80 lines
1.5 KiB
Go
80 lines
1.5 KiB
Go
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package parse
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import (
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"fmt"
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"io"
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"strings"
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"github.com/tdewolff/parse/buffer"
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)
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// Position returns the line and column number for a certain position in a file. It is useful for recovering the position in a file that caused an error.
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// It only treates \n, \r, and \r\n as newlines, which might be different from some languages also recognizing \f, \u2028, and \u2029 to be newlines.
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func Position(r io.Reader, offset int) (line, col int, context string, err error) {
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l := buffer.NewLexer(r)
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line = 1
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for {
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c := l.Peek(0)
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if c == 0 {
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col = l.Pos() + 1
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context = positionContext(l, line, col)
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err = l.Err()
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if err == nil {
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err = io.EOF
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}
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return
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}
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if offset == l.Pos() {
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col = l.Pos() + 1
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context = positionContext(l, line, col)
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return
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}
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if c == '\n' {
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l.Move(1)
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line++
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offset -= l.Pos()
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l.Skip()
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} else if c == '\r' {
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if l.Peek(1) == '\n' {
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if offset == l.Pos()+1 {
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l.Move(1)
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continue
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}
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l.Move(2)
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} else {
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l.Move(1)
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}
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line++
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offset -= l.Pos()
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l.Skip()
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} else {
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l.Move(1)
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}
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}
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}
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func positionContext(l *buffer.Lexer, line, col int) (context string) {
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for {
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c := l.Peek(0)
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if c == 0 && l.Err() != nil || c == '\n' || c == '\r' {
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break
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}
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l.Move(1)
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}
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// replace unprintable characters by a space
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b := l.Lexeme()
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for i, c := range b {
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if c < 0x20 || c == 0x7F {
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b[i] = ' '
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}
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}
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context += fmt.Sprintf("%5d: %s\n", line, string(b))
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context += fmt.Sprintf("%s^", strings.Repeat(" ", col+6))
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return
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}
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