php小编小新带来了一篇关于使用goroutine构建Zip的技巧文章。在这篇文章中，我们将了解如何利用goroutine并发执行Zip操作，以提高程序的效率。此外，我们还将讨论切片超出范围的问题，并介绍如何使用容量为4096的切片来解决这个问题。无论你是初学者还是有经验的开发者，本文都将帮助你更好地理解和应用goroutine和切片相关的知识。让我们一起来探索吧！
问题内容
我正在尝试通过添加 goroutine 来处理每个必须存档的文件来改进构建 zip 的函数。
但最终却以恐慌告终
panic：运行时错误：切片超出范围[4126：4096]
目标目录包含 190 个文件（500 mo）。
我实在不明白出了什么问题
预先感谢您的帮助
功能：
func buildarchive() error {
var files []string
err := filepath.walk("/tmp/dir-to-zip", func(filepath string, info os.fileinfo, err error) error {
if info.isdir() {
return nil
}
if err != nil {
fmt.println(err)
return err
}
files = append(files, filepath)
return nil
})
if err != nil {
return err
}
bundle, err := os.create("/tmp/archive.zip")
if err != nil {
return err
}
bundlewriter := zip.newwriter(bundle)
var wg sync.waitgroup
wg.add(len(files))
for _, filepath := range files {
go func(filepath string) {
defer wg.done()
relpath := strings.trimprefix(filepath, fmt.sprintf("%v/", filepath.dir("/tmp/dir-to-zip")))
bundlefile, err := bundlewriter.create(relpath)
if err != nil {
fmt.println(err)
}
fsfile, err := os.open(filepath)
if err != nil {
fmt.println(err)
}
_, err = io.copy(bundlefile, fsfile)
if err != nil {
fmt.println(err)
}
}(filepath)
}
wg.wait()
err = bundlewriter.close()
if err != nil {
return err
}
return nil
}
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错误发生在这里：
_, err = io.copy(bundlefile, fsfile)
if err != nil {
fmt.println(err)
}
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堆栈跟踪：
goroutine 48 [running]:
bufio.(*Writer).Write(0xc00002a100, {0xc00041a400?, 0x3d?, 0xc00041a400?})
/usr/local/go/src/bufio/bufio.go:670 +0x1c8
archive/zip.(*countWriter).Write(0xc00000c138, {0xc00041a400?, 0x3d?, 0x4afa20?})
/usr/local/go/src/archive/zip/writer.go:601 +0x2e
io.WriteString({0x4e7538, 0xc00000c138}, {0xc0000212c9, 0x3d})
/usr/local/go/src/io/io.go:314 +0x91
archive/zip.writeHeader({0x4e7538, 0xc00000c138}, 0xc000220090)
/usr/local/go/src/archive/zip/writer.go:422 +0x5ec
archive/zip.(*Writer).CreateHeader(0xc0000760a0, 0xc00021e1b0)
/usr/local/go/src/archive/zip/writer.go:378 +0x797
archive/zip.(*Writer).Create(0x4e7698?, {0xc0000212c9, 0x3d})
/usr/local/go/src/archive/zip/writer.go:223 +0x6c
main.BuildArchive.func2({0xc0000212c0, 0x46})
/home/simba/go/src/foobar/main.go:79 +0x1c5
created by main.BuildArchive
/home/simba/go/src/foobar/main.go:73 +0x5aa
panic: runtime error: slice bounds out of range [:4126] with capacity 4096
goroutine 6 [running]:
bufio.(*Writer).Flush(0xc00002a100)
/usr/local/go/src/bufio/bufio.go:634 +0x171
bufio.(*Writer).Write(0xc00002a100, {0xc0001b4200?, 0xc000199b20?, 0xc000199b20?})
/usr/local/go/src/bufio/bufio.go:672 +0xd8
archive/zip.(*countWriter).Write(0xc00000c138, {0xc0001b4200?, 0x0?, 0xc000199b40?})
/usr/local/go/src/archive/zip/writer.go:601 +0x2e
archive/zip.(*countWriter).Write(0xc000220018, {0xc0001b4200?, 0xc0001b02c0?, 0xc0001b02f0?})
/usr/local/go/src/archive/zip/writer.go:601 +0x2e
compress/flate.(*huffmanBitWriter).write(...)
/usr/local/go/src/compress/flate/huffman_bit_writer.go:136
compress/flate.(*huffmanBitWriter).writeCode(0xc0001b41e0?, {0x6000?, 0x22?})
/usr/local/go/src/compress/flate/huffman_bit_writer.go:347 +0xe5
compress/flate.(*huffmanBitWriter).writeTokens(0xc0001b41e0, {0xc002558000, 0x4001, 0x403f800000403f?}, {0xc0001aa900, 0x11e, 0x108129000000000f?}, {0xc0001ac100, 0x1e, 0x1e})
/usr/local/go/src/compress/flate/huffman_bit_writer.go:583 +0xb9
compress/flate.(*huffmanBitWriter).writeBlock(0xc0001b41e0, {0xc002558000?, 0x20?, 0xd79?}, 0x0, {0x0, 0x0, 0x0})
/usr/local/go/src/compress/flate/huffman_bit_writer.go:495 +0x490
compress/flate.(*compressor).writeBlock(0xc0005a2000, {0xc002558000?, 0xc000032f00?, 0xc000199d28?}, 0x47739b?)
/usr/local/go/src/compress/flate/deflate.go:170 +0x9c
compress/flate.(*compressor).deflate(0xc0005a2000)
/usr/local/go/src/compress/flate/deflate.go:509 +0x59b
compress/flate.(*compressor).write(0xc0005a2000, {0xc00256a000?, 0x8000, 0xf311b6fd?})
/usr/local/go/src/compress/flate/deflate.go:554 +0x82
compress/flate.(*Writer).Write(...)
/usr/local/go/src/compress/flate/deflate.go:712
archive/zip.(*pooledFlateWriter).Write(0xc00020c040?, {0xc00256a000?, 0x8000?, 0x4af140?})
/usr/local/go/src/archive/zip/register.go:51 +0xc5
archive/zip.(*countWriter).Write(...)
/usr/local/go/src/archive/zip/writer.go:601
archive/zip.(*fileWriter).Write(0xc000222000, {0xc00256a000, 0x8000, 0x8000})
/usr/local/go/src/archive/zip/writer.go:533 +0x97
io.copyBuffer({0x4e7558, 0xc000222000}, {0x4e7678, 0xc0001f8008}, {0x0, 0x0, 0x0})
/usr/local/go/src/io/io.go:428 +0x204
io.Copy(...)
/usr/local/go/src/io/io.go:385
main.BuildArchive.func2({0xc00001c0c0, 0x35})
/home/simba/go/src/foobar/main.go:89 +0x385
created by main.BuildArchive
/home/simba/go/src/foobar/main.go:73 +0x5aa
exit status 2
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解决方法
zip.Writer 并发使用不安全。您启动多个 goroutine，每个 goroutine 创建并写入 zip 条目（文件）。
Writer.Create() 记录：
创建使用提供的名称将文件添加到 zip 文件中。它返回一个 Writer，文件内容应写入其中。
[...] 在下次调用 Create、CreateHeader 或 Close 之前，必须将文件内容写入 io.Writer。
您不能同时创建 zip。每个 zip 条目的 io.Writers 写入相同的底层文件（或一般情况下相同的 io.Writer），即使您的应用程序没有出现恐慌或崩溃，生成的 zip 存档也可能无效。
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