missile.cpp

00001 #include "missile_private.h"
00002 
00003 MISSILE missile_record[MAX_NUM_MISSILE];
00004 int missile_tick=0;
00005 int missile_interval = 10;
00006 int missile_speed = 4;
00007 
00008 // See the comments in missile_public.h
00009 void missile_generator(void){
00010     missile_tick++;
00011     // only fire the missile at certain ticks
00012     if((missile_tick % missile_interval)==0 || missile_tick==0){
00013         missile_create();
00014     }
00015     
00016     // update the missiles and draw them
00017     missile_update_position();
00018 }
00019 
00020 // set missile speed (default speed is 4)
00021 void set_missile_speed(int speed){
00022     ASSERT_P(speed>=1 && speed<=8,ERROR_MISSILE_SPEED);
00023     if(speed>=1 && speed<=8){  
00024         missile_speed = speed;
00025     }
00026 }
00027 
00028 // set missile interval (default interval is 10)
00029 void set_missile_interval(int interval){
00030     ASSERT_P(interval>=1 && interval<=100,ERROR_MISSILE_INTERVAL);
00031     if(interval>=1 && interval<=100){
00032         missile_interval = interval;
00033     }
00034 }
00035 
00036 // See the comments in missile_public.h
00037 MISSILE missile_get_info(int index){
00038     // All interface for user should have error checking
00039     ASSERT_P(index<MAX_NUM_MISSILE,ERROR_MISSILE_INDEX_GET_INFO);
00040     
00041     return missile_record[index];
00042 }
00043 
00044 // See the comments in missile_public.h
00045 void missile_set_exploded(int index){
00046     // All interface for user should have error checking
00047     ASSERT_P(index<MAX_NUM_MISSILE,ERROR_MISSILE_INDEX_UPDATE_STATUS);
00048     
00049     missile_record[index].status = MISSILE_EXPLODED;
00050 }
00051 
00052 /** This function finds an empty slot of missile record, and active it.
00053 */
00054 void missile_create(void){
00055     int i;
00056     for(i=0;i<MAX_NUM_MISSILE;i++){
00057         if(missile_record[i].status == MISSILE_DEACTIVE){
00058             missile_record[i].y = 0;
00059             //each missile has its own tick
00060             missile_record[i].tick = 0;
00061             //set a random source for the missile
00062             missile_record[i].source_x = rand() % SIZE_X;
00063             //set a random target for the missile
00064             missile_record[i].target_x = rand() % SIZE_X;
00065             //the missile starts at its source
00066             missile_record[i].x = missile_record[i].source_x;
00067             missile_record[i].status = MISSILE_ACTIVE;
00068             break;
00069         }
00070     }
00071 }
00072 
00073 /** This function update the position of all missiles and draw them
00074 */
00075 void missile_update_position(void){
00076     int i;
00077     //controls how fast the missile will move
00078     int rate = missile_speed * 25;
00079     //delta_x and delta_y account for the slope of the missile
00080     double delta_x,delta_y;
00081     for(i=0;i<MAX_NUM_MISSILE;i++){
00082         if(missile_record[i].status == MISSILE_ACTIVE){
00083             // update missile position
00084             delta_y = 200/rate;
00085             delta_x = (missile_record[i].target_x - missile_record[i].source_x)/rate;
00086             missile_draw(missile_record[i], BACKGROUND_COLOR);
00087             missile_record[i].y = (int)(delta_y*(missile_record[i].tick%rate));
00088             missile_record[i].x = (int)(missile_record[i].source_x + delta_x*(missile_record[i].tick%rate));
00089             // draw missile
00090             missile_draw(missile_record[i], MISSILE_COLOR);
00091             //update missile's internal tick
00092             missile_record[i].tick++;
00093         }       
00094         else if(missile_record[i].status == MISSILE_EXPLODED){
00095             // clear the missile on the screen
00096             missile_draw(missile_record[i], BACKGROUND_COLOR);
00097             
00098             // we have done with this missile, remove it from record
00099             missile_record[i].status = MISSILE_DEACTIVE;
00100             //resets the missile's internal tick
00101             missile_record[i].tick = 0;
00102         }
00103         
00104     }
00105 }
00106 
00107 /** This function draw a missile.
00108     @param missile The missile to be drawn
00109     @param color The color of the missile
00110 */
00111 void missile_draw(MISSILE missile, int color){
00112     int init_x,init_y,current_x,current_y;
00113 
00114     init_x = missile.source_x;
00115     init_y = 0;
00116     current_x = missile.x;
00117     current_y = missile.y;
00118     uLCD.line(init_x, init_y, current_x, current_y, color);
00119 }
00120 
00121