refactor regex API again

This time making it easier to use from Lua side.
- regex is now a proper userdata instead of a table wrapped in userdata
- add regex:get_metadata()
- remove regex:nametable() option in favor of regex:get_metadata()

src/api/regex.c

@@ -6,28 +6,10 @@
 #include <string.h>
 #include <pcre2.h>
 
-
-// something similiar to luaL_checkudata() but for regex only
-static pcre2_code* check_regex(lua_State* L, int arg) {
-  luaL_checktype(L, arg, LUA_TTABLE);
-  int hasmt = 0; 
-  pcre2_code* re = NULL;
-
-  if (lua_getmetatable(L, arg)) {
-    luaL_getmetatable(L, API_TYPE_REGEX);
-    hasmt = lua_rawequal(L, -1, -2);
-    lua_pop(L, 2);
-  }
-
-  lua_rawgeti(L, arg, 1);
-  re = lua_touserdata(L, -1);
-  lua_pop(L, 1);
-
-  if (!hasmt || re == NULL)
-    luaL_argerror(L, arg, "invalid regex object");
-
-  return re;
-}
+typedef struct regex_t {
+  pcre2_code *re;
+  int metadata;
+} regex_t;
 
 static int pcre2_error(lua_State *L, int rc, const char *fmt, ...) {
   va_list ap;
@@ -45,9 +27,10 @@ static int pcre2_error(lua_State *L, int rc, const char *fmt, ...) {
 }
 
 static int f_pcre_gc(lua_State* L) {
-  pcre2_code* re = check_regex(L, 1);
-  if (re)
-    pcre2_code_free(re);
+  regex_t *re = luaL_checkudata(L, 1, API_TYPE_REGEX);
+  luaL_unref(L, LUA_REGISTRYINDEX, re->metadata);
+  if (re->re)
+    pcre2_code_free(re->re);
   return 0;
 }
 
@@ -76,25 +59,25 @@ static int f_pcre_compile(lua_State *L) {
 
   if (re == NULL)
     return pcre2_error(L, error, "regex compilation failed at %d: ", error_offset);
+    
+  regex_t *regex = (regex_t*) lua_newuserdata(L, sizeof(regex_t));
+  luaL_setmetatable(L, API_TYPE_REGEX);
+  regex->re = re;
 
   lua_newtable(L);
-  luaL_setmetatable(L, API_TYPE_REGEX);
-
-  lua_pushlightuserdata(L, (void*) re);
-  lua_rawseti(L, -2, 1);
 
   lua_pushvalue(L, 1);
   lua_setfield(L, -2, "source");
 
   lua_pushstring(L, optstr);
   lua_setfield(L, -2, "flags");
+  
+  regex->metadata = luaL_ref(L, LUA_REGISTRYINDEX);
 
   return 1;
 }
 
-// get nametable (useful for named captures)
-static int f_pcre_nametable(lua_State* L) {
-  pcre2_code* re = check_regex(L, 1);
+static int get_nametable(lua_State *L, pcre2_code *re) {
   int ret;
   uint32_t namecount, entrysize;
   PCRE2_SPTR nametable;
@@ -107,7 +90,7 @@ static int f_pcre_nametable(lua_State* L) {
   pcre2_pattern_info(re, PCRE2_INFO_NAMEENTRYSIZE, &entrysize);
 
   lua_createtable(L, namecount, 0);
-  for (uint32_t i = 0; i < namecount; i++) {
+  for (uint32_t i = 1; i <= namecount; i++) {
     uint16_t index = (nametable[1] << 0) | (nametable[0] << 8);
     nametable += 2;
     
@@ -116,7 +99,7 @@ static int f_pcre_nametable(lua_State* L) {
     lua_setfield(L, -2, "index");
     lua_pushstring(L, (const char *) nametable);
     lua_setfield(L, -2, "name");
-    lua_rawseti(L, -2, i + 1);
+    lua_rawseti(L, -2, i);
 
     nametable += (entrysize - 2);
   }
@@ -124,26 +107,52 @@ static int f_pcre_nametable(lua_State* L) {
   return 1;
 }
 
+static int f_pcre_get_metadata(lua_State *L) {
+  regex_t *re = luaL_checkudata(L, 1, API_TYPE_REGEX);
+  
+  lua_rawgeti(L, LUA_REGISTRYINDEX, re->metadata);
+  lua_getfield(L, -1, "nametable");
+  if (lua_type(L, -1) == LUA_TTABLE) {
+    lua_pop(L, 1);
+  } else {
+    lua_pop(L, 1);
+    get_nametable(L, re->re);
+    lua_setfield(L, -2, "nametable");
+  }
+  
+  return 1;
+}
+
+static size_t check_bitfield(lua_State *L, int t) {
+  size_t size, bit = 0;
+  luaL_checktype(L, t, LUA_TTABLE);
+  size = lua_rawlen(L, t);
+  for (size_t i = 1; i <= size; i++) {
+    lua_rawgeti(L, t, i);
+    bit |= luaL_checkinteger(L, -1);
+    lua_pop(L, 1);
+  }
+  return bit;
+}
+
 // Takes string, compiled regex, returns list of indices of matched groups
 // (including the whole match), if a match was found.
 static int f_pcre_match(lua_State *L) {
   size_t len, offset, options;
-  pcre2_code* re = check_regex(L, 1);
+  regex_t *re = luaL_checkudata(L, 1, API_TYPE_REGEX);
   const char* str = luaL_checklstring(L, 2, &len);
 
   offset = luaL_optnumber(L, 3, 1);
-  options = luaL_optnumber(L, 4, 0);
+  options = lua_gettop(L) == 4 ? check_bitfield(L, 4) : 0;
 
-  pcre2_match_data* md = pcre2_match_data_create_from_pattern(re, NULL);
-  int rc = pcre2_match(re, (PCRE2_SPTR)str, len, offset - 1, options, md, NULL);
+  pcre2_match_data* md = pcre2_match_data_create_from_pattern(re->re, NULL);
+  int rc = pcre2_match(re->re, (PCRE2_SPTR)str, len, offset - 1, options, md, NULL);
   if (rc < 0) {
     pcre2_match_data_free(md);
-    if (rc != PCRE2_ERROR_NOMATCH) {
-      PCRE2_UCHAR buffer[256];
-      pcre2_get_error_message(rc, buffer, sizeof(buffer));
-      luaL_error(L, "regex matching error: %s", buffer);
-    }
-    return 0;
+    if (rc != PCRE2_ERROR_NOMATCH)
+      return pcre2_error(L, rc, "regex matching error: ");
+    else
+      return 0;
   }
 
   PCRE2_SIZE* ovector = pcre2_get_ovector_pointer(md);
@@ -152,9 +161,8 @@ static int f_pcre_match(lua_State *L) {
     /* We must guard against patterns such as /(?=.\K)/ that use \K in an
     assertion  to set the start of a match later than its end. In the editor,
     we just detect this case and give up. */
-    luaL_error(L, "regex matching error: \\K was used in an assertion to "
-    " set the match start after its end");
-    return 0;
+    return luaL_error(L, "regex matching error: \\K was used in an assertion to "
+                          " set the match start after its end");
   }
 
   rc *= 2;
@@ -167,11 +175,11 @@ static int f_pcre_match(lua_State *L) {
 }
 
 static const luaL_Reg lib[] = {
-  { "nametable", f_pcre_nametable },
-  { "compile",  f_pcre_compile },
-  { "cmatch",   f_pcre_match },
-  { "__gc",     f_pcre_gc },
-  { NULL,       NULL }
+  { "get_metadata", f_pcre_get_metadata },
+  { "compile",      f_pcre_compile },
+  { "cmatch",       f_pcre_match },
+  { "__gc",         f_pcre_gc },
+  { NULL,           NULL }
 };
 
 int luaopen_regex(lua_State *L) {