mirror of
https://github.com/golang/go
synced 2024-11-24 13:10:11 -07:00
91 lines
1.6 KiB
Go
91 lines
1.6 KiB
Go
// Copyright 2009 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 main
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import (
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"./file"
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"flag"
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"fmt"
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"os"
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)
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var rot13Flag = flag.Bool("rot13", false, "rot13 the input")
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func rot13(b byte) byte {
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if 'a' <= b && b <= 'z' {
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b = 'a' + ((b-'a')+13)%26
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}
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if 'A' <= b && b <= 'Z' {
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b = 'A' + ((b-'A')+13)%26
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}
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return b
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}
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type reader interface {
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Read(b []byte) (ret int, err error)
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String() string
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}
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type rotate13 struct {
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source reader
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}
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func newRotate13(source reader) *rotate13 {
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return &rotate13{source}
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}
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func (r13 *rotate13) Read(b []byte) (ret int, err error) {
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r, e := r13.source.Read(b)
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for i := 0; i < r; i++ {
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b[i] = rot13(b[i])
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}
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return r, e
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}
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func (r13 *rotate13) String() string {
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return r13.source.String()
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}
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// end of rotate13 implementation
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func cat(r reader) {
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const NBUF = 512
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var buf [NBUF]byte
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if *rot13Flag {
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r = newRotate13(r)
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}
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for {
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switch nr, er := r.Read(buf[:]); {
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case nr < 0:
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fmt.Fprintf(os.Stderr, "cat: error reading from %s: %s\n", r, er)
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os.Exit(1)
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case nr == 0: // EOF
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return
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case nr > 0:
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nw, ew := file.Stdout.Write(buf[0:nr])
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if nw != nr {
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fmt.Fprintf(os.Stderr, "cat: error writing from %s: %s\n", r, ew)
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os.Exit(1)
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}
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}
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}
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}
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func main() {
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flag.Parse() // Scans the arg list and sets up flags
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if flag.NArg() == 0 {
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cat(file.Stdin)
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}
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for i := 0; i < flag.NArg(); i++ {
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f, err := file.Open(flag.Arg(i))
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if f == nil {
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fmt.Fprintf(os.Stderr, "cat: can't open %s: error %s\n", flag.Arg(i), err)
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os.Exit(1)
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}
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cat(f)
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f.Close()
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}
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}
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