mirror of https://github.com/golang/go.git
79 lines
2.0 KiB
Go
79 lines
2.0 KiB
Go
// Copyright 2019 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package diff implements a Diff function that compare two inputs
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// using the 'diff' tool.
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package diff
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import (
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"bytes"
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exec "internal/execabs"
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"io/ioutil"
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"os"
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"runtime"
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)
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// Returns diff of two arrays of bytes in diff tool format.
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func Diff(prefix string, b1, b2 []byte) ([]byte, error) {
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f1, err := writeTempFile(prefix, b1)
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if err != nil {
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return nil, err
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}
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defer os.Remove(f1)
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f2, err := writeTempFile(prefix, b2)
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if err != nil {
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return nil, err
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}
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defer os.Remove(f2)
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cmd := "diff"
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if runtime.GOOS == "plan9" {
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cmd = "/bin/ape/diff"
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}
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data, err := exec.Command(cmd, "-u", f1, f2).CombinedOutput()
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if len(data) > 0 {
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// diff exits with a non-zero status when the files don't match.
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// Ignore that failure as long as we get output.
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err = nil
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}
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// If we are on Windows and the diff is Cygwin diff,
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// machines can get into a state where every Cygwin
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// command works fine but prints a useless message like:
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//
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// Cygwin WARNING:
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// Couldn't compute FAST_CWD pointer. This typically occurs if you're using
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// an older Cygwin version on a newer Windows. Please update to the latest
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// available Cygwin version from https://cygwin.com/. If the problem persists,
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// please see https://cygwin.com/problems.html
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//
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// Skip over that message and just return the actual diff.
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if len(data) > 0 && !bytes.HasPrefix(data, []byte("--- ")) {
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i := bytes.Index(data, []byte("\n--- "))
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if i >= 0 && i < 80*10 && bytes.Contains(data[:i], []byte("://cygwin.com/")) {
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data = data[i+1:]
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}
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}
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return data, err
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}
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func writeTempFile(prefix string, data []byte) (string, error) {
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file, err := ioutil.TempFile("", prefix)
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if err != nil {
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return "", err
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}
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_, err = file.Write(data)
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if err1 := file.Close(); err == nil {
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err = err1
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}
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if err != nil {
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os.Remove(file.Name())
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return "", err
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}
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return file.Name(), nil
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}
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