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https://github.com/VictoriaMetrics/VictoriaMetrics.git
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80 lines
2.5 KiB
Go
80 lines
2.5 KiB
Go
package common
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import (
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"bytes"
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"fmt"
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"io"
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"github.com/VictoriaMetrics/VictoriaMetrics/lib/bytesutil"
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)
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// The maximum size of a single line returned by ReadLinesBlock.
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const maxLineSize = 256 * 1024
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// Default size in bytes of a single block returned by ReadLinesBlock.
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const defaultBlockSize = 64 * 1024
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// ReadLinesBlock reads a block of lines delimited by '\n' from tailBuf and r into dstBuf.
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//
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// Trailing chars after the last newline are put into tailBuf.
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//
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// Returns (dstBuf, tailBuf).
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func ReadLinesBlock(r io.Reader, dstBuf, tailBuf []byte) ([]byte, []byte, error) {
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return ReadLinesBlockExt(r, dstBuf, tailBuf, maxLineSize)
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}
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// ReadLinesBlockExt reads a block of lines delimited by '\n' from tailBuf and r into dstBuf.
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//
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// Trailing chars after the last newline are put into tailBuf.
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//
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// Returns (dstBuf, tailBuf).
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//
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// maxLineLen limits the maximum length of a single line.
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func ReadLinesBlockExt(r io.Reader, dstBuf, tailBuf []byte, maxLineLen int) ([]byte, []byte, error) {
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if cap(dstBuf) < defaultBlockSize {
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dstBuf = bytesutil.Resize(dstBuf, defaultBlockSize)
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}
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dstBuf = append(dstBuf[:0], tailBuf...)
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tailBuf = tailBuf[:0]
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again:
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n, err := r.Read(dstBuf[len(dstBuf):cap(dstBuf)])
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// Check for error only if zero bytes read from r, i.e. no forward progress made.
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// Otherwise process the read data.
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if n == 0 {
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if err == nil {
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return dstBuf, tailBuf, fmt.Errorf("no forward progress made")
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}
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if err == io.EOF && len(dstBuf) > 0 {
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// Missing newline in the end of stream. This is OK,
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// so suppress io.EOF for now. It will be returned during the next
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// call to ReadLinesBlock.
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// This fixes https://github.com/VictoriaMetrics/VictoriaMetrics/issues/60 .
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return dstBuf, tailBuf, nil
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}
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return dstBuf, tailBuf, err
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}
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dstBuf = dstBuf[:len(dstBuf)+n]
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// Search for the last newline in dstBuf and put the rest into tailBuf.
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nn := bytes.LastIndexByte(dstBuf[len(dstBuf)-n:], '\n')
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if nn < 0 {
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// Didn't found at least a single line.
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if len(dstBuf) > maxLineLen {
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return dstBuf, tailBuf, fmt.Errorf("too long line: more than %d bytes", maxLineLen)
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}
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if cap(dstBuf) < 2*len(dstBuf) {
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// Increase dsbBuf capacity, so more data could be read into it.
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dstBufLen := len(dstBuf)
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dstBuf = bytesutil.Resize(dstBuf, 2*cap(dstBuf))
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dstBuf = dstBuf[:dstBufLen]
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}
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goto again
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}
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// Found at least a single line. Return it.
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nn += len(dstBuf) - n
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tailBuf = append(tailBuf[:0], dstBuf[nn+1:]...)
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dstBuf = dstBuf[:nn]
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return dstBuf, tailBuf, nil
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}
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