| // Copyright 2019 The Go Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| // +build !go1.12 |
| |
| package span |
| |
| import ( |
| "go/token" |
| ) |
| |
| // lineStart is the pre-Go 1.12 version of (*token.File).LineStart. For Go |
| // versions <= 1.11, we borrow logic from the analysisutil package. |
| // TODO(rstambler): Delete this file when we no longer support Go 1.11. |
| func lineStart(f *token.File, line int) token.Pos { |
| // Use binary search to find the start offset of this line. |
| |
| min := 0 // inclusive |
| max := f.Size() // exclusive |
| for { |
| offset := (min + max) / 2 |
| pos := f.Pos(offset) |
| posn := f.Position(pos) |
| if posn.Line == line { |
| return pos - (token.Pos(posn.Column) - 1) |
| } |
| |
| if min+1 >= max { |
| return token.NoPos |
| } |
| |
| if posn.Line < line { |
| min = offset |
| } else { |
| max = offset |
| } |
| } |
| } |
