// 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 }