Add lua_setpico8memory() entry point to support operators @ @@ and $.

Author: samhocevar

lapi.c

@@ -134,6 +134,13 @@ LUA_API lua_CFunction lua_atpanic (lua_State *L, lua_CFunction panicf) {
 }
 
 
+LUA_API void lua_setpico8memory (lua_State *L, unsigned char const *p) {
+  lua_lock(L);
+  G(L)->pico8memory = p;
+  lua_unlock(L);
+}
+
+
 LUA_API const lua_Number *lua_version (lua_State *L) {
   static const lua_Number version = LUA_VERSION_NUM;
   if (L == NULL) return &version;

lstate.h

@@ -140,6 +140,7 @@ typedef struct global_State {
   int gcmajorinc;  /* pause between major collections (only in gen. mode) */
   int gcstepmul;  /* GC `granularity' */
   lua_CFunction panic;  /* to be called in unprotected errors */
+  lu_byte const *pico8memory;  /* pointer to PICO-8 RAM */
   struct lua_State *mainthread;
   const lua_Number *version;  /* pointer to version number */
   TString *memerrmsg;  /* memory-error message */

lua.h

@@ -252,6 +252,7 @@ LUA_API void  (lua_rawsetp) (lua_State *L, int idx, const void *p);
 LUA_API int   (lua_setmetatable) (lua_State *L, int objindex);
 LUA_API void  (lua_setuservalue) (lua_State *L, int idx);
 
+LUA_API void  (lua_setpico8memory) (lua_State *L, unsigned char const *p);
 
 /*
 ** 'load' and 'call' functions (load and run Lua code)

luaconf.h

@@ -583,9 +583,9 @@
 #define luai_numshr(L,a,b)	((a)>>int((b)))
 #define luai_numlshr(L,a,b)	(l_mathop(lshr)((a),(b)))
 #define luai_numbnot(L,a)	(~(a))
-#define luai_numpeek(L,a)	((void)(a),0)
-#define luai_numpeek2(L,a)	((void)(a),0)
-#define luai_numpeek4(L,a)	((void)(a),0)
+#define luai_numpeek(L,a)	(lua_peek(L,a,1))
+#define luai_numpeek2(L,a)	(lua_peek(L,a,2))
+#define luai_numpeek4(L,a)	(lua_peek(L,a,4))
 
 #define lua_number2str(s,n) [&]() { \
   int i = sprintf(s, "%1.4f", (double)n); \

lvm.c

@@ -206,6 +206,28 @@ static int call_orderTM (lua_State *L, const TValue *p1, const TValue *p2,
 }
 
 
+#define PEEK(ram, address) (ram && (address < 0x8000) ? ram[address] : 0)
+
+static z8::fix32 lua_peek(struct lua_State *L, z8::fix32 a, int count)
+{
+  unsigned char const *p = G(L)->pico8memory;
+  int address = int(a) & 0x7fff;
+  uint32_t ret = 0;
+  switch (count) {
+    case 4:
+      ret |= PEEK(p, address + 1) << 8;
+      ret |= PEEK(p, address);
+      address += 2;
+    case 2:
+      ret |= PEEK(p, address + 1) << 24;
+    case 1:
+      ret |= PEEK(p, address) << 16;
+      break;
+  }
+  return z8::fix32::frombits(ret);
+}
+
+
 static int l_strcmp (const TString *ls, const TString *rs) {
   const char *l = getstr(ls);
   size_t ll = ls->tsv.len;