90 lines
2 KiB
Go
90 lines
2 KiB
Go
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package ansiescape
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import "bytes"
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// dropCR drops a leading or terminal \r from the data.
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func dropCR(data []byte) []byte {
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if len(data) > 0 && data[len(data)-1] == '\r' {
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data = data[0 : len(data)-1]
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}
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if len(data) > 0 && data[0] == '\r' {
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data = data[1:]
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}
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return data
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}
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// escapeSequenceLength calculates the length of an ANSI escape sequence
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// If there is not enough characters to match a sequence, -1 is returned,
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// if there is no valid sequence 0 is returned, otherwise the number
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// of bytes in the sequence is returned. Only returns length for
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// line moving sequences.
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func escapeSequenceLength(data []byte) int {
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next := 0
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if len(data) <= next {
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return -1
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}
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if data[next] != '[' {
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return 0
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}
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for {
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next = next + 1
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if len(data) <= next {
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return -1
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}
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if (data[next] > '9' || data[next] < '0') && data[next] != ';' {
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break
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}
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}
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if len(data) <= next {
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return -1
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}
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// Only match line moving codes
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switch data[next] {
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case 'A', 'B', 'E', 'F', 'H', 'h':
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return next + 1
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}
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return 0
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}
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// ScanANSILines is a scanner function which splits the
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// input based on ANSI escape codes and new lines.
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func ScanANSILines(data []byte, atEOF bool) (advance int, token []byte, err error) {
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if atEOF && len(data) == 0 {
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return 0, nil, nil
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}
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// Look for line moving escape sequence
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if i := bytes.IndexByte(data, '\x1b'); i >= 0 {
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last := 0
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for i >= 0 {
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last = last + i
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// get length of ANSI escape sequence
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sl := escapeSequenceLength(data[last+1:])
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if sl == -1 {
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return 0, nil, nil
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}
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if sl == 0 {
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// If no relevant sequence was found, skip
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last = last + 1
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i = bytes.IndexByte(data[last:], '\x1b')
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continue
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}
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return last + 1 + sl, dropCR(data[0:(last)]), nil
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}
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}
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if i := bytes.IndexByte(data, '\n'); i >= 0 {
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// No escape sequence, check for new line
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return i + 1, dropCR(data[0:i]), nil
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}
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// If we're at EOF, we have a final, non-terminated line. Return it.
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if atEOF {
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return len(data), dropCR(data), nil
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}
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// Request more data.
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return 0, nil, nil
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}
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