Concepts and API surface

Terminology

• Outer: the method being patched.
• Inner: the target method being called inside the outer method.
• Call site: one occurrence of a call to the inner method.

Attributes

Names are placeholders. Adjust to Harmony naming once decided.

• [HarmonyPatch] on a class or method: selects the outer target (existing).
• [HarmonyInfixTarget] on an inner prefix/postfix method: identifies the inner target method and optional call index within the outer.
• [HarmonyInfixPrefix] marks an inner prefix.
• [HarmonyInfixPostfix] marks an inner postfix.

Call selection

• Indexing: index = 1..N, -1 means “all occurrences”. Optional future: int[] indices.

Parameter injection (summary)

Inner defaults:

• __instance = inner call instance (or null if static).
• Inner arg names map to captured arg locals.
• __result = inner call result (for prefix by‑ref and postfix by‑value).

Outer access with o_ prefix:

• o___instance, o_paramName, o___fieldName, o___result (rarely needed).

Outer locals:

• _var<index> → outer local by index.

Synthetic locals scoped to the outer method:

• _var<name> → new local shared across all infix patches at this outer method.

Use by‑ref to request mutability where supported.

Details in 04-parameter-binding.md.