diff options
Diffstat (limited to 'battle')
| -rw-r--r-- | battle/magikarp_length.asm | 205 |
1 files changed, 100 insertions, 105 deletions
diff --git a/battle/magikarp_length.asm b/battle/magikarp_length.asm index 7b2d5e386..b4e20c288 100644 --- a/battle/magikarp_length.asm +++ b/battle/magikarp_length.asm @@ -1,27 +1,24 @@ CalcMagikarpLength: ; fbbfc -; Return Magikarp's length (in mm) in MagikarpLength (big endian) +; Return Magikarp's length (in mm) at MagikarpLength (big endian). ; ; input: ; de: EnemyMonDVs ; bc: PlayerID -; This function is needlessly convoluted, and poorly commented. -; Reading is discouraged. +; 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 -; scrutinized in GetEnemyMon to make longer Magikarp even rarer. +; filtered in LoadEnemyMon to make longer Magikarp even rarer. -; This is done by calculating the value using operands from -; a conversion lookup table. +; The value is generated from a lookup table. +; The index is determined by the dv xored with the player's trainer id. -; Our index is calculated by xoring DVs with the trainer ID: +; bc = rrc(dv[0]) ++ rrc(dv[1]) ^ rrc(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 +; 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: @@ -38,12 +35,10 @@ CalcMagikarpLength: ; fbbfc ; 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. + ; bc = rrc(dv[0]) ++ rrc(dv[1]) ^ rrc(id) -; b = rrcrrc(atkdefdv) xor rrc(id[0]) - -; id + ; id ld h, b ld l, c ld a, [hli] @@ -51,123 +46,125 @@ CalcMagikarpLength: ; fbbfc ld c, [hl] rrc b rrc c - -; dvs + + ; dv 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: + + ; if bc < 10: + ; de = bc + 190 + ; break + ld a, b and a - jr nz, .loadtable + jr nz, .no ld a, c - cp a, $a - jr nc, .loadtable - -; de = hl = bc + $be - ld hl, $be + cp 10 + jr nc, .no + + ld hl, 190 add hl, bc ld d, h ld e, l - jr .endtable - -.loadtable - ld hl, .MagikarpLengthTable - ld a, $02 + jr .done + +.no + + ld hl, .Lengths + ld a, 2 ld [$d265], a - -.readtable + +.read ld a, [hli] ld e, a ld a, [hli] ld d, a - call .BLessThanD - jr nc, .advancetable - -; c = bc / [hl] + call .BCLessThanDE + jr nc, .next + + ; c = (bc - de) / [hl] call .BCMinusDE ld a, b - ld [$ffb3], a + ld [hDividend + 0], a ld a, c - ld [$ffb4], a + ld [hDividend + 1], a ld a, [hl] - ld [$ffb7], a - ld b, $02 + ld [hDivisor], a + ld b, 2 call Divide - ld a, [$ffb6] + ld a, [hQuotient + 2] ld c, a - -; de = c + 100 * (2 + number of rows down the table) + + ; de = c + 100 * (2 + i) xor a - ld [$ffb4], a - ld [$ffb5], a - ld a, $64 - ld [$ffb6], a + ld [hMultiplicand + 0], a + ld [hMultiplicand + 1], a + ld a, 100 + ld [hMultiplicand + 2], a ld a, [$d265] - ld [$ffb7], a + ld [hMultiplier], a call Multiply - ld b, $00 - ld a, [$ffb6] + ld b, 0 + ld a, [hProduct + 3] add c ld e, a - ld a, [$ffb5] + ld a, [hProduct + 2] adc b ld d, a - jr .endtable - -.advancetable + jr .done + +.next inc hl ; align to next triplet ld a, [$d265] inc a ld [$d265], a - cp a, $10 - jr c, .readtable - + cp 16 + jr c, .read + call .BCMinusDE - ld hl, $0640 + ld hl, 1600 add hl, bc ld d, h ld e, l - -.endtable + +.done + ; hl = de * 10 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 + add hl, hl + + ; hl = hl / 254 + ld de, -254 + ld a, -1 +.div_254 inc a - add hl, de ; - 254 - jr c, .loop - - ld d, $00 - -; mod $0c -.modloop - cp a, $0c - jr c, .done - sub a, $0c + 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 .modloop - -.done + jr .mod_12 +.ok ld e, a + ld hl, MagikarpLength ld [hl], d inc hl @@ -175,22 +172,19 @@ CalcMagikarpLength: ; fbbfc ret ; fbc9a -.BLessThanD ; fbc9a -; return carry if b < d +.BCLessThanDE: ; fbc9a +; Intention: Return bc < de. +; Reality: Return b < d. ld a, b cp d ret c - ret nc -; fbc9e - -.CLessThanE ; fbc9e -; unused + ret nc ; whoops ld a, c cp e ret ; fbca1 -.BCMinusDE ; fbca1 +.BCMinusDE: ; fbca1 ; bc -= de ld a, c sub e @@ -201,20 +195,21 @@ CalcMagikarpLength: ; fbbfc ret ; fbca8 -.MagikarpLengthTable ; fbca8 +.Lengths: ; 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 + 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 |