Golden Sun (Coaltergeist's goldensun-decomp)

In the matching C of the North American and European release, eight unnamed functions (Func_80bf250 to Func_80bf484) each count down one of a unit's turn counters by 1 per call: the attack, defense, and resist modifiers (attackModTurns, defenseModTurns, resistModTurns, field names from the decompilers' struct Unit), and delude, confuse, charm, stun, and sleep. A counter that reaches 0 ends the effect, and for a modifier also zeroes the modifier. Otherwise the unnamed Func_80bf208 rolls for an early end, with the turns left T and a base B per counter: 30 for an attack modifier, 20 for defense and resist, 30 for delude, 60 for confuse, 70 for charm, 40 for stun, 50 for sleep. A modifier rolls only while it is negative (a lowered stat), so a raised stat lasts its full count. The roll happens only when T is 5 or less, and succeeds when (3 × the unit's luck − 5T + B) × 655 is at least a 16-bit RPGRandom result, so a check succeeds about (3 × Luck − 5T + B)% of the time (computed: 655 is about 1% of 65,536; the comparison is signed, so a negative sum never succeeds, and a sum over 100 always does). Success zeroes the counter, and a modifier's value too. Func_80bf208 calls _GetUnit with no argument, so the unit it reads is whatever its first argument left in r0, the unit being checked (the atlas's reading of the matching build). Which routines call these eight, and how often, is still assembly. golden-sun/status-recovery

About: Golden Sun Status recovery

{
 "luckFactor": 3,
 "turnsFactor": 5,
 "maxTurnsLeft": 5,
 "percentScale": 655,
 "randomRange": 65536,
 "baseAttackDown": 30,
 "baseDefenseDown": 20,
 "baseResistDown": 20,
 "baseDelude": 30,
 "baseConfuse": 60,
 "baseCharm": 70,
 "baseStun": 40,
 "baseSleep": 50
}

The decompilers' C is matching: src/battle/mechanics.c is a src/<module>/ file, with unfinished functions as INCLUDE_ASM stubs and parked C under src/non_matching/. The mapping of 0x132..0x13C to field names comes from include/rpg.h, since the functions use raw offsets.

Cited by: Golden Sun, Status recovery

Golden Sun's RPGRandom is a linear congruential generator, $x\leftarrow 1103515245x+12345(\mathrm{mod}{2}^{32})$ (0x41C64E6D and 0x3039; the state sRPGRNGState is a 32-bit unsigned int on the GBA), returning state >> 8 as an unsigned short: bits 8 to 23 of the state. RPGRandom2 scales one result to 0 to 99, as RPGRandom × 100 >> 16 (computed). These are the constants of the C standard's example rand, which returns bits 16 to 30 instead. Pokémon Emerald's Random keeps the multiplier but adds 24691 and returns the top 16 bits; pret's random.h defines a second step, ISO_RANDOMIZE2, with Golden Sun's 12345. golden-sun/rng

About: Golden Sun Random number generator

{
 "multiplier": 1103515245,
 "increment": 12345,
 "stateBits": 32,
 "outputShift": 8,
 "outputBits": 16
}

The C standard's next is an unsigned long, at least 32 bits (rpg-battle/c99-example-lcg).

Cited by: Golden Sun