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gitea/vendor/github.com/mschoch/smat/smat.go

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2018-05-19 08:49:46 -04:00
// Copyright (c) 2016 Marty Schoch
// 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 smat
import (
"bufio"
"bytes"
"fmt"
"io"
"io/ioutil"
"log"
"math/rand"
)
// Logger is a configurable logger used by this package
// by default output is discarded
var Logger = log.New(ioutil.Discard, "smat ", log.LstdFlags)
// Context is a container for any user state
type Context interface{}
// State is a function which describes which action to perform in the event
// that a particular byte is seen
type State func(next byte) ActionID
// PercentAction describes the frequency with which an action should occur
// for example: Action{Percent:10, Action:DonateMoney} means that 10% of
// the time you should donate money.
type PercentAction struct {
Percent int
Action ActionID
}
// Action is any function which returns the next state to transition to
// it can optionally mutate the provided context object
// if any error occurs, it may return an error which will abort execution
type Action func(Context) (State, error)
// ActionID is a unique identifier for an action
type ActionID int
// NopAction does nothing and simply continues to the next input
var NopAction ActionID = -1
// ActionMap is a mapping form ActionID to Action
type ActionMap map[ActionID]Action
func (a ActionMap) findSetupTeardown(setup, teardown ActionID) (Action, Action, error) {
setupFunc, ok := a[setup]
if !ok {
return nil, nil, ErrSetupMissing
}
teardownFunc, ok := a[teardown]
if !ok {
return nil, nil, ErrTeardownMissing
}
return setupFunc, teardownFunc, nil
}
// Fuzz runs the fuzzing state machine with the provided context
// first, the setup action is executed unconditionally
// the start state is determined by this action
// actionMap is a lookup table for all actions
// the data byte slice determines all future state transitions
// finally, the teardown action is executed unconditionally for cleanup
func Fuzz(ctx Context, setup, teardown ActionID, actionMap ActionMap, data []byte) int {
reader := bytes.NewReader(data)
err := runReader(ctx, setup, teardown, actionMap, reader, nil)
if err != nil {
panic(err)
}
return 1
}
// Longevity runs the state machine with the provided context
// first, the setup action is executed unconditionally
// the start state is determined by this action
// actionMap is a lookup table for all actions
// random bytes are generated to determine all future state transitions
// finally, the teardown action is executed unconditionally for cleanup
func Longevity(ctx Context, setup, teardown ActionID, actionMap ActionMap, seed int64, closeChan chan struct{}) error {
source := rand.NewSource(seed)
return runReader(ctx, setup, teardown, actionMap, rand.New(source), closeChan)
}
var (
// ErrSetupMissing is returned when the setup action cannot be found
ErrSetupMissing = fmt.Errorf("setup action missing")
// ErrTeardownMissing is returned when the teardown action cannot be found
ErrTeardownMissing = fmt.Errorf("teardown action missing")
// ErrClosed is returned when the closeChan was closed to cancel the op
ErrClosed = fmt.Errorf("closed")
// ErrActionNotPossible is returned when an action is encountered in a
// FuzzCase that is not possible in the current state
ErrActionNotPossible = fmt.Errorf("action not possible in state")
)
func runReader(ctx Context, setup, teardown ActionID, actionMap ActionMap, r io.Reader, closeChan chan struct{}) error {
setupFunc, teardownFunc, err := actionMap.findSetupTeardown(setup, teardown)
if err != nil {
return err
}
Logger.Printf("invoking setup action")
state, err := setupFunc(ctx)
if err != nil {
return err
}
defer func() {
Logger.Printf("invoking teardown action")
_, _ = teardownFunc(ctx)
}()
reader := bufio.NewReader(r)
for next, err := reader.ReadByte(); err == nil; next, err = reader.ReadByte() {
select {
case <-closeChan:
return ErrClosed
default:
actionID := state(next)
action, ok := actionMap[actionID]
if !ok {
Logger.Printf("no such action defined, continuing")
continue
}
Logger.Printf("invoking action - %d", actionID)
state, err = action(ctx)
if err != nil {
Logger.Printf("it was action %d that returned err %v", actionID, err)
return err
}
}
}
return err
}
// PercentExecute interprets the next byte as a random value and normalizes it
// to values 0-99, it then looks to see which action should be execued based
// on the action distributions
func PercentExecute(next byte, pas ...PercentAction) ActionID {
percent := int(99 * int(next) / 255)
sofar := 0
for _, pa := range pas {
sofar = sofar + pa.Percent
if percent < sofar {
return pa.Action
}
}
return NopAction
}