diff --git a/LUA_API.rst b/LUA_API.rst index 0b6ae863b..f40b786d2 100644 --- a/LUA_API.rst +++ b/LUA_API.rst @@ -121,6 +121,12 @@ or as a result of calling the ``_field()`` method. They behave as structs with one field ``value`` of the right type. +To make working with numeric buffers easier, they also allow +numeric indices. Note that other than excluding negative values +no bound checking is performed, since buffer length is not available. +Index 0 is equivalent to the ``value`` field. + + Struct references ----------------- diff --git a/Lua API.html b/Lua API.html index 2df8a7f22..3edcfd274 100644 --- a/Lua API.html +++ b/Lua API.html @@ -453,6 +453,10 @@ that don't fit any of the other reference types. Such references can only appear as a value of a pointer field, or as a result of calling the _field() method.

They behave as structs with one field value of the right type.

+

To make working with numeric buffers easier, they also allow +numeric indices. Note that other than excluding negative values +no bound checking is performed, since buffer length is not available. +Index 0 is equivalent to the value field.

Struct references

diff --git a/library/LuaTypes.cpp b/library/LuaTypes.cpp index c58c25d11..8548c5d0a 100644 --- a/library/LuaTypes.cpp +++ b/library/LuaTypes.cpp @@ -635,6 +635,28 @@ static int meta_struct_next(lua_State *state) return 2; } +/** + * Field lookup for primitive refs: behave as a quasi-array with numeric indices. + */ +static type_identity *find_primitive_field(lua_State *state, int field, const char *mode, uint8_t **ptr) +{ + if (lua_type(state, field) == LUA_TNUMBER) + { + int idx = lua_tointeger(state, field); + if (idx < 0) + field_error(state, 2, "negative index", mode); + + lua_rawgetp(state, UPVAL_METATABLE, &DFHACK_IDENTITY_FIELD_TOKEN); + auto id = (type_identity *)lua_touserdata(state, -1); + lua_pop(state, 1); + + *ptr += int(id->byte_size()) * idx; + return id; + } + + return (type_identity*)find_field(state, field, mode); +} + /** * Metamethod: __index for primitives, i.e. simple object references. * Fields point to identity, or NULL for metafields. @@ -642,7 +664,7 @@ static int meta_struct_next(lua_State *state) static int meta_primitive_index(lua_State *state) { uint8_t *ptr = get_object_addr(state, 1, 2, "read"); - auto type = (type_identity*)find_field(state, 2, "read"); + auto type = find_primitive_field(state, 2, "read", &ptr); if (!type) return 1; type->lua_read(state, 2, ptr); @@ -655,7 +677,7 @@ static int meta_primitive_index(lua_State *state) static int meta_primitive_newindex(lua_State *state) { uint8_t *ptr = get_object_addr(state, 1, 2, "write"); - auto type = (type_identity*)find_field(state, 2, "write"); + auto type = find_primitive_field(state, 2, "write", &ptr); if (!type) field_error(state, 2, "builtin property or method", "write"); type->lua_write(state, 2, ptr, 3);