a98e96b0f0
Chasing where the event code comes from turned up the level above and corrected my own framing three sections running. sub_821C6458 has exactly one caller, sub_821C7850, and that caller is itself a dispatcher -- on a SECOND, outer state field at this+132, five phases, gated on this+16 == 3. Phase 4 is the title/menu machine I have been decoding. Phase 0 is sub_821C5690, which the iterate3E notes had already fingered as the splash mechanics from a completely different direction. That agreement is the useful check here. So GamePart_Title has two nested state fields: a phase at this+132 choosing which sub-machine runs, and the state at this+136 inside phase 4. Everything I decoded over the last three iterations -- ten states, eighteen edges, the event dispatch -- is phase 4 ONLY. Phases 1, 2 and 3 are untouched. I have called that out in REFUTED against my own earlier wording rather than quietly restating it. And the event code is forwarded, not created: all five phase handlers are called with the same (this, r29, r28), where r28 is sub_821C7850's own third argument passed through untouched. So the event vocabulary is defined at least one level further up, and finding what 3, 5, 8, 10 and 25 mean means going up again. Not done.
98 lines
3.6 KiB
Plaintext
98 lines
3.6 KiB
Plaintext
GamePart_Title has TWO nested state fields.
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OUTER -- sub_821C7850, the part's dispatcher
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821c786c lwz r11, 16(r30) ; only runs when this+16 == 3
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821c7870 cmpwi cr6, r11, 3
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821c7874 bne cr6, <exit>
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821c787c lwz r11, 132(r30) ; phase = this+0x84
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821c7880 cmplwi cr6, r11, 0x4 ; five phases, 0..4
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821c7888 lis/addi r12, 0x821C78A0 ; jump table
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821c789c bctr
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phase 0 -> sub_821C5690 (the splash -- independently identified as the
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splash mechanics in the iterate3E notes)
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phase 1 -> inline block at 0x821c790c
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phase 2 -> sub_821C5818
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phase 3 -> sub_821C5EC0
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phase 4 -> sub_821C6458 (the title/menu machine, below)
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All four call sites forward the SAME three arguments: (this, r29, r28),
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where r28 is this function's own third argument -- an EVENT CODE passed
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through unchanged from ITS caller.
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INNER -- sub_821C6458, the title/menu machine (phase 4 only)
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DISPATCH
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821c6474 lwz r11, 136(r30) ; state = this+0x88
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821c6478 cmplwi cr6, r11, 0x9 ; 10 states, 0..9
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821c647c bgt cr6, 0x821C75B8 ; out of range -> default
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821c6480 lis r12, 0x821C
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821c6484 addi r12, r12, 25752 ; jump table at 0x821C6498
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821c6488 slwi r0, r11, 2
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821c648c lwzx r0, r12, r0
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821c6490 mtctr r0
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821c6494 bctr
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NOTE: a disassembler decodes 0x821C6498..0x821C64BC as `lwz r16, N(r28)`
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instructions. They are the jump TABLE's ten words, not code.
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STATES
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case 0 -> 0x821c64c0 installs "TITLE_SCREEN"
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case 1 -> 0x821c65d0
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case 2 -> 0x821c66e4 installs "TITLE_MENU"
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case 3 -> 0x821c6b18
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case 4 -> 0x821c6b5c nested switch, table at 0x821c6b7c (live: 0,3,5,8)
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case 5 -> 0x821c6fd4
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case 6 -> 0x821c7028
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case 7 -> 0x821c72dc
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case 8 -> 0x821c733c installs "LOADING"
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case 9 -> 0x821c7558
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TRANSITIONS -- every `li rX,N ; stw rX,136(r30)` in the function
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from to at
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0 1 0x821c6598
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0 2 0x821c65c8
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1 2 0x821c66a4
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1 2 0x821c66dc
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2 4 0x821c6afc
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3 4 0x821c6b54
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4 0 0x821c6e00
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4 5 0x821c6e70
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4 8 0x821c6ed0
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4 8 0x821c6f20
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4 8 0x821c6f7c
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4 8 0x821c6fcc
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5 6 0x821c7020
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6 7 0x821c725c
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6 9 0x821c72a8
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6 2 0x821c72d4
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7 9 0x821c7334
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8 2 0x821c7548
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(state 9 stores nothing -- terminal within this function)
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THE CONDITION ON STATE 4's EDGES -- decoded
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sub_821C6458(this, ?, r5) takes an EVENT CODE in its third argument.
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State 4 -- the input-waiting state -- dispatches on it:
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821c6b5c cmplwi cr6, r27, 0x19 ; 26 events, 0..25
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821c6b60 bgt cr6, <default>
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821c6b68 addi r12, r12, 27516 ; table at 0x821c6b7c
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821c6b78 bctr
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Only 6 of the 26 are handled; the other 20 fall through with no state change.
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event 0 -> block 0x821c6be4 -> state 0 (TITLE_SCREEN -- back to the title)
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event 3 -> block 0x821c6e78 -> state 8 (LOADING)
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event 5 -> block 0x821c6f84 -> state 8 (LOADING)
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event 8 -> block 0x821c6f34 -> state 8 (LOADING)
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event 10 -> block 0x821c6e28 -> state 5
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event 25 -> block 0x821c6ed8 -> state 8 (LOADING)
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WHAT IS NOT DECODED
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* what the event NUMBERS mean -- they are forwarded unchanged from
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sub_821C7850's caller, so the vocabulary is defined at least one level up -- button id, menu-item id or message id;
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* the conditions on edges out of states other than 4;
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* what states 1, 3, 5, 6, 7 and 9 do (they install no named screen);
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* state 3 is never a destination here, so something outside this function
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sets it.
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