/*
DESCRIPTION
  fuzz.go provides a function with the required signature such that it may be
  accessed by go-fuzz. The function will compare the output of C level_prefix
  parser with a go version.

AUTHORS
  Saxon A. Nelson-Milton <saxon@ausocean.org>

LICENSE
  Copyright (C) 2019 the Australian Ocean Lab (AusOcean).

  It is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  for more details.

  You should have received a copy of the GNU General Public License
  in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

// +build gofuzz

package fuzzParseLevelPrefix

/*
#include "../helpers.c"
#include "parse_level_prefix.h"
*/
import "C"
import (
	"bytes"
	"fmt"
	"unsafe"

	"bitbucket.org/ausocean/av/codec/h264/h264dec"
	"bitbucket.org/ausocean/av/codec/h264/h264dec/bits"
)

func Fuzz(data []byte) int {
	// Create C based BitReader based on data.
	cbr := C.new_BitReader((*C.char)(unsafe.Pointer(&data[0])), C.int(len(data)))

	// Get the level_prefix from the C code. If got is < 0, then the C code
	// doesn't like it and we shouldn't have that input in the corpus, so return -1.
	got := C.read_levelprefix(cbr)
	if got < 0 {
		return -1
	}

	// Get the level_prefix from the go code. If the C code was okay with this
	// input, but the go code isn't then that's bad, so panic - want crasher info.
	want, err := h264dec.FuzzParseLevelPrefix(bits.NewBitReader(bytes.NewReader(data)))
	if err != nil {
		panic(fmt.Sprintf("error from go parseLevelPrefix: %v", err))
	}

	// Compare the result of the C and go code. If they are not the same then
	// panic - our go code is not doing what it should.
	if int(want) != int(got) {
		panic(fmt.Sprintf("did not get expected results for input: %v\nGot: %v\nWant: %v\n", data, got, want))
	}
	return 1
}