ref: 3922ad2c3cf4bc15ede67b3b1814e4c2fced9243
dir: /battle/magikarp_length.asm/
CalcMagikarpLength: ; fbbfc ; Return Magikarp's length (in mm) at MagikarpLength (big endian). ; ; input: ; de: EnemyMonDVs ; bc: PlayerID ; This function is poorly commented. ; In short, it generates a value between 190 and 1786 using ; a Magikarp's DVs and its trainer ID. This value is further ; filtered in LoadEnemyMon to make longer Magikarp even rarer. ; The value is generated from a lookup table. ; The index is determined by the dv xored with the player's trainer id. ; bc = rrc(dv[0]) ++ rrc(dv[1]) ^ rrc(id) ; if bc < 10: [MagikarpLength] = c + 190 ; if bc >= $ff00: [MagikarpLength] = c + 1370 ; else: [MagikarpLength] = z * 100 + (bc - x) / y ; X, Y, and Z depend on the value of b as follows: ; if b = 0: x = 310, y = 2, z = 3 ; if b = 1: x = 710, y = 4, z = 4 ; if b = 2-9: x = 2710, y = 20, z = 5 ; if b = 10-29: x = 7710, y = 50, z = 6 ; if b = 30-68: x = 17710, y = 100, z = 7 ; if b = 69-126: x = 32710, y = 150, z = 8 ; if b = 127-185: x = 47710, y = 150, z = 9 ; if b = 186-224: x = 57710, y = 100, z = 10 ; if b = 225-243: x = 62710, y = 50, z = 11 ; if b = 244-251: x = 64710, y = 20, z = 12 ; if b = 252-253: x = 65210, y = 5, z = 13 ; if b = 254: x = 65410, y = 2, z = 14 ; bc = rrc(dv[0]) ++ rrc(dv[1]) ^ rrc(id) ; id ld h, b ld l, c ld a, [hli] ld b, a ld c, [hl] rrc b rrc c ; dv ld a, [de] inc de rrca rrca xor b ld b, a ld a, [de] rrca rrca xor c ld c, a ; if bc < 10: ; de = bc + 190 ; break ld a, b and a jr nz, .no ld a, c cp 10 jr nc, .no ld hl, 190 add hl, bc ld d, h ld e, l jr .done .no ld hl, .Lengths ld a, 2 ld [wd265], a .read ld a, [hli] ld e, a ld a, [hli] ld d, a call .BCLessThanDE jr nc, .next ; c = (bc - de) / [hl] call .BCMinusDE ld a, b ld [hDividend + 0], a ld a, c ld [hDividend + 1], a ld a, [hl] ld [hDivisor], a ld b, 2 call Divide ld a, [hQuotient + 2] ld c, a ; de = c + 100 * (2 + i) xor a ld [hMultiplicand + 0], a ld [hMultiplicand + 1], a ld a, 100 ld [hMultiplicand + 2], a ld a, [wd265] ld [hMultiplier], a call Multiply ld b, 0 ld a, [hProduct + 3] add c ld e, a ld a, [hProduct + 2] adc b ld d, a jr .done .next inc hl ; align to next triplet ld a, [wd265] inc a ld [wd265], a cp 16 jr c, .read call .BCMinusDE ld hl, 1600 add hl, bc ld d, h ld e, l .done ; hl = de * 10 ld h, d ld l, e rept 2 add hl, hl endr add hl, de add hl, hl ; hl = hl / 254 ld de, -254 ld a, -1 .div_254 inc a add hl, de jr c, .div_254 ; d, e = hl / 12, hl % 12 ld d, 0 .mod_12 cp 12 jr c, .ok sub 12 inc d jr .mod_12 .ok ld e, a ld hl, MagikarpLength ld [hl], d inc hl ld [hl], e ret ; fbc9a .BCLessThanDE: ; fbc9a ; Intention: Return bc < de. ; Reality: Return b < d. ld a, b cp d ret c ret nc ; whoops ld a, c cp e ret ; fbca1 .BCMinusDE: ; fbca1 ; bc -= de ld a, c sub e ld c, a ld a, b sbc d ld b, a ret ; fbca8 .Lengths: ; fbca8 ; ????, divisor dwb 110, 1 dwb 310, 2 dwb 710, 4 dwb 2710, 20 dwb 7710, 50 dwb 17710, 100 dwb 32710, 150 dwb 47710, 150 dwb 57710, 100 dwb 62710, 50 dwb 64710, 20 dwb 65210, 5 dwb 65410, 2 dwb 65510, 1 ; not used ; fbcd2