Well, have I got news for ya! Introducing the magical world of Cython where Python meets C-level speed!
Did you know that with just a few lines of code, you can convert your precious byte strings to lightning-fast C char*? Say goodbye to those ***** encoding/decoding steps and hello to pure efficiency.
Before anything else the basics. In Cython land, there are four types of Python string: bytes, str (which is now called unicode in Python 3), bytearray, and c_string_type. The latter two behave like their counterparts in normal Python, but with a twist they can be used to implicitly insert encoding/decoding steps when passing between C and Python strings.
Now, Let’s jump right into the juicy part: converting your byte string to a C char*. Here’s how it works:
# Import the necessary libraries
import cython # Importing the cython library for C-Python integration
from libc.string cimport strlen # Importing the strlen function from the C library
# Define a function to convert a byte string to a C char*
@cython.boundscheck(False) # Disable bounds checking for faster execution
def convert_to_char_star(bytes str): # Function takes in a byte string as input
# Get the length of the Python byte string
len_str = len(str) # Using the len() function to get the length of the byte string
# Allocate memory for C char* and copy over bytes
cdef char *c_string = <char *>malloc(len_str + 1) # Using the malloc() function to allocate memory for the C char* pointer
memcpy(c_string, str, len_str) # Using the memcpy() function to copy the bytes from the Python string to the C char* pointer
c_string[len_str] = '\0' # Adding a null terminator at the end of the C char* pointer
# Return the C char* pointer
return c_string # Returning the C char* pointer to the caller
But wait, there’s a better way! You can skip all that memory allocation and copying by using Cython’s built-in encoding/decoding feature. Here’s how:
# Import the necessary libraries
import cython # Import the Cython library
from libc.stdlib cimport free # Import the free function from the standard library
# Define a function with boundscheck set to False to improve performance
@cython.boundscheck(False)
def convert_to_char_star(bytes str): # Function to convert a Python byte string to a C char* pointer
# Get the length of the Python byte string
len_str = len(str)
# Encode the Python byte string to a C char* pointer
cdef char *c_string = <char *>PyBytes_AsString(str)[:len_str] # Use the PyBytes_AsString function to convert the byte string to a C char* pointer
# Add a null terminator at the end of the C char* pointer for safety
c_string[len_str] = '\0'
# Return the C char* pointer and free up the memory used by the Python byte string
return c_string, <void *>free(PyBytes_AsString(str)[len_str:]) # Use the free function to free up the memory used by the Python byte string
That’s it! You now have a lightning-fast C char* that you can pass to your favorite C function. And the best part? No more ***** encoding/decoding steps cluttering up your code.
But wait, there’s one more thing if you’re working with Windows APIs, Cython supports wide strings (in the form of Py_UNICODE*) and implicitly converts them to and from unicode string objects. This means that you can use Python’s built-in len() function to compute the length of zero-terminated Py_UNICODE* string or array, without any extra hassle.
Say goodbye to slow Python scripts and hello to lightning-fast C code.