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Augusto Roman 5 years ago
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  1. 21
      LICENSE
  2. 35
      README.md
  3. 71
      main.go

21
LICENSE

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MIT License
Copyright (c) 2016 Augusto Roman
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

35
README.md

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# CRC
CRC is a simple command-line utility to compute various CRC values for one or
more files.
It supports three CRC algorithms (selected via `--mode=<alg>`):
* `crc64-ecma` (*default*) uses the [ECMA polynomial](https://godoc.org/hash/crc64#pkg-constants) to compute a 64-bit CRC.
* `crc64-iso` uses the [ISO polynomial](https://godoc.org/hash/crc64#pkg-constants) to compute a 64-bit CRC.
* `crc32` uses the [IEEE polynomial](https://godoc.org/hash/crc32#pkg-constants) to compute a 32-bit CRC. This is equivalent to the `crc32` linux binary.
If only a single file is specified on the command line, then only the hexadecimal hash is printed. If more than one file is specified, the output will be
```
<hash><tab><filename>
```
for each file.
## Installation
```bash
go get github.com/augustoroman/crc
```
## Usage
```bash
# Compute the default hash (crc64 w/ ECMA polynomial) of one or more files.
crc <file> [<file> ...]
# Compute the crc64 hash with ISO polynomial.
crc --mode=crc64-iso <file> [<file> ...]
# Compute the crc32 hash (with the IEEE polynomial).
crc --mode=crc32 <file> [<file> ...]
```
## License
This is released under the MIT license

71
main.go

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// CRC is a simple command-line utility to compute CRC values for one or more files.
package main
import (
"flag"
"fmt"
"hash"
"hash/crc32"
"hash/crc64"
"io"
"os"
)
func main() {
mode := flag.String("mode", "crc64-ecma",
"CRC method to use. Valid values are 'crc32' (IEEE), 'crc64-iso', and 'crc64-ecma'")
flag.Usage = func() {
fmt.Fprintf(os.Stderr, "Usage: %s [-mode=<MODE>] file [file ...]\n", os.Args[0])
flag.PrintDefaults()
}
flag.Parse()
hasher, err := NewHasher(*mode)
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(1)
}
if flag.NArg() == 0 {
fmt.Fprintf(os.Stderr, "Specify one or more filenames to checksum.\n")
os.Exit(2)
}
exitCode := 0
for _, filename := range flag.Args() {
hasher, _ = NewHasher(*mode)
f, err := os.Open(filename)
if err != nil {
exitCode = 3
fmt.Fprintf(os.Stderr, "Cannot open %q: %v\n", filename, err)
continue
}
_, err = io.Copy(hasher, f)
f.Close()
if err != nil {
exitCode = 3
fmt.Fprintf(os.Stderr, "Error reading %q: %v\n", filename, err)
continue
}
if flag.NArg() == 1 {
fmt.Printf("%0*x\n", hasher.Size(), hasher.Sum(nil))
} else {
fmt.Printf("%0*x\t%s\n", hasher.Size(), hasher.Sum(nil), filename)
}
}
os.Exit(exitCode)
}
func NewHasher(mode string) (hash.Hash, error) {
switch mode {
case "crc32", "crc32-ieee":
return crc32.NewIEEE(), nil
case "crc64-iso":
return crc64.New(crc64.MakeTable(crc64.ISO)), nil
case "crc64-ecma":
return crc64.New(crc64.MakeTable(crc64.ECMA)), nil
default:
return nil, fmt.Errorf("ERROR: Invalid mode %q", mode)
}
}
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