pc-tools/ldc2/src/tape_block.hh

   1 #ifndef TAPE_BLOCK_H
   2 #define TAPE_BLOCK_H
   3
   4
   5 /*!
   6  *\brief Tape data block base class
   7  *
   8  * This class represents a Honeywell paper tape block.
   9  * That may be some kind of data block or a end of tape mark.
  10  */
  11 class tape_block{
  12
  13 public: // types
  14
  15   /*!
  16    * The block's initialisation state
  17    */
  18   typedef enum {
  19     TBS_OK,          //!< Block successfully initialised
  20     TBS_EOF_LEGAL,   //!< Legal EOF while initialising
  21     TBS_EOF_ILLEGAL, //!< Illegal EOF while initialising
  22     TBS_CHECKSUM,    //!< Checksum error
  23     TBS_IOERR,       //!< I/O-Error while reading
  24     TBS_DEFAULT      //!< Block not initialised.
  25   } tb_state_t;
  26
  27   /*!
  28    * Tape block types
  29    */
  30   typedef enum {
  31     TBT_DATA=0x10,   //!< Data block
  32     TBT_EOT,         //!< End of tape block
  33     TBT_DISCARD      //!< Invalid block, check block_type
  34   } tb_type_t;
  35
  36 protected: // methods
  37   /*!
  38    *\brief Protected default constructor
  39    */
  40   tape_block();
  41
  42 public: // methods
  43
  44   tape_block(tape_block &);
  45
  46   /*!
  47    *\brief Read-in constructor for file descriptor
  48    *
  49    * This constructor is used to read in the block's data via a file
  50    * descriptor.\\
  51    * This is done in the following way:\\
  52    * - input_start() is called.\\
  53    * - Data is read from fd. Stops on end of file or end of block
  54    * or IO error. On EOF or IO error input_stop() is NOT called.\\
  55    * - If there was no IO error the block's checksum is calculated
  56    * and checked.\
  57    * - The block's type field is initialised.\\
  58    * - input_stop() is called.\\
  59    *\param fd_p A pointer to the device descriptor where
  60    * the data is taken from \\
  61    *\param input_stop A pointer to a function called at the end of input\\
  62    *\param input_start A pointer to a function called at the beginning
  63    * of input\\
  64    *\param start_stop_arg A pointer passed to input_start and input_stop().
  65   */
  66   tape_block (int  fd_p,
  67               void(*input_start)(void *)=0,
  68               void (*input_stop)(void *)=0,
  69               void * start_stop_arg=0
  70               );
  71
  72   /*!
  73    * The virtual destructor
  74    */
  75   virtual ~tape_block();
  76
  77   /*!
  78    *\brief Query the block's state.
  79    *
  80    * If the state is not TBS_OK, the block must be discarded.
  81    *\return The block's initialisation state
  82    */
  83   tb_state_t get_state();
  84
  85   /*!
  86    *\brief Get size of the internal raw data buffer
  87    *\return The size of the internal raw data buffer
  88    */
  89   int get_raw_size();
  90
  91   /*!
  92    *\brief Access internal raw data buffer
  93    *
  94    * The raw data buffer contains all block data except the \\
  95    * block start delimiter and block end delimiter.
  96    *\return Pointer to internal raw data buffer of the block
  97    */
  98   unsigned char * get_raw_data();
  99
 100   /*
 101    *\brief Determine the block's type
 102    *
 103    * This routine returns the block's type.\\
 104    *\retval TBT_DATA if it's a data block
 105    *\retval TBT_EOT if it's an end of tape mark
 106    *\retval TBR_DISCARD if the block is unusable
 107    *
 108    *\note This function is virtual. That means that if the tape block in
 109    * question is of the subtype data_block which overwrites this method,
 110    * it will return the block type contained in the upper 4 bits of the
 111    * first data word! Try to avoid testing for TBT_DATA.
 112    */
 113   virtual int get_type();
 114
 115   /*!
 116    *\brief Determine the block's subtype
 117    *
 118    * Some data block types have a subtype. This can be determined this way.
 119    *\return Block subtype if the block object is of a suitable subclass
 120    */
 121   virtual int get_subtype();
 122
 123 private:   // methods
 124   /*!
 125    *\brief Initialize word representation of data
 126    *\retval 0 on success
 127    *\retval 1 on error
 128    */
 129   int init_words(void);
 130
 131   /*!
 132    *\brief Calculate and check checksum
 133    *\retval 0 on success
 134    *\retval 1 on error
 135    */
 136   int test_checksum();
 137
 138 protected: // members
 139   int block_type;             //!< type of this block
 140   tb_state_t init_state;      //!< Initialisation state
 141   int data_read;              //!< Total data consumption during intialisation
 142   unsigned char * raw_data;   //!< Raw block data in bytes
 143   int raw_size;               //!< Size of the raw data
 144   unsigned short * word_data; //!< Data organized in machine words
 145   int word_size;              //!< Size of the blocks in machine words
 146
 147 }; // tape_block
 148
 149
 150 #endif