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// Copyright 2021 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 fuzz
import (
"reflect"
)
func isMinimizable(t reflect.Type) bool {
return t == reflect.TypeOf("") || t == reflect.TypeOf([]byte(nil))
}
func minimizeBytes(v []byte, try func([]byte) bool, shouldStop func() bool) {
tmp := make([]byte, len(v))
// If minimization was successful at any point during minimizeBytes,
// then the vals slice in (*workerServer).minimizeInput will point to
// tmp. Since tmp is altered while making new candidates, we need to
// make sure that it is equal to the correct value, v, before exiting
// this function.
defer copy(tmp, v)
// First, try to cut the tail.
for n := 1024; n != 0; n /= 2 {
for len(v) > n {
if shouldStop() {
return
}
candidate := v[:len(v)-n]
if !try(candidate) {
break
}
// Set v to the new value to continue iterating.
v = candidate
}
}
// Then, try to remove each individual byte.
for i := 0; i < len(v)-1; i++ {
if shouldStop() {
return
}
candidate := tmp[:len(v)-1]
copy(candidate[:i], v[:i])
copy(candidate[i:], v[i+1:])
if !try(candidate) {
continue
}
// Update v to delete the value at index i.
copy(v[i:], v[i+1:])
v = v[:len(candidate)]
// v[i] is now different, so decrement i to redo this iteration
// of the loop with the new value.
i--
}
// Then, try to remove each possible subset of bytes.
for i := 0; i < len(v)-1; i++ {
copy(tmp, v[:i])
for j := len(v); j > i+1; j-- {
if shouldStop() {
return
}
candidate := tmp[:len(v)-j+i]
copy(candidate[i:], v[j:])
if !try(candidate) {
continue
}
// Update v and reset the loop with the new length.
copy(v[i:], v[j:])
v = v[:len(candidate)]
j = len(v)
}
}
// Then, try to make it more simplified and human-readable by trying to replace each
// byte with a printable character.
printableChars := []byte("012789ABCXYZabcxyz !\"#$%&'()*+,.")
for i, b := range v {
if shouldStop() {
return
}
for _, pc := range printableChars {
v[i] = pc
if try(v) {
// Successful. Move on to the next byte in v.
break
}
// Unsuccessful. Revert v[i] back to original value.
v[i] = b
}
}
}
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