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// Copyright (C) 2022 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package diskio
import (
"fmt"
"io"
)
// interface /////////////////////////////////////////////////////////
type Sequence[K ~int64, V any] interface {
// Get the value at 'pos' in the sequence. Positions start at
// 0 and increment naturally. Return an error that is io.EOF
// if 'pos' is past the end of the sequence'.
Get(pos K) (V, error)
}
// implementation: slice /////////////////////////////////////////////
type SliceSequence[K ~int64, V any] []V
var _ Sequence[assertAddr, byte] = SliceSequence[assertAddr, byte]([]byte(nil))
func (s SliceSequence[K, V]) Get(i K) (V, error) {
if i >= K(len(s)) {
var v V
return v, io.EOF
}
return s[int(i)], nil
}
// implementation: string ////////////////////////////////////////////
type StringSequence[K ~int64] string
var _ Sequence[assertAddr, byte] = StringSequence[assertAddr]("")
func (s StringSequence[K]) Get(i K) (byte, error) {
if i >= K(len(s)) {
return 0, io.EOF
}
return s[int(i)], nil
}
// implementation: io.ByteReader /////////////////////////////////////
type ByteReaderSequence[K ~int64] struct {
R io.ByteReader
pos K
}
var _ Sequence[assertAddr, byte] = &ByteReaderSequence[assertAddr]{R: nil}
func (s *ByteReaderSequence[K]) Get(i K) (byte, error) {
if i != s.pos {
return 0, fmt.Errorf("%T.Get(%v): can only call .Get(%v)",
s, i, s.pos)
}
chr, err := s.R.ReadByte()
if err != nil {
return chr, err
}
s.pos++
return chr, nil
}
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