mirror of
https://github.com/golang/go
synced 2024-11-12 08:00:22 -07:00
92 lines
1.6 KiB
Go
92 lines
1.6 KiB
Go
// Copyright 2009 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 main
|
|
|
|
import (
|
|
"./file"
|
|
"flag"
|
|
"fmt"
|
|
"os"
|
|
)
|
|
|
|
var rot13Flag = flag.Bool("rot13", false, "rot13 the input")
|
|
|
|
func rot13(b byte) byte {
|
|
if 'a' <= b && b <= 'z' {
|
|
b = 'a' + ((b-'a')+13)%26
|
|
}
|
|
if 'A' <= b && b <= 'Z' {
|
|
b = 'A' + ((b-'A')+13)%26
|
|
}
|
|
return b
|
|
}
|
|
|
|
type reader interface {
|
|
Read(b []byte) (ret int, err error)
|
|
String() string
|
|
}
|
|
|
|
type rotate13 struct {
|
|
source reader
|
|
}
|
|
|
|
func newRotate13(source reader) *rotate13 {
|
|
return &rotate13{source}
|
|
}
|
|
|
|
func (r13 *rotate13) Read(b []byte) (ret int, err error) {
|
|
r, e := r13.source.Read(b)
|
|
for i := 0; i < r; i++ {
|
|
b[i] = rot13(b[i])
|
|
}
|
|
return r, e
|
|
}
|
|
|
|
func (r13 *rotate13) String() string {
|
|
return r13.source.String()
|
|
}
|
|
|
|
// end of rotate13 implementation OMIT
|
|
|
|
func cat(r reader) {
|
|
const NBUF = 512
|
|
var buf [NBUF]byte
|
|
|
|
if *rot13Flag {
|
|
r = newRotate13(r)
|
|
}
|
|
for {
|
|
switch nr, er := r.Read(buf[:]); {
|
|
case nr < 0:
|
|
fmt.Fprintf(os.Stderr, "cat: error reading from %s: %s\n", r, er)
|
|
os.Exit(1)
|
|
case nr == 0: // EOF
|
|
return
|
|
case nr > 0:
|
|
nw, ew := file.Stdout.Write(buf[0:nr])
|
|
if nw != nr {
|
|
fmt.Fprintf(os.Stderr, "cat: error writing from %s: %s\n", r, ew)
|
|
os.Exit(1)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
func main() {
|
|
flag.Parse() // Scans the arg list and sets up flags
|
|
if flag.NArg() == 0 {
|
|
cat(file.Stdin)
|
|
}
|
|
for i := 0; i < flag.NArg(); i++ {
|
|
f, err := file.Open(flag.Arg(i))
|
|
if f == nil {
|
|
fmt.Fprintf(os.Stderr, "cat: can't open %s: error %s\n", flag.Arg(i), err)
|
|
os.Exit(1)
|
|
}
|
|
cat(f)
|
|
f.Close()
|
|
}
|
|
}
|