CoCalc -- experience.asm

GitHub Repository: pret/pokered
Path: blob/master/engine/pokemon/experience.asm
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; calculates the level a mon should be based on its current exp
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CalcLevelFromExperience::
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	ld a, [wLoadedMonSpecies]
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	ld [wCurSpecies], a
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	call GetMonHeader
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	ld d, $1 ; init level to 1
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.loop
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	inc d ; increment level
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	call CalcExperience
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	push hl
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	ld hl, wLoadedMonExp + 2 ; current exp
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; compare exp needed for level d with current exp
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	ldh a, [hExperience + 2]
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	ld c, a
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	ld a, [hld]
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	sub c
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	ldh a, [hExperience + 1]
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	ld c, a
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	ld a, [hld]
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	sbc c
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	ldh a, [hExperience]
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	ld c, a
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	ld a, [hl]
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	sbc c
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	pop hl
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	jr nc, .loop ; if exp needed for level d is not greater than exp, try the next level
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	dec d ; since the exp was too high on the last loop iteration, go back to the previous value and return
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	ret
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; calculates the amount of experience needed for level d
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CalcExperience::
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	ld a, [wMonHGrowthRate]
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	add a
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	add a
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	ld c, a
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	ld b, 0
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	ld hl, GrowthRateTable
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	add hl, bc
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	call CalcDSquared
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	ld a, d
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	ldh [hMultiplier], a
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	call Multiply
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	ld a, [hl]
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	and $f0
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	swap a
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	ldh [hMultiplier], a
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	call Multiply
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	ld a, [hli]
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	and $f
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	ldh [hDivisor], a
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	ld b, $4
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	call Divide
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	ldh a, [hQuotient + 1]
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	push af
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	ldh a, [hQuotient + 2]
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	push af
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	ldh a, [hQuotient + 3]
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	push af
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	call CalcDSquared
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	ld a, [hl]
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	and $7f
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	ldh [hMultiplier], a
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	call Multiply
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	ldh a, [hProduct + 1]
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	push af
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	ldh a, [hProduct + 2]
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	push af
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	ldh a, [hProduct + 3]
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	push af
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	ld a, [hli]
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	push af
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	xor a
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	ldh [hMultiplicand], a
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	ldh [hMultiplicand + 1], a
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	ld a, d
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	ldh [hMultiplicand + 2], a
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	ld a, [hli]
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	ldh [hMultiplier], a
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	call Multiply
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	ld b, [hl]
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	ldh a, [hProduct + 3]
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	sub b
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	ldh [hProduct + 3], a
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	ld b, $0
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	ldh a, [hProduct + 2]
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	sbc b
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	ldh [hProduct + 2], a
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	ldh a, [hProduct + 1]
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	sbc b
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	ldh [hProduct + 1], a
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; The difference of the linear term and the constant term consists of 3 bytes
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; starting at hProduct + 1. Below, hExperience (an alias of that address) will
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; be used instead for the further work of adding or subtracting the squared
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; term and adding the cubed term.
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	pop af
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	and $80
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	jr nz, .subtractSquaredTerm ; check sign
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	pop bc
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	ldh a, [hExperience + 2]
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	add b
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	ldh [hExperience + 2], a
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	pop bc
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	ldh a, [hExperience + 1]
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	adc b
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	ldh [hExperience + 1], a
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	pop bc
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	ldh a, [hExperience]
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	adc b
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	ldh [hExperience], a
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	jr .addCubedTerm
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.subtractSquaredTerm
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	pop bc
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	ldh a, [hExperience + 2]
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	sub b
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	ldh [hExperience + 2], a
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	pop bc
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	ldh a, [hExperience + 1]
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	sbc b
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	ldh [hExperience + 1], a
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	pop bc
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	ldh a, [hExperience]
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	sbc b
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	ldh [hExperience], a
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.addCubedTerm
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	pop bc
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	ldh a, [hExperience + 2]
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	add b
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	ldh [hExperience + 2], a
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	pop bc
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	ldh a, [hExperience + 1]
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	adc b
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	ldh [hExperience + 1], a
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	pop bc
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	ldh a, [hExperience]
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	adc b
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	ldh [hExperience], a
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	ret
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; calculates d*d
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CalcDSquared:
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	xor a
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	ldh [hMultiplicand], a
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	ldh [hMultiplicand + 1], a
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	ld a, d
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	ldh [hMultiplicand + 2], a
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	ldh [hMultiplier], a
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	jp Multiply
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INCLUDE "data/growth_rates.asm"
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