gma-puzzles/gma/reader.go

package gma

import (
	"bufio"
	"bytes"
	"crypto/sha256"
	"encoding/binary"
	"fmt"
	"hash/crc32"
	"io"
	"os"
)

type GMAReader struct {
	FileHandle *os.File
	//gmaStream       io.Reader
	gmaStreamReader *bufio.Reader
	cursorOffset    uint32
	//h    header
}

func NewReader(fileName string) (_ GMAReader, err error) {
	return GMAReader{}.NewReader(fileName)
}
func (r GMAReader) NewReader(fileName string) (_ GMAReader, err error) {
	r.FileHandle, err = os.Open(fileName)
	if err != nil {
		return r, err
	}
	r.gmaStreamReader = bufio.NewReader(r.FileHandle)
	return r, nil
}

func (r *GMAReader) IsValidGMAD() (isValid bool, err error) {
	gmadHeader, err := r.gmaStreamReader.Peek(4)
	if err != nil {
		return false, err
	}
	return string(gmadHeader) == "GMAD", nil
}
func (r *GMAReader) IsCompressed() (isValid bool, err error) {
	gmadHeader, err := r.gmaStreamReader.Peek(4)
	if err != nil {
		return false, err
	}
	return gmadHeader[0] == 93 && gmadHeader[1] == 0 && gmadHeader[1] == gmadHeader[2] && gmadHeader[1] == gmadHeader[3], nil
}

func (r *GMAReader) Close() {
	r.FileHandle.Close()
}

func (r *GMAReader) ReadHeader() (_ GMAHeader, err error) {
	header := GMAHeader{}

	r.gmaStreamReader.Discard(4)
	r.cursorOffset += 4
	if r.cursorOffset != 4 {
		return header, fmt.Errorf("%d invalid offset", r.cursorOffset)
	}

	// Read the format version
	header.FormatVersion, err = r.gmaStreamReader.ReadByte()
	if err != nil {
		return header, err
	}
	r.cursorOffset++

	// Read the SteamID
	steamIDBytes := make([]byte, 8)
	_, err = r.gmaStreamReader.Read(steamIDBytes)
	if err != nil {
		return header, err
	}
	r.cursorOffset += 8
	header.SteamID = binary.LittleEndian.Uint64(steamIDBytes)

	// Read the Timestamp
	timestampBytes := make([]byte, 8)
	_, err = r.gmaStreamReader.Read(timestampBytes)
	if err != nil {
		return header, err
	}
	r.cursorOffset += 8
	header.Timestamp = binary.LittleEndian.Uint64(timestampBytes)

	if header.FormatVersion > 1 {
		header.FormatVersionDiscardByte, err = r.gmaStreamReader.ReadByte()
		if err != nil {
			return header, err
		}
		r.cursorOffset++
	}

	// Read the Title
	header.Title, err = r.gmaStreamReader.ReadString(byte(0))
	if err != nil {
		return header, err
	}
	header.Title = header.Title[:len(header.Title)-1] // remove nullbyte
	r.cursorOffset += uint32(len(header.Title) + 1)   // Add title length + null byte

	// Read the Description
	header.Description, err = r.gmaStreamReader.ReadString(byte(0))
	if err != nil {
		return header, err
	}
	header.Description = header.Description[:len(header.Description)-1] // remove nullbyte
	//fmt.Printf("Desc Start %d\n", r.cursorOffset)
	r.cursorOffset += uint32(len(header.Description) + 1) // Add description length + null byte
	//fmt.Printf("Desc End %d\n", r.cursorOffset)

	// Read the Author
	header.Author, err = r.gmaStreamReader.ReadString(byte(0))
	if err != nil {
		return header, err
	}
	header.Author = header.Author[:len(header.Author)-1] // remove nullbyte
	r.cursorOffset += uint32(len(header.Author) + 1)     // Add author length + null byte

	// Read the AddonVersion
	addonVersionBytes := make([]byte, 4)
	_, err = r.gmaStreamReader.Read(addonVersionBytes)
	if err != nil {
		return header, err
	}
	r.cursorOffset += 4
	header.AddonVersion = int32(binary.LittleEndian.Uint32(addonVersionBytes))

	return header, nil
}

func (r *GMAReader) readFileMetadata() (GMAFileMetadata, error) {
	metadata := GMAFileMetadata{}

	// Read the file name
	fileName, err := r.gmaStreamReader.ReadString(byte(0))
	if err != nil {
		return metadata, err
	}
	//fmt.Printf("bufio ReadString(byte(0)) = len(%d) data=%x\n", len(fileName), fileName)
	/*if len(fileName) == 1 { //fucky retry
		fileName, err := r.gmaStreamReader.ReadString(byte(0))
		if err != nil {
			return metadata, err
		}
		fmt.Printf("RETRY!! bufio ReadString(byte(0)) = len(%d) data=%x\n", len(fileName), fileName)
	}*/
	fileName = fileName[:len(fileName)-1]       // remove nullbyte that causes go string fuckyness
	r.cursorOffset += uint32(len(fileName) + 1) // Add name length + null byte
	metadata.FileName = fileName

	// Read the file size
	fileSizeBytes := make([]byte, 8)
	_, err = io.ReadFull(r.gmaStreamReader, fileSizeBytes)
	if err != nil {
		return metadata, err
	}
	r.cursorOffset += 8
	//fmt.Printf("bufio Read([]byte(4)]) fileSizeBytes = bytesRead(%d) data=%x\n", bytesRead, fileSizeBytes)
	metadata.FileSize = int64(binary.LittleEndian.Uint64(fileSizeBytes))

	// Read the file crc
	crcBytes := make([]byte, 4)
	_, err = io.ReadFull(r.gmaStreamReader, crcBytes)
	if err != nil {
		return metadata, err
	}
	r.cursorOffset += 4
	//fmt.Printf("bufio Read([]byte(4)]) crcBytes = bytesRead(%d) data=%x\n", bytesRead, crcBytes)
	metadata.CRC = binary.LittleEndian.Uint32(crcBytes)

	// Read the next type
	nextTypeBytes := make([]byte, 4)
	_, err = io.ReadFull(r.gmaStreamReader, nextTypeBytes)
	if err != nil {
		return metadata, err
	}
	r.cursorOffset += 4
	metadata.NextType = binary.LittleEndian.Uint32(nextTypeBytes)
	//fmt.Printf("bufio Read([]byte(4)]) nextTypeBytes = bytesRead(%d) data=%x\n", bytesRead, nextTypeBytes)

	return metadata, nil
}
func (r *GMAReader) ReadAddonCRC(lastOffset int64) (crc uint32, err error) {

	limitReader := io.NewSectionReader(r.FileHandle, int64(r.cursorOffset)+lastOffset, int64(4))

	crcBytes := make([]byte, 4)
	_, err = limitReader.Read(crcBytes)
	if err != nil {
		return 0, err
	}
	r.cursorOffset += 4
	CRC := binary.LittleEndian.Uint32(crcBytes)
	return CRC, nil
}

func (r *GMAReader) ReadFiles() (firstType int32, files []GMAFileMetadata, err error) {
	// read nType 4byte
	firstTypeBytes := make([]byte, 4)
	_, err = r.gmaStreamReader.Read(firstTypeBytes)
	if err != nil {
		return 0, files, err
	}
	r.cursorOffset += 4
	firstType = int32(binary.LittleEndian.Uint32(firstTypeBytes))

	if firstType == 0 {
		return 0, files, nil
	}
	fileOffset := int64(0)
	fileNumber := int32(1)
	for {
		fileMeta, err := r.readFileMetadata()
		if err != nil {
			if err == io.EOF {
				break
			}
			return firstType, files, err
		}
		fileMeta.FileNumber = fileNumber
		fileMeta.Offset = fileOffset
		//fmt.Printf("%s CRC: %d Offset: %d Size: %d\n", fileMeta.FileName, fileMeta.CRC, fileMeta.Offset, fileMeta.FileSize)
		//fmt.Printf("[% x]\n", fileMeta.FileName)
		files = append(files, fileMeta)
		fileOffset += fileMeta.FileSize
		fileNumber++
		if fileMeta.NextType == 0 {
			break
		}
	}

	return firstType, files, nil
}
func (r *GMAReader) GetOffset() (offset uint32) {
	return r.cursorOffset
}
func (r *GMAReader) ExtractFileTo(fileMeta GMAFileMetadata, writer io.Writer) (extractMeta GMAExtractionMeta, err error) {
	extractMeta.OriginalMeta = fileMeta
	// Seek to the specified offset in the reader
	limitReader := io.NewSectionReader(r.FileHandle, int64(r.cursorOffset)+fileMeta.Offset, int64(fileMeta.FileSize))
	// Copy the specified length of data from the reader to the output file
	buf := bytes.NewBuffer(nil)
	_, err = io.CopyN(buf, limitReader, int64(fileMeta.FileSize))
	if err != nil {
		return extractMeta, err
	}
	shaHasher := sha256.New()

	extractMeta.ExtractedCRC = crc32.Checksum(buf.Bytes(), crc32.MakeTable(crc32.IEEE))
	shaHasher.Write(buf.Bytes())
	extractMeta.ExtractedSHA256 = fmt.Sprintf("%x", shaHasher.Sum(nil))
	buf.WriteTo(writer)

	return extractMeta, nil
}
func (r *GMAReader) GetSHA256() (hash string, err error) {
	shaHasher := sha256.New()
	if _, err := io.Copy(shaHasher, r.FileHandle); err != nil {
		return "", err
	}
	return fmt.Sprintf("%x", shaHasher.Sum(nil)), nil
}