Package mars.util

Class SystemIO

java.lang.Object
mars.util.SystemIO
public class SystemIO extends Object
Provides standard i/o services needed to simulate the MIPS syscall routines. These methods will detect whether the simulator is being run from the command line or through the GUI, then do I/O to System.in and System.out in the former situation, and interact with the GUI in the latter.
Version:
August 2003-2005
Author:
Pete Sanderson and Ken Vollmar

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static String
    fileErrorString
    String used for description of file error
    static int
    SYSCALL_BUFSIZE
    Buffer size for syscalls for file I/O
    static int
    SYSCALL_MAXFILES
    Maximum number of files that can be open

  • Method Summary

    Modifier and Type
    Method
    Description
    static void
    closeFile​(int fd)
    Close the file with specified file descriptor
    static String
    getFileErrorMessage()
    Retrieve file operation or error message
    static int
    openFile​(String filename, int flag)
    Open a file for either reading or writing.
    static void
    printString​(String string)
    Implements syscall having 4 in $v0, to print a string.
    static int
    readChar​(int serviceNumber)
    Implements syscall having 12 in $v0, to read a char value.
    static double
    readDouble​(int serviceNumber)
    Implements syscall to read a double value.
    static float
    readFloat​(int serviceNumber)
    Implements syscall to read a float value.
    static int
    readFromFile​(int fd, byte[] myBuffer, int lengthRequested)
    Read bytes from file.
    static int
    readInteger​(int serviceNumber)
    Implements syscall to read an integer value.
    static String
    readString​(int serviceNumber, int maxLength)
    Implements syscall to read a string.
    static void
    resetFiles()
    Reset all files -- clears out the file descriptor table.
    static int
    writeToFile​(int fd, byte[] myBuffer, int lengthRequested)
    Write bytes to file.

    Methods inherited from class java.lang.Object

    equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • SYSCALL_BUFSIZE

      public static final int SYSCALL_BUFSIZE
      Buffer size for syscalls for file I/O
      See Also:
      Constant Field Values

    • SYSCALL_MAXFILES

      public static final int SYSCALL_MAXFILES
      Maximum number of files that can be open
      See Also:
      Constant Field Values

    • fileErrorString

      public static String fileErrorString
      String used for description of file error

  • Method Details

    • readInteger

      public static int readInteger​(int serviceNumber)
      Implements syscall to read an integer value. Client is responsible for catching NumberFormatException.
      Parameters:
      serviceNumber - the number assigned to Read Int syscall (default 5)
      Returns:
      int value corresponding to user input

    • readFloat

      public static float readFloat​(int serviceNumber)
      Implements syscall to read a float value. Client is responsible for catching NumberFormatException.
      Parameters:
      serviceNumber - the number assigned to Read Float syscall (default 6)
      Returns:
      float value corresponding to user input Feb 14 2005 Ken Vollmar

    • readDouble

      public static double readDouble​(int serviceNumber)
      Implements syscall to read a double value. Client is responsible for catching NumberFormatException.
      Parameters:
      serviceNumber - the number assigned to Read Double syscall (default 7)
      Returns:
      double value corresponding to user input

    • printString

      public static void printString​(String string)
      Implements syscall having 4 in $v0, to print a string.

    • readString

      public static String readString​(int serviceNumber, int maxLength)
      Implements syscall to read a string.
      Parameters:
      serviceNumber - the number assigned to Read String syscall (default 8)
      maxLength - the maximum string length
      Returns:
      the entered string, truncated to maximum length if necessary

    • readChar

      public static int readChar​(int serviceNumber)
      Implements syscall having 12 in $v0, to read a char value.
      Parameters:
      serviceNumber - the number assigned to Read Char syscall (default 12)
      Returns:
      int value with lowest byte corresponding to user input

    • writeToFile

      public static int writeToFile​(int fd, byte[] myBuffer, int lengthRequested)
      Write bytes to file.
      Parameters:
      fd - file descriptor
      myBuffer - byte array containing characters to write
      lengthRequested - number of bytes to write
      Returns:
      number of bytes written, or -1 on error

    • readFromFile

      public static int readFromFile​(int fd, byte[] myBuffer, int lengthRequested)
      Read bytes from file.
      Parameters:
      fd - file descriptor
      myBuffer - byte array to contain bytes read
      lengthRequested - number of bytes to read
      Returns:
      number of bytes read, 0 on EOF, or -1 on error

    • openFile

      public static int openFile​(String filename, int flag)
      Open a file for either reading or writing. Note that read/write flag is NOT IMPLEMENTED. Also note that file permission modes are also NOT IMPLEMENTED.
      Parameters:
      filename - string containing filename
      flag - 0 for read, 1 for write
      Returns:
      file descriptor in the range 0 to SYSCALL_MAXFILES-1, or -1 if error

    • closeFile

      public static void closeFile​(int fd)
      Close the file with specified file descriptor
      Parameters:
      fd - the file descriptor of an open file

    • resetFiles

      public static void resetFiles()
      Reset all files -- clears out the file descriptor table.

    • getFileErrorMessage

      public static String getFileErrorMessage()
      Retrieve file operation or error message
      Returns:
      string containing message