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// Go support for Protocol Buffers - Google's data interchange format
//
// Copyright 2017 The Go Authors. All rights reserved.
// https://github.com/golang/protobuf
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
/*
Package remap handles tracking the locations of Go tokens in a source text
across a rewrite by the Go formatter.
*/
package remap
import (
"fmt"
"go/scanner"
"go/token"
)
// A Location represents a span of byte offsets in the source text.
type Location struct {
Pos, End int // End is exclusive
}
// A Map represents a mapping between token locations in an input source text
// and locations in the correspnding output text.
type Map map[Location]Location
// Find reports whether the specified span is recorded by m, and if so returns
// the new location it was mapped to. If the input span was not found, the
// returned location is the same as the input.
func (m Map) Find(pos, end int) (Location, bool) {
key := Location{
Pos: pos,
End: end,
}
if loc, ok := m[key]; ok {
return loc, true
}
return key, false
}
func (m Map) add(opos, oend, npos, nend int) {
m[Location{Pos: opos, End: oend}] = Location{Pos: npos, End: nend}
}
// Compute constructs a location mapping from input to output. An error is
// reported if any of the tokens of output cannot be mapped.
func Compute(input, output []byte) (Map, error) {
itok := tokenize(input)
otok := tokenize(output)
if len(itok) != len(otok) {
return nil, fmt.Errorf("wrong number of tokens, %d ≠ %d", len(itok), len(otok))
}
m := make(Map)
for i, ti := range itok {
to := otok[i]
if ti.Token != to.Token {
return nil, fmt.Errorf("token %d type mismatch: %s ≠ %s", i+1, ti, to)
}
m.add(ti.pos, ti.end, to.pos, to.end)
}
return m, nil
}
// tokinfo records the span and type of a source token.
type tokinfo struct {
pos, end int
token.Token
}
func tokenize(src []byte) []tokinfo {
fs := token.NewFileSet()
var s scanner.Scanner
s.Init(fs.AddFile("src", fs.Base(), len(src)), src, nil, scanner.ScanComments)
var info []tokinfo
for {
pos, next, lit := s.Scan()
switch next {
case token.SEMICOLON:
continue
}
info = append(info, tokinfo{
pos: int(pos - 1),
end: int(pos + token.Pos(len(lit)) - 1),
Token: next,
})
if next == token.EOF {
break
}
}
return info
}
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