initial

2025-09-05 03:34:32 +02:00
commit ab799e113d
5 changed files with 498 additions and 0 deletions
--- a/pakUtils.go
+++ b/pakUtils.go
@@ -0,0 +1,215 @@
+package reforger_utils
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io"
+)
+
+func readString(r io.Reader, expected string) error {
+	buf := make([]byte, 4)
+	if _, err := io.ReadFull(r, buf); err != nil {
+		return fmt.Errorf("failed to read identifier: %w", err)
+	}
+	if string(buf) != expected {
+		return fmt.Errorf("expected identifier '%s', but got '%s'", expected, string(buf))
+	}
+	return nil
+}
+
+func parseEntry(r *bytes.Reader) (PakEntry, error) {
+	var pakEntry PakEntry
+	if err := binary.Read(r, binary.LittleEndian, &pakEntry.Offset); err != nil {
+		return PakEntry{}, fmt.Errorf("failed to read file offset: %w", err)
+	}
+
+	if err := binary.Read(r, binary.LittleEndian, &pakEntry.Size); err != nil {
+		return PakEntry{}, fmt.Errorf("failed to read file size: %w", err)
+	}
+
+	if err := binary.Read(r, binary.LittleEndian, &pakEntry.OriginalSize); err != nil {
+		return PakEntry{}, fmt.Errorf("failed to read uncompressed size: %w", err)
+	}
+
+	r.Seek(4, io.SeekCurrent) // NULL
+
+	if err := binary.Read(r, binary.BigEndian, &pakEntry.CompressType); err != nil {
+		return PakEntry{}, fmt.Errorf("failed to read compression type: %w", err)
+	}
+
+	if err := binary.Read(r, binary.BigEndian, &pakEntry.UnknownData); err != nil {
+		return PakEntry{}, fmt.Errorf("failed to read unknown data: %w", err)
+	}
+
+	return pakEntry, nil
+}
+
+func parseEntries(r *bytes.Reader, dataBlockLength int64) ([]PakEntry, error) {
+	var entries []PakEntry
+	read := 0
+
+	for r.Len() > 0 {
+		// read byte to determine entry type
+		entryType, err := r.ReadByte()
+		if err != nil {
+			return nil, fmt.Errorf("failed to read entry type: %w", err)
+		}
+
+		nameLength, err := r.ReadByte()
+		if err != nil {
+			return nil, fmt.Errorf("failed to read name length: %w", err)
+		}
+
+		name := make([]byte, nameLength)
+		if _, err := io.ReadFull(r, name); err != nil {
+			return nil, fmt.Errorf("failed to read name: %w", err)
+		}
+
+		switch entryType {
+		case 0x00: // Directory
+			ent, size, err := parseDirectory(r, string(name), dataBlockLength)
+			if err != nil {
+				return nil, fmt.Errorf("failed to parse directory '%s': %w", string(name), err)
+			}
+			read += 1 + 1 + int(nameLength) + size
+			entries = append(entries, ent...)
+		case 0x01: // File
+			pakEntry, err := parseEntry(r)
+			if err != nil {
+				return nil, fmt.Errorf("failed to parse entry for file '%s': %w", string(name), err)
+			}
+
+			pakEntry.Name = string(name)
+
+			entries = append(entries, pakEntry)
+			read += 1 + 1 + int(nameLength) + 4 + 4 + 4 + 4 + 4 + 4 // entryType + nameLength + name + offset + size + originalSize + NULL + compressType + unknownData
+
+		default:
+			return nil, fmt.Errorf("unknown entry type: %d", entryType)
+		}
+	}
+
+	return entries, nil
+}
+
+func parseDirectory(r *bytes.Reader, path string, dataBlockOffset int64) ([]PakEntry, int, error) {
+	var entries []PakEntry
+	var totalSize int
+
+	// read the number of entries in the directory
+	var entryCount uint32
+	if err := binary.Read(r, binary.LittleEndian, &entryCount); err != nil {
+		return nil, 0, fmt.Errorf("failed to read entry count for directory '%s': %w", path, err)
+	}
+
+	totalSize += 4
+
+	for i := 0; i < int(entryCount); i++ {
+		// read byte to determine entry type
+		entryType, err := r.ReadByte()
+		if err != nil {
+			return nil, 0, fmt.Errorf("failed to read entry type: %w", err)
+		}
+
+		nameLength, err := r.ReadByte()
+		if err != nil {
+			return nil, 0, fmt.Errorf("failed to read name length: %w", err)
+		}
+
+		name := make([]byte, nameLength)
+		if _, err := io.ReadFull(r, name); err != nil {
+			return nil, 0, fmt.Errorf("failed to read name: %w", err)
+		}
+
+		totalSize += 1 + 1 + int(nameLength)
+
+		switch entryType {
+		case 0x00: // Directory
+			subEntries, size, err := parseDirectory(r, path+"/"+string(name), dataBlockOffset)
+			if err != nil {
+				return nil, 0, fmt.Errorf("failed to parse directory '%s': %w", path+"/"+string(name), err)
+			}
+			entries = append(entries, subEntries...)
+			totalSize += size
+		case 0x01: // File
+			pakEntry, err := parseEntry(r)
+			if err != nil {
+				return nil, 0, fmt.Errorf("failed to parse entry for file '%s': %w", path+"/"+string(name), err)
+			}
+			pakEntry.Name = path + "/" + string(name)
+			entries = append(entries, pakEntry)
+			totalSize += 4 + 4 + 4 + 4 + 4 + 4
+		}
+	}
+
+	return entries, totalSize, nil
+}
+
+func GetPakFileInfo(data []byte) ([]PakEntry, error) {
+	r := bytes.NewReader(data)
+
+	// Read FORM header
+	if err := readString(r, "FORM"); err != nil {
+		return nil, err
+	}
+	r.Seek(4, io.SeekCurrent) // Skip total file size
+
+	// Read PAC1 header
+	if err := readString(r, "PAC1"); err != nil {
+		return nil, err
+	}
+
+	var dataBlockOffset int64 = -1
+
+	// Find DATA and FILE chunks
+	for {
+		chunkIDBytes := make([]byte, 4)
+		_, err := io.ReadFull(r, chunkIDBytes)
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, fmt.Errorf("failed to read chunk ID: %w", err)
+		}
+		chunkID := string(chunkIDBytes)
+
+		var chunkSize uint32
+		if err := binary.Read(r, binary.BigEndian, &chunkSize); err != nil {
+			return nil, fmt.Errorf("failed to read chunk size for %s: %w", chunkID, err)
+		}
+
+		switch chunkID {
+		case "HEAD":
+			r.Seek(int64(chunkSize), io.SeekCurrent)
+		case "DATA":
+			// The file offsets are relative to the start of the data within this block.
+			// So we record the start position of the data block.
+			dataBlockOffset, err = r.Seek(0, io.SeekCurrent)
+			if err != nil {
+				return nil, fmt.Errorf("could not get DATA block offset: %w", err)
+			}
+			r.Seek(int64(chunkSize), io.SeekCurrent)
+		case "FILE":
+			if dataBlockOffset == -1 {
+				return nil, fmt.Errorf("FILE chunk found before DATA chunk")
+			}
+
+			// skip unknown data
+			r.Seek(6, io.SeekCurrent)
+
+			entries, err := parseEntries(r, dataBlockOffset)
+
+			if err != nil {
+				return nil, fmt.Errorf("failed to parse FILE entries: %w", err)
+			}
+
+			return entries, nil
+		default:
+			// Skip unknown chunks
+			r.Seek(int64(chunkSize), io.SeekCurrent)
+		}
+	}
+
+	return nil, fmt.Errorf("FILE chunk not found in archive")
+}