--- /dev/null
+// Copyright 2017, 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.md file.
+
+// Package cmp determines equality of values.
+//
+// This package is intended to be a more powerful and safer alternative to
+// reflect.DeepEqual for comparing whether two values are semantically equal.
+// It is intended to only be used in tests, as performance is not a goal and
+// it may panic if it cannot compare the values. Its propensity towards
+// panicking means that its unsuitable for production environments where a
+// spurious panic may be fatal.
+//
+// The primary features of cmp are:
+//
+// • When the default behavior of equality does not suit the needs of the test,
+// custom equality functions can override the equality operation.
+// For example, an equality function may report floats as equal so long as they
+// are within some tolerance of each other.
+//
+// • Types that have an Equal method may use that method to determine equality.
+// This allows package authors to determine the equality operation for the types
+// that they define.
+//
+// • If no custom equality functions are used and no Equal method is defined,
+// equality is determined by recursively comparing the primitive kinds on both
+// values, much like reflect.DeepEqual. Unlike reflect.DeepEqual, unexported
+// fields are not compared by default; they result in panics unless suppressed
+// by using an Ignore option (see cmpopts.IgnoreUnexported) or explicitly
+// compared using the Exporter option.
+package cmp
+
+import (
+ "fmt"
+ "reflect"
+ "strings"
+
+ "github.com/google/go-cmp/cmp/internal/diff"
+ "github.com/google/go-cmp/cmp/internal/flags"
+ "github.com/google/go-cmp/cmp/internal/function"
+ "github.com/google/go-cmp/cmp/internal/value"
+)
+
+// Equal reports whether x and y are equal by recursively applying the
+// following rules in the given order to x and y and all of their sub-values:
+//
+// • Let S be the set of all Ignore, Transformer, and Comparer options that
+// remain after applying all path filters, value filters, and type filters.
+// If at least one Ignore exists in S, then the comparison is ignored.
+// If the number of Transformer and Comparer options in S is greater than one,
+// then Equal panics because it is ambiguous which option to use.
+// If S contains a single Transformer, then use that to transform the current
+// values and recursively call Equal on the output values.
+// If S contains a single Comparer, then use that to compare the current values.
+// Otherwise, evaluation proceeds to the next rule.
+//
+// • If the values have an Equal method of the form "(T) Equal(T) bool" or
+// "(T) Equal(I) bool" where T is assignable to I, then use the result of
+// x.Equal(y) even if x or y is nil. Otherwise, no such method exists and
+// evaluation proceeds to the next rule.
+//
+// • Lastly, try to compare x and y based on their basic kinds.
+// Simple kinds like booleans, integers, floats, complex numbers, strings, and
+// channels are compared using the equivalent of the == operator in Go.
+// Functions are only equal if they are both nil, otherwise they are unequal.
+//
+// Structs are equal if recursively calling Equal on all fields report equal.
+// If a struct contains unexported fields, Equal panics unless an Ignore option
+// (e.g., cmpopts.IgnoreUnexported) ignores that field or the Exporter option
+// explicitly permits comparing the unexported field.
+//
+// Slices are equal if they are both nil or both non-nil, where recursively
+// calling Equal on all non-ignored slice or array elements report equal.
+// Empty non-nil slices and nil slices are not equal; to equate empty slices,
+// consider using cmpopts.EquateEmpty.
+//
+// Maps are equal if they are both nil or both non-nil, where recursively
+// calling Equal on all non-ignored map entries report equal.
+// Map keys are equal according to the == operator.
+// To use custom comparisons for map keys, consider using cmpopts.SortMaps.
+// Empty non-nil maps and nil maps are not equal; to equate empty maps,
+// consider using cmpopts.EquateEmpty.
+//
+// Pointers and interfaces are equal if they are both nil or both non-nil,
+// where they have the same underlying concrete type and recursively
+// calling Equal on the underlying values reports equal.
+//
+// Before recursing into a pointer, slice element, or map, the current path
+// is checked to detect whether the address has already been visited.
+// If there is a cycle, then the pointed at values are considered equal
+// only if both addresses were previously visited in the same path step.
+func Equal(x, y interface{}, opts ...Option) bool {
+ s := newState(opts)
+ s.compareAny(rootStep(x, y))
+ return s.result.Equal()
+}
+
+// Diff returns a human-readable report of the differences between two values.
+// It returns an empty string if and only if Equal returns true for the same
+// input values and options.
+//
+// The output is displayed as a literal in pseudo-Go syntax.
+// At the start of each line, a "-" prefix indicates an element removed from x,
+// a "+" prefix to indicates an element added to y, and the lack of a prefix
+// indicates an element common to both x and y. If possible, the output
+// uses fmt.Stringer.String or error.Error methods to produce more humanly
+// readable outputs. In such cases, the string is prefixed with either an
+// 's' or 'e' character, respectively, to indicate that the method was called.
+//
+// Do not depend on this output being stable. If you need the ability to
+// programmatically interpret the difference, consider using a custom Reporter.
+func Diff(x, y interface{}, opts ...Option) string {
+ s := newState(opts)
+
+ // Optimization: If there are no other reporters, we can optimize for the
+ // common case where the result is equal (and thus no reported difference).
+ // This avoids the expensive construction of a difference tree.
+ if len(s.reporters) == 0 {
+ s.compareAny(rootStep(x, y))
+ if s.result.Equal() {
+ return ""
+ }
+ s.result = diff.Result{} // Reset results
+ }
+
+ r := new(defaultReporter)
+ s.reporters = append(s.reporters, reporter{r})
+ s.compareAny(rootStep(x, y))
+ d := r.String()
+ if (d == "") != s.result.Equal() {
+ panic("inconsistent difference and equality results")
+ }
+ return d
+}
+
+// rootStep constructs the first path step. If x and y have differing types,
+// then they are stored within an empty interface type.
+func rootStep(x, y interface{}) PathStep {
+ vx := reflect.ValueOf(x)
+ vy := reflect.ValueOf(y)
+
+ // If the inputs are different types, auto-wrap them in an empty interface
+ // so that they have the same parent type.
+ var t reflect.Type
+ if !vx.IsValid() || !vy.IsValid() || vx.Type() != vy.Type() {
+ t = reflect.TypeOf((*interface{})(nil)).Elem()
+ if vx.IsValid() {
+ vvx := reflect.New(t).Elem()
+ vvx.Set(vx)
+ vx = vvx
+ }
+ if vy.IsValid() {
+ vvy := reflect.New(t).Elem()
+ vvy.Set(vy)
+ vy = vvy
+ }
+ } else {
+ t = vx.Type()
+ }
+
+ return &pathStep{t, vx, vy}
+}
+
+type state struct {
+ // These fields represent the "comparison state".
+ // Calling statelessCompare must not result in observable changes to these.
+ result diff.Result // The current result of comparison
+ curPath Path // The current path in the value tree
+ curPtrs pointerPath // The current set of visited pointers
+ reporters []reporter // Optional reporters
+
+ // recChecker checks for infinite cycles applying the same set of
+ // transformers upon the output of itself.
+ recChecker recChecker
+
+ // dynChecker triggers pseudo-random checks for option correctness.
+ // It is safe for statelessCompare to mutate this value.
+ dynChecker dynChecker
+
+ // These fields, once set by processOption, will not change.
+ exporters []exporter // List of exporters for structs with unexported fields
+ opts Options // List of all fundamental and filter options
+}
+
+func newState(opts []Option) *state {
+ // Always ensure a validator option exists to validate the inputs.
+ s := &state{opts: Options{validator{}}}
+ s.curPtrs.Init()
+ s.processOption(Options(opts))
+ return s
+}
+
+func (s *state) processOption(opt Option) {
+ switch opt := opt.(type) {
+ case nil:
+ case Options:
+ for _, o := range opt {
+ s.processOption(o)
+ }
+ case coreOption:
+ type filtered interface {
+ isFiltered() bool
+ }
+ if fopt, ok := opt.(filtered); ok && !fopt.isFiltered() {
+ panic(fmt.Sprintf("cannot use an unfiltered option: %v", opt))
+ }
+ s.opts = append(s.opts, opt)
+ case exporter:
+ s.exporters = append(s.exporters, opt)
+ case reporter:
+ s.reporters = append(s.reporters, opt)
+ default:
+ panic(fmt.Sprintf("unknown option %T", opt))
+ }
+}
+
+// statelessCompare compares two values and returns the result.
+// This function is stateless in that it does not alter the current result,
+// or output to any registered reporters.
+func (s *state) statelessCompare(step PathStep) diff.Result {
+ // We do not save and restore curPath and curPtrs because all of the
+ // compareX methods should properly push and pop from them.
+ // It is an implementation bug if the contents of the paths differ from
+ // when calling this function to when returning from it.
+
+ oldResult, oldReporters := s.result, s.reporters
+ s.result = diff.Result{} // Reset result
+ s.reporters = nil // Remove reporters to avoid spurious printouts
+ s.compareAny(step)
+ res := s.result
+ s.result, s.reporters = oldResult, oldReporters
+ return res
+}
+
+func (s *state) compareAny(step PathStep) {
+ // Update the path stack.
+ s.curPath.push(step)
+ defer s.curPath.pop()
+ for _, r := range s.reporters {
+ r.PushStep(step)
+ defer r.PopStep()
+ }
+ s.recChecker.Check(s.curPath)
+
+ // Cycle-detection for slice elements (see NOTE in compareSlice).
+ t := step.Type()
+ vx, vy := step.Values()
+ if si, ok := step.(SliceIndex); ok && si.isSlice && vx.IsValid() && vy.IsValid() {
+ px, py := vx.Addr(), vy.Addr()
+ if eq, visited := s.curPtrs.Push(px, py); visited {
+ s.report(eq, reportByCycle)
+ return
+ }
+ defer s.curPtrs.Pop(px, py)
+ }
+
+ // Rule 1: Check whether an option applies on this node in the value tree.
+ if s.tryOptions(t, vx, vy) {
+ return
+ }
+
+ // Rule 2: Check whether the type has a valid Equal method.
+ if s.tryMethod(t, vx, vy) {
+ return
+ }
+
+ // Rule 3: Compare based on the underlying kind.
+ switch t.Kind() {
+ case reflect.Bool:
+ s.report(vx.Bool() == vy.Bool(), 0)
+ case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+ s.report(vx.Int() == vy.Int(), 0)
+ case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+ s.report(vx.Uint() == vy.Uint(), 0)
+ case reflect.Float32, reflect.Float64:
+ s.report(vx.Float() == vy.Float(), 0)
+ case reflect.Complex64, reflect.Complex128:
+ s.report(vx.Complex() == vy.Complex(), 0)
+ case reflect.String:
+ s.report(vx.String() == vy.String(), 0)
+ case reflect.Chan, reflect.UnsafePointer:
+ s.report(vx.Pointer() == vy.Pointer(), 0)
+ case reflect.Func:
+ s.report(vx.IsNil() && vy.IsNil(), 0)
+ case reflect.Struct:
+ s.compareStruct(t, vx, vy)
+ case reflect.Slice, reflect.Array:
+ s.compareSlice(t, vx, vy)
+ case reflect.Map:
+ s.compareMap(t, vx, vy)
+ case reflect.Ptr:
+ s.comparePtr(t, vx, vy)
+ case reflect.Interface:
+ s.compareInterface(t, vx, vy)
+ default:
+ panic(fmt.Sprintf("%v kind not handled", t.Kind()))
+ }
+}
+
+func (s *state) tryOptions(t reflect.Type, vx, vy reflect.Value) bool {
+ // Evaluate all filters and apply the remaining options.
+ if opt := s.opts.filter(s, t, vx, vy); opt != nil {
+ opt.apply(s, vx, vy)
+ return true
+ }
+ return false
+}
+
+func (s *state) tryMethod(t reflect.Type, vx, vy reflect.Value) bool {
+ // Check if this type even has an Equal method.
+ m, ok := t.MethodByName("Equal")
+ if !ok || !function.IsType(m.Type, function.EqualAssignable) {
+ return false
+ }
+
+ eq := s.callTTBFunc(m.Func, vx, vy)
+ s.report(eq, reportByMethod)
+ return true
+}
+
+func (s *state) callTRFunc(f, v reflect.Value, step Transform) reflect.Value {
+ v = sanitizeValue(v, f.Type().In(0))
+ if !s.dynChecker.Next() {
+ return f.Call([]reflect.Value{v})[0]
+ }
+
+ // Run the function twice and ensure that we get the same results back.
+ // We run in goroutines so that the race detector (if enabled) can detect
+ // unsafe mutations to the input.
+ c := make(chan reflect.Value)
+ go detectRaces(c, f, v)
+ got := <-c
+ want := f.Call([]reflect.Value{v})[0]
+ if step.vx, step.vy = got, want; !s.statelessCompare(step).Equal() {
+ // To avoid false-positives with non-reflexive equality operations,
+ // we sanity check whether a value is equal to itself.
+ if step.vx, step.vy = want, want; !s.statelessCompare(step).Equal() {
+ return want
+ }
+ panic(fmt.Sprintf("non-deterministic function detected: %s", function.NameOf(f)))
+ }
+ return want
+}
+
+func (s *state) callTTBFunc(f, x, y reflect.Value) bool {
+ x = sanitizeValue(x, f.Type().In(0))
+ y = sanitizeValue(y, f.Type().In(1))
+ if !s.dynChecker.Next() {
+ return f.Call([]reflect.Value{x, y})[0].Bool()
+ }
+
+ // Swapping the input arguments is sufficient to check that
+ // f is symmetric and deterministic.
+ // We run in goroutines so that the race detector (if enabled) can detect
+ // unsafe mutations to the input.
+ c := make(chan reflect.Value)
+ go detectRaces(c, f, y, x)
+ got := <-c
+ want := f.Call([]reflect.Value{x, y})[0].Bool()
+ if !got.IsValid() || got.Bool() != want {
+ panic(fmt.Sprintf("non-deterministic or non-symmetric function detected: %s", function.NameOf(f)))
+ }
+ return want
+}
+
+func detectRaces(c chan<- reflect.Value, f reflect.Value, vs ...reflect.Value) {
+ var ret reflect.Value
+ defer func() {
+ recover() // Ignore panics, let the other call to f panic instead
+ c <- ret
+ }()
+ ret = f.Call(vs)[0]
+}
+
+// sanitizeValue converts nil interfaces of type T to those of type R,
+// assuming that T is assignable to R.
+// Otherwise, it returns the input value as is.
+func sanitizeValue(v reflect.Value, t reflect.Type) reflect.Value {
+ // TODO(≥go1.10): Workaround for reflect bug (https://golang.org/issue/22143).
+ if !flags.AtLeastGo110 {
+ if v.Kind() == reflect.Interface && v.IsNil() && v.Type() != t {
+ return reflect.New(t).Elem()
+ }
+ }
+ return v
+}
+
+func (s *state) compareStruct(t reflect.Type, vx, vy reflect.Value) {
+ var addr bool
+ var vax, vay reflect.Value // Addressable versions of vx and vy
+
+ var mayForce, mayForceInit bool
+ step := StructField{&structField{}}
+ for i := 0; i < t.NumField(); i++ {
+ step.typ = t.Field(i).Type
+ step.vx = vx.Field(i)
+ step.vy = vy.Field(i)
+ step.name = t.Field(i).Name
+ step.idx = i
+ step.unexported = !isExported(step.name)
+ if step.unexported {
+ if step.name == "_" {
+ continue
+ }
+ // Defer checking of unexported fields until later to give an
+ // Ignore a chance to ignore the field.
+ if !vax.IsValid() || !vay.IsValid() {
+ // For retrieveUnexportedField to work, the parent struct must
+ // be addressable. Create a new copy of the values if
+ // necessary to make them addressable.
+ addr = vx.CanAddr() || vy.CanAddr()
+ vax = makeAddressable(vx)
+ vay = makeAddressable(vy)
+ }
+ if !mayForceInit {
+ for _, xf := range s.exporters {
+ mayForce = mayForce || xf(t)
+ }
+ mayForceInit = true
+ }
+ step.mayForce = mayForce
+ step.paddr = addr
+ step.pvx = vax
+ step.pvy = vay
+ step.field = t.Field(i)
+ }
+ s.compareAny(step)
+ }
+}
+
+func (s *state) compareSlice(t reflect.Type, vx, vy reflect.Value) {
+ isSlice := t.Kind() == reflect.Slice
+ if isSlice && (vx.IsNil() || vy.IsNil()) {
+ s.report(vx.IsNil() && vy.IsNil(), 0)
+ return
+ }
+
+ // NOTE: It is incorrect to call curPtrs.Push on the slice header pointer
+ // since slices represents a list of pointers, rather than a single pointer.
+ // The pointer checking logic must be handled on a per-element basis
+ // in compareAny.
+ //
+ // A slice header (see reflect.SliceHeader) in Go is a tuple of a starting
+ // pointer P, a length N, and a capacity C. Supposing each slice element has
+ // a memory size of M, then the slice is equivalent to the list of pointers:
+ // [P+i*M for i in range(N)]
+ //
+ // For example, v[:0] and v[:1] are slices with the same starting pointer,
+ // but they are clearly different values. Using the slice pointer alone
+ // violates the assumption that equal pointers implies equal values.
+
+ step := SliceIndex{&sliceIndex{pathStep: pathStep{typ: t.Elem()}, isSlice: isSlice}}
+ withIndexes := func(ix, iy int) SliceIndex {
+ if ix >= 0 {
+ step.vx, step.xkey = vx.Index(ix), ix
+ } else {
+ step.vx, step.xkey = reflect.Value{}, -1
+ }
+ if iy >= 0 {
+ step.vy, step.ykey = vy.Index(iy), iy
+ } else {
+ step.vy, step.ykey = reflect.Value{}, -1
+ }
+ return step
+ }
+
+ // Ignore options are able to ignore missing elements in a slice.
+ // However, detecting these reliably requires an optimal differencing
+ // algorithm, for which diff.Difference is not.
+ //
+ // Instead, we first iterate through both slices to detect which elements
+ // would be ignored if standing alone. The index of non-discarded elements
+ // are stored in a separate slice, which diffing is then performed on.
+ var indexesX, indexesY []int
+ var ignoredX, ignoredY []bool
+ for ix := 0; ix < vx.Len(); ix++ {
+ ignored := s.statelessCompare(withIndexes(ix, -1)).NumDiff == 0
+ if !ignored {
+ indexesX = append(indexesX, ix)
+ }
+ ignoredX = append(ignoredX, ignored)
+ }
+ for iy := 0; iy < vy.Len(); iy++ {
+ ignored := s.statelessCompare(withIndexes(-1, iy)).NumDiff == 0
+ if !ignored {
+ indexesY = append(indexesY, iy)
+ }
+ ignoredY = append(ignoredY, ignored)
+ }
+
+ // Compute an edit-script for slices vx and vy (excluding ignored elements).
+ edits := diff.Difference(len(indexesX), len(indexesY), func(ix, iy int) diff.Result {
+ return s.statelessCompare(withIndexes(indexesX[ix], indexesY[iy]))
+ })
+
+ // Replay the ignore-scripts and the edit-script.
+ var ix, iy int
+ for ix < vx.Len() || iy < vy.Len() {
+ var e diff.EditType
+ switch {
+ case ix < len(ignoredX) && ignoredX[ix]:
+ e = diff.UniqueX
+ case iy < len(ignoredY) && ignoredY[iy]:
+ e = diff.UniqueY
+ default:
+ e, edits = edits[0], edits[1:]
+ }
+ switch e {
+ case diff.UniqueX:
+ s.compareAny(withIndexes(ix, -1))
+ ix++
+ case diff.UniqueY:
+ s.compareAny(withIndexes(-1, iy))
+ iy++
+ default:
+ s.compareAny(withIndexes(ix, iy))
+ ix++
+ iy++
+ }
+ }
+}
+
+func (s *state) compareMap(t reflect.Type, vx, vy reflect.Value) {
+ if vx.IsNil() || vy.IsNil() {
+ s.report(vx.IsNil() && vy.IsNil(), 0)
+ return
+ }
+
+ // Cycle-detection for maps.
+ if eq, visited := s.curPtrs.Push(vx, vy); visited {
+ s.report(eq, reportByCycle)
+ return
+ }
+ defer s.curPtrs.Pop(vx, vy)
+
+ // We combine and sort the two map keys so that we can perform the
+ // comparisons in a deterministic order.
+ step := MapIndex{&mapIndex{pathStep: pathStep{typ: t.Elem()}}}
+ for _, k := range value.SortKeys(append(vx.MapKeys(), vy.MapKeys()...)) {
+ step.vx = vx.MapIndex(k)
+ step.vy = vy.MapIndex(k)
+ step.key = k
+ if !step.vx.IsValid() && !step.vy.IsValid() {
+ // It is possible for both vx and vy to be invalid if the
+ // key contained a NaN value in it.
+ //
+ // Even with the ability to retrieve NaN keys in Go 1.12,
+ // there still isn't a sensible way to compare the values since
+ // a NaN key may map to multiple unordered values.
+ // The most reasonable way to compare NaNs would be to compare the
+ // set of values. However, this is impossible to do efficiently
+ // since set equality is provably an O(n^2) operation given only
+ // an Equal function. If we had a Less function or Hash function,
+ // this could be done in O(n*log(n)) or O(n), respectively.
+ //
+ // Rather than adding complex logic to deal with NaNs, make it
+ // the user's responsibility to compare such obscure maps.
+ const help = "consider providing a Comparer to compare the map"
+ panic(fmt.Sprintf("%#v has map key with NaNs\n%s", s.curPath, help))
+ }
+ s.compareAny(step)
+ }
+}
+
+func (s *state) comparePtr(t reflect.Type, vx, vy reflect.Value) {
+ if vx.IsNil() || vy.IsNil() {
+ s.report(vx.IsNil() && vy.IsNil(), 0)
+ return
+ }
+
+ // Cycle-detection for pointers.
+ if eq, visited := s.curPtrs.Push(vx, vy); visited {
+ s.report(eq, reportByCycle)
+ return
+ }
+ defer s.curPtrs.Pop(vx, vy)
+
+ vx, vy = vx.Elem(), vy.Elem()
+ s.compareAny(Indirect{&indirect{pathStep{t.Elem(), vx, vy}}})
+}
+
+func (s *state) compareInterface(t reflect.Type, vx, vy reflect.Value) {
+ if vx.IsNil() || vy.IsNil() {
+ s.report(vx.IsNil() && vy.IsNil(), 0)
+ return
+ }
+ vx, vy = vx.Elem(), vy.Elem()
+ if vx.Type() != vy.Type() {
+ s.report(false, 0)
+ return
+ }
+ s.compareAny(TypeAssertion{&typeAssertion{pathStep{vx.Type(), vx, vy}}})
+}
+
+func (s *state) report(eq bool, rf resultFlags) {
+ if rf&reportByIgnore == 0 {
+ if eq {
+ s.result.NumSame++
+ rf |= reportEqual
+ } else {
+ s.result.NumDiff++
+ rf |= reportUnequal
+ }
+ }
+ for _, r := range s.reporters {
+ r.Report(Result{flags: rf})
+ }
+}
+
+// recChecker tracks the state needed to periodically perform checks that
+// user provided transformers are not stuck in an infinitely recursive cycle.
+type recChecker struct{ next int }
+
+// Check scans the Path for any recursive transformers and panics when any
+// recursive transformers are detected. Note that the presence of a
+// recursive Transformer does not necessarily imply an infinite cycle.
+// As such, this check only activates after some minimal number of path steps.
+func (rc *recChecker) Check(p Path) {
+ const minLen = 1 << 16
+ if rc.next == 0 {
+ rc.next = minLen
+ }
+ if len(p) < rc.next {
+ return
+ }
+ rc.next <<= 1
+
+ // Check whether the same transformer has appeared at least twice.
+ var ss []string
+ m := map[Option]int{}
+ for _, ps := range p {
+ if t, ok := ps.(Transform); ok {
+ t := t.Option()
+ if m[t] == 1 { // Transformer was used exactly once before
+ tf := t.(*transformer).fnc.Type()
+ ss = append(ss, fmt.Sprintf("%v: %v => %v", t, tf.In(0), tf.Out(0)))
+ }
+ m[t]++
+ }
+ }
+ if len(ss) > 0 {
+ const warning = "recursive set of Transformers detected"
+ const help = "consider using cmpopts.AcyclicTransformer"
+ set := strings.Join(ss, "\n\t")
+ panic(fmt.Sprintf("%s:\n\t%s\n%s", warning, set, help))
+ }
+}
+
+// dynChecker tracks the state needed to periodically perform checks that
+// user provided functions are symmetric and deterministic.
+// The zero value is safe for immediate use.
+type dynChecker struct{ curr, next int }
+
+// Next increments the state and reports whether a check should be performed.
+//
+// Checks occur every Nth function call, where N is a triangular number:
+// 0 1 3 6 10 15 21 28 36 45 55 66 78 91 105 120 136 153 171 190 ...
+// See https://en.wikipedia.org/wiki/Triangular_number
+//
+// This sequence ensures that the cost of checks drops significantly as
+// the number of functions calls grows larger.
+func (dc *dynChecker) Next() bool {
+ ok := dc.curr == dc.next
+ if ok {
+ dc.curr = 0
+ dc.next++
+ }
+ dc.curr++
+ return ok
+}
+
+// makeAddressable returns a value that is always addressable.
+// It returns the input verbatim if it is already addressable,
+// otherwise it creates a new value and returns an addressable copy.
+func makeAddressable(v reflect.Value) reflect.Value {
+ if v.CanAddr() {
+ return v
+ }
+ vc := reflect.New(v.Type()).Elem()
+ vc.Set(v)
+ return vc
+}
projects / dotfiles / .git / blobdiff