在 golang 中将 []byte 转换为 "virtual" 文件对象的简单方法？

Question

我知道有一些 Go 库可以创建整个文件系统，例如 VFS. But I only want to make a byte array into something that can fulfil the File 接口。

Answer 1

看起来很简单，自己可以模拟一下。

type MockFile struct {
    data    []byte
    isOpen  bool
    offset  int64
}

type MockFileInfo struct {
    mockFile *MockFile
}
func (mfi *MockFileInfo) Name() string       { return "MockFile" }
func (mfi *MockFileInfo) Size() int64        { return len(mfi.data) }
func (mfi *MockFileInfo) Mode() os.FileMode  { return os.ModeIrregular }
func (mfi *MockFileInfo) ModTime() time.Time { return time.Now() }
func (mfi *MockFileInfo) IsDir() bool        { return false }
func (mfi *MockFileInfo) Sys() interface     { return nil }

func (mf *MockFile) Read(p []byte) (n int, err error) {
    if mf.isOpen {
        n = copy(p, mf.data[mf.offset:])
        mf.offset += n
    } else {
        err = errors.New("Cannot read from closed MockFile")
    }
    return
}

func (mf *MockFile) Close() error {
    if !mf.isOpen {
        return errors.New("Cannot close an already closed MockFile")
    mf.isOpen = false
    return nil
}

func (mf *MockFile) Seek(offset int64, whence int) (ret int64, err error) {
    var relativeTo int64
    switch whence {
        case 0:
            relativeTo = 0
        case 1:
            relativeTo = mf.offset
        case 2:
            relativeTo = len(mf.data)
    }
    ret := relativeTo + offset
    if ret < 0 || ret > len(mf.data) {
        return -1, errors.New("New offset would fall outside of the MockFile")
    }
    mf.offset = ret
    return
}

func (mf *MockFile) Readdir(count int) ([]os.FileInfo, error) {
    if count <= 0 {
        return []os.FileInfo{}, nil
    }
    return []os.FileInfo{}, errors.New("MockFiles have no associated directory")
}

func (mf *MockFile) Stat() (os.FileInfo, error) {
    return MockFileInfo{mf}
}

func OpenMockFile(data []byte) *MockFile {
    mf := MockFile{data, true, 0}
}

Answer 2

标准库中没有现成的解决方案，但自己做起来并不难。

我们需要的是这个http.File接口：

type File interface {
        io.Closer
        io.Reader
        io.Seeker
        Readdir(count int) ([]os.FileInfo, error)
        Stat() (os.FileInfo, error)
}

请注意，我们可以利用 bytes.Reader to do the heavy task, as that alone implements io.Reader and io.Seeker. io.Closer 可以是 noop，并且 Readdir() 可以 return nil, nil 因为我们模拟的是文件而不是目录，它Readdir() 甚至不会被调用。

"hardest" 部分是将 Stat() 模拟为 return 实现 os.FileInfo.

的值

这是一个简单的模拟 FileInfo:

type myFileInfo struct {
    name string
    data []byte
}

func (mif myFileInfo) Name() string       { return mif.name }
func (mif myFileInfo) Size() int64        { return int64(len(mif.data)) }
func (mif myFileInfo) Mode() os.FileMode  { return 0444 }        // Read for all
func (mif myFileInfo) ModTime() time.Time { return time.Time{} } // Return anything
func (mif myFileInfo) IsDir() bool        { return false }
func (mif myFileInfo) Sys() interface{}   { return nil }

有了这些，我们就拥有了创建模拟 http.File:

的一切

type MyFile struct {
    *bytes.Reader
    mif myFileInfo
}

func (mf *MyFile) Close() error { return nil } // Noop, nothing to do

func (mf *MyFile) Readdir(count int) ([]os.FileInfo, error) {
    return nil, nil // We are not a directory but a single file
}

func (mf *MyFile) Stat() (os.FileInfo, error) {
    return mf.mif, nil
}

使用示例（在 Go Playground 上试用）：

data := []byte{0, 1, 2, 3}

mf := &MyFile{
    Reader: bytes.NewReader(data),
    mif: myFileInfo{
        name: "somename.txt",
        data: data,
    },
}

var f http.File = mf
_ = f

Answer 3

如果您正在寻找 gzip http2 推送的这个答案，您可以只使用以下选项：

options := &http.PushOptions{
                Header: http.Header{
                    "Accept-Encoding": r.Header["Accept-Encoding"],
                },
            }
            if err := pusher.Push(filePush, options); err != nil {
                log.Printf("Failed to push: %v", err)
                return
            }

在 golang 中将 []byte 转换为 "virtual" 文件对象的简单方法？

Simples way to make a []byte into a "virtual" File object in golang?

go

virtual-file