GoToSocial/vendor/github.com/google/go-cmp/cmp/report_references.go

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// Copyright 2020, 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.
package cmp
import (
"fmt"
"reflect"
"strings"
"github.com/google/go-cmp/cmp/internal/flags"
"github.com/google/go-cmp/cmp/internal/value"
)
const (
pointerDelimPrefix = "⟪"
pointerDelimSuffix = "⟫"
)
// formatPointer prints the address of the pointer.
func formatPointer(p value.Pointer, withDelims bool) string {
v := p.Uintptr()
if flags.Deterministic {
v = 0xdeadf00f // Only used for stable testing purposes
}
if withDelims {
return pointerDelimPrefix + formatHex(uint64(v)) + pointerDelimSuffix
}
return formatHex(uint64(v))
}
// pointerReferences is a stack of pointers visited so far.
type pointerReferences [][2]value.Pointer
func (ps *pointerReferences) PushPair(vx, vy reflect.Value, d diffMode, deref bool) (pp [2]value.Pointer) {
if deref && vx.IsValid() {
vx = vx.Addr()
}
if deref && vy.IsValid() {
vy = vy.Addr()
}
switch d {
case diffUnknown, diffIdentical:
pp = [2]value.Pointer{value.PointerOf(vx), value.PointerOf(vy)}
case diffRemoved:
pp = [2]value.Pointer{value.PointerOf(vx), value.Pointer{}}
case diffInserted:
pp = [2]value.Pointer{value.Pointer{}, value.PointerOf(vy)}
}
*ps = append(*ps, pp)
return pp
}
func (ps *pointerReferences) Push(v reflect.Value) (p value.Pointer, seen bool) {
p = value.PointerOf(v)
for _, pp := range *ps {
if p == pp[0] || p == pp[1] {
return p, true
}
}
*ps = append(*ps, [2]value.Pointer{p, p})
return p, false
}
func (ps *pointerReferences) Pop() {
*ps = (*ps)[:len(*ps)-1]
}
// trunkReferences is metadata for a textNode indicating that the sub-tree
// represents the value for either pointer in a pair of references.
type trunkReferences struct{ pp [2]value.Pointer }
// trunkReference is metadata for a textNode indicating that the sub-tree
// represents the value for the given pointer reference.
type trunkReference struct{ p value.Pointer }
// leafReference is metadata for a textNode indicating that the value is
// truncated as it refers to another part of the tree (i.e., a trunk).
type leafReference struct{ p value.Pointer }
func wrapTrunkReferences(pp [2]value.Pointer, s textNode) textNode {
switch {
case pp[0].IsNil():
return &textWrap{Value: s, Metadata: trunkReference{pp[1]}}
case pp[1].IsNil():
return &textWrap{Value: s, Metadata: trunkReference{pp[0]}}
case pp[0] == pp[1]:
return &textWrap{Value: s, Metadata: trunkReference{pp[0]}}
default:
return &textWrap{Value: s, Metadata: trunkReferences{pp}}
}
}
func wrapTrunkReference(p value.Pointer, printAddress bool, s textNode) textNode {
var prefix string
if printAddress {
prefix = formatPointer(p, true)
}
return &textWrap{Prefix: prefix, Value: s, Metadata: trunkReference{p}}
}
func makeLeafReference(p value.Pointer, printAddress bool) textNode {
out := &textWrap{Prefix: "(", Value: textEllipsis, Suffix: ")"}
var prefix string
if printAddress {
prefix = formatPointer(p, true)
}
return &textWrap{Prefix: prefix, Value: out, Metadata: leafReference{p}}
}
// resolveReferences walks the textNode tree searching for any leaf reference
// metadata and resolves each against the corresponding trunk references.
// Since pointer addresses in memory are not particularly readable to the user,
// it replaces each pointer value with an arbitrary and unique reference ID.
func resolveReferences(s textNode) {
var walkNodes func(textNode, func(textNode))
walkNodes = func(s textNode, f func(textNode)) {
f(s)
switch s := s.(type) {
case *textWrap:
walkNodes(s.Value, f)
case textList:
for _, r := range s {
walkNodes(r.Value, f)
}
}
}
// Collect all trunks and leaves with reference metadata.
var trunks, leaves []*textWrap
walkNodes(s, func(s textNode) {
if s, ok := s.(*textWrap); ok {
switch s.Metadata.(type) {
case leafReference:
leaves = append(leaves, s)
case trunkReference, trunkReferences:
trunks = append(trunks, s)
}
}
})
// No leaf references to resolve.
if len(leaves) == 0 {
return
}
// Collect the set of all leaf references to resolve.
leafPtrs := make(map[value.Pointer]bool)
for _, leaf := range leaves {
leafPtrs[leaf.Metadata.(leafReference).p] = true
}
// Collect the set of trunk pointers that are always paired together.
// This allows us to assign a single ID to both pointers for brevity.
// If a pointer in a pair ever occurs by itself or as a different pair,
// then the pair is broken.
pairedTrunkPtrs := make(map[value.Pointer]value.Pointer)
unpair := func(p value.Pointer) {
if !pairedTrunkPtrs[p].IsNil() {
pairedTrunkPtrs[pairedTrunkPtrs[p]] = value.Pointer{} // invalidate other half
}
pairedTrunkPtrs[p] = value.Pointer{} // invalidate this half
}
for _, trunk := range trunks {
switch p := trunk.Metadata.(type) {
case trunkReference:
unpair(p.p) // standalone pointer cannot be part of a pair
case trunkReferences:
p0, ok0 := pairedTrunkPtrs[p.pp[0]]
p1, ok1 := pairedTrunkPtrs[p.pp[1]]
switch {
case !ok0 && !ok1:
// Register the newly seen pair.
pairedTrunkPtrs[p.pp[0]] = p.pp[1]
pairedTrunkPtrs[p.pp[1]] = p.pp[0]
case ok0 && ok1 && p0 == p.pp[1] && p1 == p.pp[0]:
// Exact pair already seen; do nothing.
default:
// Pair conflicts with some other pair; break all pairs.
unpair(p.pp[0])
unpair(p.pp[1])
}
}
}
// Correlate each pointer referenced by leaves to a unique identifier,
// and print the IDs for each trunk that matches those pointers.
var nextID uint
ptrIDs := make(map[value.Pointer]uint)
newID := func() uint {
id := nextID
nextID++
return id
}
for _, trunk := range trunks {
switch p := trunk.Metadata.(type) {
case trunkReference:
if print := leafPtrs[p.p]; print {
id, ok := ptrIDs[p.p]
if !ok {
id = newID()
ptrIDs[p.p] = id
}
trunk.Prefix = updateReferencePrefix(trunk.Prefix, formatReference(id))
}
case trunkReferences:
print0 := leafPtrs[p.pp[0]]
print1 := leafPtrs[p.pp[1]]
if print0 || print1 {
id0, ok0 := ptrIDs[p.pp[0]]
id1, ok1 := ptrIDs[p.pp[1]]
isPair := pairedTrunkPtrs[p.pp[0]] == p.pp[1] && pairedTrunkPtrs[p.pp[1]] == p.pp[0]
if isPair {
var id uint
assert(ok0 == ok1) // must be seen together or not at all
if ok0 {
assert(id0 == id1) // must have the same ID
id = id0
} else {
id = newID()
ptrIDs[p.pp[0]] = id
ptrIDs[p.pp[1]] = id
}
trunk.Prefix = updateReferencePrefix(trunk.Prefix, formatReference(id))
} else {
if print0 && !ok0 {
id0 = newID()
ptrIDs[p.pp[0]] = id0
}
if print1 && !ok1 {
id1 = newID()
ptrIDs[p.pp[1]] = id1
}
switch {
case print0 && print1:
trunk.Prefix = updateReferencePrefix(trunk.Prefix, formatReference(id0)+","+formatReference(id1))
case print0:
trunk.Prefix = updateReferencePrefix(trunk.Prefix, formatReference(id0))
case print1:
trunk.Prefix = updateReferencePrefix(trunk.Prefix, formatReference(id1))
}
}
}
}
}
// Update all leaf references with the unique identifier.
for _, leaf := range leaves {
if id, ok := ptrIDs[leaf.Metadata.(leafReference).p]; ok {
leaf.Prefix = updateReferencePrefix(leaf.Prefix, formatReference(id))
}
}
}
func formatReference(id uint) string {
return fmt.Sprintf("ref#%d", id)
}
func updateReferencePrefix(prefix, ref string) string {
if prefix == "" {
return pointerDelimPrefix + ref + pointerDelimSuffix
}
suffix := strings.TrimPrefix(prefix, pointerDelimPrefix)
return pointerDelimPrefix + ref + ": " + suffix
}