feat: reduce string conversion overhead for bluetooth addresses (#12)

src/bluetooth_data_tools/_utils_impl.pyx

@@ -1,13 +1,22 @@
-from libcpp.string cimport string
-
 import cython
 
+from libc.stdlib cimport malloc
+
 
 cdef extern from "stdint.h":
     ctypedef unsigned long long uint64_t
 
 cdef extern from "utils_wrapper.h":
-    string _cpp_uint64_to_bdaddr(uint64_t addr)
+    void _uint64_to_bdaddr(uint64_t addr, char *bdaddr)
+
+cdef char* uint64_to_bdaddr(uint64_t address):
+    cdef char* bdaddr = <char *> malloc((18) * sizeof(char))
+    if not bdaddr:
+        return NULL  # malloc failed
+    _uint64_to_bdaddr(address, bdaddr)
+    return bdaddr
+
+
 
 def _int_to_bluetooth_address(addr: int) -> str:
-    return _cpp_uint64_to_bdaddr(addr).decode('ascii')
+    return uint64_to_bdaddr(addr).decode('ascii')

src/bluetooth_data_tools/utils.py

@@ -1,18 +1,17 @@
 """Bluetooth utils."""
-
-
 from __future__ import annotations
 
+from functools import lru_cache
 
-def int_to_bluetooth_address(address: int) -> str:
-    """Convert an integer to a bluetooth address."""
-    mac_hex = f"{address:012X}"
-    return f"{mac_hex[0:2]}:{mac_hex[2:4]}:{mac_hex[4:6]}:{mac_hex[6:8]}:{mac_hex[8:10]}:{mac_hex[10:12]}"  # noqa: E501
+try:
+    from ._utils_impl import _int_to_bluetooth_address  # noqa: F811 F401
 
+    int_to_bluetooth_address = lru_cache(maxsize=256)(_int_to_bluetooth_address)
 
-try:
-    from ._utils_impl import (  # type: ignore[no-redef] # noqa: F811 F401
-        _int_to_bluetooth_address as int_to_bluetooth_address,
-    )
 except ImportError:
-    pass
+
+    @lru_cache(maxsize=256)
+    def int_to_bluetooth_address(address: int) -> str:
+        """Convert an integer to a bluetooth address."""
+        mac_hex = f"{address:012X}"
+        return f"{mac_hex[0:2]}:{mac_hex[2:4]}:{mac_hex[4:6]}:{mac_hex[6:8]}:{mac_hex[8:10]}:{mac_hex[10:12]}"  # noqa: E501

src/bluetooth_data_tools/utils_wrapper.h

@@ -1,19 +1,11 @@
 
 
 #include <stdint.h>
-#include <string>
-#include <memory>
+#include <stdio.h>
 
-#define BDADDR_SIZE 18  // 17 + '\0'
-
-using namespace std;
-
-
-std::string _cpp_uint64_to_bdaddr(uint64_t address) {
-    std::unique_ptr<char[]> buf( new char[ BDADDR_SIZE ] );
-    std::snprintf( buf.get(), BDADDR_SIZE, "%02X:%02X:%02X:%02X:%02X:%02X", (uint8_t) (address >> 40) & 0xff,
+void _uint64_to_bdaddr(uint64_t address, char *bdaddr) {
+    snprintf(bdaddr, 18, "%02X:%02X:%02X:%02X:%02X:%02X", (uint8_t) (address >> 40) & 0xff,
                        (uint8_t) (address >> 32) & 0xff, (uint8_t) (address >> 24) & 0xff,
                        (uint8_t) (address >> 16) & 0xff, (uint8_t) (address >> 8) & 0xff,
-                       (uint8_t) (address >> 0) & 0xff );
-    return std::string( buf.get(), buf.get() + BDADDR_SIZE - 1 ); // We don't want the '\0' inside
+                       (uint8_t) (address >> 0) & 0xff);
 }