feat(gobplustree): 实现B+树存储基础模块
新增BlockFile结构体及其实现，用于支持B+树数据的持久化存储。 该模块提供固定大小页面的文件读写功能，包括页面的创建、打开、关闭、 读取与写入等操作，并在文件容量不足时自动扩展。同时添加了相关单元测试 以确保功能正确性。初始化Go模块配置文件go.mod。
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commit
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// Package gobplustree implements a B+ tree data structure and related utilities.
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package gobplustree
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import (
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"errors"
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"os"
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)
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var (
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// ErrPageIdOutOfRange is returned when trying to access a page that doesn't exist in the file.
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ErrPageIdOutOfRange = errors.New("page id out of range")
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)
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// BlockFile represents a file divided into fixed-size blocks or pages.
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// It provides methods for reading and writing these pages.
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type BlockFile struct {
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PageCount int64
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FileName string
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file *os.File
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}
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// Constants defining the structure of the block file.
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const (
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// BlockFileHeaderSize is the size of the file header in bytes.
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BlockFileHeaderSize = 8
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// BlockFilePageSize is the size of each page in bytes.
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BlockFilePageSize = 4096
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// InitPageCount is the initial number of pages when creating a new file.
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InitPageCount = 1024
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)
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// NewBlockFile creates a new BlockFile instance.
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// fileName: the name of the file to be created or opened.
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// initialPageCount: the initial number of pages for the file.
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func NewBlockFile(fileName string, initialPageCount int64) (*BlockFile, error) {
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return &BlockFile{
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PageCount: initialPageCount,
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FileName: fileName,
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file: nil,
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}, nil
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}
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// Open opens the file and initializes it if it's empty.
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// Returns an error if the file cannot be opened or initialized.
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func (bf *BlockFile) Open() error {
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file, err := os.OpenFile(bf.FileName, os.O_RDWR|os.O_CREATE, 0666)
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if err != nil {
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return err
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}
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bf.file = file
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fileInfo, err := file.Stat()
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if err != nil {
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return err
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}
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// If file is empty, initialize it with default pages
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if fileInfo.Size() == 0 {
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// bf.PageCount = InitPageCount
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_, err := bf.file.Write(make([]byte, BlockFileHeaderSize))
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if err != nil {
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return err
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}
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_, err = bf.file.Write(make([]byte, BlockFilePageSize*InitPageCount))
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if err != nil {
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return err
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}
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} else {
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bf.PageCount = fileInfo.Size() / BlockFilePageSize
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}
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return nil
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}
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// Close closes the underlying file.
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// Returns an error if the file cannot be closed.
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func (bf *BlockFile) Close() error {
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return bf.file.Close()
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}
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// Read reads a page from the file by its page ID.
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// pageId: the ID of the page to read.
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// Returns the page data and an error if the operation fails.
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func (bf *BlockFile) Read(pageId int64) ([]byte, error) {
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if pageId >= bf.PageCount || pageId < 0 {
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return nil, ErrPageIdOutOfRange
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}
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data := make([]byte, BlockFilePageSize)
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n, err := bf.file.ReadAt(data, pageId*BlockFilePageSize)
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if err != nil {
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return nil, err
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}
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// Check if we read the full page
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if n != BlockFilePageSize {
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return nil, ErrPageIdOutOfRange
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}
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return data, nil
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}
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// enlarge increases the file size by adding more pages.
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// count: the number of pages to add.
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// Returns an error if the operation fails.
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func (bf *BlockFile) enlarge(count int64) error {
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_, err := bf.file.WriteAt(make([]byte, BlockFilePageSize*count), bf.PageCount*BlockFilePageSize)
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if err != nil {
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return err
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}
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bf.PageCount += count
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return nil
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}
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// Write writes data to a specific page in the file.
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// pageId: the ID of the page to write to.
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// data: the data to write.
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// Returns an error if the operation fails.
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func (bf *BlockFile) Write(pageId int64, data []byte) error {
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if pageId >= bf.PageCount {
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err := bf.enlarge(pageId - bf.PageCount + 1)
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if err != nil {
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return err
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}
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}
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_, err := bf.file.WriteAt(data, pageId*BlockFilePageSize)
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if err != nil {
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return err
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}
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return nil
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}
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@ -0,0 +1,162 @@
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package gobplustree
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import (
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"bytes"
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"os"
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"testing"
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)
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// TestNewBlockFile tests the creation of a new BlockFile instance.
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func TestNewBlockFile(t *testing.T) {
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bf, err := NewBlockFile("test.db", 100)
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if err != nil {
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t.Fatalf("Failed to create BlockFile: %v", err)
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}
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if bf.FileName != "test.db" {
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t.Errorf("Expected filename 'test.db', got '%s'", bf.FileName)
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}
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if bf.PageCount != 100 {
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t.Errorf("Expected PageCount 100, got %d", bf.PageCount)
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}
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if bf.file != nil {
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t.Errorf("Expected file to be nil, got %v", bf.file)
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}
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}
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// TestBlockFileOpenAndClose tests opening and closing a BlockFile.
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func TestBlockFileOpenAndClose(t *testing.T) {
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filename := "test_open.db"
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bf, err := NewBlockFile(filename, InitPageCount)
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if err != nil {
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t.Fatalf("Failed to create BlockFile: %v", err)
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}
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// Test opening the file
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err = bf.Open()
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if err != nil {
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t.Fatalf("Failed to open BlockFile: %v", err)
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}
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// Check that file was created
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if _, err := os.Stat(filename); os.IsNotExist(err) {
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t.Error("File was not created")
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}
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// Test closing the file
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err = bf.Close()
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if err != nil {
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t.Errorf("Failed to close BlockFile: %v", err)
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}
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// Clean up
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os.Remove(filename)
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}
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// TestBlockFileReadWrite tests reading and writing pages to a BlockFile.
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func TestBlockFileReadWrite(t *testing.T) {
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filename := "test_rw.db"
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bf, err := NewBlockFile(filename, 10)
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if err != nil {
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t.Fatalf("Failed to create BlockFile: %v", err)
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}
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err = bf.Open()
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if err != nil {
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t.Fatalf("Failed to open BlockFile: %v", err)
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}
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// Test writing data
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testData := []byte("Hello, BlockFile!")
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err = bf.Write(0, testData)
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if err != nil {
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t.Fatalf("Failed to write to BlockFile: %v", err)
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}
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// Pad testData to full page size for comparison
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paddedTestData := make([]byte, BlockFilePageSize)
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copy(paddedTestData, testData)
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// Test reading data
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data, err := bf.Read(0)
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if err != nil {
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t.Fatalf("Failed to read from BlockFile: %v", err)
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}
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// Check that we got the data we wrote
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if !bytes.Equal(data, paddedTestData) {
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t.Errorf("Read data does not match written data. Expected: %s, Got: %s",
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string(testData), string(data[:len(testData)]))
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}
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// Test reading a non-existent page
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_, err = bf.Read(100)
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if err != ErrPageIdOutOfRange {
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t.Errorf("Expected ErrPageIdOutOfRange, got %v", err)
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}
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// Test writing to a page that requires enlarging the file
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longData := make([]byte, 100)
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for i := range longData {
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longData[i] = byte(i % 256)
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}
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err = bf.Write(15, longData)
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if err != nil {
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t.Fatalf("Failed to write to page requiring file enlargement: %v", err)
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}
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// Read the data back
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readData, err := bf.Read(15)
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if err != nil {
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t.Fatalf("Failed to read enlarged page: %v", err)
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}
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if !bytes.Equal(readData[:len(longData)], longData) {
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t.Error("Read data from enlarged page does not match written data")
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}
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err = bf.Close()
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if err != nil {
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t.Errorf("Failed to close BlockFile: %v", err)
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}
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// Clean up
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os.Remove(filename)
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}
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// TestBlockFileEnlarge tests the internal enlarge method.
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func TestBlockFileEnlarge(t *testing.T) {
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filename := "test_enlarge.db"
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bf, err := NewBlockFile(filename, 5)
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if err != nil {
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t.Fatalf("Failed to create BlockFile: %v", err)
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}
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err = bf.Open()
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if err != nil {
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t.Fatalf("Failed to open BlockFile: %v", err)
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}
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initialPageCount := bf.PageCount
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// Manually call enlarge
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err = bf.enlarge(10)
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if err != nil {
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t.Fatalf("Failed to enlarge BlockFile: %v", err)
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}
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if bf.PageCount != initialPageCount+10 {
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t.Errorf("Expected PageCount to be %d, got %d", initialPageCount+10, bf.PageCount)
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}
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err = bf.Close()
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if err != nil {
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t.Errorf("Failed to close BlockFile: %v", err)
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}
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// Clean up
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os.Remove(filename)
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}
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