Add ReadFile helper function, ReadFileFS interface, and test.
Add ReadFile method to fstest.MapFS.
Add testing of ReadFile method to fstest.TestFS.
For #41190.
Change-Id: I5b6a41e2e582824e570463b698b635abaa436c32
Reviewed-on: https://go-review.googlesource.com/c/go/+/243912
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
os/signal, STR
< path/filepath
- < io/ioutil, os/exec
+ < io/ioutil, os/exec;
+
+ io/ioutil, os/exec, os/signal
< OS;
reflect !< OS;
--- /dev/null
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fs
+
+import "io"
+
+// ReadFileFS is the interface implemented by a file system
+// that provides an optimized implementation of ReadFile.
+type ReadFileFS interface {
+ FS
+
+ // ReadFile reads the named file and returns its contents.
+ // A successful call returns a nil error, not io.EOF.
+ // (Because ReadFile reads the whole file, the expected EOF
+ // from the final Read is not treated as an error to be reported.)
+ ReadFile(name string) ([]byte, error)
+}
+
+// ReadFile reads the named file from the file system fs and returns its contents.
+// A successful call returns a nil error, not io.EOF.
+// (Because ReadFile reads the whole file, the expected EOF
+// from the final Read is not treated as an error to be reported.)
+//
+// If fs implements ReadFileFS, ReadFile calls fs.ReadFile.
+// Otherwise ReadFile calls fs.Open and uses Read and Close
+// on the returned file.
+func ReadFile(fsys FS, name string) ([]byte, error) {
+ if fsys, ok := fsys.(ReadFileFS); ok {
+ return fsys.ReadFile(name)
+ }
+
+ file, err := fsys.Open(name)
+ if err != nil {
+ return nil, err
+ }
+ defer file.Close()
+
+ var size int
+ if info, err := file.Stat(); err == nil {
+ size64 := info.Size()
+ if int64(int(size64)) == size64 {
+ size = int(size64)
+ }
+ }
+
+ data := make([]byte, 0, size+1)
+ for {
+ if len(data) >= cap(data) {
+ d := append(data[:cap(data)], 0)
+ data = d[:len(data)]
+ }
+ n, err := file.Read(data[len(data):cap(data)])
+ data = data[:len(data)+n]
+ if err != nil {
+ if err == io.EOF {
+ err = nil
+ }
+ return data, err
+ }
+ }
+}
--- /dev/null
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package fs_test
+
+import (
+ . "io/fs"
+ "testing"
+ "testing/fstest"
+ "time"
+)
+
+var testFsys = fstest.MapFS{
+ "hello.txt": {
+ Data: []byte("hello, world"),
+ Mode: 0456,
+ ModTime: time.Now(),
+ Sys: &sysValue,
+ },
+}
+
+var sysValue int
+
+type readFileOnly struct{ ReadFileFS }
+
+func (readFileOnly) Open(name string) (File, error) { return nil, ErrNotExist }
+
+type openOnly struct{ FS }
+
+func TestReadFile(t *testing.T) {
+ // Test that ReadFile uses the method when present.
+ data, err := ReadFile(readFileOnly{testFsys}, "hello.txt")
+ if string(data) != "hello, world" || err != nil {
+ t.Fatalf(`ReadFile(readFileOnly, "hello.txt") = %q, %v, want %q, nil`, data, err, "hello, world")
+ }
+
+ // Test that ReadFile uses Open when the method is not present.
+ data, err = ReadFile(openOnly{testFsys}, "hello.txt")
+ if string(data) != "hello, world" || err != nil {
+ t.Fatalf(`ReadFile(openOnly, "hello.txt") = %q, %v, want %q, nil`, data, err, "hello, world")
+ }
+}
return &mapDir{name, mapFileInfo{elem, file}, list, 0}, nil
}
+// fsOnly is a wrapper that hides all but the fs.FS methods,
+// to avoid an infinite recursion when implementing special
+// methods in terms of helpers that would use them.
+// (In general, implementing these methods using the package fs helpers
+// is redundant and unnecessary, but having the methods may make
+// MapFS exercise more code paths when used in tests.)
+type fsOnly struct{ fs.FS }
+
+func (fsys MapFS) ReadFile(name string) ([]byte, error) {
+ return fs.ReadFile(fsOnly{fsys}, name)
+}
+
// A mapFileInfo implements fs.FileInfo and fs.DirEntry for a given map file.
type mapFileInfo struct {
name string
// The return value doesn't matter.
f.Close()
+ // Check that ReadFile works if present.
+ if fsys, ok := t.fsys.(fs.ReadFileFS); ok {
+ data2, err := fsys.ReadFile(file)
+ if err != nil {
+ t.errorf("%s: fsys.ReadFile: %v", file, err)
+ return
+ }
+ t.checkFileRead(file, "ReadAll vs fsys.ReadFile", data, data2)
+
+ t.checkBadPath(file, "ReadFile",
+ func(name string) error { _, err := fsys.ReadFile(name); return err })
+ }
+
+ // Check that fs.ReadFile works with t.fsys.
+ data2, err := fs.ReadFile(t.fsys, file)
+ if err != nil {
+ t.errorf("%s: fs.ReadFile: %v", file, err)
+ return
+ }
+ t.checkFileRead(file, "ReadAll vs fs.ReadFile", data, data2)
+
// Use iotest.TestReader to check small reads, Seek, ReadAt.
f, err = t.fsys.Open(file)
if err != nil {
}
}
-// checkOpen checks that various invalid forms of file's name cannot be opened.
+// checkBadPath checks that various invalid forms of file's name cannot be opened using t.fsys.Open.
func (t *fsTester) checkOpen(file string) {
+ t.checkBadPath(file, "Open", func(file string) error {
+ f, err := t.fsys.Open(file)
+ if err == nil {
+ f.Close()
+ }
+ return err
+ })
+}
+
+// checkBadPath checks that various invalid forms of file's name cannot be opened using open.
+func (t *fsTester) checkBadPath(file string, desc string, open func(string) error) {
bad := []string{
"/" + file,
file + "/.",
}
for _, b := range bad {
- if f, err := t.fsys.Open(b); err == nil {
- f.Close()
- t.errorf("%s: Open(%s) succeeded, want error", file, b)
+ if err := open(b); err == nil {
+ t.errorf("%s: %s(%s) succeeded, want error", file, desc, b)
}
}
}