[Redbean] Add UuidV4 method (#1140)

tool/net/definitions.lua

@@ -1977,6 +1977,10 @@ function VisualizeControlCodes(str) end
 ---@nodiscard
 function Underlong(str) end
 
+--- Generate a uuid_v4
+--- @return string
+function UuidV4() end
+
 ---@param x integer
 ---@return integer # position of first bit set.
 --- Passing `0` will raise an error. Same as the Intel x86 instruction BSF.

tool/net/help.txt

@@ -1062,6 +1062,9 @@ FUNCTIONS
           Server Name Indicator (SNI) when performing Fetch() requests.
           This function is not available in unsecure mode.
 
+  UuidV4() -> str
+          Returns an uuid v4 string.
+
   Fetch(url:str[,body:str|{method=value:str,body=value:str,headers=table,...}])
       ├─→ status:int, {header:str=value:str,...}, body:str
       └─→ nil, error:str

tool/net/lfuncs.c

@@ -829,6 +829,31 @@ int LuaVisualizeControlCodes(lua_State *L) {
   return LuaCoder(L, VisualizeControlCodes);
 }
 
+int LuaUuidV4(lua_State *L) {
+  static const char v[] = {'0', '1', '2', '3', '4', '5', '6', '7',
+                           '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+  char uuid_str[37] = {0};
+  uint64_t r = _rand64();
+  int j = 0;
+  for (int i = 0; i < 36; ++i, ++j) {
+    if (j == 16) {
+      r = _rand64();
+      j = 0;
+    }
+    uuid_str[i] = v[(r & (0xfull << (j * 4ull))) >> (j * 4ull)];
+  }
+
+  uuid_str[8] = '-';
+  uuid_str[13] = '-';
+  uuid_str[14] = '4';
+  uuid_str[18] = '-';
+  uuid_str[19] = v[8 | (r & (0x3ull << (j * 4ull))) >> (j * 4ull)];
+  uuid_str[23] = '-';
+  uuid_str[36] = '\0';
+  lua_pushfstring(L, uuid_str);
+  return 1;
+}
+
 static dontinline int LuaHasherImpl(lua_State *L, size_t k,
                                     int H(const void *, size_t, uint8_t *)) {
   size_t n;

tool/net/lfuncs.h

@@ -90,6 +90,7 @@ int LuaSleep(lua_State *);
 int LuaSlurp(lua_State *);
 int LuaUncompress(lua_State *);
 int LuaUnderlong(lua_State *);
+int LuaUuidV4(lua_State *);
 int LuaVisualizeControlCodes(lua_State *);
 
 void LuaPushUrlView(lua_State *, struct UrlView *);

tool/net/redbean.c

@@ -5287,6 +5287,7 @@ static const luaL_Reg kLuaFuncs[] = {
     {"StoreAsset", LuaStoreAsset},                              //
     {"Uncompress", LuaUncompress},                              //
     {"Underlong", LuaUnderlong},                                //
+    {"UuidV4", LuaUuidV4},                                      //
     {"VisualizeControlCodes", LuaVisualizeControlCodes},        //
     {"Write", LuaWrite},                                        //
     {"bin", LuaBin},                                            //