mirror of
https://github.com/golang/go
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40 lines
888 B
Go
40 lines
888 B
Go
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// Copyright 2019 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build !go1.12
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package span
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import (
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"go/token"
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)
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// lineStart is the pre-Go 1.12 version of (*token.File).LineStart. For Go
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// versions <= 1.11, we borrow logic from the analysisutil package.
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// TODO(rstambler): Delete this file when we no longer support Go 1.11.
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func lineStart(f *token.File, line int) token.Pos {
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// Use binary search to find the start offset of this line.
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min := 0 // inclusive
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max := f.Size() // exclusive
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for {
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offset := (min + max) / 2
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pos := f.Pos(offset)
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posn := f.Position(pos)
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if posn.Line == line {
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return pos - (token.Pos(posn.Column) - 1)
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}
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if min+1 >= max {
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return token.NoPos
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}
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if posn.Line < line {
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min = offset
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} else {
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max = offset
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}
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}
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}
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