Add PCRE to support regular expressions

Use regular expressions instead of Lua patterns for find and replace editor commands.

Syntax files can now use regex or Lua patterns as before keeping backward compatibility for plugins.

src/api/api.c

@@ -3,11 +3,13 @@
 
 int luaopen_system(lua_State *L);
 int luaopen_renderer(lua_State *L);
+int luaopen_regex(lua_State *L);
 
 
 static const luaL_Reg libs[] = {
   { "system",    luaopen_system     },
   { "renderer",  luaopen_renderer   },
+  { "regex",     luaopen_regex   },
   { NULL, NULL }
 };
 

src/api/regex.c

@@ -0,0 +1,115 @@
+#include "api.h"
+
+#define PCRE2_CODE_UNIT_WIDTH 8
+
+#include <string.h>
+#include <pcre2.h>
+
+static int f_pcre_gc(lua_State* L) {
+  lua_rawgeti(L, -1, 1);
+  pcre2_code* re = (pcre2_code*)lua_touserdata(L, -1);
+  if (re)
+    pcre2_code_free(re);
+  return 0;
+}
+
+static int f_pcre_compile(lua_State *L) {
+  size_t len;
+  PCRE2_SIZE errorOffset;
+  int errorNumber;
+  int pattern = PCRE2_UTF;
+  const char* str = luaL_checklstring(L, 1, &len);
+  if (lua_gettop(L) > 1) {
+    const char* options = luaL_checkstring(L, 2);
+    if (strstr(options,"i"))
+      pattern |= PCRE2_CASELESS;
+    if (strstr(options,"m"))
+      pattern |= PCRE2_MULTILINE;
+    if (strstr(options,"s"))
+      pattern |= PCRE2_DOTALL;
+  }
+  pcre2_code* re = pcre2_compile(
+    (PCRE2_SPTR)str,
+    len,
+    pattern,
+    &errorNumber,
+    &errorOffset,
+    NULL
+  );
+  if (re) {
+    lua_newtable(L);
+    lua_pushlightuserdata(L, re);
+    lua_rawseti(L, -2, 1);
+    luaL_setmetatable(L, "regex");
+    return 1;
+  }
+  PCRE2_UCHAR buffer[256];
+  pcre2_get_error_message(errorNumber, buffer, sizeof(buffer));
+  luaL_error(L, "regex compilation failed at offset %d: %s", 
+    (int)errorOffset, buffer);
+  return 0;
+}
+
+// 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;
+  luaL_checktype(L, 1, LUA_TTABLE);
+  const char* str = luaL_checklstring(L, 2, &len);
+  if (lua_gettop(L) > 2)
+    offset = luaL_checknumber(L, 3);
+  if (lua_gettop(L) > 3)
+    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);
+  if (rc < 0) {
+    pcre2_match_data_free(md);
+    if (rc != PCRE2_ERROR_NOMATCH)
+      luaL_error(L, "regex matching error %d", rc);
+    return 0;
+  }
+  PCRE2_SIZE* ovector = pcre2_get_ovector_pointer(md);
+  if (ovector[0] > ovector[1]) {
+    /* 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);
+  pcre2_match_data_free(md);
+  return rc*2;
+}
+
+static const luaL_Reg lib[] = {
+  { "compile",  f_pcre_compile },
+  { "cmatch",   f_pcre_match },
+  { "__gc",     f_pcre_gc },
+  { NULL,       NULL }
+};
+
+int luaopen_regex(lua_State *L) {
+  luaL_newlib(L, lib);
+  lua_pushliteral(L, "regex");
+  lua_setfield(L, -2, "__name");
+  lua_pushvalue(L, -1);
+  lua_setfield(L, LUA_REGISTRYINDEX, "regex");
+  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;
+}