70 lines
1.3 KiB
Go
70 lines
1.3 KiB
Go
/*
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* Copyright 2022 The Dragonfly Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package main
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import (
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"crypto/sha256"
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"encoding/hex"
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"flag"
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"fmt"
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"io"
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"os"
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)
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var (
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offset = flag.Int64("offset", 0, "")
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length = flag.Int64("length", -1, "")
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file = flag.String("file", "", "")
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)
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func main() {
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flag.Parse()
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if len(*file) == 0 {
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os.Exit(1)
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}
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f, err := os.Open(*file)
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if err != nil {
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panic(err)
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}
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defer f.Close()
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if *offset > 0 {
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_, err := f.Seek(*offset, io.SeekStart)
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if err != nil {
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panic(err)
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}
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}
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var rd io.Reader = f
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if *length > -1 {
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rd = io.LimitReader(f, *length)
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}
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hash := sha256.New()
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n, err := io.Copy(hash, rd)
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if err != nil {
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panic(err)
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}
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if *length > -1 && n != *length {
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panic(io.ErrShortWrite)
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}
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fmt.Printf("%s %s", hex.EncodeToString(hash.Sum(nil)), *file)
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}
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