Class Kernel 

java.lang.Object
   |
   +----Kernel
public class Kernel
extends Object
A simple kernel simulation. There is only one public interface to this class: interrupt(). System calls, disk notification, and power on messages all arrive by way of this function.

Author:
Douglas Thain (thain@cs.wisc.edu)
See Also:
Disk, Library

Variable Index

o ERROR_BAD_ARGUMENT_TYPE
One of the system call parameters made no sense
o ERROR_BAD_COMMAND
A command passed to SYSCALL_EXEC could not be executed
o ERROR_END_OF_FILE
End of file was reached.
o ERROR_IN_CHILD
A child program caused an exception and crashed.
o ERROR_IO
Miscellaneous error while performing I/O.
o ERROR_OUT_OF_RANGE
One parameter was too big or too small
o INTERRUPT_DISK
Indicates that a disk caused the interrupt.
o INTERRUPT_POWER_ON
Indicates that it's time to start the system.
o INTERRUPT_USER
Indicates that a user caused the interrupt.
o SYSCALL_EXEC
System call to execute a new program.
o SYSCALL_EXEC_AND_WAIT
System call to execute a new program.
o SYSCALL_INPUT
System call to read text from the console.
o SYSCALL_OUTPUT
System call to output text on the console.

Constructor Index

o Kernel()

Method Index

o interrupt(int, int, int, Object, Object, byte[])
This is the only entry into the kernel.

Variables

o INTERRUPT_USER 
 public static final int INTERRUPT_USER
Indicates that a user caused the interrupt.
Parameter i1 -- a valid system call number. Other parameters depend on the call number.

o INTERRUPT_DISK 
 public static final int INTERRUPT_DISK
Indicates that a disk caused the interrupt. All other parameters will be null or zero.

o INTERRUPT_POWER_ON 
 public static final int INTERRUPT_POWER_ON
Indicates that it's time to start the system.
The Kernel should set up any internal state and begin executing the first program.
Parameter i1 -- the number of blocks to use in the disk cache.
Parameter o1 -- the Disk to be used.

o SYSCALL_OUTPUT 
 public static final int SYSCALL_OUTPUT
System call to output text on the console.
Parameter o1 -- A string to display
Returns -- Zero.

o SYSCALL_INPUT 
 public static final int SYSCALL_INPUT
System call to read text from the console.
This function returns when the user presses [return].
Parameter o1 -- A StringBuffer to fill with input text.
Returns -- Zero, ERROR_BAD_ARGUMENT_TYPE, ERROR_END_OF_FILE, or ERROR_IO.

o SYSCALL_EXEC 
 public static final int SYSCALL_EXEC
System call to execute a new program.
The new program will run in parallel to the current program.
Parameter o1 - The name of a Java class to execute.
Parameter o2 - An array for String arguments.
Returns Zero, ERROR_BAD_ARGUMENT_TYPE, or ERROR_BAD_COMMAND.

o SYSCALL_EXEC_AND_WAIT 
 public static final int SYSCALL_EXEC_AND_WAIT
System call to execute a new program.
This call will not return until the newly created program has run to completion.
Parameter o1 -- The name of a Java class to execute.
Parameter o2 -- An array for String arguments.
Returns -- Zero, ERROR_BAD_ARGUMENT TYPE, ERROR_BAD_COMMAND, or ERROR_IN_CHILD.

o ERROR_BAD_ARGUMENT_TYPE 
 public static final int ERROR_BAD_ARGUMENT_TYPE
One of the system call parameters made no sense

o ERROR_BAD_COMMAND 
 public static final int ERROR_BAD_COMMAND
A command passed to SYSCALL_EXEC could not be executed

o ERROR_OUT_OF_RANGE 
 public static final int ERROR_OUT_OF_RANGE
One parameter was too big or too small

o ERROR_END_OF_FILE 
 public static final int ERROR_END_OF_FILE
End of file was reached.

o ERROR_IO 
 public static final int ERROR_IO
Miscellaneous error while performing I/O.

o ERROR_IN_CHILD 
 public static final int ERROR_IN_CHILD
A child program caused an exception and crashed.

Constructors

o Kernel 
 public Kernel()

Methods

o interrupt 
 public static int interrupt(int kind,
                             int i1,
                             int i2,
                             Object o1,
                             Object o2,
                             byte a[])
This is the only entry into the kernel.

A user may call this function to perform a system call. In that case, set kind to INTERRUPT_USER and set i1 to the system call number. Other parameters should be set as the system call requires.

A disk may call this function to indicate the current operation has completed. In that case, kind will be INTERRUPT_DISK and all parameters will be zero or null. Important: If the Disk calls interrupt(), the Kernel should take care of business and return from the interrupt as soon as possible. All Disk I/O is halted while the interrupt is being processed.

The boot code may call this function to indicate that the computer has been turned on and it is time to start the first program and use the disk. In that case, kind will be INTERRUPT_POWER_ON, o1 will point to the Disk to be used, i1 will indicate the size of the buffer cache, and all other parameters will be zero or null.

Returns:
A negative number indicating an error code, or other values depending on the system call.