forked from u-root/u-root
/
reader.go
62 lines (54 loc) · 1.15 KB
/
reader.go
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// Copyright 2019 the u-root 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 multiboot
import (
"compress/gzip"
"fmt"
"io"
"io/ioutil"
"os"
)
type kernelReader struct {
buf []byte
off int
}
func (kr kernelReader) ReadAt(p []byte, off int64) (n int, err error) {
if off < 0 || off > int64(len(kr.buf)) {
return 0, fmt.Errorf("bad offset %v", off)
}
if n = copy(p, kr.buf[off:]); n < len(p) {
err = io.EOF
}
return n, err
}
func (kr *kernelReader) Read(p []byte) (n int, err error) {
if n = copy(p, kr.buf[kr.off:]); n < len(p) {
err = io.EOF
}
kr.off += n
return n, err
}
func readGzip(r io.Reader) ([]byte, error) {
z, err := gzip.NewReader(r)
if err != nil {
return nil, err
}
defer z.Close()
return ioutil.ReadAll(z)
}
func readFile(name string) ([]byte, error) {
f, err := os.Open(name)
if err != nil {
return nil, err
}
defer f.Close()
b, err := readGzip(f)
if err == nil {
return b, err
}
if _, err := f.Seek(0, io.SeekStart); err != nil {
return nil, fmt.Errorf("cannot rewind file: %v", err)
}
return ioutil.ReadAll(f)
}