| // 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 | |
| } | |
| } | |
| } |