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Merge branch 'reverse-offsetof-macro' into 'next'

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Turn the lua sector lines hack into a macro

See merge request STJr/SRB2!1187
This commit is contained in:
James R 2020-10-23 16:44:29 -04:00
commit 86c38e6d9a
3 changed files with 14 additions and 6 deletions
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8
src/doomtype.h
View file

@ -371,4 +371,12 @@ typedef UINT32 tic_t;
#define WSTRING2(s) L ## s
#define WSTRING(s) WSTRING2 (s)
/*
A hack by Monster Iestyn: Return a pointer to a field of
a struct from a pointer to another field in the struct.
Needed for some lua shenanigans.
*/
#define FIELDFROM( type, field, have, want ) \
(void *)((intptr_t)(field) - offsetof (type, have) + offsetof (type, want))
#endif //__DOOMTYPE__

4
src/lua_maplib.c
View file

@ -489,7 +489,7 @@ static int sectorlines_get(lua_State *L)
// get the "linecount" by shifting our retrieved memory address of "lines" to where "linecount" is in the sector_t, then dereferencing the result
// we need this to determine the array's actual size, and therefore also the maximum value allowed as an index
// this only works if seclines is actually a pointer to a sector's lines member in memory, oh boy
numoflines = (size_t)(*(size_t *)(((size_t)seclines) - (offsetof(sector_t, lines) - offsetof(sector_t, linecount))));
numoflines = *(size_t *)FIELDFROM (sector_t, seclines, lines,/* -> */linecount);
/* OLD HACK
// check first linedef to figure which of its sectors owns this sector->lines pointer
@ -523,7 +523,7 @@ static int sectorlines_num(lua_State *L)
return luaL_error(L, "accessed sector_t.lines doesn't exist anymore.");
// see comments in the _get function above
numoflines = (size_t)(*(size_t *)(((size_t)seclines) - (offsetof(sector_t, lines) - offsetof(sector_t, linecount))));
numoflines = *(size_t *)FIELDFROM (sector_t, seclines, lines,/* -> */linecount);
lua_pushinteger(L, numoflines);
return 1;
}

8
src/lua_polyobjlib.c
View file

@ -99,7 +99,7 @@ static int polyobjvertices_get(lua_State *L)
}
}
numofverts = (size_t)(*(size_t *)(((size_t)polyverts) - (offsetof(polyobj_t, vertices) - offsetof(polyobj_t, numVertices))));
numofverts = *(size_t *)FIELDFROM (polyobj_t, polyverts, vertices,/* -> */numVertices);
if (!numofverts)
return luaL_error(L, "no vertices found!");
@ -120,7 +120,7 @@ static int polyobjvertices_num(lua_State *L)
if (!polyverts || !(*polyverts))
return luaL_error(L, "accessed polyobj_t.vertices doesn't exist anymore.");
numofverts = (size_t)(*(size_t *)(((size_t)polyverts) - (offsetof(polyobj_t, vertices) - offsetof(polyobj_t, numVertices))));
numofverts = *(size_t *)FIELDFROM (polyobj_t, polyverts, vertices,/* -> */numVertices);
lua_pushinteger(L, numofverts);
return 1;
}
@ -156,7 +156,7 @@ static int polyobjlines_get(lua_State *L)
}
}
numoflines = (size_t)(*(size_t *)(((size_t)polylines) - (offsetof(polyobj_t, lines) - offsetof(polyobj_t, numLines))));
numoflines = *(size_t *)FIELDFROM (polyobj_t, polylines, lines,/* -> */numLines);
if (!numoflines)
return luaL_error(L, "no lines found!");
@ -177,7 +177,7 @@ static int polyobjlines_num(lua_State *L)
if (!polylines || !(*polylines))
return luaL_error(L, "accessed polyobj_t.lines doesn't exist anymore.");
numoflines = (size_t)(*(size_t *)(((size_t)polylines) - (offsetof(polyobj_t, lines) - offsetof(polyobj_t, numLines))));
numoflines = *(size_t *)FIELDFROM (polyobj_t, polylines, lines,/* -> */numLines);
lua_pushinteger(L, numoflines);
return 1;
}