regex code refactor

- declare API_TYPE_REGEX
- move error report code to a function
- move regex table check to a function
- add regex.source and regex.flags
- add regex:nametable()
- ensure stack size in regex:cmatch()
- fix wrong match indices

src/api/api.h

@@ -8,6 +8,7 @@
 #define API_TYPE_FONT "Font"
 #define API_TYPE_REPLACE "Replace"
 #define API_TYPE_PROCESS "Process"
+#define API_TYPE_REGEX "Regex"
 
 void api_load_libs(lua_State *L);
 

src/api/regex.c

@@ -2,12 +2,50 @@
 
 #define PCRE2_CODE_UNIT_WIDTH 8
 
+#include <stdarg.h>
 #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;
+}
+
+static int pcre2_error(lua_State *L, int rc, const char *fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+  lua_pushvfstring(L, fmt, ap);
+  va_end(ap);
+
+  PCRE2_UCHAR err[256];
+  pcre2_get_error_message(rc, err, sizeof(err));
+  lua_pushstring(L, (const char *) err);
+
+  lua_concat(L, 2);
+  lua_error(L);
+  return 0;
+}
+
 static int f_pcre_gc(lua_State* L) {
-  lua_rawgeti(L, -1, 1);
+  pcre2_code* re = check_regex(L, 1);
-  pcre2_code* re = (pcre2_code*)lua_touserdata(L, -1);
   if (re)
     pcre2_code_free(re);
   return 0;
@@ -15,80 +53,121 @@ static int f_pcre_gc(lua_State* L) {
 
 static int f_pcre_compile(lua_State *L) {
   size_t len; 
-  PCRE2_SIZE errorOffset;
+  int options = PCRE2_UTF;
-  int errorNumber;
+  const char* pattern = luaL_checklstring(L, 1, &len);
-  int pattern = PCRE2_UTF;
+  const char* optstr = luaL_optstring(L, 2, "");
-  const char* str = luaL_checklstring(L, 1, &len);
+  if (strstr(optstr,"i"))
-  if (lua_gettop(L) > 1) {
+    options |= PCRE2_CASELESS;
-    const char* options = luaL_checkstring(L, 2);
+  if (strstr(optstr,"m"))
-    if (strstr(options,"i"))
+    options |= PCRE2_MULTILINE;
-      pattern |= PCRE2_CASELESS;
+  if (strstr(optstr,"s"))
-    if (strstr(options,"m"))
+    options |= PCRE2_DOTALL;
-      pattern |= PCRE2_MULTILINE;
+  
-    if (strstr(options,"s"))
+  int error;
-      pattern |= PCRE2_DOTALL;
+  PCRE2_SIZE error_offset;
-  }
   pcre2_code* re = pcre2_compile(
-    (PCRE2_SPTR)str,
+    (PCRE2_SPTR)pattern,
     len,
-    pattern,
+    options,
-    &errorNumber,
+    &error,
-    &errorOffset,
+    &error_offset,
     NULL
   );
-  if (re) {
+
+  if (re == NULL)
+    return pcre2_error(L, error, "regex compilation failed at %d: ", error_offset);
+
   lua_newtable(L);
-    lua_pushlightuserdata(L, re);
+  luaL_setmetatable(L, API_TYPE_REGEX);
+
+  lua_pushlightuserdata(L, (void*) re);
   lua_rawseti(L, -2, 1);
-    luaL_setmetatable(L, "regex");
+
+  lua_pushvalue(L, 1);
+  lua_setfield(L, -2, "source");
+
+  lua_pushstring(L, optstr);
+  lua_setfield(L, -2, "flags");
+
   return 1;
 }
-  PCRE2_UCHAR buffer[256];
+
-  pcre2_get_error_message(errorNumber, buffer, sizeof(buffer));
+// get nametable (useful for named captures)
-  lua_pushnil(L);
+static int f_pcre_nametable(lua_State* L) {
-  char message[1024];
+  pcre2_code* re = check_regex(L, 1);
-  len = snprintf(message, sizeof(message), "regex compilation failed at offset %d: %s", (int)errorOffset, buffer);
+  int ret;
-  lua_pushlstring(L, message, len);
+  uint32_t namecount, entrysize;
-  return 2;
+  PCRE2_SPTR nametable;
+
+  ret = pcre2_pattern_info(re, PCRE2_INFO_NAMETABLE, &nametable);
+  if (ret)
+    return pcre2_error(L, ret, "cannot get PCRE2_INFO_NAMETABLE: ");
+
+  pcre2_pattern_info(re, PCRE2_INFO_NAMECOUNT, &namecount);
+  pcre2_pattern_info(re, PCRE2_INFO_NAMEENTRYSIZE, &entrysize);
+
+  lua_createtable(L, namecount, 0);
+  for (uint32_t i = 0; i < namecount; i++) {
+    uint16_t index = (nametable[1] << 0) | (nametable[0] << 8);
+    nametable += 2;
+    
+    lua_createtable(L, 0, 2);
+    lua_pushnumber(L, index);
+    lua_setfield(L, -2, "index");
+    lua_pushstring(L, (const char *) nametable);
+    lua_setfield(L, -2, "name");
+    lua_rawseti(L, -2, i + 1);
+
+    nametable += (entrysize - 2);
+  }
+
+  return 1;
 }
 
 // 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 = 1, opts = 0;
+  size_t len, offset, options;
-  luaL_checktype(L, 1, LUA_TTABLE);
+  pcre2_code* re = check_regex(L, 1);
   const char* str = luaL_checklstring(L, 2, &len);
-  if (lua_gettop(L) > 2)
+
-    offset = luaL_checknumber(L, 3);
+  offset = luaL_optnumber(L, 3, 1);
-  if (lua_gettop(L) > 3)
+  options = luaL_optnumber(L, 4, 0);
-    opts = luaL_checknumber(L, 4);
+
-  lua_rawgeti(L, 1, 1);
-  pcre2_code* re = (pcre2_code*)lua_touserdata(L, -1);
   pcre2_match_data* md = pcre2_match_data_create_from_pattern(re, NULL);
-  int rc = pcre2_match(re, (PCRE2_SPTR)str, len, offset - 1, opts, md, NULL);
+  int rc = pcre2_match(re, (PCRE2_SPTR)str, len, offset - 1, options, md, NULL);
   if (rc < 0) {
     pcre2_match_data_free(md);
-    if (rc != PCRE2_ERROR_NOMATCH)
+    if (rc != PCRE2_ERROR_NOMATCH) {
-      luaL_error(L, "regex matching error %d", rc);
+      PCRE2_UCHAR buffer[256];
+      pcre2_get_error_message(rc, buffer, sizeof(buffer));
+      luaL_error(L, "regex matching error: %s", buffer);
+    }
     return 0;
   }
+
   PCRE2_SIZE* ovector = pcre2_get_ovector_pointer(md);
   if (ovector[0] > ovector[1]) {
+    pcre2_match_data_free(md);
     /* 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");
-    pcre2_match_data_free(md);
     return 0;
   }
-  for (int i = 0; i < rc*2; i++)
+
-    lua_pushnumber(L, ovector[i]+1);
+  rc *= 2;
+  luaL_checkstack(L, rc, NULL);
+  for (int i = 0; i < rc; i++)
+    // for every even vector (the end of a pair), we do not increment by 1
+    lua_pushnumber(L, ovector[i] + (i + 1) % 2);
   pcre2_match_data_free(md);
-  return rc*2;
+  return rc;
 }
 
 static const luaL_Reg lib[] = {
+  { "nametable", f_pcre_nametable },
   { "compile",  f_pcre_compile },
   { "cmatch",   f_pcre_match },
   { "__gc",     f_pcre_gc },
@@ -96,22 +175,28 @@ static const luaL_Reg lib[] = {
 };
 
 int luaopen_regex(lua_State *L) {
-  luaL_newlib(L, lib);
+  luaL_newmetatable(L, API_TYPE_REGEX);
-  lua_pushliteral(L, "regex");
+  luaL_setfuncs(L, lib, 0);
-  lua_setfield(L, -2, "__name");
   lua_pushvalue(L, -1);
-  lua_setfield(L, LUA_REGISTRYINDEX, "regex");
+  lua_setfield(L, -2, "__index");
+
   lua_pushnumber(L, PCRE2_ANCHORED);
   lua_setfield(L, -2, "ANCHORED");
+  
   lua_pushnumber(L, PCRE2_ANCHORED) ;
   lua_setfield(L, -2, "ENDANCHORED");
+  
   lua_pushnumber(L, PCRE2_NOTBOL);
   lua_setfield(L, -2, "NOTBOL");
+  
   lua_pushnumber(L, PCRE2_NOTEOL);
   lua_setfield(L, -2, "NOTEOL");
+  
   lua_pushnumber(L, PCRE2_NOTEMPTY);
   lua_setfield(L, -2, "NOTEMPTY");
+  
   lua_pushnumber(L, PCRE2_NOTEMPTY_ATSTART);
   lua_setfield(L, -2, "NOTEMPTY_ATSTART");
+  
   return 1;
 }