557eb7ef6b
Extract reset, selection, entered-world, and route construction behind LiveSessionHost while preserving the sole LiveSessionController authority. Retain partial route and subscription cleanup for retry, and replace the embedded ACE-only shortcut with the exact named-retail unsigned skill formula. Co-authored-by: Codex <codex@openai.com>
65 lines
2.8 KiB
Markdown
65 lines
2.8 KiB
Markdown
# Retail skill-formula calculation
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## Oracle
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- Named retail: `SkillFormula::Calculate @ 0x00591960` in
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`named-retail/acclient_2013_pseudo_c.txt`.
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- Retail layout: `SkillFormula` in `named-retail/acclient.h:40199` stores six
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unsigned 32-bit fields in wire order: `W`, `X`, `Y`, `Z`, `Attr1`, `Attr2`.
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The signed-looking branches in the recovered x87 code are not signed formula
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semantics. They are the compiler's unsigned-32-bit-to-floating-point fix-up:
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when the high bit is set, it adds `2^32` after the initial signed conversion.
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## Pseudocode
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```text
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bool SkillFormula.Calculate(uint attribute1, uint attribute2, out uint result)
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{
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uint divisor = Z;
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if (divisor == 0)
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return false;
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// Every operation on this line is uint32 and wraps modulo 2^32.
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uint numerator = X * attribute1 + Y * attribute2 + W;
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// Formula values are non-negative. Retail rounds to nearest integer,
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// with exact halves rounding upward.
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result = uint(floor(double(numerator) / double(divisor) + 0.5));
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return true;
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}
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```
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Consequences pinned by the port:
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- `Z == 0` is the only failure gate. `X == 0` remains a valid formula.
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- `W` participates in the numerator before division; it is not added after
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division.
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- multiplication and addition wrap as unsigned 32-bit arithmetic before the
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floating-point division.
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- the division rounds half-up; it does not truncate.
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## Reference cross-check
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ACE's [`SkillFormula`](https://github.com/ACEmulator/ACE/blob/master/Source/ACE.DatLoader/Entity/SkillFormula.cs)
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confirms the unsigned DAT order `W, X, Y, Z, Attr1, Attr2`. ACE's
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[`AttributeFormula.GetFormula`](https://github.com/ACEmulator/ACE/blob/master/Source/ACE.Server/Entity/AttributeFormula.cs)
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is only an interpretation aid: it rejects `X == 0`, assumes unit multipliers,
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omits `W`, and rounds a summed-attribute quotient. That is sufficient for
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ordinary stock ACE data but is not the general retail algorithm.
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Chorizite DatReaderWriter's generated
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[`SkillFormula`](https://github.com/Chorizite/DatReaderWriter/blob/master/DatReaderWriter/Generated/Types/SkillFormula.generated.cs)
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independently confirms the same six-field order and maps its public names to
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`W`, `X`, `Y`, and `Z`. It exposes the four arithmetic words as signed `int`,
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so the retail port must reinterpret their bits as `uint`. Its summary places
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the additive value after division; the named retail function proves that the
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actual client adds `W` to the numerator instead.
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## Port decision
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`RetailSkillFormula` is the sole App-layer calculation seam. It reinterprets
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the DAT words as unsigned, performs the exact unchecked 32-bit numerator, and
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uses the retail half-up division. `LiveSkillCreditResolver` performs only the
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skill-table lookup and treats a missing attribute as zero, matching the prior
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live-property projection behavior.
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