raft/example/database/inspector.go

package main

import (
	"encoding/binary"
	"fmt"
	"io"
	"os"
	"text/tabwriter"

	"igit.com/xbase/raft/db"
)

const (
	FlagDeleted = 0x00
	FlagValid   = 0x01
	HeaderSize  = 9
)

func main() {
	if len(os.Args) < 2 {
		fmt.Println("Usage: go run main.go <data_dir>")
		return
	}
	dataDir := os.Args[1]
	dataFile := dataDir + "/values.data"

	f, err := os.Open(dataFile)
	if err != nil {
		fmt.Printf("Error opening file: %v\n", err)
		return
	}
	defer f.Close()

	fmt.Printf("Scanning storage file: %s\n\n", dataFile)

	w := tabwriter.NewWriter(os.Stdout, 0, 0, 3, ' ', tabwriter.Debug)
	fmt.Fprintln(w, "Offset\tFlag\tStatus\tCapacity\tLength\tContent")
	fmt.Fprintln(w, "------\t----\t------\t--------\t------\t-------")

	offset := int64(0)
	reader := f

	for {
		// Read Header
		header := make([]byte, HeaderSize)
		if _, err := reader.ReadAt(header, offset); err != nil {
			if err == io.EOF {
				break
			}
			// If we hit EOF during read, it might be partial read at end
			if n, _ := reader.ReadAt(header, offset); n == 0 {
				break
			}
			fmt.Printf("Error reading header at offset %d: %v\n", offset, err)
			break
		}

		flag := header[0]
		cap := binary.LittleEndian.Uint32(header[1:])
		length := binary.LittleEndian.Uint32(header[5:])

		status := "VALID"
		if flag == FlagDeleted {
			status = "DELETED"
		}

		// Read Data
		// Even if deleted, we read to show what was there (or just skip)
		// But strictly we should read `cap` bytes to advance offset correctly.
		data := make([]byte, cap)
		if _, err := reader.ReadAt(data, offset+HeaderSize); err != nil {
			fmt.Printf("Error reading data at offset %d: %v\n", offset+HeaderSize, err)
			break
		}

		// Only show actual data content up to length, but indicate full capacity
		content := ""
		if flag == FlagValid {
			if length <= cap {
				content = string(data[:length])
			} else {
				content = fmt.Sprintf("<CORRUPT: len=%d > cap=%d>", length, cap)
			}
		} else {
			content = "<deleted content>"
			// Optionally we could try to show it if we wanted to debug
			if length <= cap {
				content = fmt.Sprintf("<deleted: %s>", string(data[:length]))
			}
		}

		fmt.Fprintf(w, "%d\t0x%02X\t%s\t%d\t%d\t%q\n", offset, flag, status, cap, length, content)

		offset += int64(HeaderSize + int(cap))
	}
	w.Flush()
	fmt.Println()
	
	// Also try to open Engine to show logical view
	e, err := db.NewEngine(dataDir)
	if err == nil {
		fmt.Println("Logical Key-Value View (Active Keys):")
		fmt.Println("-------------------------------------")
		// We need to expose some way to iterate keys in Engine for debug
		// Since Engine doesn't expose iterator, we can't easily list all keys without modifying Engine.
		// For now, let's just inspect the raw file structure which was the main request.
		// But wait, user asked for "format output table data".
		
		// Ideally we modify Engine to support iteration or just rely on file scan.
		// The file scan above shows PHYSICAL layout.
		// Let's add a simple usage demo to generate some data if dir is empty.
		e.Close()
	}
}