Documentation
¶
Overview ¶
Package api defines the tag method (metamethod) system.
Lua supports 25 metamethods that customize object behavior. The fasttm optimization caches metamethod absence in the table's flags byte.
Reference: .analysis/07-runtime-infrastructure.md §5
Tag method (metamethod) lookup functions.
Provides GetTM and GetTMByObj for metamethod resolution. CallTM and TryBinTM require the VM call machinery and will be implemented in Phase 7 (vm).
Reference: lua-master/ltm.c
Index ¶
Constants ¶
const ( // MaskFlags is the bitmask for fast-access metamethods (bits 0-5). MaskFlags byte = 0x3F // BitDummy is bit 6 in table flags, indicating the hash part uses dummynode. BitDummy byte = 0x40 )
--------------------------------------------------------------------------- fasttm cache constants
The first 6 metamethods (TM_INDEX through TM_EQ) are cached in the table's flags byte. A set bit means "metamethod is ABSENT". ---------------------------------------------------------------------------
Variables ¶
var TMNames = [TM_N]string{
"__index", "__newindex", "__gc", "__mode", "__len", "__eq",
"__add", "__sub", "__mul", "__mod", "__pow", "__div", "__idiv",
"__band", "__bor", "__bxor", "__shl", "__shr",
"__unm", "__bnot", "__lt", "__le",
"__concat", "__call", "__close",
}
TMNames maps TMS values to their Lua string names.
Functions ¶
func GetTM ¶
GetTM looks up a metamethod in the given metatable. Returns the metamethod TValue, or Nil if not found. For events <= TM_EQ, uses the fasttm cache on the table's Flags.
func GetTMByObj ¶
GetTMByObj looks up a metamethod for the given value. Returns the metamethod TValue, or Nil if not found.
func ObjTypeName ¶
func ObjTypeName(g *state.GlobalState, obj object.TValue) string
ObjTypeName returns the type name for a Lua value. Checks __name metamethod for tables and userdata.
Types ¶
type TMS ¶
type TMS int
--------------------------------------------------------------------------- TMS is the tag method selector (metamethod index). ---------------------------------------------------------------------------
const ( TM_INDEX TMS = iota // __index (0) — fast access TM_NEWINDEX // __newindex (1) — fast access TM_GC // __gc (2) — fast access TM_MODE // __mode (3) — fast access TM_LEN // __len (4) — fast access TM_EQ // __eq (5) — fast access (last) TM_ADD // __add (6) TM_SUB // __sub TM_MUL // __mul TM_MOD // __mod TM_POW // __pow TM_DIV // __div TM_IDIV // __idiv TM_BAND // __band TM_BOR // __bor TM_BXOR // __bxor TM_SHL // __shl TM_SHR // __shr TM_UNM // __unm (18) TM_BNOT // __bnot (19) TM_LT // __lt (20) TM_LE // __le (21) TM_CONCAT // __concat (22) TM_CALL // __call (23) TM_CLOSE // __close (24) TM_N // total count = 25 )
Source Files