// Copyright 2025 The etcd Authors
//
// 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 crc provides utility function for cyclic redundancy check
// algorithms.
package crc

import (
	"hash"
	"hash/crc32"
)

// The size of a CRC-32 checksum in bytes.
const Size = 4

type digest struct {
	crc uint32
	tab *crc32.Table
}

// New creates a new hash.Hash32 computing the CRC-32 checksum
// using the polynomial represented by the Table.
// Modified by xiangli to take a prevcrc.
func New(prev uint32, tab *crc32.Table) hash.Hash32 { return &digest{prev, tab} }

func (d *digest) Size() int { return Size }

func (d *digest) BlockSize() int { return 1 }

func (d *digest) Reset() { d.crc = 0 }

func (d *digest) Write(p []byte) (n int, err error) {
	d.crc = crc32.Update(d.crc, d.tab, p)
	return len(p), nil
}

func (d *digest) Sum32() uint32 { return d.crc }

func (d *digest) Sum(in []byte) []byte {
	s := d.Sum32()
	return append(in, byte(s>>24), byte(s>>16), byte(s>>8), byte(s))
}