md5sum.go

Documentation: github.com/bazelbuild/rules_go/go/tools/builders

     1  // Copyright 2017 The Bazel Authors. All rights reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //    http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // md5sum replicates the equivalent functionality of the unix tool of the same name.
    16  package main
    17  
    18  import (
    19  	"crypto/md5"
    20  	"flag"
    21  	"fmt"
    22  	"io"
    23  	"log"
    24  	"os"
    25  	"path/filepath"
    26  )
    27  
    28  func md5SumFile(filename string) ([]byte, error) {
    29  	var result []byte
    30  	f, err := os.Open(filename)
    31  	if err != nil {
    32  		return result, err
    33  	}
    34  	defer f.Close()
    35  	hash := md5.New()
    36  	if _, err := io.Copy(hash, f); err != nil {
    37  		return nil, err
    38  	}
    39  	return hash.Sum(result), nil
    40  }
    41  
    42  func run(args []string) error {
    43  	// Prepare our flags
    44  	flags := flag.NewFlagSet("md5sum", flag.ExitOnError)
    45  	output := flags.String("output", "", "If set, write the results to this file, instead of stdout.")
    46  	if err := flags.Parse(args); err != nil {
    47  		return err
    48  	}
    49  	// print the outputs if we need not
    50  	to := os.Stdout
    51  	if *output != "" {
    52  		f, err := os.Create(*output)
    53  		if err != nil {
    54  			return err
    55  		}
    56  		defer f.Close()
    57  		to = f
    58  	}
    59  	for _, path := range flags.Args() {
    60  		walkFn := func(path string, info os.FileInfo, err error) error {
    61  			if err != nil {
    62  				return err
    63  			}
    64  			if info.IsDir() {
    65  				return nil
    66  			}
    67  
    68  			if b, err := md5SumFile(path); err != nil {
    69  				return err
    70  			} else {
    71  				fmt.Fprintf(to, "%s  %x\n", path, b)
    72  			}
    73  			return nil
    74  		}
    75  
    76  		if err := filepath.Walk(path, walkFn); err != nil {
    77  			return err
    78  		}
    79  	}
    80  	return nil
    81  }
    82  
    83  func main() {
    84  	log.SetFlags(0)
    85  	log.SetPrefix("GoMd5sum: ")
    86  	if err := run(os.Args[1:]); err != nil {
    87  		log.Fatal(err)
    88  	}
    89  }
    90
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