Diff calculates difference between two reflists
(r *PackageRefList, packageCollection *PackageCollection)
| 188 | |
| 189 | // Diff calculates difference between two reflists |
| 190 | func (l *PackageRefList) Diff(r *PackageRefList, packageCollection *PackageCollection) (result PackageDiffs, err error) { |
| 191 | result = make(PackageDiffs, 0, 128) |
| 192 | |
| 193 | // pointer to left and right reflists |
| 194 | il, ir := 0, 0 |
| 195 | // length of reflists |
| 196 | ll, lr := l.Len(), r.Len() |
| 197 | // cached loaded packages on the left & right |
| 198 | pl, pr := (*Package)(nil), (*Package)(nil) |
| 199 | |
| 200 | // until we reached end of both lists |
| 201 | for il < ll || ir < lr { |
| 202 | var rl, rr []byte |
| 203 | if il < ll { |
| 204 | rl = l.Refs[il] |
| 205 | } |
| 206 | if ir < lr { |
| 207 | rr = r.Refs[ir] |
| 208 | } |
| 209 | |
| 210 | // compare refs |
| 211 | rel := bytes.Compare(rl, rr) |
| 212 | // an unset ref is less than all others, but since it represents the end |
| 213 | // of a reflist, it should be *greater*, so flip the comparison result |
| 214 | if rl == nil || rr == nil { |
| 215 | rel = -rel |
| 216 | } |
| 217 | |
| 218 | if rel == 0 { |
| 219 | // refs are identical, so are packages, advance pointer |
| 220 | il++ |
| 221 | ir++ |
| 222 | pl, pr = nil, nil |
| 223 | } else { |
| 224 | // load pl & pr if they haven't been loaded before |
| 225 | if pl == nil && rl != nil { |
| 226 | pl, err = packageCollection.ByKey(rl) |
| 227 | if err != nil { |
| 228 | return nil, err |
| 229 | } |
| 230 | } |
| 231 | |
| 232 | if pr == nil && rr != nil { |
| 233 | pr, err = packageCollection.ByKey(rr) |
| 234 | if err != nil { |
| 235 | return nil, err |
| 236 | } |
| 237 | } |
| 238 | |
| 239 | // otherwise pl or pr is missing on one of the sides |
| 240 | if rel < 0 { |
| 241 | // compaction: +(,A) -(B,) --> !(A,B) |
| 242 | if len(result) > 0 && result[len(result)-1].Left == nil && result[len(result)-1].Right.Name == pl.Name && |
| 243 | result[len(result)-1].Right.Architecture == pl.Architecture { |
| 244 | result[len(result)-1] = PackageDiff{Left: pl, Right: result[len(result)-1].Right} |
| 245 | } else { |
| 246 | result = append(result, PackageDiff{Left: pl, Right: nil}) |
| 247 | } |