David K. Bainbridge | 0663189 | 2021-08-19 13:07:00 +0000 | [diff] [blame^] | 1 | // Copyright 2020, The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | package cmp |
| 6 | |
| 7 | import ( |
| 8 | "fmt" |
| 9 | "reflect" |
| 10 | "strings" |
| 11 | |
| 12 | "github.com/google/go-cmp/cmp/internal/flags" |
| 13 | "github.com/google/go-cmp/cmp/internal/value" |
| 14 | ) |
| 15 | |
| 16 | const ( |
| 17 | pointerDelimPrefix = "⟪" |
| 18 | pointerDelimSuffix = "⟫" |
| 19 | ) |
| 20 | |
| 21 | // formatPointer prints the address of the pointer. |
| 22 | func formatPointer(p value.Pointer, withDelims bool) string { |
| 23 | v := p.Uintptr() |
| 24 | if flags.Deterministic { |
| 25 | v = 0xdeadf00f // Only used for stable testing purposes |
| 26 | } |
| 27 | if withDelims { |
| 28 | return pointerDelimPrefix + formatHex(uint64(v)) + pointerDelimSuffix |
| 29 | } |
| 30 | return formatHex(uint64(v)) |
| 31 | } |
| 32 | |
| 33 | // pointerReferences is a stack of pointers visited so far. |
| 34 | type pointerReferences [][2]value.Pointer |
| 35 | |
| 36 | func (ps *pointerReferences) PushPair(vx, vy reflect.Value, d diffMode, deref bool) (pp [2]value.Pointer) { |
| 37 | if deref && vx.IsValid() { |
| 38 | vx = vx.Addr() |
| 39 | } |
| 40 | if deref && vy.IsValid() { |
| 41 | vy = vy.Addr() |
| 42 | } |
| 43 | switch d { |
| 44 | case diffUnknown, diffIdentical: |
| 45 | pp = [2]value.Pointer{value.PointerOf(vx), value.PointerOf(vy)} |
| 46 | case diffRemoved: |
| 47 | pp = [2]value.Pointer{value.PointerOf(vx), value.Pointer{}} |
| 48 | case diffInserted: |
| 49 | pp = [2]value.Pointer{value.Pointer{}, value.PointerOf(vy)} |
| 50 | } |
| 51 | *ps = append(*ps, pp) |
| 52 | return pp |
| 53 | } |
| 54 | |
| 55 | func (ps *pointerReferences) Push(v reflect.Value) (p value.Pointer, seen bool) { |
| 56 | p = value.PointerOf(v) |
| 57 | for _, pp := range *ps { |
| 58 | if p == pp[0] || p == pp[1] { |
| 59 | return p, true |
| 60 | } |
| 61 | } |
| 62 | *ps = append(*ps, [2]value.Pointer{p, p}) |
| 63 | return p, false |
| 64 | } |
| 65 | |
| 66 | func (ps *pointerReferences) Pop() { |
| 67 | *ps = (*ps)[:len(*ps)-1] |
| 68 | } |
| 69 | |
| 70 | // trunkReferences is metadata for a textNode indicating that the sub-tree |
| 71 | // represents the value for either pointer in a pair of references. |
| 72 | type trunkReferences struct{ pp [2]value.Pointer } |
| 73 | |
| 74 | // trunkReference is metadata for a textNode indicating that the sub-tree |
| 75 | // represents the value for the given pointer reference. |
| 76 | type trunkReference struct{ p value.Pointer } |
| 77 | |
| 78 | // leafReference is metadata for a textNode indicating that the value is |
| 79 | // truncated as it refers to another part of the tree (i.e., a trunk). |
| 80 | type leafReference struct{ p value.Pointer } |
| 81 | |
| 82 | func wrapTrunkReferences(pp [2]value.Pointer, s textNode) textNode { |
| 83 | switch { |
| 84 | case pp[0].IsNil(): |
| 85 | return &textWrap{Value: s, Metadata: trunkReference{pp[1]}} |
| 86 | case pp[1].IsNil(): |
| 87 | return &textWrap{Value: s, Metadata: trunkReference{pp[0]}} |
| 88 | case pp[0] == pp[1]: |
| 89 | return &textWrap{Value: s, Metadata: trunkReference{pp[0]}} |
| 90 | default: |
| 91 | return &textWrap{Value: s, Metadata: trunkReferences{pp}} |
| 92 | } |
| 93 | } |
| 94 | func wrapTrunkReference(p value.Pointer, printAddress bool, s textNode) textNode { |
| 95 | var prefix string |
| 96 | if printAddress { |
| 97 | prefix = formatPointer(p, true) |
| 98 | } |
| 99 | return &textWrap{Prefix: prefix, Value: s, Metadata: trunkReference{p}} |
| 100 | } |
| 101 | func makeLeafReference(p value.Pointer, printAddress bool) textNode { |
| 102 | out := &textWrap{Prefix: "(", Value: textEllipsis, Suffix: ")"} |
| 103 | var prefix string |
| 104 | if printAddress { |
| 105 | prefix = formatPointer(p, true) |
| 106 | } |
| 107 | return &textWrap{Prefix: prefix, Value: out, Metadata: leafReference{p}} |
| 108 | } |
| 109 | |
| 110 | // resolveReferences walks the textNode tree searching for any leaf reference |
| 111 | // metadata and resolves each against the corresponding trunk references. |
| 112 | // Since pointer addresses in memory are not particularly readable to the user, |
| 113 | // it replaces each pointer value with an arbitrary and unique reference ID. |
| 114 | func resolveReferences(s textNode) { |
| 115 | var walkNodes func(textNode, func(textNode)) |
| 116 | walkNodes = func(s textNode, f func(textNode)) { |
| 117 | f(s) |
| 118 | switch s := s.(type) { |
| 119 | case *textWrap: |
| 120 | walkNodes(s.Value, f) |
| 121 | case textList: |
| 122 | for _, r := range s { |
| 123 | walkNodes(r.Value, f) |
| 124 | } |
| 125 | } |
| 126 | } |
| 127 | |
| 128 | // Collect all trunks and leaves with reference metadata. |
| 129 | var trunks, leaves []*textWrap |
| 130 | walkNodes(s, func(s textNode) { |
| 131 | if s, ok := s.(*textWrap); ok { |
| 132 | switch s.Metadata.(type) { |
| 133 | case leafReference: |
| 134 | leaves = append(leaves, s) |
| 135 | case trunkReference, trunkReferences: |
| 136 | trunks = append(trunks, s) |
| 137 | } |
| 138 | } |
| 139 | }) |
| 140 | |
| 141 | // No leaf references to resolve. |
| 142 | if len(leaves) == 0 { |
| 143 | return |
| 144 | } |
| 145 | |
| 146 | // Collect the set of all leaf references to resolve. |
| 147 | leafPtrs := make(map[value.Pointer]bool) |
| 148 | for _, leaf := range leaves { |
| 149 | leafPtrs[leaf.Metadata.(leafReference).p] = true |
| 150 | } |
| 151 | |
| 152 | // Collect the set of trunk pointers that are always paired together. |
| 153 | // This allows us to assign a single ID to both pointers for brevity. |
| 154 | // If a pointer in a pair ever occurs by itself or as a different pair, |
| 155 | // then the pair is broken. |
| 156 | pairedTrunkPtrs := make(map[value.Pointer]value.Pointer) |
| 157 | unpair := func(p value.Pointer) { |
| 158 | if !pairedTrunkPtrs[p].IsNil() { |
| 159 | pairedTrunkPtrs[pairedTrunkPtrs[p]] = value.Pointer{} // invalidate other half |
| 160 | } |
| 161 | pairedTrunkPtrs[p] = value.Pointer{} // invalidate this half |
| 162 | } |
| 163 | for _, trunk := range trunks { |
| 164 | switch p := trunk.Metadata.(type) { |
| 165 | case trunkReference: |
| 166 | unpair(p.p) // standalone pointer cannot be part of a pair |
| 167 | case trunkReferences: |
| 168 | p0, ok0 := pairedTrunkPtrs[p.pp[0]] |
| 169 | p1, ok1 := pairedTrunkPtrs[p.pp[1]] |
| 170 | switch { |
| 171 | case !ok0 && !ok1: |
| 172 | // Register the newly seen pair. |
| 173 | pairedTrunkPtrs[p.pp[0]] = p.pp[1] |
| 174 | pairedTrunkPtrs[p.pp[1]] = p.pp[0] |
| 175 | case ok0 && ok1 && p0 == p.pp[1] && p1 == p.pp[0]: |
| 176 | // Exact pair already seen; do nothing. |
| 177 | default: |
| 178 | // Pair conflicts with some other pair; break all pairs. |
| 179 | unpair(p.pp[0]) |
| 180 | unpair(p.pp[1]) |
| 181 | } |
| 182 | } |
| 183 | } |
| 184 | |
| 185 | // Correlate each pointer referenced by leaves to a unique identifier, |
| 186 | // and print the IDs for each trunk that matches those pointers. |
| 187 | var nextID uint |
| 188 | ptrIDs := make(map[value.Pointer]uint) |
| 189 | newID := func() uint { |
| 190 | id := nextID |
| 191 | nextID++ |
| 192 | return id |
| 193 | } |
| 194 | for _, trunk := range trunks { |
| 195 | switch p := trunk.Metadata.(type) { |
| 196 | case trunkReference: |
| 197 | if print := leafPtrs[p.p]; print { |
| 198 | id, ok := ptrIDs[p.p] |
| 199 | if !ok { |
| 200 | id = newID() |
| 201 | ptrIDs[p.p] = id |
| 202 | } |
| 203 | trunk.Prefix = updateReferencePrefix(trunk.Prefix, formatReference(id)) |
| 204 | } |
| 205 | case trunkReferences: |
| 206 | print0 := leafPtrs[p.pp[0]] |
| 207 | print1 := leafPtrs[p.pp[1]] |
| 208 | if print0 || print1 { |
| 209 | id0, ok0 := ptrIDs[p.pp[0]] |
| 210 | id1, ok1 := ptrIDs[p.pp[1]] |
| 211 | isPair := pairedTrunkPtrs[p.pp[0]] == p.pp[1] && pairedTrunkPtrs[p.pp[1]] == p.pp[0] |
| 212 | if isPair { |
| 213 | var id uint |
| 214 | assert(ok0 == ok1) // must be seen together or not at all |
| 215 | if ok0 { |
| 216 | assert(id0 == id1) // must have the same ID |
| 217 | id = id0 |
| 218 | } else { |
| 219 | id = newID() |
| 220 | ptrIDs[p.pp[0]] = id |
| 221 | ptrIDs[p.pp[1]] = id |
| 222 | } |
| 223 | trunk.Prefix = updateReferencePrefix(trunk.Prefix, formatReference(id)) |
| 224 | } else { |
| 225 | if print0 && !ok0 { |
| 226 | id0 = newID() |
| 227 | ptrIDs[p.pp[0]] = id0 |
| 228 | } |
| 229 | if print1 && !ok1 { |
| 230 | id1 = newID() |
| 231 | ptrIDs[p.pp[1]] = id1 |
| 232 | } |
| 233 | switch { |
| 234 | case print0 && print1: |
| 235 | trunk.Prefix = updateReferencePrefix(trunk.Prefix, formatReference(id0)+","+formatReference(id1)) |
| 236 | case print0: |
| 237 | trunk.Prefix = updateReferencePrefix(trunk.Prefix, formatReference(id0)) |
| 238 | case print1: |
| 239 | trunk.Prefix = updateReferencePrefix(trunk.Prefix, formatReference(id1)) |
| 240 | } |
| 241 | } |
| 242 | } |
| 243 | } |
| 244 | } |
| 245 | |
| 246 | // Update all leaf references with the unique identifier. |
| 247 | for _, leaf := range leaves { |
| 248 | if id, ok := ptrIDs[leaf.Metadata.(leafReference).p]; ok { |
| 249 | leaf.Prefix = updateReferencePrefix(leaf.Prefix, formatReference(id)) |
| 250 | } |
| 251 | } |
| 252 | } |
| 253 | |
| 254 | func formatReference(id uint) string { |
| 255 | return fmt.Sprintf("ref#%d", id) |
| 256 | } |
| 257 | |
| 258 | func updateReferencePrefix(prefix, ref string) string { |
| 259 | if prefix == "" { |
| 260 | return pointerDelimPrefix + ref + pointerDelimSuffix |
| 261 | } |
| 262 | suffix := strings.TrimPrefix(prefix, pointerDelimPrefix) |
| 263 | return pointerDelimPrefix + ref + ": " + suffix |
| 264 | } |