Wolfenstein 3D ID_US_A.ASM

IDEAL
MODEL   MEDIUM,C

;   Assembly portion of the User Mgr. This is just John Carmack's table
;       driven pseudo-random number generator, and we put it in the User Mgr
;       because we couldn't figure out where it should go


;============================================================================
;
;                           RANDOM ROUTINES
;
;============================================================================

    FARDATA

rndindex    dw  ?

rndtable db    0,   8, 109, 220, 222, 241, 149, 107,  75, 248, 254, 140,  16,  66
    db   74,  21, 211,  47,  80, 242, 154,  27, 205, 128, 161,  89,  77,  36
    db   95, 110,  85,  48, 212, 140, 211, 249,  22,  79, 200,  50,  28, 188
    db   52, 140, 202, 120,  68, 145,  62,  70, 184, 190,  91, 197, 152, 224
    db  149, 104,  25, 178, 252, 182, 202, 182, 141, 197,   4,  81, 181, 242
    db  145,  42,  39, 227, 156, 198, 225, 193, 219,  93, 122, 175, 249,   0
    db  175, 143,  70, 239,  46, 246, 163,  53, 163, 109, 168, 135,   2, 235
    db   25,  92,  20, 145, 138,  77,  69, 166,  78, 176, 173, 212, 166, 113
    db   94, 161,  41,  50, 239,  49, 111, 164,  70,  60,   2,  37, 171,  75
    db  136, 156,  11,  56,  42, 146, 138, 229,  73, 146,  77,  61,  98, 196
    db  135, 106,  63, 197, 195,  86,  96, 203, 113, 101, 170, 247, 181, 113
    db   80, 250, 108,   7, 255, 237, 129, 226,  79, 107, 112, 166, 103, 241
    db   24, 223, 239, 120, 198,  58,  60,  82, 128,   3, 184,  66, 143, 224
    db  145, 224,  81, 206, 163,  45,  63,  90, 168, 114,  59,  33, 159,  95
    db   28, 139, 123,  98, 125, 196,  15,  70, 194, 253,  54,  14, 109, 226
    db   71,  17, 161,  93, 186,  87, 244, 138,  20,  52, 123, 251,  26,  36
    db   17,  46,  52, 231, 232,  76,  31, 221,  84,  37, 216, 165, 212, 106
    db  197, 242,  98,  43,  39, 175, 254, 145, 190,  84, 118, 222, 187, 136
    db  120, 163, 236, 249

PUBLIC  rndtable

    CODESEG

LastRnd     dw  ?

;=================================================
;
; void US_InitRndT (boolean randomize)
; Init table based RND generator
; if randomize is false, the counter is set to 0
;
;=================================================

PROC    US_InitRndT randomize:word
    uses    si,di
    public  US_InitRndT

    mov ax,SEG rndtable
    mov es,ax

    mov ax,[randomize]
    or  ax,ax
    jne @@timeit        ;if randomize is true, really random

    mov dx,0            ;set to a definite value
    jmp @@setit

@@timeit:
    mov ah,2ch
    int 21h         ;GetSystemTime
    and dx,0ffh

@@setit:
    mov [es:rndindex],dx
    ret

ENDP

;=================================================
;
; int US_RndT (void)
; Return a random # between 0-255
; Exit : AX = value
;
;=================================================
PROC    US_RndT
    public  US_RndT

    mov ax,SEG rndtable
    mov es,ax
    mov bx,[es:rndindex]
    inc bx
    and bx,0ffh
    mov [es:rndindex],bx
    mov al,[es:rndtable+BX]
    xor ah,ah
    ret

ENDP

END