go-fds/reader.go

package fds

import (
	//"os"
	"fmt"
	"io"
	"bufio"
	"bytes"
	"encoding/binary"

	"github.com/sigurn/crc16"
)

func ReadRom(r io.Reader, IsFds bool) (*Rom, error) {
	reader := bufio.NewReader(r)
	magic, err := reader.Peek(4)
	if err != nil {
		return nil, fmt.Errorf("Unable to peek header: %w", err)
	}

	rom := &Rom{Header: &FdsHeader{}}

	// "FDS" + EOF.  header may be omitted.
	if bytes.Equal(magic, FdsHeaderMagic) {
		err = binary.Read(reader, binary.LittleEndian, rom.Header)
		if err != nil {
			return nil, fmt.Errorf("Error reading header: %w", err)
		}
	}

	rom.Blocks, err = ReadBlocks(reader, IsFds)
	return rom, err
}

func ReadBlocks(r io.Reader, IsFds bool) ([]DiskBlock, error) {
	blocks := []DiskBlock{}
	dataSize := -1
	readBytes := 0

	reader := bufio.NewReader(r)

	for {
		raw, err := reader.Peek(1)
		if err != nil {
			if err == io.EOF {
				break
			}

			return blocks, fmt.Errorf("error peeking block type: %w", err)
		}

		var readLen int
		var block DiskBlock
		idByte := raw[0]

		switch idByte {
		case 0x01:
			block = &BlockInfo{}
		case 0x02:
			block = &BlockFileAmount{}
		case 0x03:
			block = &BlockFileHeader{}
		case 0x04:
			block = &BlockFileData{}

			// variable length
			readLen = dataSize+3

		case 0x00:
			reader.Discard(1)
			continue

		default:
			fmt.Printf("readBytes: %d ($%04X)\n", readBytes, readBytes)
			return blocks, fmt.Errorf("Invalid block type: $%02X", idByte)
		}
		//fmt.Println("")

		if idByte != 0x04 {
			readLen = binary.Size(block)
		}

		//fmt.Println("readLen:;", readLen)
		// FDS doesn't have the two byte CRC in the data
		if IsFds {
			readLen -=2
		}

		//fmt.Println("readLen::", readLen)
		buf := make([]byte, readLen)
		n, err := io.ReadFull(reader, buf)
		if err != nil {
			return blocks, fmt.Errorf("Error reading block id 0x%02X: %w", idByte, err)
		}
		readBytes += n

		//var sum uint16
		if IsFds {
			//sum = crc16.Checksum(buf, crc16.MakeTable(crc16.CRC16_KERMIT))
			//fmt.Printf("checksum: %04X\n", sum)
			buf = append(buf, []byte{0x00, 0x00}...)
		}

		//fmt.Printf("idByte:$%02X\nreadLen:%d\nlen(buf):%d\nblocksize:%d\n", idByte, readLen, len(buf), binary.Size(block))

		if idByte != 0x04 {
			_, err = binary.Decode(buf, binary.LittleEndian, block)
			if err != nil {
				return blocks, fmt.Errorf("Error decoding block id 0x%02X: %w", idByte, err)
			}

			if idByte == 0x03 {
				fh := block.(*BlockFileHeader)
				dataSize = int(fh.FileSize)
			} else {
				dataSize = -1
			}

		} else {
			db := block.(*BlockFileData)
			db.BlockCode = buf[0]

			if !IsFds {
				db.CRC = uint16(buf[len(buf)-2]) | (uint16(buf[len(buf)-2])<<8)
				readLen -= 2

			} else {
				db.CRC = crc16.Checksum(buf[:len(buf)-2], crc16.MakeTable(crc16.CRC16_KERMIT))
			}

			db.Data = buf[1:readLen]
			//fmt.Println("len(db.Data)", len(db.Data))
			block = db
			//fmt.Printf("Block:%#v\n", block)
		}

		blocks = append(blocks, block)
	}

	return blocks, nil
}

//func ReadBlocksFds(r io.Reader) ([]FdsBlock, error) {
//	reader := bufio.NewReader(r)
//
//	var dataSize int
//	blocks := []FdsBlock{}
//	for {
//		typ, err := reader.Peek(1)
//		if err != nil {
//			if err == io.EOF {
//				break
//			} else {
//				return nil, err
//			}
//		}
//
//		if len(typ) != 1 {
//			return nil, fmt.Errorf("typ read length error")
//		}
//		//fmt.Printf("typ: %v\n", typ)
//
//		if typ[0] == 0x00 {
//			//fmt.Println("00 'block'")
//			break
//		}
//
//		var block FdsBlock
//		switch BlockType(typ[0]) {
//		case BlockInfo:
//			block = &FdsBlockInfo{}
//		case BlockFileAmount:
//			block = &FdsFileAmount{}
//		case BlockFileHeader:
//			block = &FdsFileHeader{}
//		case BlockFileData:
//			block = &FdsFileData{}
//		default:
//			return nil, fmt.Errorf("invalid block type: %02X", typ[0])
//		}
//
//		if block.Type() != BlockFileData {
//			err = binary.Read(reader, binary.LittleEndian, block)
//			if err != nil {
//				return nil, fmt.Errorf("decode error: %w", err)
//			}
//		} else {
//			fb := block.(*FdsFileData)
//			fb.BlockCode = byte(BlockFileData)
//			reader.Discard(1)
//
//			if dataSize == 0 {
//				return nil, fmt.Errorf("FileData without size")
//			}
//			fmt.Println("dataSize:", dataSize)
//
//			fb.Data = make([]byte, dataSize)
//			_, err = reader.Read(fb.Data)
//			if err != nil {
//				return nil, fmt.Errorf("data read err: %w", err)
//			}
//			dataSize = 0
//		}
//
//		switch block.Type() {
//		case BlockFileHeader:
//			bh := block.(*FdsFileHeader)
//			dataSize = int(bh.FileSize)
//		}
//
//		fmt.Println(block)
//		blocks = append(blocks, block)
//	}
//
//	return blocks, nil
//}