reader/validate.go

// Copyright 2014 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 reader // import "golang.org/x/tour/reader"

import (
	"fmt"
	"io"
	"os"
)

func Validate(r io.Reader) {
	b := make([]byte, 1024, 2048)
	i, o := 0, 0
	for ; i < 1<<20 && o < 1<<20; i++ { // test 1mb
		n, err := r.Read(b)
		for i, v := range b[:n] {
			if v != 'A' {
				fmt.Fprintf(os.Stderr, "got byte %x at offset %v, want 'A'\n", v, o+i)
				return
			}
		}
		o += n
		if err != nil {
			fmt.Fprintf(os.Stderr, "read error: %v\n", err)
			return
		}
	}
	if o == 0 {
		fmt.Fprintf(os.Stderr, "read zero bytes after %d Read calls\n", i)
		return
	}
	fmt.Println("OK!")
}