Supermodel/Src/BlockFile.h

/**
 ** Supermodel
 ** A Sega Model 3 Arcade Emulator.
 ** Copyright 2011 Bart Trzynadlowski, Nik Henson
 **
 ** This file is part of Supermodel.
 **
 ** Supermodel is free software: you can redistribute it and/or modify it under
 ** the terms of the GNU General Public License as published by the Free 
 ** Software Foundation, either version 3 of the License, or (at your option)
 ** any later version.
 **
 ** Supermodel is distributed in the hope that it will be useful, but WITHOUT
 ** ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 ** FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 ** more details.
 **
 ** You should have received a copy of the GNU General Public License along
 ** with Supermodel.  If not, see <http://www.gnu.org/licenses/>.
 **/
 
/*
 * BlockFile.h
 * 
 * Header file for block format container file management.
 */

#ifndef INCLUDED_BLOCKFILE_H
#define INCLUDED_BLOCKFILE_H

#include <cstdint>

/*
 * CBlockFile:
 *
 * Block format container file. The file format is a series of consecutive,
 * variable-length blocks referenced by unique name strings. 
 *
 * All strings (comments and names) will be truncated to 1024 bytes, not
 * including the null terminator.
 *
 * Members do not generate any output messages.
 */
class CBlockFile
{
public:
  /*
   * Read(data, numBytes):
   *
   * Reads data from the current file position. 
   *
   * Parameters:
   *    data      Buffer to read to.
   *    numBytes  Number of bytes to read.
   *
   * Returns:
   *    Number of bytes read. If not the same as numBytes, an error
   *    occurred.
   */
  unsigned Read(void *data, unsigned numBytes);
  
  /*
   * FindBlock(name):
   *
   * Scans the file for a block with the given name string. When it is found,
   * the file pointer is set to the beginning of the data region.
   *
   * Parameters:
   *    name  Name of block to locate.
   *
   * Returns:
   *    OKAY if found, FAIL if unable to locate.
   */
  bool FindBlock(const char *name);
  
  /*
   * Write(data, numBytes):
   *
   * Outputs data at the current file pointer position. Updates the block
   * header appropriately.
   *
   * Parameters:
   *    data      Data to write.
   *    numBytes  Number of bytes to write.
   */
  void Write(const void *data, unsigned numBytes);

  /*
   * NewBlock(name, comment):
   *
   * Begins a new block. Writes the block header and sets the file pointer to
   * the beginning of its data area.
   *
   * Parameters:
   *    name      Block name. Must be unique and not NULL.
   *    comment   Comment string to embed in the block header.
   */
  void NewBlock(const char *title, const char *comment);

  /*
   * Create(file, headerName, comment):
   *
   * Opens a block file for writing and creates the header block. This  
   * function must be called before attempting to write data. Otherwise, all
   * write commands will be silently ignored. Read commands will be ignored
   * and will always return 0's.
   * 
   * Parameters:
   *    file        File path.
   *    headerName  Block name for header. Must be unique and not NULL.
   *    comment     Comment string that will be embedded into file header.
   *
   * Returns:
     *    OKAY if successfully opened, otherwise FAIL.
   */
  bool Create(const char *file, const char *headerName, const char *comment);

  /*
   * Load(file):
   *
   * Open a block file file for reading.
   *
   * Parameters:
   *    file  File path.
   *
   * Returns:
   *    OKAY if successfully opened and confirmed to be a valid Supermodel
   *    block file, otherwise FAIL. If the file could not be opened, all 
   *    subsequent operations will be silently ignored (reads will return
   *    0's). Write commands will be ignored.
   */
  bool Load(const char *file);

  /*
   * Close(void):
   *
   * Closes the file.
   */
  void Close(void);

  /*
   * CBlockFile(void):
   * ~CBlockFile(void):
   * 
   * Constructor and destructor.
   */
  CBlockFile(void);
  ~CBlockFile(void);

private:
  // Helper functions
  void      ReadString(char *str, unsigned strLen, unsigned maxLen);
  unsigned  ReadBytes(void *data, unsigned numBytes);
  unsigned  ReadDWord(uint32_t *data);
  void      UpdateBlockSize(void);
  void      WriteByte(uint8_t data);
  void      WriteDWord(uint32_t data);
  void      WriteBytes(const void *data, unsigned numBytes);
  void      WriteBlockHeader(const char *name, const char *comment);

  // File state data
  char      strBuf[1026];   // buffers up to a 1024-character string, its terminator, and an extra terminator (just in case)
  FILE      *fp;
  int       mode;           // 'r' for read, 'w' for write
  long int  fileSize;       // size of file in bytes
  long int  blockStartPos;  // points to beginning of current block (or file) header
  long int  dataStartPos;   // points to beginning of current block's data section 
};


#endif  // INCLUDED_BLOCKFILE_H