114 lines
2.2 KiB
Go
114 lines
2.2 KiB
Go
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package writebuffer
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import (
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"io"
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"github.com/kshvakov/clickhouse/lib/leakypool"
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)
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const InitialSize = 256 * 1024
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func New(initSize int) *WriteBuffer {
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wb := &WriteBuffer{}
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wb.addChunk(0, initSize)
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return wb
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}
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type WriteBuffer struct {
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chunks [][]byte
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}
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func (wb *WriteBuffer) Write(data []byte) (int, error) {
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var (
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chunkIdx = len(wb.chunks) - 1
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dataSize = len(data)
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)
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for {
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freeSize := cap(wb.chunks[chunkIdx]) - len(wb.chunks[chunkIdx])
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if freeSize >= len(data) {
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wb.chunks[chunkIdx] = append(wb.chunks[chunkIdx], data...)
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return dataSize, nil
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}
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wb.chunks[chunkIdx] = append(wb.chunks[chunkIdx], data[:freeSize]...)
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data = data[freeSize:]
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wb.addChunk(0, wb.calcCap(len(data)))
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chunkIdx++
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}
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}
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func (wb *WriteBuffer) WriteTo(w io.Writer) (int64, error) {
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var size int64
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for _, chunk := range wb.chunks {
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ln, err := w.Write(chunk)
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if err != nil {
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wb.Reset()
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return 0, err
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}
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size += int64(ln)
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}
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wb.Reset()
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return size, nil
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}
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func (wb *WriteBuffer) Bytes() []byte {
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if len(wb.chunks) == 1 {
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return wb.chunks[0]
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}
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bytes := make([]byte, 0, wb.len())
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for _, chunk := range wb.chunks {
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bytes = append(bytes, chunk...)
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}
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return bytes
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}
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func (wb *WriteBuffer) addChunk(size, capacity int) {
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chunk := leakypool.GetBytes(size, capacity)
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if cap(chunk) >= size {
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chunk = chunk[:size]
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}
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wb.chunks = append(wb.chunks, chunk)
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}
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func (wb *WriteBuffer) len() int {
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var v int
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for _, chunk := range wb.chunks {
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v += len(chunk)
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}
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return v
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}
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func (wb *WriteBuffer) calcCap(dataSize int) int {
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dataSize = max(dataSize, 64)
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if len(wb.chunks) == 0 {
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return dataSize
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}
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// Always double the size of the last chunk
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return max(dataSize, cap(wb.chunks[len(wb.chunks)-1])*2)
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}
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func (wb *WriteBuffer) Reset() {
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if len(wb.chunks) == 0 {
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return
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}
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// Recycle all chunks except the last one
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chunkSizeThreshold := cap(wb.chunks[0])
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for _, chunk := range wb.chunks[:len(wb.chunks)-1] {
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// Drain chunks smaller than the initial size
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if cap(chunk) >= chunkSizeThreshold {
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leakypool.PutBytes(chunk[:0])
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} else {
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chunkSizeThreshold = cap(chunk)
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}
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}
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// Keep the largest chunk
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wb.chunks[0] = wb.chunks[len(wb.chunks)-1][:0]
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wb.chunks = wb.chunks[:1]
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}
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func max(a, b int) int {
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if b > a {
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return b
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}
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return a
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}
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