67 lines
1.8 KiB
Go
67 lines
1.8 KiB
Go
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// Copyright 2020 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 fs
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import "io"
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// ReadFileFS is the interface implemented by a file system
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// that provides an optimized implementation of ReadFile.
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type ReadFileFS interface {
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FS
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// ReadFile reads the named file and returns its contents.
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// A successful call returns a nil error, not io.EOF.
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// (Because ReadFile reads the whole file, the expected EOF
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// from the final Read is not treated as an error to be reported.)
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//
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// The caller is permitted to modify the returned byte slice.
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// This method should return a copy of the underlying data.
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ReadFile(name string) ([]byte, error)
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}
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// ReadFile reads the named file from the file system fs and returns its contents.
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// A successful call returns a nil error, not io.EOF.
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// (Because ReadFile reads the whole file, the expected EOF
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// from the final Read is not treated as an error to be reported.)
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//
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// If fs implements ReadFileFS, ReadFile calls fs.ReadFile.
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// Otherwise ReadFile calls fs.Open and uses Read and Close
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// on the returned file.
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func ReadFile(fsys FS, name string) ([]byte, error) {
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if fsys, ok := fsys.(ReadFileFS); ok {
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return fsys.ReadFile(name)
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}
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file, err := fsys.Open(name)
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if err != nil {
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return nil, err
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}
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defer file.Close()
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var size int
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if info, err := file.Stat(); err == nil {
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size64 := info.Size()
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if int64(int(size64)) == size64 {
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size = int(size64)
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}
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}
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data := make([]byte, 0, size+1)
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for {
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if len(data) >= cap(data) {
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d := append(data[:cap(data)], 0)
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data = d[:len(data)]
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}
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n, err := file.Read(data[len(data):cap(data)])
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data = data[:len(data)+n]
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if err != nil {
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if err == io.EOF {
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err = nil
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}
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return data, err
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}
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}
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}
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