diff options
Diffstat (limited to 'cmp/report_slices.go')
| -rw-r--r-- | cmp/report_slices.go | 152 |
1 files changed, 142 insertions, 10 deletions
diff --git a/cmp/report_slices.go b/cmp/report_slices.go index 168f92f..f985cc9 100644 --- a/cmp/report_slices.go +++ b/cmp/report_slices.go @@ -338,8 +338,11 @@ func (opts formatOptions) formatDiffSlice( vx, vy reflect.Value, chunkSize int, name string, makeRec func(reflect.Value, diffMode) textRecord, ) (list textList) { - es := diff.Difference(vx.Len(), vy.Len(), func(ix int, iy int) diff.Result { - return diff.BoolResult(vx.Index(ix).Interface() == vy.Index(iy).Interface()) + eq := func(ix, iy int) bool { + return vx.Index(ix).Interface() == vy.Index(iy).Interface() + } + es := diff.Difference(vx.Len(), vy.Len(), func(ix, iy int) diff.Result { + return diff.BoolResult(eq(ix, iy)) }) appendChunks := func(v reflect.Value, d diffMode) int { @@ -364,6 +367,7 @@ func (opts formatOptions) formatDiffSlice( groups := coalesceAdjacentEdits(name, es) groups = coalesceInterveningIdentical(groups, chunkSize/4) + groups = cleanupSurroundingIdentical(groups, eq) maxGroup := diffStats{Name: name} for i, ds := range groups { if maxLen >= 0 && numDiffs >= maxLen { @@ -416,25 +420,36 @@ func (opts formatOptions) formatDiffSlice( // coalesceAdjacentEdits coalesces the list of edits into groups of adjacent // equal or unequal counts. +// +// Example: +// +// Input: "..XXY...Y" +// Output: [ +// {NumIdentical: 2}, +// {NumRemoved: 2, NumInserted 1}, +// {NumIdentical: 3}, +// {NumInserted: 1}, +// ] +// func coalesceAdjacentEdits(name string, es diff.EditScript) (groups []diffStats) { - var prevCase int // Arbitrary index into which case last occurred - lastStats := func(i int) *diffStats { - if prevCase != i { + var prevMode byte + lastStats := func(mode byte) *diffStats { + if prevMode != mode { groups = append(groups, diffStats{Name: name}) - prevCase = i + prevMode = mode } return &groups[len(groups)-1] } for _, e := range es { switch e { case diff.Identity: - lastStats(1).NumIdentical++ + lastStats('=').NumIdentical++ case diff.UniqueX: - lastStats(2).NumRemoved++ + lastStats('!').NumRemoved++ case diff.UniqueY: - lastStats(2).NumInserted++ + lastStats('!').NumInserted++ case diff.Modified: - lastStats(2).NumModified++ + lastStats('!').NumModified++ } } return groups @@ -444,6 +459,35 @@ func coalesceAdjacentEdits(name string, es diff.EditScript) (groups []diffStats) // equal groups into adjacent unequal groups that currently result in a // dual inserted/removed printout. This acts as a high-pass filter to smooth // out high-frequency changes within the windowSize. +// +// Example: +// +// WindowSize: 16, +// Input: [ +// {NumIdentical: 61}, // group 0 +// {NumRemoved: 3, NumInserted: 1}, // group 1 +// {NumIdentical: 6}, // ├── coalesce +// {NumInserted: 2}, // ├── coalesce +// {NumIdentical: 1}, // ├── coalesce +// {NumRemoved: 9}, // └── coalesce +// {NumIdentical: 64}, // group 2 +// {NumRemoved: 3, NumInserted: 1}, // group 3 +// {NumIdentical: 6}, // ├── coalesce +// {NumInserted: 2}, // ├── coalesce +// {NumIdentical: 1}, // ├── coalesce +// {NumRemoved: 7}, // ├── coalesce +// {NumIdentical: 1}, // ├── coalesce +// {NumRemoved: 2}, // └── coalesce +// {NumIdentical: 63}, // group 4 +// ] +// Output: [ +// {NumIdentical: 61}, +// {NumIdentical: 7, NumRemoved: 12, NumInserted: 3}, +// {NumIdentical: 64}, +// {NumIdentical: 8, NumRemoved: 12, NumInserted: 3}, +// {NumIdentical: 63}, +// ] +// func coalesceInterveningIdentical(groups []diffStats, windowSize int) []diffStats { groups, groupsOrig := groups[:0], groups for i, ds := range groupsOrig { @@ -463,3 +507,91 @@ func coalesceInterveningIdentical(groups []diffStats, windowSize int) []diffStat } return groups } + +// cleanupSurroundingIdentical scans through all unequal groups, and +// moves any leading sequence of equal elements to the preceding equal group and +// moves and trailing sequence of equal elements to the succeeding equal group. +// +// This is necessary since coalesceInterveningIdentical may coalesce edit groups +// together such that leading/trailing spans of equal elements becomes possible. +// Note that this can occur even with an optimal diffing algorithm. +// +// Example: +// +// Input: [ +// {NumIdentical: 61}, +// {NumIdentical: 1 , NumRemoved: 11, NumInserted: 2}, // assume 3 leading identical elements +// {NumIdentical: 67}, +// {NumIdentical: 7, NumRemoved: 12, NumInserted: 3}, // assume 10 trailing identical elements +// {NumIdentical: 54}, +// ] +// Output: [ +// {NumIdentical: 64}, // incremented by 3 +// {NumRemoved: 9}, +// {NumIdentical: 67}, +// {NumRemoved: 9}, +// {NumIdentical: 64}, // incremented by 10 +// ] +// +func cleanupSurroundingIdentical(groups []diffStats, eq func(i, j int) bool) []diffStats { + var ix, iy int // indexes into sequence x and y + for i, ds := range groups { + // Handle equal group. + if ds.NumDiff() == 0 { + ix += ds.NumIdentical + iy += ds.NumIdentical + continue + } + + // Handle unequal group. + nx := ds.NumIdentical + ds.NumRemoved + ds.NumModified + ny := ds.NumIdentical + ds.NumInserted + ds.NumModified + var numLeadingIdentical, numTrailingIdentical int + for i := 0; i < nx && i < ny && eq(ix+i, iy+i); i++ { + numLeadingIdentical++ + } + for i := 0; i < nx && i < ny && eq(ix+nx-1-i, iy+ny-1-i); i++ { + numTrailingIdentical++ + } + if numIdentical := numLeadingIdentical + numTrailingIdentical; numIdentical > 0 { + if numLeadingIdentical > 0 { + // Remove leading identical span from this group and + // insert it into the preceding group. + if i-1 >= 0 { + groups[i-1].NumIdentical += numLeadingIdentical + } else { + // No preceding group exists, so prepend a new group, + // but do so after we finish iterating over all groups. + defer func() { + groups = append([]diffStats{{Name: groups[0].Name, NumIdentical: numLeadingIdentical}}, groups...) + }() + } + // Increment indexes since the preceding group would have handled this. + ix += numLeadingIdentical + iy += numLeadingIdentical + } + if numTrailingIdentical > 0 { + // Remove trailing identical span from this group and + // insert it into the succeeding group. + if i+1 < len(groups) { + groups[i+1].NumIdentical += numTrailingIdentical + } else { + // No succeeding group exists, so append a new group, + // but do so after we finish iterating over all groups. + defer func() { + groups = append(groups, diffStats{Name: groups[len(groups)-1].Name, NumIdentical: numTrailingIdentical}) + }() + } + // Do not increment indexes since the succeeding group will handle this. + } + + // Update this group since some identical elements were removed. + nx -= numIdentical + ny -= numIdentical + groups[i] = diffStats{Name: ds.Name, NumRemoved: nx, NumInserted: ny} + } + ix += nx + iy += ny + } + return groups +} |