957b39cba5
Patch and PatchList provide an API for making changes to substrings of a Blueprint file by parsing the AST and using the token positions to perform text replacements. Test: modify_test.go Change-Id: Ibb8993221982b54602ba5a05486198fab8d35a67
120 lines
3.2 KiB
Go
120 lines
3.2 KiB
Go
// Copyright 2014 Google Inc. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package parser
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import (
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"fmt"
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"io"
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"math"
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"sort"
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)
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func AddStringToList(list *List, s string) (modified bool) {
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for _, v := range list.Values {
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if v.Type() != StringType {
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panic(fmt.Errorf("expected string in list, got %s", v.Type()))
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}
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if sv, ok := v.(*String); ok && sv.Value == s {
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// string already exists
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return false
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}
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}
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list.Values = append(list.Values, &String{
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LiteralPos: list.RBracePos,
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Value: s,
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})
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return true
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}
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func RemoveStringFromList(list *List, s string) (modified bool) {
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for i, v := range list.Values {
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if v.Type() != StringType {
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panic(fmt.Errorf("expected string in list, got %s", v.Type()))
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}
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if sv, ok := v.(*String); ok && sv.Value == s {
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list.Values = append(list.Values[:i], list.Values[i+1:]...)
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return true
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}
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}
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return false
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}
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// A Patch represents a region of a text buffer to be replaced [Start, End) and its Replacement
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type Patch struct {
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Start, End int
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Replacement string
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}
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// A PatchList is a list of sorted, non-overlapping Patch objects
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type PatchList []Patch
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type PatchOverlapError error
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// Add adds a Patch to a PatchList. It returns a PatchOverlapError if the patch cannot be added.
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func (list *PatchList) Add(start, end int, replacement string) error {
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patch := Patch{start, end, replacement}
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if patch.Start > patch.End {
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return fmt.Errorf("invalid patch, start %d is after end %d", patch.Start, patch.End)
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}
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for _, p := range *list {
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if (patch.Start >= p.Start && patch.Start < p.End) ||
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(patch.End >= p.Start && patch.End < p.End) ||
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(p.Start >= patch.Start && p.Start < patch.End) ||
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(p.Start == patch.Start && p.End == patch.End) {
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return PatchOverlapError(fmt.Errorf("new patch %d-%d overlaps with existing patch %d-%d",
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patch.Start, patch.End, p.Start, p.End))
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}
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}
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*list = append(*list, patch)
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list.sort()
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return nil
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}
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func (list *PatchList) sort() {
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sort.SliceStable(*list,
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func(i, j int) bool {
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return (*list)[i].Start < (*list)[j].Start
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})
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}
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// Apply applies all the Patch objects in PatchList to the data from an input ReaderAt to an output Writer.
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func (list *PatchList) Apply(in io.ReaderAt, out io.Writer) error {
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var offset int64
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for _, patch := range *list {
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toWrite := int64(patch.Start) - offset
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written, err := io.Copy(out, io.NewSectionReader(in, offset, toWrite))
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if err != nil {
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return err
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}
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offset += toWrite
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if written != toWrite {
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return fmt.Errorf("unexpected EOF at %d", offset)
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}
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_, err = io.WriteString(out, patch.Replacement)
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if err != nil {
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return err
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}
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offset += int64(patch.End - patch.Start)
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}
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_, err := io.Copy(out, io.NewSectionReader(in, offset, math.MaxInt64-offset))
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return err
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}
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