DB2Reader.h

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#pragma once
 
#include <cstdint>
#include <map>
#include <string>
#include <vector>
#include <unordered_map>
 
#include "CASCFile.h"
 
class DB2Reader : public CASCFile
{
public:
    explicit DB2Reader(const std::string& file);
    ~DB2Reader() override;
 
    bool open();
    bool close();
 
private:
    friend class DB2Table;
 
    // ── compression types (same enum values as the on-disk format) ────────
    enum FieldCompression : uint32_t
    {
        COMP_NONE = 0,
        COMP_BITPACKED = 1,
        COMP_COMMON_DATA = 2,
        COMP_BITPACKED_INDEXED = 3,
        COMP_BITPACKED_INDEXED_ARRAY = 4,
        COMP_BITPACKED_SIGNED = 5
    };
 
    // ── on-disk structures ───────────────────────────────────────────────
#pragma pack(push, 1)
    struct WDCHeader
    {
        char     magic[4];
        uint32_t record_count;
        uint32_t field_count;
        uint32_t record_size;
        uint32_t string_table_size;
        uint32_t table_hash;
        uint32_t layout_hash;
        uint32_t min_id;
        uint32_t max_id;
        uint32_t locale;
        uint16_t flags;
        uint16_t id_index;
        uint32_t total_field_count;
        uint32_t bitpacked_data_offset;
        uint32_t lookup_column_count;
        uint32_t field_storage_info_size;
        uint32_t common_data_size;
        uint32_t pallet_data_size;
        uint32_t section_count;
    };
 
    struct SectionHeaderWDC2
    {
        uint64_t tact_key_hash;
        uint32_t file_offset;
        uint32_t record_count;
        uint32_t string_table_size;
        uint32_t copy_table_size;
        uint32_t offset_map_offset;
        uint32_t id_list_size;
        uint32_t relationship_data_size;
    };
 
    struct SectionHeaderWDC3
    {
        uint64_t tact_key_hash;
        uint32_t file_offset;
        uint32_t record_count;
        uint32_t string_table_size;
        uint32_t offset_records_end;
        uint32_t id_list_size;
        uint32_t relationship_data_size;
        uint32_t offset_map_id_count;
        uint32_t copy_table_count;
    };
 
    struct FieldStructure
    {
        int16_t  size;
        uint16_t position;
    };
 
    struct FieldStorageInfo
    {
        uint16_t field_offset_bits;
        uint16_t field_size_bits;
        uint32_t additional_data_size;
        uint32_t storage_type;
        uint32_t val1;
        uint32_t val2;
        uint32_t val3;
    };
 
    struct OffsetMapEntry
    {
        uint32_t offset;
        uint16_t size;
    };
 
    struct CopyTableEntry
    {
        uint32_t newRowId;
        uint32_t copiedRowId;
    };
#pragma pack(pop)
 
    // ── per-section runtime data ─────────────────────────────────────────
    struct SectionData
    {
        // normalised header values (valid for both WDC2 and WDC3+)
        uint64_t tactKeyHash = 0;
        uint32_t fileOffset = 0;
        uint32_t recordCount = 0;
        uint32_t stringTableSize = 0;
        uint32_t offsetRecordsEnd = 0;   // WDC3+; for WDC2 = offsetMapOffset
        uint32_t idListSize = 0;
        uint32_t relationshipDataSize = 0;
        uint32_t offsetMapIdCount = 0;   // WDC3+ only
        uint32_t copyTableCount = 0;     // WDC3+ (for WDC2 = copyTableSize / 8)
 
        bool     isNormal = true;        // !(flags & 0x01)
        bool     isEncrypted = false;
 
        // pointers into m_fileData
        unsigned char* recordDataPtr = nullptr;
        uint32_t       recordDataSize = 0;
        uint32_t       stringTableOffset = 0; // absolute position of this section's string block
        uint32_t       previousStringTableSize = 0; // cumulative string table size of earlier sections
 
        std::vector<uint32_t> idList;
        std::vector<OffsetMapEntry> offsetMap;
        std::map<uint32_t, uint32_t> relationshipMap; // recordIndex -> foreignID
    };
 
    // ── reading helpers ──────────────────────────────────────────────────
    uint64_t readBitpackedValue64(const FieldStorageInfo& info, const unsigned char* recordOffset) const;
 
    bool readFieldValue(unsigned int sectionIndex, unsigned int recordIndexInSection,
                        unsigned int fieldIndex, unsigned int arrayIndex, unsigned int arraySize,
                        uint32_t recordID, unsigned int& result) const;
 
    const unsigned char* getRecordOffset(unsigned int sectionIndex, unsigned int recordIndexInSection) const;
 
    // ── member data ──────────────────────────────────────────────────────
    int m_wdcVersion = 0;
 
    WDCHeader m_header{};
 
    std::vector<FieldStorageInfo>              m_fieldStorageInfo;
    std::map<uint32_t, uint32_t>               m_palletBlockOffsets;
    unsigned char*                             m_palletData = nullptr;
    std::map<uint32_t, std::map<uint32_t, uint32_t>> m_commonData;
 
    std::vector<SectionData> m_sections;
 
    // flat index that maps a linear recordIndex (0..totalRecords-1) used by the
    // DBFile iterator to (sectionIndex, recordIndexInSection, recordID).
    struct RecordLocation
    {
        uint32_t sectionIndex;
        uint32_t localIndex;
        uint32_t recordID;
    };
    std::vector<RecordLocation> m_recordLocations;
 
    // recordID -> index in m_recordLocations for O(1) getRow() by ID
    std::unordered_map<uint32_t, size_t> m_idToRecordIndex;
 
    // relationship reverse lookup: foreignID -> list of recordIDs
    std::unordered_map<uint32_t, std::vector<uint32_t>> m_relationshipLookup;
 
    // copy table: destID -> srcID
    std::map<uint32_t, uint32_t> m_copyTable;
 
    // keep the raw file data alive for the lifetime of the reader so that
    // record-offset pointers remain valid.
    unsigned char* m_fileData = nullptr;
    size_t         m_fileDataSize = 0;
 
    std::map<int, int> m_fieldSizes;
};