Bruce/lua-immutable
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Improving hash.

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This commit is contained in:
Bruce Hill 2018-02-10 16:37:26 -08:00
parent e7e59d4b0e
commit 21d8c27e73
1 changed files with 31 additions and 14 deletions
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45
limmutable.c
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@ -24,6 +24,10 @@
#define luaL_register(L, _, R) luaL_setfuncs(L, R, 0)
#endif
#if !defined(LUAI_HASHLIMIT)
#define LUAI_HASHLIMIT 5
#endif
static int Lcreate_instance(lua_State *L)
{
int n_args = lua_gettop(L);
@ -47,20 +51,22 @@ static int Lcreate_instance(lua_State *L)
// Stack [inst]
// Copy in all the values, and simultaneously compute the hash:
lua_Integer hash = 0;
lua_Integer hash = (lua_Integer)lua_topointer(L, 1); // Hash depends on the metatable used in creation
for (lua_Integer i=1; i <=(lua_Integer)n; i++) {
lua_pushvalue(L, i+1);
// Stack [inst, args[i+1]]
lua_Integer item_hash;
switch (lua_type(L, -1)) {
case LUA_TNIL:
item_hash = 0;
// Arbitrarily chosen value
item_hash = 0x97167da9;
break;
case LUA_TNUMBER:
item_hash = (lua_Integer)lua_tonumber(L, -1);
break;
case LUA_TBOOLEAN:
item_hash = (lua_Integer)lua_toboolean(L, -1);
// Arbitrarily chosen values
item_hash = lua_toboolean(L, -1)? 0x82684f71 : 0x88d66f2a;
break;
case LUA_TTABLE:
case LUA_TFUNCTION:
@ -71,12 +77,13 @@ static int Lcreate_instance(lua_State *L)
break;
case LUA_TSTRING:
{
size_t strlen;
const char *str = lua_tolstring(L, -1, &strlen);
item_hash = *str << 7;
for (const char *end = &str[strlen]; str < end; str++)
item_hash = (1000003*item_hash) ^ *str;
item_hash ^= strlen;
// Algorithm taken from Lua 5.3's implementation
size_t len;
const char *str = lua_tolstring(L, -1, &len);
item_hash = len ^ 0xd2e9e9ac; // Arbitrary seed
size_t step = (len >> LUAI_HASHLIMIT) + 1;
for (; len >= step; len -= step)
item_hash ^= ((item_hash<<5) + (item_hash>>2) + (unsigned char)(str[len - 1]));
break;
}
default:
@ -196,7 +203,9 @@ static int Lfrom_table(lua_State *L)
static int Llen(lua_State *L)
{
lua_getmetatable(L, 1);
if (! lua_getmetatable(L, 1)) {
luaL_error(L, "invalid type");
}
// Stack: [mt]
lua_getfield(L, -1, "__fields");
// Stack: [mt, fields]
@ -206,7 +215,9 @@ static int Llen(lua_State *L)
static int Lindex(lua_State *L)
{
lua_getmetatable(L, 1);
if (! lua_getmetatable(L, 1)) {
luaL_error(L, "invalid type");
}
// Stack: [mt]
lua_getfield(L, -1, "__indices");
// Stack: [mt, indices]
@ -242,7 +253,9 @@ static int Ltostring(lua_State *L)
luaL_Buffer b;
luaL_buffinit(L, &b);
lua_getmetatable(L, 1);
if (! lua_getmetatable(L, 1)) {
luaL_error(L, "invalid type");
}
// Stack: [mt]
lua_getfield(L, -1, "name");
@ -298,7 +311,9 @@ static int Ltostring(lua_State *L)
static int Lnexti(lua_State *L)
{
lua_getmetatable(L, 1);
if (! lua_getmetatable(L, 1)) {
luaL_error(L, "invalid type");
}
// Stack: [mt]
lua_getfield(L, -1, "__instances");
// Stack: [mt, buckets]
@ -336,7 +351,9 @@ static int Lipairs(lua_State *L)
static int Lnext(lua_State *L)
{
lua_getmetatable(L, 1);
if (! lua_getmetatable(L, 1)) {
luaL_error(L, "invalid type");
}
// Stack: [mt]
lua_getfield(L, -1, "__instances");
// Stack: [mt, buckets]