449 lines
14 KiB
Go
449 lines
14 KiB
Go
// Copyright 2019, The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package cmp
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import (
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"bytes"
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"fmt"
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"reflect"
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"strconv"
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"strings"
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"unicode"
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"unicode/utf8"
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"github.com/google/go-cmp/cmp/internal/diff"
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)
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// CanFormatDiffSlice reports whether we support custom formatting for nodes
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// that are slices of primitive kinds or strings.
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func (opts formatOptions) CanFormatDiffSlice(v *valueNode) bool {
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switch {
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case opts.DiffMode != diffUnknown:
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return false // Must be formatting in diff mode
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case v.NumDiff == 0:
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return false // No differences detected
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case !v.ValueX.IsValid() || !v.ValueY.IsValid():
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return false // Both values must be valid
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case v.Type.Kind() == reflect.Slice && (v.ValueX.Len() == 0 || v.ValueY.Len() == 0):
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return false // Both slice values have to be non-empty
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case v.NumIgnored > 0:
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return false // Some ignore option was used
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case v.NumTransformed > 0:
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return false // Some transform option was used
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case v.NumCompared > 1:
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return false // More than one comparison was used
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case v.NumCompared == 1 && v.Type.Name() != "":
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// The need for cmp to check applicability of options on every element
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// in a slice is a significant performance detriment for large []byte.
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// The workaround is to specify Comparer(bytes.Equal),
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// which enables cmp to compare []byte more efficiently.
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// If they differ, we still want to provide batched diffing.
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// The logic disallows named types since they tend to have their own
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// String method, with nicer formatting than what this provides.
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return false
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}
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switch t := v.Type; t.Kind() {
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case reflect.String:
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case reflect.Array, reflect.Slice:
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// Only slices of primitive types have specialized handling.
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switch t.Elem().Kind() {
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
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reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr,
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reflect.Bool, reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
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default:
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return false
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}
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// If a sufficient number of elements already differ,
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// use specialized formatting even if length requirement is not met.
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if v.NumDiff > v.NumSame {
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return true
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}
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default:
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return false
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}
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// Use specialized string diffing for longer slices or strings.
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const minLength = 64
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return v.ValueX.Len() >= minLength && v.ValueY.Len() >= minLength
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}
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// FormatDiffSlice prints a diff for the slices (or strings) represented by v.
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// This provides custom-tailored logic to make printing of differences in
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// textual strings and slices of primitive kinds more readable.
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func (opts formatOptions) FormatDiffSlice(v *valueNode) textNode {
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assert(opts.DiffMode == diffUnknown)
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t, vx, vy := v.Type, v.ValueX, v.ValueY
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// Auto-detect the type of the data.
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var isLinedText, isText, isBinary bool
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var sx, sy string
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switch {
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case t.Kind() == reflect.String:
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sx, sy = vx.String(), vy.String()
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isText = true // Initial estimate, verify later
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case t.Kind() == reflect.Slice && t.Elem() == reflect.TypeOf(byte(0)):
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sx, sy = string(vx.Bytes()), string(vy.Bytes())
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isBinary = true // Initial estimate, verify later
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case t.Kind() == reflect.Array:
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// Arrays need to be addressable for slice operations to work.
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vx2, vy2 := reflect.New(t).Elem(), reflect.New(t).Elem()
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vx2.Set(vx)
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vy2.Set(vy)
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vx, vy = vx2, vy2
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}
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if isText || isBinary {
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var numLines, lastLineIdx, maxLineLen int
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isBinary = !utf8.ValidString(sx) || !utf8.ValidString(sy)
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for i, r := range sx + sy {
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if !(unicode.IsPrint(r) || unicode.IsSpace(r)) || r == utf8.RuneError {
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isBinary = true
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break
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}
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if r == '\n' {
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if maxLineLen < i-lastLineIdx {
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maxLineLen = i - lastLineIdx
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}
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lastLineIdx = i + 1
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numLines++
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}
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}
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isText = !isBinary
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isLinedText = isText && numLines >= 4 && maxLineLen <= 1024
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}
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// Format the string into printable records.
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var list textList
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var delim string
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switch {
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// If the text appears to be multi-lined text,
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// then perform differencing across individual lines.
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case isLinedText:
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ssx := strings.Split(sx, "\n")
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ssy := strings.Split(sy, "\n")
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list = opts.formatDiffSlice(
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reflect.ValueOf(ssx), reflect.ValueOf(ssy), 1, "line",
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func(v reflect.Value, d diffMode) textRecord {
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s := formatString(v.Index(0).String())
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return textRecord{Diff: d, Value: textLine(s)}
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},
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)
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delim = "\n"
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// If possible, use a custom triple-quote (""") syntax for printing
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// differences in a string literal. This format is more readable,
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// but has edge-cases where differences are visually indistinguishable.
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// This format is avoided under the following conditions:
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// • A line starts with `"""`
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// • A line starts with "..."
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// • A line contains non-printable characters
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// • Adjacent different lines differ only by whitespace
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//
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// For example:
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// """
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// ... // 3 identical lines
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// foo
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// bar
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// - baz
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// + BAZ
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// """
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isTripleQuoted := true
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prevRemoveLines := map[string]bool{}
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prevInsertLines := map[string]bool{}
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var list2 textList
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list2 = append(list2, textRecord{Value: textLine(`"""`), ElideComma: true})
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for _, r := range list {
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if !r.Value.Equal(textEllipsis) {
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line, _ := strconv.Unquote(string(r.Value.(textLine)))
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line = strings.TrimPrefix(strings.TrimSuffix(line, "\r"), "\r") // trim leading/trailing carriage returns for legacy Windows endline support
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normLine := strings.Map(func(r rune) rune {
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if unicode.IsSpace(r) {
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return -1 // drop whitespace to avoid visually indistinguishable output
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}
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return r
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}, line)
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isPrintable := func(r rune) bool {
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return unicode.IsPrint(r) || r == '\t' // specially treat tab as printable
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}
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isTripleQuoted = !strings.HasPrefix(line, `"""`) && !strings.HasPrefix(line, "...") && strings.TrimFunc(line, isPrintable) == ""
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switch r.Diff {
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case diffRemoved:
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isTripleQuoted = isTripleQuoted && !prevInsertLines[normLine]
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prevRemoveLines[normLine] = true
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case diffInserted:
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isTripleQuoted = isTripleQuoted && !prevRemoveLines[normLine]
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prevInsertLines[normLine] = true
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}
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if !isTripleQuoted {
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break
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}
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r.Value = textLine(line)
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r.ElideComma = true
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}
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if !(r.Diff == diffRemoved || r.Diff == diffInserted) { // start a new non-adjacent difference group
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prevRemoveLines = map[string]bool{}
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prevInsertLines = map[string]bool{}
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}
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list2 = append(list2, r)
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}
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if r := list2[len(list2)-1]; r.Diff == diffIdentical && len(r.Value.(textLine)) == 0 {
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list2 = list2[:len(list2)-1] // elide single empty line at the end
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}
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list2 = append(list2, textRecord{Value: textLine(`"""`), ElideComma: true})
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if isTripleQuoted {
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var out textNode = &textWrap{Prefix: "(", Value: list2, Suffix: ")"}
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switch t.Kind() {
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case reflect.String:
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if t != reflect.TypeOf(string("")) {
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out = opts.FormatType(t, out)
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}
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case reflect.Slice:
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// Always emit type for slices since the triple-quote syntax
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// looks like a string (not a slice).
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opts = opts.WithTypeMode(emitType)
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out = opts.FormatType(t, out)
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}
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return out
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}
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// If the text appears to be single-lined text,
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// then perform differencing in approximately fixed-sized chunks.
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// The output is printed as quoted strings.
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case isText:
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list = opts.formatDiffSlice(
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reflect.ValueOf(sx), reflect.ValueOf(sy), 64, "byte",
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func(v reflect.Value, d diffMode) textRecord {
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s := formatString(v.String())
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return textRecord{Diff: d, Value: textLine(s)}
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},
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)
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delim = ""
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// If the text appears to be binary data,
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// then perform differencing in approximately fixed-sized chunks.
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// The output is inspired by hexdump.
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case isBinary:
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list = opts.formatDiffSlice(
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reflect.ValueOf(sx), reflect.ValueOf(sy), 16, "byte",
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func(v reflect.Value, d diffMode) textRecord {
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var ss []string
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for i := 0; i < v.Len(); i++ {
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ss = append(ss, formatHex(v.Index(i).Uint()))
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}
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s := strings.Join(ss, ", ")
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comment := commentString(fmt.Sprintf("%c|%v|", d, formatASCII(v.String())))
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return textRecord{Diff: d, Value: textLine(s), Comment: comment}
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},
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)
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// For all other slices of primitive types,
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// then perform differencing in approximately fixed-sized chunks.
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// The size of each chunk depends on the width of the element kind.
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default:
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var chunkSize int
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if t.Elem().Kind() == reflect.Bool {
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chunkSize = 16
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} else {
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switch t.Elem().Bits() {
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case 8:
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chunkSize = 16
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case 16:
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chunkSize = 12
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case 32:
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chunkSize = 8
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default:
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chunkSize = 8
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}
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}
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list = opts.formatDiffSlice(
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vx, vy, chunkSize, t.Elem().Kind().String(),
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func(v reflect.Value, d diffMode) textRecord {
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var ss []string
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for i := 0; i < v.Len(); i++ {
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switch t.Elem().Kind() {
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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ss = append(ss, fmt.Sprint(v.Index(i).Int()))
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case reflect.Uint, reflect.Uint16, reflect.Uint32, reflect.Uint64:
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ss = append(ss, fmt.Sprint(v.Index(i).Uint()))
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case reflect.Uint8, reflect.Uintptr:
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ss = append(ss, formatHex(v.Index(i).Uint()))
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case reflect.Bool, reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
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ss = append(ss, fmt.Sprint(v.Index(i).Interface()))
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}
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}
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s := strings.Join(ss, ", ")
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return textRecord{Diff: d, Value: textLine(s)}
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},
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)
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}
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// Wrap the output with appropriate type information.
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var out textNode = &textWrap{Prefix: "{", Value: list, Suffix: "}"}
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if !isText {
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// The "{...}" byte-sequence literal is not valid Go syntax for strings.
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// Emit the type for extra clarity (e.g. "string{...}").
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if t.Kind() == reflect.String {
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opts = opts.WithTypeMode(emitType)
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}
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return opts.FormatType(t, out)
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}
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switch t.Kind() {
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case reflect.String:
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out = &textWrap{Prefix: "strings.Join(", Value: out, Suffix: fmt.Sprintf(", %q)", delim)}
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if t != reflect.TypeOf(string("")) {
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out = opts.FormatType(t, out)
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}
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case reflect.Slice:
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out = &textWrap{Prefix: "bytes.Join(", Value: out, Suffix: fmt.Sprintf(", %q)", delim)}
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if t != reflect.TypeOf([]byte(nil)) {
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out = opts.FormatType(t, out)
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}
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}
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return out
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}
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// formatASCII formats s as an ASCII string.
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// This is useful for printing binary strings in a semi-legible way.
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func formatASCII(s string) string {
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b := bytes.Repeat([]byte{'.'}, len(s))
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for i := 0; i < len(s); i++ {
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if ' ' <= s[i] && s[i] <= '~' {
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b[i] = s[i]
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}
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}
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return string(b)
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}
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func (opts formatOptions) formatDiffSlice(
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vx, vy reflect.Value, chunkSize int, name string,
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makeRec func(reflect.Value, diffMode) textRecord,
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) (list textList) {
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es := diff.Difference(vx.Len(), vy.Len(), func(ix int, iy int) diff.Result {
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return diff.BoolResult(vx.Index(ix).Interface() == vy.Index(iy).Interface())
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})
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appendChunks := func(v reflect.Value, d diffMode) int {
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n0 := v.Len()
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for v.Len() > 0 {
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n := chunkSize
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if n > v.Len() {
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n = v.Len()
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}
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list = append(list, makeRec(v.Slice(0, n), d))
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v = v.Slice(n, v.Len())
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}
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return n0 - v.Len()
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}
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var numDiffs int
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maxLen := -1
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if opts.LimitVerbosity {
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maxLen = (1 << opts.verbosity()) << 2 // 4, 8, 16, 32, 64, etc...
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opts.VerbosityLevel--
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}
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groups := coalesceAdjacentEdits(name, es)
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groups = coalesceInterveningIdentical(groups, chunkSize/4)
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maxGroup := diffStats{Name: name}
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for i, ds := range groups {
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if maxLen >= 0 && numDiffs >= maxLen {
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maxGroup = maxGroup.Append(ds)
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continue
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}
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// Print equal.
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if ds.NumDiff() == 0 {
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// Compute the number of leading and trailing equal bytes to print.
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var numLo, numHi int
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numEqual := ds.NumIgnored + ds.NumIdentical
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for numLo < chunkSize*numContextRecords && numLo+numHi < numEqual && i != 0 {
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numLo++
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}
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for numHi < chunkSize*numContextRecords && numLo+numHi < numEqual && i != len(groups)-1 {
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numHi++
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}
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if numEqual-(numLo+numHi) <= chunkSize && ds.NumIgnored == 0 {
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numHi = numEqual - numLo // Avoid pointless coalescing of single equal row
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}
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// Print the equal bytes.
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appendChunks(vx.Slice(0, numLo), diffIdentical)
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if numEqual > numLo+numHi {
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ds.NumIdentical -= numLo + numHi
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list.AppendEllipsis(ds)
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}
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appendChunks(vx.Slice(numEqual-numHi, numEqual), diffIdentical)
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vx = vx.Slice(numEqual, vx.Len())
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vy = vy.Slice(numEqual, vy.Len())
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continue
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}
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// Print unequal.
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len0 := len(list)
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nx := appendChunks(vx.Slice(0, ds.NumIdentical+ds.NumRemoved+ds.NumModified), diffRemoved)
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vx = vx.Slice(nx, vx.Len())
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ny := appendChunks(vy.Slice(0, ds.NumIdentical+ds.NumInserted+ds.NumModified), diffInserted)
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vy = vy.Slice(ny, vy.Len())
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numDiffs += len(list) - len0
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}
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if maxGroup.IsZero() {
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assert(vx.Len() == 0 && vy.Len() == 0)
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} else {
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list.AppendEllipsis(maxGroup)
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}
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return list
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}
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// coalesceAdjacentEdits coalesces the list of edits into groups of adjacent
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// equal or unequal counts.
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func coalesceAdjacentEdits(name string, es diff.EditScript) (groups []diffStats) {
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var prevCase int // Arbitrary index into which case last occurred
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lastStats := func(i int) *diffStats {
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if prevCase != i {
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groups = append(groups, diffStats{Name: name})
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prevCase = i
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}
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return &groups[len(groups)-1]
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}
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for _, e := range es {
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switch e {
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case diff.Identity:
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lastStats(1).NumIdentical++
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case diff.UniqueX:
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lastStats(2).NumRemoved++
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case diff.UniqueY:
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lastStats(2).NumInserted++
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case diff.Modified:
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lastStats(2).NumModified++
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}
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}
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return groups
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}
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// coalesceInterveningIdentical coalesces sufficiently short (<= windowSize)
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// equal groups into adjacent unequal groups that currently result in a
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// dual inserted/removed printout. This acts as a high-pass filter to smooth
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// out high-frequency changes within the windowSize.
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func coalesceInterveningIdentical(groups []diffStats, windowSize int) []diffStats {
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groups, groupsOrig := groups[:0], groups
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for i, ds := range groupsOrig {
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if len(groups) >= 2 && ds.NumDiff() > 0 {
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prev := &groups[len(groups)-2] // Unequal group
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curr := &groups[len(groups)-1] // Equal group
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next := &groupsOrig[i] // Unequal group
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hadX, hadY := prev.NumRemoved > 0, prev.NumInserted > 0
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hasX, hasY := next.NumRemoved > 0, next.NumInserted > 0
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if ((hadX || hasX) && (hadY || hasY)) && curr.NumIdentical <= windowSize {
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*prev = prev.Append(*curr).Append(*next)
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groups = groups[:len(groups)-1] // Truncate off equal group
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continue
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}
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}
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groups = append(groups, ds)
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}
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return groups
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}
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