Initial commit.

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.

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

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)
+	}
+}