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Diffstat (limited to 'src/pkg/reflect/deepequal.go')
-rw-r--r-- | src/pkg/reflect/deepequal.go | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/src/pkg/reflect/deepequal.go b/src/pkg/reflect/deepequal.go new file mode 100644 index 000000000..a483135b0 --- /dev/null +++ b/src/pkg/reflect/deepequal.go @@ -0,0 +1,126 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +// Deep equality test via reflection + +package reflect + +// During deepValueEqual, must keep track of checks that are +// in progress. The comparison algorithm assumes that all +// checks in progress are true when it reencounters them. +// Visited are stored in a map indexed by 17 * a1 + a2; +type visit struct { + a1 uintptr + a2 uintptr + typ Type + next *visit +} + +// Tests for deep equality using reflected types. The map argument tracks +// comparisons that have already been seen, which allows short circuiting on +// recursive types. +func deepValueEqual(v1, v2 Value, visited map[uintptr]*visit, depth int) (b bool) { + if !v1.IsValid() || !v2.IsValid() { + return v1.IsValid() == v2.IsValid() + } + if v1.Type() != v2.Type() { + return false + } + + // if depth > 10 { panic("deepValueEqual") } // for debugging + + if v1.CanAddr() && v2.CanAddr() { + addr1 := v1.UnsafeAddr() + addr2 := v2.UnsafeAddr() + if addr1 > addr2 { + // Canonicalize order to reduce number of entries in visited. + addr1, addr2 = addr2, addr1 + } + + // Short circuit if references are identical ... + if addr1 == addr2 { + return true + } + + // ... or already seen + h := 17*addr1 + addr2 + seen := visited[h] + typ := v1.Type() + for p := seen; p != nil; p = p.next { + if p.a1 == addr1 && p.a2 == addr2 && p.typ == typ { + return true + } + } + + // Remember for later. + visited[h] = &visit{addr1, addr2, typ, seen} + } + + switch v1.Kind() { + case Array: + if v1.Len() != v2.Len() { + return false + } + for i := 0; i < v1.Len(); i++ { + if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) { + return false + } + } + return true + case Slice: + if v1.Len() != v2.Len() { + return false + } + for i := 0; i < v1.Len(); i++ { + if !deepValueEqual(v1.Index(i), v2.Index(i), visited, depth+1) { + return false + } + } + return true + case Interface: + if v1.IsNil() || v2.IsNil() { + return v1.IsNil() == v2.IsNil() + } + return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1) + case Ptr: + return deepValueEqual(v1.Elem(), v2.Elem(), visited, depth+1) + case Struct: + for i, n := 0, v1.NumField(); i < n; i++ { + if !deepValueEqual(v1.Field(i), v2.Field(i), visited, depth+1) { + return false + } + } + return true + case Map: + if v1.Len() != v2.Len() { + return false + } + for _, k := range v1.MapKeys() { + if !deepValueEqual(v1.MapIndex(k), v2.MapIndex(k), visited, depth+1) { + return false + } + } + return true + default: + // Normal equality suffices + return v1.Interface() == v2.Interface() + } + + panic("Not reached") +} + +// DeepEqual tests for deep equality. It uses normal == equality where possible +// but will scan members of arrays, slices, and fields of structs. It correctly +// handles recursive types. +func DeepEqual(a1, a2 interface{}) bool { + if a1 == nil || a2 == nil { + return a1 == a2 + } + v1 := ValueOf(a1) + v2 := ValueOf(a2) + if v1.Type() != v2.Type() { + return false + } + return deepValueEqual(v1, v2, make(map[uintptr]*visit), 0) +} |