ref: bd49428c4a4e98f9a7bbbcdd79d75d461c0c12b1
dir: /battle/magikarp_length.asm/
CalcMagikarpLength: ; fbbfc ; Return Magikarp's length (in mm) in MagikarpLength (big endian) ; ; input: ; de: EnemyMonDVs ; bc: PlayerID ; This function is needlessly convoluted, and poorly commented. ; Reading is discouraged. ; In short, it generates a value between 190 and 1786 using ; a Magikarp's DVs and its trainer ID. This value is further ; scrutinized in GetEnemyMon to make longer Magikarp even rarer. ; This is done by calculating the value using operands from ; a conversion lookup table. ; Our index is calculated by xoring DVs with the trainer ID: ; bc = rrc(rrc(dvs)) xor rrc(id) ; if bc < $a: 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 ; These values represent arbitrary conversion points. ; b = rrcrrc(atkdefdv) xor rrc(id[0]) ; id ld h, b ld l, c ld a, [hli] ld b, a ld c, [hl] rrc b rrc c ; dvs ld a, [de] inc de rrca rrca xor b ld b, a ; c = rrcrrc(spdspcdv) xor rrc(id[1]) ld a, [de] rrca rrca xor c ld c, a ; if bc < $000a: ld a, b and a jr nz, .loadtable ld a, c cp a, $a jr nc, .loadtable ; de = hl = bc + $be ld hl, $be add hl, bc ld d, h ld e, l jr .endtable .loadtable ld hl, .MagikarpLengthTable ld a, $02 ld [$d265], a .readtable ld a, [hli] ld e, a ld a, [hli] ld d, a call .BLessThanD jr nc, .advancetable ; c = bc / [hl] call .BCMinusDE ld a, b ld [$ffb3], a ld a, c ld [$ffb4], a ld a, [hl] ld [$ffb7], a ld b, $02 call Divide ld a, [$ffb6] ld c, a ; de = c + 100 * (2 + number of rows down the table) xor a ld [$ffb4], a ld [$ffb5], a ld a, $64 ld [$ffb6], a ld a, [$d265] ld [$ffb7], a call Multiply ld b, $00 ld a, [$ffb6] add c ld e, a ld a, [$ffb5] adc b ld d, a jr .endtable .advancetable inc hl ; align to next triplet ld a, [$d265] inc a ld [$d265], a cp a, $10 jr c, .readtable call .BCMinusDE ld hl, $0640 add hl, bc ld d, h ld e, l .endtable ld h, d ld l, e add hl, hl add hl, hl add hl, de add hl, hl ; hl = de * 10 ld de, $ff02 ld a, $ff .loop inc a add hl, de ; - 254 jr c, .loop ld d, $00 ; mod $0c .modloop cp a, $0c jr c, .done sub a, $0c inc d jr .modloop .done ld e, a ld hl, MagikarpLength ld [hl], d inc hl ld [hl], e ret ; fbc9a .BLessThanD ; fbc9a ; return carry if b < d ld a, b cp d ret c ret nc ; fbc9e .CLessThanE ; fbc9e ; unused 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 .MagikarpLengthTable ; fbca8 ; ????, divisor dwb $006e, $01 dwb $0136, $02 dwb $02c6, $04 dwb $0a96, $14 dwb $1e1e, $32 dwb $452e, $64 dwb $7fc6, $96 dwb $ba5e, $96 dwb $e16e, $64 dwb $f4f6, $32 dwb $fcc6, $14 dwb $feba, $05 dwb $ff82, $02 ; fbccf