diff options
Diffstat (limited to 'home/random.asm')
| -rw-r--r-- | home/random.asm | 103 |
1 files changed, 56 insertions, 47 deletions
diff --git a/home/random.asm b/home/random.asm index e2b8c32..ce34f69 100644 --- a/home/random.asm +++ b/home/random.asm @@ -2,18 +2,18 @@ GenRandom: ; 0x959 push bc push de push hl - ld a, [wd811] + ld a, [wRNGPointer] ld c, a ld b, $0 ;load ??? into c inc a cp 54 + 1 ;inc ???, if ??? is 55 do alot of subtraction and make ??? 0 jr nz, .asm_96e - call Func_9fa + call UpdateRNG xor a ld bc, $0000 .asm_96e - ld [wd811], a ;place wd811 + 1 back in - ld hl, wd812 ;choose number generated based on wd811 and all the subtraction + ld [wRNGPointer], a ;place wRNGPointer + 1 back in + ld hl, wRNGValues ;choose number generated based on wRNGPointer and all the subtraction add hl, bc ld a, [hl] pop hl @@ -21,53 +21,55 @@ GenRandom: ; 0x959 pop bc ret -Func_97a: ; 0x97a - ld a, [wd810] +ResetRNG: ; 0x97a + ld a, [wRNGModulus] ld d, a - ld a, $0 + ld a, $0 ; wasted instruction (debug that was never commented out?) + ; [wRNGSub] = [sRNGMod] % [wRNGModulus] ld a, [sRNGMod] -.asm_983 +.modulo cp d - jr c, .asm_989 + jr c, .okay sub d - jr .asm_983 + jr .modulo -.asm_989 - ld [wd80f], a - ld [wd848], a +.okay + ld [wRNGSub], a + ld [wRNGSub2], a ld e, $1 - ld hl, Data_9c4 - ld a, $36 -.asm_996 + ld hl, .Data + ld a, 54 +.copy_prng push af ld c, [hl] inc hl ld b, $0 push hl - ld hl, wd812 + ld hl, wRNGValues add hl, bc ld [hl], e - ld a, [wd80f] + ld a, [wRNGSub] sub e - jr nc, .asm_9a8 + jr nc, .next add d -.asm_9a8 +.next ld e, a ld a, [hl] - ld [wd80f], a + ld [wRNGSub], a pop hl pop af dec a - jr nz, .asm_996 - call Func_9fa - call Func_9fa - call Func_9fa - ld a, $0 + jr nz, .copy_prng + call UpdateRNG + call UpdateRNG + call UpdateRNG + ld a, $0 ; wasted instruction (debug that was never commented out?) call GenRandom ld [sRNGMod], a ret -Data_9c4: +.Data +; offsets from wRNGValues db $14, $29, $07, $1c, $31, $0f, $24, $02, $17 db $2c, $0a, $1f, $34, $12, $27, $05, $1a, $2f db $0d, $22, $00, $15, $2a, $08, $1d, $32, $10 @@ -75,45 +77,49 @@ Data_9c4: db $06, $1b, $30, $0e, $23, $01, $16, $2b, $09 db $1e, $33, $11, $26, $04, $19, $2e, $0c, $21 -Func_9fa: ; 0x9fa - ld a, [wd810] +UpdateRNG: ; 0x9fa +; Adjusts two RNG values using wRNGModulus + ld a, [wRNGModulus] ld d, a - ld bc, wd812 - ld hl, wd812 + $1f ;d831 + ; [d812] = ([d812] - 24 * [d831]) % [d810] + ld bc, wRNGValues + ld hl, wRNGValues + $1f ld e, $18 -.asm_a06 +.loop ld a, [bc] - sub [hl] ;sub d831 from wd812, add wd810 if it does not carry, put result in wd812. repeat 24 times - jr nc, .asm_a0b + sub [hl] + jr nc, .no_carry add d -.asm_a0b +.no_carry ld [bc], a dec e - jr nz, .asm_a06 - ld bc, wd812 + $18 - ld hl, wd812 + jr nz, .loop + ; [d82a] = ([d82a] - 31 * [d812]) % [d810] + ld bc, wRNGValues + $18 ; d82a + ld hl, wRNGValues ld e, $1f -.asm_a17 +.loop2 ld a, [bc] sub [hl] - jr nc, .asm_a1c + jr nc, .no_carry2 add d -.asm_a1c +.no_carry2 ld [bc], a dec e - jr nz, .asm_a17 + jr nz, .loop2 ret -Func_a21: ; 0xa21 +RandomRange: ; 0xa21 +; Random value 0 <= x < a push bc push hl ld c, a ld b, $0 - ld hl, Data_a38 ;jump to c in table, load (twice c?) into l + ld hl, EvensAndOdds add hl, bc ld l, [hl] - call GenRandom ;a = a psuedo random number - call Func_dd4 ;a * l + call GenRandom + call HorrendousMultiplyAbyL inc h srl h ld a, h @@ -121,7 +127,10 @@ Func_a21: ; 0xa21 pop bc ret -Data_a38: ;starting from 0, go up 2 each byte +EvensAndOdds: +; The first 128 bytes are the first 128 even numbers starting at 0. +; The next 128 bytes are the first 128 odd numbers starting at 1. +; The (a)th element is essentially what you'd get from rlca. x = 0 REPT 128 db x | ((x >> 7) & 1) |