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// 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 os.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 os.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
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.String(), er.String())
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.String(), ew.String())
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()
}
}
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