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package pktline
// Utility functions for working with the Git pkt-line format. See
// https://github.com/git/git/blob/master/Documentation/technical/protocol-common.txt
import (
"bufio"
"bytes"
"fmt"
"io"
"strconv"
)
const (
maxPktSize = 0xffff
pktDelim = "0001"
)
// NewScanner returns a bufio.Scanner that splits on Git pktline boundaries
func NewScanner(r io.Reader) *bufio.Scanner {
scanner := bufio.NewScanner(r)
scanner.Buffer(make([]byte, maxPktSize), maxPktSize)
scanner.Split(pktLineSplitter)
return scanner
}
// IsDone detects the special flush packet '0009done\n'
func IsDone(pkt []byte) bool {
return bytes.Equal(pkt, PktDone())
}
// PktDone returns the bytes for a "done" packet.
func PktDone() []byte {
return []byte("0009done\n")
}
func pktLineSplitter(data []byte, atEOF bool) (advance int, token []byte, err error) {
if len(data) < 4 {
if atEOF && len(data) > 0 {
return 0, nil, fmt.Errorf("pktLineSplitter: incomplete length prefix on %q", data)
}
return 0, nil, nil // want more data
}
// We have at least 4 bytes available so we can decode the 4-hex digit
// length prefix of the packet line.
pktLength64, err := strconv.ParseInt(string(data[:4]), 16, 0)
if err != nil {
return 0, nil, fmt.Errorf("pktLineSplitter: decode length: %v", err)
}
// Cast is safe because we requested an int-size number from strconv.ParseInt
pktLength := int(pktLength64)
if pktLength < 0 {
return 0, nil, fmt.Errorf("pktLineSplitter: invalid length: %d", pktLength)
}
if pktLength < 4 {
// Special case: magic empty packet 0000, 0001, 0002 or 0003.
return 4, data[:4], nil
}
if len(data) < pktLength {
// data contains incomplete packet
if atEOF {
return 0, nil, fmt.Errorf("pktLineSplitter: less than %d bytes in input %q", pktLength, data)
}
return 0, nil, nil // want more data
}
return pktLength, data[:pktLength], nil
}
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