Cache immutable Wasm server configuration encoding

src/lib/dvalue.cpp

@@ -1175,6 +1175,87 @@ bool ucb_decode(const String& encoded, DValue& out, String* error_out)
 	return(false);
 }
 
+#ifdef __UCE_WASM_CORE__
+static bool ucb_decode_flat_string_map(const String& encoded, StringMap& out, String* error_out)
+{
+	String error;
+	StringMap decoded;
+	size_t offset = 0;
+	auto fail = [&](String message) {
+		error = message;
+		return(false);
+	};
+	if(encoded.size() < 5 || encoded.compare(0, 4, UCEB_MAGIC) != 0)
+		fail("missing UCEB magic header");
+	else if((u8)encoded[4] != UCEB_VERSION)
+		fail("unsupported UCEB version");
+	else
+	{
+		offset = 5;
+		if(encoded.size() - offset < 2)
+			fail("unexpected end of UCEB2 string map");
+		else
+		{
+			u8 flags = (u8)encoded[offset++];
+			char type = encoded[offset++];
+			u64 scalar_len = 0, child_count = 0;
+			if(flags != 0 || type != 'M')
+				fail("UCEB2 string map root must be a map");
+			else if(!ucb_read_varint(encoded, offset, scalar_len) || scalar_len != 0)
+				fail("UCEB2 string map root must have no scalar");
+			else if(!ucb_read_varint(encoded, offset, child_count))
+				fail("invalid UCEB2 string map child count");
+			else
+			{
+				for(u64 i = 0; error == "" && i < child_count; i++)
+				{
+					u64 key_len = 0, value_len = 0, value_children = 0;
+					if(!ucb_read_varint(encoded, offset, key_len) || key_len > encoded.size() - offset)
+					{
+						fail("invalid UCEB2 string map key");
+						break;
+					}
+					String key(encoded.data() + offset, (size_t)key_len);
+					offset += (size_t)key_len;
+					if(encoded.size() - offset < 2)
+					{
+						fail("unexpected end of UCEB2 string map value");
+						break;
+					}
+					u8 value_flags = (u8)encoded[offset++];
+					char value_type = encoded[offset++];
+					if(value_flags != 0 || value_type != 'S' || !ucb_read_varint(encoded, offset, value_len) || value_len > encoded.size() - offset)
+					{
+						fail("UCEB2 string map value must be a string scalar");
+						break;
+					}
+					String value(encoded.data() + offset, (size_t)value_len);
+					offset += (size_t)value_len;
+					if(!ucb_read_varint(encoded, offset, value_children) || value_children != 0)
+					{
+						fail("UCEB2 string map value cannot have children");
+						break;
+					}
+					decoded[std::move(key)] = std::move(value);
+				}
+				if(error == "" && offset != encoded.size())
+					fail("trailing bytes after UCEB2 string map");
+			}
+		}
+	}
+	if(error != "")
+	{
+		if(error_out)
+			*error_out = error;
+		return(false);
+	}
+	out = std::move(decoded);
+	if(error_out)
+		*error_out = "";
+	return(true);
+}
+#endif
+
 DValue ucb_decode(const String& encoded)
 {
 	DValue out;