初步实现bfs原型（仅用于实验）

internal/utils/bfs/file_reader.go

@@ -0,0 +1,67 @@
+// Copyright 2024 GoEdge CDN goedge.cdn@gmail.com. All rights reserved. Official site: https://goedge.cn .
+
+package bfs
+
+import (
+	"errors"
+	"github.com/iwind/TeaGo/types"
+	"io"
+	"os"
+)
+
+type FileReader struct {
+	bFile  *BlocksFile
+	fp     *os.File
+	header *FileHeader
+
+	pos int64
+}
+
+func NewFileReader(bFile *BlocksFile, fp *os.File, header *FileHeader) *FileReader {
+	return &FileReader{
+		bFile:  bFile,
+		fp:     fp,
+		header: header,
+	}
+}
+
+func (this *FileReader) Read(b []byte) (n int, err error) {
+	n, err = this.ReadAt(b, this.pos)
+	this.pos += int64(n)
+
+	return
+}
+
+func (this *FileReader) ReadAt(b []byte, offset int64) (n int, err error) {
+	if offset >= this.header.MaxOffset() {
+		err = io.EOF
+		return
+	}
+
+	blockInfo, ok := this.header.BlockAt(offset)
+	if !ok {
+		err = errors.New("could not find block at '" + types.String(offset) + "'")
+		return
+	}
+
+	var delta = offset - blockInfo.OriginOffsetFrom
+	var bFrom = blockInfo.BFileOffsetFrom + delta
+	var bTo = blockInfo.BFileOffsetTo
+	if bFrom > bTo {
+		err = errors.New("invalid block information")
+		return
+	}
+
+	var bufLen = len(b)
+	if int64(bufLen) > bTo-bFrom {
+		bufLen = int(bTo - bFrom)
+	}
+
+	n, err = this.fp.ReadAt(b[:bufLen], bFrom)
+
+	return
+}
+
+func (this *FileReader) Close() error {
+	return this.fp.Close()
+}