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A span with column 0 is intended to mean the start of the line, which in utf16 mode must be the 1st character Change-Id: I4b98fe86528b889bbfe4b5ed3ae79c4da81017b1 Reviewed-on: https://go-review.googlesource.com/c/tools/+/167459 Run-TryBot: Ian Cottrell <iancottrell@google.com> Reviewed-by: Rebecca Stambler <rstambler@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
75 lines
2.2 KiB
Go
75 lines
2.2 KiB
Go
// 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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package span
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import (
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"unicode/utf16"
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"unicode/utf8"
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)
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// ToUTF16Column calculates the utf16 column expressed by the point given the
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// supplied file contents.
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// This is used to convert from the native (always in bytes) column
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// representation and the utf16 counts used by some editors.
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func ToUTF16Column(offsets Offsets, p Point, content []byte) int {
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if content == nil || p.Column < 0 {
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return -1
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}
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if p.Column == 0 {
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return 1
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}
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// make sure we have a valid offset
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p.updateOffset(offsets)
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lineOffset := p.Offset - (p.Column - 1)
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if lineOffset < 0 || p.Offset > len(content) {
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return -1
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}
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// use the offset to pick out the line start
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start := content[lineOffset:]
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// now truncate down to the supplied column
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start = start[:p.Column]
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// and count the number of utf16 characters
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// in theory we could do this by hand more efficiently...
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return len(utf16.Encode([]rune(string(start))))
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}
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// FromUTF16Column calculates the byte column expressed by the utf16 character
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// offset given the supplied file contents.
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// This is used to convert from the utf16 counts used by some editors to the
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// native (always in bytes) column representation.
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func FromUTF16Column(offsets Offsets, line, chr int, content []byte) Point {
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// first build a point for the start of the line the normal way
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p := Point{Line: line, Column: 1, Offset: 0}
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// now use that to work out the byte offset of the start of the line
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p.updateOffset(offsets)
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if chr <= 1 {
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return p
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}
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// use that to pick the line out of the file content
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remains := content[p.Offset:]
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// and now scan forward the specified number of characters
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for count := 1; count < chr; count++ {
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if len(remains) <= 0 {
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return Point{Offset: -1}
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}
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r, w := utf8.DecodeRune(remains)
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if r == '\n' {
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return Point{Offset: -1}
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}
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remains = remains[w:]
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if r >= 0x10000 {
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// a two point rune
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count++
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// if we finished in a two point rune, do not advance past the first
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if count >= chr {
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break
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}
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}
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p.Column += w
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p.Offset += w
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}
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return p
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}
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