Methods:

Timer ISR:

_timerInstall proc near

This function replaces the IVT by the address of _timerHandler and saves the 4 byte address in oldTimerIsr

_timerInstall endp

Inputs: none
Purpose: To provide a tick once every 72 times in a second
Outputs: timerFlag

_timerHandler proc near

Set tickFlag to 1 and call the oldTimerISR once every 4 times.

_timerHandler endp

_timerUninstall proc near

This function replaces the 4 byte address in saved in oldTimerIsr back into the IVT

_timerUninstall endp

Keyboard ISR:

_keyboardInstall proc near

This function replaces the IVT by the address of _timerHandler and saves the 4 byte address in oldKeyboardIsr

_keyboardInstall endp

Inputs: menuOption, arcadeOption
Purpose: To process the Keyboard input when in appropriate game modes
Outputs: menuOption, keyboardFlag

_keyboardHandler proc near

Fetch a character from the keyboard buffer
Set keyboardFlag accordingly [ -1 = Esc, 1 = Enter, 2 = menuOption ]
Set menuOption accordingly

_keyboardHandler endp

_keyboardUninstall proc near

This function replaces the 4 byte address in saved in oldKeyboardIsr back into the IVT

keyboardUninstall endp

Engine Methods:

Main Function:

Inputs: none
Purpose: Main program control routine, at beginning of program execution. It also handles the Menu Window
Outputs: Depending on modeOption, appropriate method is called

_main proc near

Load all PCX files and switch to GMode

Main Loop
Draw Wallpaper

Loop for Options:
Draw Options
Poll the menuOption flag untill an enter is pressed
End of Options Loop

If Quit Option is selected
Break out of Loop

Begin appropriate Game Mode
End of Main Loop

Switch to TMode

_main endp

Gaming Mode Functions:

Inputs: None
Purpose: Routine for Arcade Mode Gaming
Outputs: <miss> and <hits>

_arcadeMode proc near

Loop for each Level:
Draw Wallpaper
Draw Sprite

Loop for each Round:
Set shootPerm ON

Loop for Animation:
Animate Sprite
Poll shotStatus flag
Check if time has run out
End of Animation Loop

Blow sprite
Reset varaibles
Update Scores
End of Round Loop

Go to the next round
End of Level Loop - 3 levels each with 5 rounds

_arcadeMode endp

Inputs: None
Purpose: Routine for Practice Mode Gaming
Outputs: none

_practiceMode

Loop for each Game:
Draw Wallpaper
Draw Sprite

Loop for Animation:
Animate Sprite
Poll shotStatus flag
If shot is successful display [blown up] sprite
Check if time has run out
End of Animation Loop

Check if Esc key is pressed
End of Game Loop

_practiceMode endp

Inputs: None
Purpose: Routine for Versus Mode Gaming [This algorithm also contains functioning of NetPost routine]
Outputs: <miss> <hits>

_versusMode proc near

Draw Wallpaper [Initial waiting screen]
Send searchMsg packet
Wait for rsvpMsg packet

Send acceptMsg packet and begin game
If game underway, send rejectMsg packet

If Server: [ lower of the two numbers as assigned by NetBios ]
Draw Wallpaper

Send serverMsg packet
Check if blowFlag is 1 - This flag is set when an updatePacket comes
If so, Blow the sprite

Check if serverFlag is 1 - If so, draw sprite on screen from packet

If shotStatus is 1, send updateMsg packet

Check if Esc Key was pressed
If so, Send goodbyeMsg packet

Loop 15 times
End of Network Game

If Client:
Draw Wallpaper

Check if blowFlag is 1 - This flag is set when an updatePacket comes
If so, Blow the sprite

Check if serverFlag is 1 - If so, draw sprite on screen from packet

If shotStatus is 1, send updateMsg packet

Check if Esc Key was pressed
If so, Send goodbyeMsg packet

Loop till server send goodbyeMsg packet

_versusMode endp

_mouseMove

This routine sets the mouse boundaries and obtains the position of the mouse on the screen.
[Input none, Output mousePosition]

_randGenerator

This routine generates a random location for the sprite. It constitutes the AI for the game
[Input <randRow>, <randCol>, Output <randRow> <randCol> <randLoc>]

 

_checkShootStatus

This routine checks if the player has shot the sprite
[Input <mousePosition>, <randLoc>, Output shotStatus]

 

Graphic Methods:

_load PCX

This routine loads a PCX file into the appropriate location in the Image Array and sets the video pallette DAC
[Input AX - sprite ID, DX - offset of filename, No Output]

 

_drawWallpaper

This routine draws the wallpaper to buffer
[Input DX - offset of wallpaper, No Output]

 

_fadeOut

This routine fades the screen to blank by masking every "fadeNum"th pixel then "fadeNum-1"th pixel and so on
[Input <fadeNum>, No Output]

 

_animateSpriteIn

This routine cycles through images of a sprite of different sizes to give a fade out effect
[Input AX - sprite ID, DI - location in buffer No Output]

_animateSpriteOut

This routine cycles through images of a sprite of different sizes to give a fade out effect
[Input AX - sprite ID, DI - location in buffer, Output none]

 

_drawToBuffer

This routine draws a sprite onto the buffer. It takes care of invisible color
[Input AX - sprite ID, DI - location in buffer, No Output]

_drawToScreen

This routine waits for V_Sync to go high and dumps the buffer onto the video memory
[Input none, No Output]

_netScores

This routine displays the appropriate splash screen after a Network game
[Input <miss>, <hits>, No Output]

_drawNum

This routine takes draws the score on the screen
[Input DX - buffer offset, AL - number, Ouput none]

 

_scoreDisplay

This routine displays the score on the screen at the end of an arcade game
[Input <miss>, <hits>, Ouput none, Call _drawNum]

Sound Methods:

_playMidi

This routine registers the midi file and plays it. Reference: MIDPAK API
[Input none, Output none]

_stopMidi

This routine stops the currently playing midi file. Reference: MIDPAK API
[Input none, Ouput none]

 

_initializeSoundSeg

This routine is called in the beginning of the program. It calculates sound variables
[Input none, Ouput <sbuf_length>, <sbuf_page>, <sbuf_offset>, <snd_offset>]

 

_openWav

This routine opens the Wav file to be played
[Input DX - offset of filename, Output <loadbuf> stores Wav header and SoundSeg stores Wav data]

_playWav

This routine plays the Wav file using the Library Routines to program the DMA
[Input DX - offset of filename, Output <playing> is set to 1, Calls _openWav]

 

SoundHandler

This routine is called when the Wav file completes playing. It sets playing to 0
[Input none, Output <playing> is set to 0]

All Methods written by Karan Mehra