed, p = p[:w.blockSize], p[w.blockSize:] + } else { + uncompressed, p = p, nil + } + + obuf := w.buffers.Get().([]byte)[:w.obufLen] + checksum := crc(uncompressed) + + // Set to uncompressed. + chunkType := uint8(chunkTypeUncompressedData) + chunkLen := 4 + len(uncompressed) + + // Attempt compressing. + n := binary.PutUvarint(obuf[obufHeaderLen:], uint64(len(uncompressed))) + n2 := w.encodeBlock(obuf[obufHeaderLen+n:], uncompressed) + + if n2 > 0 { + chunkType = uint8(chunkTypeCompressedData) + chunkLen = 4 + n + n2 + obuf = obuf[:obufHeaderLen+n+n2] + } else { + obuf = obuf[:8] + } + + // Fill in the per-chunk header that comes before the body. + obuf[0] = chunkType + obuf[1] = uint8(chunkLen >> 0) + obuf[2] = uint8(chunkLen >> 8) + obuf[3] = uint8(chunkLen >> 16) + obuf[4] = uint8(checksum >> 0) + obuf[5] = uint8(checksum >> 8) + obuf[6] = uint8(checksum >> 16) + obuf[7] = uint8(checksum >> 24) + + n, err := w.writer.Write(obuf) + if err != nil { + return 0, w.err(err) + } + if n != len(obuf) { + return 0, w.err(io.ErrShortWrite) + } + w.err(w.index.add(w.written, w.uncompWritten)) + w.written += int64(n) + w.uncompWritten += int64(len(uncompressed)) + + if chunkType == chunkTypeUncompressedData { + // Write uncompressed data. + n, err := w.writer.Write(uncompressed) + if err != nil { + return 0, w.err(err) + } + if n != len(uncompressed) { + return 0, w.err(io.ErrShortWrite) + } + w.written += int64(n) + } + w.buffers.Put(obuf) + // Queue final output. + nRet += len(uncompressed) + } + return nRet, nil +} + +// Flush flushes the Writer to its underlying io.Writer. +// This does not apply padding. +func (w *Writer) Flush() error { + if err := w.err(nil); err != nil { + return err + } + + // Queue any data still in input buffer. + if len(w.ibuf) != 0 { + if !w.wroteStreamHeader { + _, err := w.writeSync(w.ibuf) + w.ibuf = w.ibuf[:0] + return w.err(err) + } else { + _, err := w.write(w.ibuf) + w.ibuf = w.ibuf[:0] + err = w.err(err) + if err != nil { + return err + } + } + } + if w.output == nil { + return w.err(nil) + } + + // Send empty buffer + res := make(chan result) + w.output <- res + // Block until this has been picked up. + res <- result{b: nil, startOffset: w.uncompWritten} + // When it is closed, we have flushed. + <-res + return w.err(nil) +} + +// Close calls Flush and then closes the Writer. +// Calling Close multiple times is ok, +// but calling CloseIndex after this will make it not return the index. +func (w *Writer) Close() error { + _, err := w.closeIndex(w.appendIndex) + return err +} + +// CloseIndex calls Close and returns an index on first call. +// This is not required if you are only adding index to a stream. +func (w *Writer) CloseIndex() ([]byte, error) { + return w.closeIndex(true) +} + +func (w *Writer) closeIndex(idx bool) ([]byte, error) { + err := w.Flush() + if w.output != nil { + close(w.output) + w.writerWg.Wait() + w.output = nil + } + + var index []byte + if w.err(err) == nil && w.writer != nil { + // Create index. + if idx { + compSize := int64(-1) + if w.pad <= 1 { + compSize = w.written + } + index = w.index.appendTo(w.ibuf[:0], w.uncompWritten, compSize) + // Count as written for padding. + if w.appendIndex { + w.written += int64(len(index)) + } + } + + if w.pad > 1 { + tmp := w.ibuf[:0] + if len(index) > 0 { + // Allocate another buffer. + tmp = w.buffers.Get().([]byte)[:0] + defer w.buffers.Put(tmp) + } + add := calcSkippableFrame(w.written, int64(w.pad)) + frame, err := skippableFrame(tmp, add, w.randSrc) + if err = w.err(err); err != nil { + return nil, err + } + n, err2 := w.writer.Write(frame) + if err2 == nil && n != len(frame) { + err2 = io.ErrShortWrite + } + _ = w.err(err2) + } + if len(index) > 0 && w.appendIndex { + n, err2 := w.writer.Write(index) + if err2 == nil && n != len(index) { + err2 = io.ErrShortWrite + } + _ = w.err(err2) + } + } + err = w.err(errClosed) + if err == errClosed { + return index, nil + } + return nil, err +} + +// calcSkippableFrame will return a total size to be added for written +// to be divisible by multiple. +// The value will always be > skippableFrameHeader. +// The function will panic if written < 0 or wantMultiple <= 0. +func calcSkippableFrame(written, wantMultiple int64) int { + if wantMultiple <= 0 { + panic("wantMultiple <= 0") + } + if written < 0 { + panic("written < 0") + } + leftOver := written % wantMultiple + if leftOver == 0 { + return 0 + } + toAdd := wantMultiple - leftOver + for toAdd < skippableFrameHeader { + toAdd += wantMultiple + } + return int(toAdd) +} + +// skippableFrame will add a skippable frame with a total size of bytes. +// total should be >= skippableFrameHeader and < maxBlockSize + skippableFrameHeader +func skippableFrame(dst []byte, total int, r io.Reader) ([]byte, error) { + if total == 0 { + return dst, nil + } + if total < skippableFrameHeader { + return dst, fmt.Errorf("s2: requested skippable frame (%d) < 4", total) + } + if int64(total) >= maxBlockSize+skippableFrameHeader { + return dst, fmt.Errorf("s2: requested skippable frame (%d) >= max 1<<24", total) + } + // Chunk type 0xfe "Section 4.4 Padding (chunk type 0xfe)" + dst = append(dst, chunkTypePadding) + f := uint32(total - skippableFrameHeader) + // Add chunk length. + dst = append(dst, uint8(f), uint8(f>>8), uint8(f>>16)) + // Add data + start := len(dst) + dst = append(dst, make([]byte, f)...) + _, err := io.ReadFull(r, dst[start:]) + return dst, err +} + +var errClosed = errors.New("s2: Writer is closed") + +// WriterOption is an option for creating a encoder. +type WriterOption func(*Writer) error + +// WriterConcurrency will set the concurrency, +// meaning the maximum number of decoders to run concurrently. +// The value supplied must be at least 1. +// By default this will be set to GOMAXPROCS. +func WriterConcurrency(n int) WriterOption { + return func(w *Writer) error { + if n <= 0 { + return errors.New("concurrency must be at least 1") + } + w.concurrency = n + return nil + } +} + +// WriterAddIndex will append an index to the end of a stream +// when it is closed. +func WriterAddIndex() WriterOption { + return func(w *Writer) error { + w.appendIndex = true + return nil + } +} + +// WriterBetterCompression will enable better compression. +// EncodeBetter compresses better than Encode but typically with a +// 10-40% speed decrease on both compression and decompression. +func WriterBetterCompression() WriterOption { + return func(w *Writer) error { + w.level = levelBetter + return nil + } +} + +// WriterBestCompression will enable better compression. +// EncodeBetter compresses better than Encode but typically with a +// big speed decrease on compression. +func WriterBestCompression() WriterOption { + return func(w *Writer) error { + w.level = levelBest + return nil + } +} + +// WriterUncompressed will bypass compression. +// The stream will be written as uncompressed blocks only. +// If concurrency is > 1 CRC and output will still be done async. +func WriterUncompressed() WriterOption { + return func(w *Writer) error { + w.level = levelUncompressed + return nil + } +} + +// WriterBlockSize allows to override the default block size. +// Blocks will be this size or smaller. +// Minimum size is 4KB and and maximum size is 4MB. +// +// Bigger blocks may give bigger throughput on systems with many cores, +// and will increase compression slightly, but it will limit the possible +// concurrency for smaller payloads for both encoding and decoding. +// Default block size is 1MB. +// +// When writing Snappy compatible output using WriterSnappyCompat, +// the maximum block size is 64KB. +func WriterBlockSize(n int) WriterOption { + return func(w *Writer) error { + if w.snappy && n > maxSnappyBlockSize || n < minBlockSize { + return errors.New("s2: block size too large. Must be <= 64K and >=4KB on for snappy compatible output") + } + if n > maxBlockSize || n < minBlockSize { + return errors.New("s2: block size too large. Must be <= 4MB and >=4KB") + } + w.blockSize = n + return nil + } +} + +// WriterPadding will add padding to all output so the size will be a multiple of n. +// This can be used to obfuscate the exact output size or make blocks of a certain size. +// The contents will be a skippable frame, so it will be invisible by the decoder. +// n must be > 0 and <= 4MB. +// The padded area will be filled with data from crypto/rand.Reader. +// The padding will be applied whenever Close is called on the writer. +func WriterPadding(n int) WriterOption { + return func(w *Writer) error { + if n <= 0 { + return fmt.Errorf("s2: padding must be at least 1") + } + // No need to waste our time. + if n == 1 { + w.pad = 0 + } + if n > maxBlockSize { + return fmt.Errorf("s2: padding must less than 4MB") + } + w.pad = n + return nil + } +} + +// WriterPaddingSrc will get random data for padding from the supplied source. +// By default crypto/rand is used. +func WriterPaddingSrc(reader io.Reader) WriterOption { + return func(w *Writer) error { + w.randSrc = reader + return nil + } +} + +// WriterSnappyCompat will write snappy compatible output. +// The output can be decompressed using either snappy or s2. +// If block size is more than 64KB it is set to that. +func WriterSnappyCompat() WriterOption { + return func(w *Writer) error { + w.snappy = true + if w.blockSize > 64<<10 { + // We choose 8 bytes less than 64K, since that will make literal emits slightly more effective. + // And allows us to skip some size checks. + w.blockSize = (64 << 10) - 8 + } + return nil + } +} + +// WriterFlushOnWrite will compress blocks on each call to the Write function. +// +// This is quite inefficient as blocks size will depend on the write size. +// +// Use WriterConcurrency(1) to also make sure that output is flushed. +// When Write calls return, otherwise they will be written when compression is done. +func WriterFlushOnWrite() WriterOption { + return func(w *Writer) error { + w.flushOnWrite = true + return nil + } +} + +// WriterCustomEncoder allows to override the encoder for blocks on the stream. +// The function must compress 'src' into 'dst' and return the bytes used in dst as an integer. +// Block size (initial varint) should not be added by the encoder. +// Returning value 0 indicates the block could not be compressed. +// Returning a negative value indicates that compression should be attempted. +// The function should expect to be called concurrently. +func WriterCustomEncoder(fn func(dst, src []byte) int) WriterOption { + return func(w *Writer) error { + w.customEnc = fn + return nil + } +} -- cgit v1.2.3