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+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package fuzz
+
+import (
+ "fmt"
+ "math/rand"
+ "reflect"
+ "time"
+)
+
+// fuzzFuncMap is a map from a type to a fuzzFunc that handles that type.
+type fuzzFuncMap map[reflect.Type]reflect.Value
+
+// Fuzzer knows how to fill any object with random fields.
+type Fuzzer struct {
+ fuzzFuncs fuzzFuncMap
+ defaultFuzzFuncs fuzzFuncMap
+ r *rand.Rand
+ nilChance float64
+ minElements int
+ maxElements int
+}
+
+// New returns a new Fuzzer. Customize your Fuzzer further by calling Funcs,
+// RandSource, NilChance, or NumElements in any order.
+func New() *Fuzzer {
+ f := &Fuzzer{
+ defaultFuzzFuncs: fuzzFuncMap{
+ reflect.TypeOf(&time.Time{}): reflect.ValueOf(fuzzTime),
+ },
+
+ fuzzFuncs: fuzzFuncMap{},
+ r: rand.New(rand.NewSource(time.Now().UnixNano())),
+ nilChance: .2,
+ minElements: 1,
+ maxElements: 10,
+ }
+ return f
+}
+
+// Funcs adds each entry in fuzzFuncs as a custom fuzzing function.
+//
+// Each entry in fuzzFuncs must be a function taking two parameters.
+// The first parameter must be a pointer or map. It is the variable that
+// function will fill with random data. The second parameter must be a
+// fuzz.Continue, which will provide a source of randomness and a way
+// to automatically continue fuzzing smaller pieces of the first parameter.
+//
+// These functions are called sensibly, e.g., if you wanted custom string
+// fuzzing, the function `func(s *string, c fuzz.Continue)` would get
+// called and passed the address of strings. Maps and pointers will always
+// be made/new'd for you, ignoring the NilChange option. For slices, it
+// doesn't make much sense to pre-create them--Fuzzer doesn't know how
+// long you want your slice--so take a pointer to a slice, and make it
+// yourself. (If you don't want your map/pointer type pre-made, take a
+// pointer to it, and make it yourself.) See the examples for a range of
+// custom functions.
+func (f *Fuzzer) Funcs(fuzzFuncs ...interface{}) *Fuzzer {
+ for i := range fuzzFuncs {
+ v := reflect.ValueOf(fuzzFuncs[i])
+ if v.Kind() != reflect.Func {
+ panic("Need only funcs!")
+ }
+ t := v.Type()
+ if t.NumIn() != 2 || t.NumOut() != 0 {
+ panic("Need 2 in and 0 out params!")
+ }
+ argT := t.In(0)
+ switch argT.Kind() {
+ case reflect.Ptr, reflect.Map:
+ default:
+ panic("fuzzFunc must take pointer or map type")
+ }
+ if t.In(1) != reflect.TypeOf(Continue{}) {
+ panic("fuzzFunc's second parameter must be type fuzz.Continue")
+ }
+ f.fuzzFuncs[argT] = v
+ }
+ return f
+}
+
+// RandSource causes f to get values from the given source of randomness.
+// Use if you want deterministic fuzzing.
+func (f *Fuzzer) RandSource(s rand.Source) *Fuzzer {
+ f.r = rand.New(s)
+ return f
+}
+
+// NilChance sets the probability of creating a nil pointer, map, or slice to
+// 'p'. 'p' should be between 0 (no nils) and 1 (all nils), inclusive.
+func (f *Fuzzer) NilChance(p float64) *Fuzzer {
+ if p < 0 || p > 1 {
+ panic("p should be between 0 and 1, inclusive.")
+ }
+ f.nilChance = p
+ return f
+}
+
+// NumElements sets the minimum and maximum number of elements that will be
+// added to a non-nil map or slice.
+func (f *Fuzzer) NumElements(atLeast, atMost int) *Fuzzer {
+ if atLeast > atMost {
+ panic("atLeast must be <= atMost")
+ }
+ if atLeast < 0 {
+ panic("atLeast must be >= 0")
+ }
+ f.minElements = atLeast
+ f.maxElements = atMost
+ return f
+}
+
+func (f *Fuzzer) genElementCount() int {
+ if f.minElements == f.maxElements {
+ return f.minElements
+ }
+ return f.minElements + f.r.Intn(f.maxElements-f.minElements+1)
+}
+
+func (f *Fuzzer) genShouldFill() bool {
+ return f.r.Float64() > f.nilChance
+}
+
+// Fuzz recursively fills all of obj's fields with something random. First
+// this tries to find a custom fuzz function (see Funcs). If there is no
+// custom function this tests whether the object implements fuzz.Interface and,
+// if so, calls Fuzz on it to fuzz itself. If that fails, this will see if
+// there is a default fuzz function provided by this package. If all of that
+// fails, this will generate random values for all primitive fields and then
+// recurse for all non-primitives.
+//
+// Not safe for cyclic or tree-like structs!
+//
+// obj must be a pointer. Only exported (public) fields can be set (thanks, golang :/ )
+// Intended for tests, so will panic on bad input or unimplemented fields.
+func (f *Fuzzer) Fuzz(obj interface{}) {
+ v := reflect.ValueOf(obj)
+ if v.Kind() != reflect.Ptr {
+ panic("needed ptr!")
+ }
+ v = v.Elem()
+ f.doFuzz(v, 0)
+}
+
+// FuzzNoCustom is just like Fuzz, except that any custom fuzz function for
+// obj's type will not be called and obj will not be tested for fuzz.Interface
+// conformance. This applies only to obj and not other instances of obj's
+// type.
+// Not safe for cyclic or tree-like structs!
+// obj must be a pointer. Only exported (public) fields can be set (thanks, golang :/ )
+// Intended for tests, so will panic on bad input or unimplemented fields.
+func (f *Fuzzer) FuzzNoCustom(obj interface{}) {
+ v := reflect.ValueOf(obj)
+ if v.Kind() != reflect.Ptr {
+ panic("needed ptr!")
+ }
+ v = v.Elem()
+ f.doFuzz(v, flagNoCustomFuzz)
+}
+
+const (
+ // Do not try to find a custom fuzz function. Does not apply recursively.
+ flagNoCustomFuzz uint64 = 1 << iota
+)
+
+func (f *Fuzzer) doFuzz(v reflect.Value, flags uint64) {
+ if !v.CanSet() {
+ return
+ }
+
+ if flags&flagNoCustomFuzz == 0 {
+ // Check for both pointer and non-pointer custom functions.
+ if v.CanAddr() && f.tryCustom(v.Addr()) {
+ return
+ }
+ if f.tryCustom(v) {
+ return
+ }
+ }
+
+ if fn, ok := fillFuncMap[v.Kind()]; ok {
+ fn(v, f.r)
+ return
+ }
+ switch v.Kind() {
+ case reflect.Map:
+ if f.genShouldFill() {
+ v.Set(reflect.MakeMap(v.Type()))
+ n := f.genElementCount()
+ for i := 0; i < n; i++ {
+ key := reflect.New(v.Type().Key()).Elem()
+ f.doFuzz(key, 0)
+ val := reflect.New(v.Type().Elem()).Elem()
+ f.doFuzz(val, 0)
+ v.SetMapIndex(key, val)
+ }
+ return
+ }
+ v.Set(reflect.Zero(v.Type()))
+ case reflect.Ptr:
+ if f.genShouldFill() {
+ v.Set(reflect.New(v.Type().Elem()))
+ f.doFuzz(v.Elem(), 0)
+ return
+ }
+ v.Set(reflect.Zero(v.Type()))
+ case reflect.Slice:
+ if f.genShouldFill() {
+ n := f.genElementCount()
+ v.Set(reflect.MakeSlice(v.Type(), n, n))
+ for i := 0; i < n; i++ {
+ f.doFuzz(v.Index(i), 0)
+ }
+ return
+ }
+ v.Set(reflect.Zero(v.Type()))
+ case reflect.Array:
+ if f.genShouldFill() {
+ n := v.Len()
+ for i := 0; i < n; i++ {
+ f.doFuzz(v.Index(i), 0)
+ }
+ return
+ }
+ v.Set(reflect.Zero(v.Type()))
+ case reflect.Struct:
+ for i := 0; i < v.NumField(); i++ {
+ f.doFuzz(v.Field(i), 0)
+ }
+ case reflect.Chan:
+ fallthrough
+ case reflect.Func:
+ fallthrough
+ case reflect.Interface:
+ fallthrough
+ default:
+ panic(fmt.Sprintf("Can't handle %#v", v.Interface()))
+ }
+}
+
+// tryCustom searches for custom handlers, and returns true iff it finds a match
+// and successfully randomizes v.
+func (f *Fuzzer) tryCustom(v reflect.Value) bool {
+ // First: see if we have a fuzz function for it.
+ doCustom, ok := f.fuzzFuncs[v.Type()]
+ if !ok {
+ // Second: see if it can fuzz itself.
+ if v.CanInterface() {
+ intf := v.Interface()
+ if fuzzable, ok := intf.(Interface); ok {
+ fuzzable.Fuzz(Continue{f: f, Rand: f.r})
+ return true
+ }
+ }
+ // Finally: see if there is a default fuzz function.
+ doCustom, ok = f.defaultFuzzFuncs[v.Type()]
+ if !ok {
+ return false
+ }
+ }
+
+ switch v.Kind() {
+ case reflect.Ptr:
+ if v.IsNil() {
+ if !v.CanSet() {
+ return false
+ }
+ v.Set(reflect.New(v.Type().Elem()))
+ }
+ case reflect.Map:
+ if v.IsNil() {
+ if !v.CanSet() {
+ return false
+ }
+ v.Set(reflect.MakeMap(v.Type()))
+ }
+ default:
+ return false
+ }
+
+ doCustom.Call([]reflect.Value{v, reflect.ValueOf(Continue{
+ f: f,
+ Rand: f.r,
+ })})
+ return true
+}
+
+// Interface represents an object that knows how to fuzz itself. Any time we
+// find a type that implements this interface we will delegate the act of
+// fuzzing itself.
+type Interface interface {
+ Fuzz(c Continue)
+}
+
+// Continue can be passed to custom fuzzing functions to allow them to use
+// the correct source of randomness and to continue fuzzing their members.
+type Continue struct {
+ f *Fuzzer
+
+ // For convenience, Continue implements rand.Rand via embedding.
+ // Use this for generating any randomness if you want your fuzzing
+ // to be repeatable for a given seed.
+ *rand.Rand
+}
+
+// Fuzz continues fuzzing obj. obj must be a pointer.
+func (c Continue) Fuzz(obj interface{}) {
+ v := reflect.ValueOf(obj)
+ if v.Kind() != reflect.Ptr {
+ panic("needed ptr!")
+ }
+ v = v.Elem()
+ c.f.doFuzz(v, 0)
+}
+
+// FuzzNoCustom continues fuzzing obj, except that any custom fuzz function for
+// obj's type will not be called and obj will not be tested for fuzz.Interface
+// conformance. This applies only to obj and not other instances of obj's
+// type.
+func (c Continue) FuzzNoCustom(obj interface{}) {
+ v := reflect.ValueOf(obj)
+ if v.Kind() != reflect.Ptr {
+ panic("needed ptr!")
+ }
+ v = v.Elem()
+ c.f.doFuzz(v, flagNoCustomFuzz)
+}
+
+// RandString makes a random string up to 20 characters long. The returned string
+// may include a variety of (valid) UTF-8 encodings.
+func (c Continue) RandString() string {
+ return randString(c.Rand)
+}
+
+// RandUint64 makes random 64 bit numbers.
+// Weirdly, rand doesn't have a function that gives you 64 random bits.
+func (c Continue) RandUint64() uint64 {
+ return randUint64(c.Rand)
+}
+
+// RandBool returns true or false randomly.
+func (c Continue) RandBool() bool {
+ return randBool(c.Rand)
+}
+
+func fuzzInt(v reflect.Value, r *rand.Rand) {
+ v.SetInt(int64(randUint64(r)))
+}
+
+func fuzzUint(v reflect.Value, r *rand.Rand) {
+ v.SetUint(randUint64(r))
+}
+
+func fuzzTime(t *time.Time, c Continue) {
+ var sec, nsec int64
+ // Allow for about 1000 years of random time values, which keeps things
+ // like JSON parsing reasonably happy.
+ sec = c.Rand.Int63n(1000 * 365 * 24 * 60 * 60)
+ c.Fuzz(&nsec)
+ *t = time.Unix(sec, nsec)
+}
+
+var fillFuncMap = map[reflect.Kind]func(reflect.Value, *rand.Rand){
+ reflect.Bool: func(v reflect.Value, r *rand.Rand) {
+ v.SetBool(randBool(r))
+ },
+ reflect.Int: fuzzInt,
+ reflect.Int8: fuzzInt,
+ reflect.Int16: fuzzInt,
+ reflect.Int32: fuzzInt,
+ reflect.Int64: fuzzInt,
+ reflect.Uint: fuzzUint,
+ reflect.Uint8: fuzzUint,
+ reflect.Uint16: fuzzUint,
+ reflect.Uint32: fuzzUint,
+ reflect.Uint64: fuzzUint,
+ reflect.Uintptr: fuzzUint,
+ reflect.Float32: func(v reflect.Value, r *rand.Rand) {
+ v.SetFloat(float64(r.Float32()))
+ },
+ reflect.Float64: func(v reflect.Value, r *rand.Rand) {
+ v.SetFloat(r.Float64())
+ },
+ reflect.Complex64: func(v reflect.Value, r *rand.Rand) {
+ panic("unimplemented")
+ },
+ reflect.Complex128: func(v reflect.Value, r *rand.Rand) {
+ panic("unimplemented")
+ },
+ reflect.String: func(v reflect.Value, r *rand.Rand) {
+ v.SetString(randString(r))
+ },
+ reflect.UnsafePointer: func(v reflect.Value, r *rand.Rand) {
+ panic("unimplemented")
+ },
+}
+
+// randBool returns true or false randomly.
+func randBool(r *rand.Rand) bool {
+ if r.Int()&1 == 1 {
+ return true
+ }
+ return false
+}
+
+type charRange struct {
+ first, last rune
+}
+
+// choose returns a random unicode character from the given range, using the
+// given randomness source.
+func (r *charRange) choose(rand *rand.Rand) rune {
+ count := int64(r.last - r.first)
+ return r.first + rune(rand.Int63n(count))
+}
+
+var unicodeRanges = []charRange{
+ {' ', '~'}, // ASCII characters
+ {'\u00a0', '\u02af'}, // Multi-byte encoded characters
+ {'\u4e00', '\u9fff'}, // Common CJK (even longer encodings)
+}
+
+// randString makes a random string up to 20 characters long. The returned string
+// may include a variety of (valid) UTF-8 encodings.
+func randString(r *rand.Rand) string {
+ n := r.Intn(20)
+ runes := make([]rune, n)
+ for i := range runes {
+ runes[i] = unicodeRanges[r.Intn(len(unicodeRanges))].choose(r)
+ }
+ return string(runes)
+}
+
+// randUint64 makes random 64 bit numbers.
+// Weirdly, rand doesn't have a function that gives you 64 random bits.
+func randUint64(r *rand.Rand) uint64 {
+ return uint64(r.Uint32())<<32 | uint64(r.Uint32())
+}