shell/File.h

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  39
  40 #ifndef __avmshell_File__
  41 #define __avmshell_File__
  42
  43 #include "avmshell.h"
  44
  45 namespace avmshell
  46 {
  47     /**
  48     * Abstract base class for performing platform-specific file operations
  49     * This class needs to be derived and its methods implemented by platform to enable the shell to perform file I/O
  50     */
  51     class File
  52     {
  53     public:
  54         /**
  55         *  An enum defining the open modes for a file
  56         */
  57         typedef enum
  58         {
  59             OPEN_READ = 0,
  60             OPEN_WRITE,
  61             OPEN_APPEND,
  62             OPEN_READ_BINARY,
  63             OPEN_WRITE_BINARY,
  64             OPEN_APPEND_BINARY
  65         }OpenAttribute;
  66
  67         /**
  68         * Virtual Destructor
  69         */
  70         virtual ~File() {}
  71
  72         /**
  73         * Method to open a file on platform's file system
  74         * The implementation should open the file with the given name and attributes for open mode
  75         * @param filename represents the path and name of the file to be opened.  filename is UTF-8
  76         * @param flags one of the values from OpenAttribute enumeration indicating the  mode of file
  77         * @return true if file was opened successfully, false otherwise
  78         * @see enum OpenAttribute
  79         */
  80         virtual bool open(const char* filename, OpenAttribute flags) = 0;
  81
  82         /**
  83         * Method to close an opened file.
  84         * If the file was not opened this method should do nothing
  85         * @return none
  86         */
  87         virtual void close() = 0;
  88
  89         /**
  90         * Method to read a chunk of data from the file
  91         * This method can return 0 in event of a read error or if the file marker was at end-of-file.
  92         * So a return value of zero should not be treated as an error condition by default.
  93         * Instead method isEOF() should be used to detect a end-of-file .
  94         * @param buffer buffer to read the data into
  95         * @param bytesToRead number of bytes to read
  96         * @return number of bytes actually read.  0 or less than bytesToRead in case of error or end-of-file was reached
  97         */
  98         virtual size_t read(void* buffer, size_t bytesToRead) = 0;
  99
 100         /**
 101         * Method to write a chunk of data to the file
 102         * @param buffer buffer containing the data to write to file
 103         * @param bytesToWrite number of bytes to write from the buffer
 104         * @return number of bytes actually written.  If this value is less than bytesToWrite then that indicates an error
 105         */
 106         virtual size_t write(const void* buffer, size_t bytesToWrite) = 0;
 107
 108         /**
 109         * Method to get the current position of the file head
 110         * @return returns the current byte position of the file head, -1 if an error occurred
 111         */
 112         virtual int64_t getPosition() const = 0;
 113
 114         /**
 115         * Method to move the file head to a certain position
 116         * @param pos number indicating the byte position in file to move the file head to
 117         * @return returns true if the operation was successful, false if an error occurred
 118         */
 119         virtual bool setPosition(int64_t pos) = 0;
 120
 121         /**
 122         * Method to get the size of file
 123         * @return size of the file, -1 if an error occurred
 124         */
 125         virtual int64_t size() const = 0;
 126
 127         /**
 128         * Method to check if the end-of-file has reached
 129         * @return true if end if reached, false otherwise
 130         */
 131         virtual bool isEOF() const = 0;
 132     };
 133 }
 134
 135 #endif /* __avmshell_File__ */