1 // Go support for Protocol Buffers - Google's data interchange format 2 // 3 // Copyright 2017 The Go Authors. All rights reserved. 4 // https://github.com/golang/protobuf 5 // 6 // Redistribution and use in source and binary forms, with or without 7 // modification, are permitted provided that the following conditions are 8 // met: 9 // 10 // * Redistributions of source code must retain the above copyright 11 // notice, this list of conditions and the following disclaimer. 12 // * Redistributions in binary form must reproduce the above 13 // copyright notice, this list of conditions and the following disclaimer 14 // in the documentation and/or other materials provided with the 15 // distribution. 16 // * Neither the name of Google Inc. nor the names of its 17 // contributors may be used to endorse or promote products derived from 18 // this software without specific prior written permission. 19 // 20 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 23 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 24 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 25 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 26 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 27 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 28 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 29 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 30 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 31 32 /* 33 Package remap handles tracking the locations of Go tokens in a source text 34 across a rewrite by the Go formatter. 35 */ 36 package remap 37 38 import ( 39 "fmt" 40 "go/scanner" 41 "go/token" 42 ) 43 44 // A Location represents a span of byte offsets in the source text. 45 type Location struct { 46 Pos, End int // End is exclusive 47 } 48 49 // A Map represents a mapping between token locations in an input source text 50 // and locations in the correspnding output text. 51 type Map map[Location]Location 52 53 // Find reports whether the specified span is recorded by m, and if so returns 54 // the new location it was mapped to. If the input span was not found, the 55 // returned location is the same as the input. 56 func (m Map) Find(pos, end int) (Location, bool) { 57 key := Location{ 58 Pos: pos, 59 End: end, 60 } 61 if loc, ok := m[key]; ok { 62 return loc, true 63 } 64 return key, false 65 } 66 67 func (m Map) add(opos, oend, npos, nend int) { 68 m[Location{Pos: opos, End: oend}] = Location{Pos: npos, End: nend} 69 } 70 71 // Compute constructs a location mapping from input to output. An error is 72 // reported if any of the tokens of output cannot be mapped. 73 func Compute(input, output []byte) (Map, error) { 74 itok := tokenize(input) 75 otok := tokenize(output) 76 if len(itok) != len(otok) { 77 return nil, fmt.Errorf("wrong number of tokens, %d ≠ %d", len(itok), len(otok)) 78 } 79 m := make(Map) 80 for i, ti := range itok { 81 to := otok[i] 82 if ti.Token != to.Token { 83 return nil, fmt.Errorf("token %d type mismatch: %s ≠ %s", i+1, ti, to) 84 } 85 m.add(ti.pos, ti.end, to.pos, to.end) 86 } 87 return m, nil 88 } 89 90 // tokinfo records the span and type of a source token. 91 type tokinfo struct { 92 pos, end int 93 token.Token 94 } 95 96 func tokenize(src []byte) []tokinfo { 97 fs := token.NewFileSet() 98 var s scanner.Scanner 99 s.Init(fs.AddFile("src", fs.Base(), len(src)), src, nil, scanner.ScanComments) 100 var info []tokinfo 101 for { 102 pos, next, lit := s.Scan() 103 switch next { 104 case token.SEMICOLON: 105 continue 106 } 107 info = append(info, tokinfo{ 108 pos: int(pos - 1), 109 end: int(pos + token.Pos(len(lit)) - 1), 110 Token: next, 111 }) 112 if next == token.EOF { 113 break 114 } 115 } 116 return info 117 } 118