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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 } } }