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Part of #18. There are some unfortunate API changes as part of this, such as the new EditScriptWithContextSize, since edit.Script is now part of a different package. Those will get ironed out as the refactoring continues.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,118 @@ | ||
| // Package edit provides edit scripts. | ||
| // Edit scripts are a core notion for diffs. | ||
| // The represent a way to go from A to B by a sequence | ||
| // of insertions, deletions, and equal elements. | ||
| package edit | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "strings" | ||
| ) | ||
|
|
||
| // A Script is an edit script to alter A into B. | ||
| type Script struct { | ||
| Ranges []Range | ||
| } | ||
|
|
||
| // NewScript returns a Script containing the ranges r. | ||
| // It is only a convenience wrapper used to reduce line noise. | ||
| func NewScript(r ...Range) Script { | ||
| return Script{Ranges: r} | ||
| } | ||
|
|
||
| // IsIdentity reports whether s is the identity edit script, | ||
| // that is, whether A and B are identical. | ||
| func (s *Script) IsIdentity() bool { | ||
| for _, r := range s.Ranges { | ||
| if !r.IsEqual() { | ||
| return false | ||
| } | ||
| } | ||
| return true | ||
| } | ||
|
|
||
| // Stat reports the number of insertions and deletions in s. | ||
| func (s *Script) Stat() (ins, del int) { | ||
| for _, r := range s.Ranges { | ||
| switch { | ||
| case r.IsDelete(): | ||
| del += r.HighA - r.LowA | ||
| case r.IsInsert(): | ||
| ins += r.HighB - r.LowB | ||
| } | ||
| } | ||
| return ins, del | ||
| } | ||
|
|
||
| // dump formats s for debugging. | ||
| func (s *Script) dump() string { | ||
| buf := new(strings.Builder) | ||
| for _, r := range s.Ranges { | ||
| fmt.Fprintln(buf, r) | ||
| } | ||
| return buf.String() | ||
| } | ||
|
|
||
| // A Range is a pair of clopen index ranges. | ||
| // It represents the elements A[LowA:HighA] and B[LowB:HighB]. | ||
| type Range struct { | ||
| LowA, HighA int | ||
| LowB, HighB int | ||
| } | ||
|
|
||
| // IsInsert reports whether r represents an insertion in a Script. | ||
| // If so, the inserted elements are B[LowB:HighB]. | ||
| func (r *Range) IsInsert() bool { | ||
| return r.LowA == r.HighA | ||
| } | ||
|
|
||
| // IsDelete reports whether r represents a deletion in a Script. | ||
| // If so, the deleted elements are A[LowA:HighA]. | ||
| func (r *Range) IsDelete() bool { | ||
| return r.LowB == r.HighB | ||
| } | ||
|
|
||
| // IsEqual reports whether r represents a series of equal elements in a Script. | ||
| // If so, the elements A[LowA:HighA] are equal to the elements B[LowB:HighB]. | ||
| func (r *Range) IsEqual() bool { | ||
| return r.HighB-r.LowB == r.HighA-r.LowA | ||
| } | ||
|
|
||
| // An Op is a edit operation used to transform A into B. | ||
| type Op int8 | ||
|
|
||
| //go:generate stringer -type Op | ||
|
|
||
| const ( | ||
| Del Op = -1 // delete | ||
| Eq Op = 0 // equal | ||
| Ins Op = 1 // insert | ||
| ) | ||
|
|
||
| // Op reports what kind of operation r represents. | ||
| // This can also be determined by calling r.IsInsert, | ||
| // r.IsDelete, and r.IsEqual, | ||
| // but this form is sometimes more convenient to use. | ||
| func (r *Range) Op() Op { | ||
| if r.IsInsert() { | ||
| return Ins | ||
| } | ||
| if r.IsDelete() { | ||
| return Del | ||
| } | ||
| if r.IsEqual() { | ||
| return Eq | ||
| } | ||
| panic("malformed Range") | ||
| } | ||
|
|
||
| // Len reports the number of elements in r. | ||
| // In a deletion, it is the number of deleted elements. | ||
| // In an insertion, it is the number of inserted elements. | ||
| // For equal elements, it is the number of equal elements. | ||
| func (r *Range) Len() int { | ||
| if r.LowA == r.HighA { | ||
| return r.HighB - r.LowB | ||
| } | ||
| return r.HighA - r.LowA | ||
| } |
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