libgo/go/io/ioutil/ioutil.go

   1 // Copyright 2009 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // Package ioutil implements some I/O utility functions.
   6 //
   7 // As of Go 1.16, the same functionality is now provided
   8 // by package io or package os, and those implementations
   9 // should be preferred in new code.
  10 // See the specific function documentation for details.
  11 package ioutil
  12
  13 import (
  14         "io"
  15         "io/fs"
  16         "os"
  17         "sort"
  18 )
  19
  20 // ReadAll reads from r until an error or EOF and returns the data it read.
  21 // A successful call returns err == nil, not err == EOF. Because ReadAll is
  22 // defined to read from src until EOF, it does not treat an EOF from Read
  23 // as an error to be reported.
  24 //
  25 // As of Go 1.16, this function simply calls io.ReadAll.
  26 func ReadAll(r io.Reader) ([]byte, error) {
  27         return io.ReadAll(r)
  28 }
  29
  30 // ReadFile reads the file named by filename and returns the contents.
  31 // A successful call returns err == nil, not err == EOF. Because ReadFile
  32 // reads the whole file, it does not treat an EOF from Read as an error
  33 // to be reported.
  34 //
  35 // As of Go 1.16, this function simply calls os.ReadFile.
  36 func ReadFile(filename string) ([]byte, error) {
  37         return os.ReadFile(filename)
  38 }
  39
  40 // WriteFile writes data to a file named by filename.
  41 // If the file does not exist, WriteFile creates it with permissions perm
  42 // (before umask); otherwise WriteFile truncates it before writing, without changing permissions.
  43 //
  44 // As of Go 1.16, this function simply calls os.WriteFile.
  45 func WriteFile(filename string, data []byte, perm fs.FileMode) error {
  46         return os.WriteFile(filename, data, perm)
  47 }
  48
  49 // ReadDir reads the directory named by dirname and returns
  50 // a list of fs.FileInfo for the directory's contents,
  51 // sorted by filename. If an error occurs reading the directory,
  52 // ReadDir returns no directory entries along with the error.
  53 //
  54 // As of Go 1.16, os.ReadDir is a more efficient and correct choice:
  55 // it returns a list of fs.DirEntry instead of fs.FileInfo,
  56 // and it returns partial results in the case of an error
  57 // midway through reading a directory.
  58 func ReadDir(dirname string) ([]fs.FileInfo, error) {
  59         f, err := os.Open(dirname)
  60         if err != nil {
  61                 return nil, err
  62         }
  63         list, err := f.Readdir(-1)
  64         f.Close()
  65         if err != nil {
  66                 return nil, err
  67         }
  68         sort.Slice(list, func(i, j int) bool { return list[i].Name() < list[j].Name() })
  69         return list, nil
  70 }
  71
  72 // NopCloser returns a ReadCloser with a no-op Close method wrapping
  73 // the provided Reader r.
  74 //
  75 // As of Go 1.16, this function simply calls io.NopCloser.
  76 func NopCloser(r io.Reader) io.ReadCloser {
  77         return io.NopCloser(r)
  78 }
  79
  80 // Discard is an io.Writer on which all Write calls succeed
  81 // without doing anything.
  82 //
  83 // As of Go 1.16, this value is simply io.Discard.
  84 var Discard io.Writer = io.Discard