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// Copyright 2015 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 elf
import (
"io"
"os"
)
// errorReader returns error from all operations.
type errorReader struct {
error
}
func (r errorReader) Read(p []byte) (n int, err error) {
return 0, r.error
}
func (r errorReader) ReadAt(p []byte, off int64) (n int, err error) {
return 0, r.error
}
func (r errorReader) Seek(offset int64, whence int) (int64, error) {
return 0, r.error
}
func (r errorReader) Close() error {
return r.error
}
// readSeekerFromReader converts an io.Reader into an io.ReadSeeker.
// In general Seek may not be efficient, but it is optimized for
// common cases such as seeking to the end to find the length of the
// data.
type readSeekerFromReader struct {
reset func() (io.Reader, error)
r io.Reader
size int64
offset int64
}
func (r *readSeekerFromReader) start() {
x, err := r.reset()
if err != nil {
r.r = errorReader{err}
} else {
r.r = x
}
r.offset = 0
}
func (r *readSeekerFromReader) Read(p []byte) (n int, err error) {
if r.r == nil {
r.start()
}
n, err = r.r.Read(p)
r.offset += int64(n)
return n, err
}
func (r *readSeekerFromReader) Seek(offset int64, whence int) (int64, error) {
var newOffset int64
switch whence {
case io.SeekStart:
newOffset = offset
case io.SeekCurrent:
newOffset = r.offset + offset
case io.SeekEnd:
newOffset = r.size + offset
default:
return 0, os.ErrInvalid
}
switch {
case newOffset == r.offset:
return newOffset, nil
case newOffset < 0, newOffset > r.size:
return 0, os.ErrInvalid
case newOffset == 0:
r.r = nil
case newOffset == r.size:
r.r = errorReader{io.EOF}
default:
if newOffset < r.offset {
// Restart at the beginning.
r.start()
}
// Read until we reach offset.
var buf [512]byte
for r.offset < newOffset {
b := buf[:]
if newOffset-r.offset < int64(len(buf)) {
b = buf[:newOffset-r.offset]
}
if _, err := r.Read(b); err != nil {
return 0, err
}
}
}
r.offset = newOffset
return r.offset, nil
}
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