MyZip/ZipDefine.h

#pragma once

#include <cstdint>

/**   Overall .ZIP file format:

      [local file header 1]   -> "PK" + 0x4b50 + ...
      [encryption header 1]
      [file data 1]
      [data descriptor 1]
      . 
      .
      .
      [local file header n]   -> "PK" + 0x4b50 + ...
      [encryption header n]
      [file data n]
      [data descriptor n]
      [archive decryption header] 
      [archive extra data record] 
      [central directory header 1]
      .
      .
      .
      [central directory header n]   -> "PK" + 0x4b50
      [zip64 end of central directory record]
      [zip64 end of central directory locator] 
      [end of central directory record]   <- 필수 포함 (단 한개)
*/

/**   Local file header:

      local file header signature     4 bytes  (0x04034b50)
      version needed to extract       2 bytes
      general purpose bit flag        2 bytes
      compression method              2 bytes
      last mod file time              2 bytes
      last mod file date              2 bytes
      crc-32                          4 bytes
      compressed size                 4 bytes
      uncompressed size               4 bytes
      file name length                2 bytes   -> Variable
      extra field length              2 bytes   -> Variable

      file name (variable size)
      extra field (variable size)
 */

#pragma pack(push, 1)
constexpr int LOCAL_FILE_HEADER_BYTE = 30;

 struct LocalFileHeader {
      uint32_t signature;
      uint16_t versionNeededToExtract;
      uint16_t generalBitFlag;
      uint16_t compressionMethod;   // no compression == 0
      uint16_t lastModTime;   // 압축 시점의 시간 (1980년 기준 시간)
      uint16_t lastModDate;   // 압축 시점의 날짜 (1980년 기준 연도)
      uint32_t crc32;
      uint32_t sizeOfCompressed;  // same as unCompression (cuz no compreesion)
      uint32_t sizeOfUncompressed;
      uint16_t lengthOfFileName;
      uint16_t lengthOfExtraField;

      // var[fileNameLength] fileName
      // var[extraFieldLength] extraField
 };

/**   Central directory structure:

      [central directory header 1]
      .
      .
      . 
      [central directory header n]
      [digital signature] 

      File header:

        central file header signature   4 bytes  (0x02014b50)
        version made by                 2 bytes
        version needed to extract       2 bytes
        general purpose bit flag        2 bytes
        compression method              2 bytes
        last mod file time              2 bytes
        last mod file date              2 bytes
        crc-32                          4 bytes
        compressed size                 4 bytes
        uncompressed size               4 bytes
        file name length                2 bytes
        extra field length              2 bytes
        file comment length             2 bytes
        disk number start               2 bytes
        internal file attributes        2 bytes
        external file attributes        4 bytes
        relative offset of local header 4 bytes

        file name (variable size)
        extra field (variable size)
        file comment (variable size)
 */

 constexpr int CENTRAL_DIRECTORY_BYTE = 46;
 struct CentralDirectory {
      uint32_t signature;
      uint16_t versionMadeBy;
      uint16_t versionNeededToExtract;
      uint16_t generalBitFlag;
      uint16_t compressionMethod;   // no compression == 0
      uint16_t lastModTime;   // 압축 시점의 시간 (1980년 기준 시간)
      uint16_t lastModDate;   // 압축 시점의 날짜 (1980년 기준 연도)
      uint32_t crc32;
      uint32_t compressedSize;  // same as unCompression (cuz no compreesion)
      uint32_t unCompressedSize;
      uint16_t fileNameLength;
      uint16_t extraFieldLength;
      uint16_t fileCommentLength;

      uint16_t diskNumStart;
      uint16_t attributeInternal;
      uint32_t attributeExternal;
      uint32_t offsetLocalHeader;

      // var[fileNameLength] fileName
      // var[extraFieldLength] extraField
      // var[fileCommentLength] fileComment
};

 /**  End of central directory record:

      end of central dir signature    4 bytes  (0x0605 + 4b50)
      number of this disk             2 bytes
      
      // 중앙 디렉터리가 시작되는 디스크의 번호.
      number of the disk with the
      start of the central directory  2 bytes
      
      // 이 디스크에 있는 중앙 디렉터리 항목의 수
      total number of entries in the
      central directory on this disk  2 bytes
      
      // .ZIP 파일 내 전체 파일 수
      total number of entries in
      the central directory           2 bytes
      
      size of the central directory   4 bytes

      // 중앙 디렉터리가 시작되는 디스크 상에서 중앙 디렉터리 시작 지점의 오프셋
      offset of start of central
      directory with respect to
      the starting disk number        4 bytes

      .ZIP file comment length        2 bytes
      .ZIP file comment       (variable size)
*/
 constexpr int EOCD_BYTE = 22;

 struct EoCDRecord {
      uint32_t signature;
      
      // central directory end record을 포함하는 이 디스크의 번호
      uint16_t diskNumber;

      // 중앙 디렉터리가 시작되는 디스크의 번호.
      uint16_t diskNumber_CentralDirStart;

      // 이 디스크에 있는 중앙 디렉터리 항목의 수
      uint16_t numOfCentralDir;

      // .ZIP 파일 내 전체 파일 수
      uint16_t numOfEntries;
      
      uint32_t SizeOfCentralDir;
      uint32_t OffsetOfCentralDirOffset;
      uint16_t LengthOfCommentLength;

      // var[zipFileCommentLength] zipFileComment
};

#pragma pack(pop)