Python中CFFI简介和使用实际示例

pip install cffi

from cffi import FFI
ffi = FFI()
ffi.cdef("""
    int printf(const char *format, ...);
""")
C = ffi.dlopen(None)  # 加载标准C库
C.printf(b"Hello, %s!\n", b"World")

from cffi import FFI
ffi = FFI()
ffi.cdef("""
    int add(int a, int b);
""")
# 内联C源代码
ffi.set_source("_example",
"""
    int add(int a, int b) {
        return a + b;
    }
""")
if __name__ == "__main__":
    ffi.compile()

from _example import ffi, lib
result = lib.add(2, 3)
print(result)  # 输出: 5

from cffi import FFI
ffi = FFI()
ffi.cdef("""
    double sin(double x);
    double cos(double x);
""")
C = ffi.dlopen(None)  # 加载标准C库
x = 3.1415926535 / 4
print("sin:", C.sin(x))
print("cos:", C.cos(x))

#ifndef EXAMPLE_H
#define EXAMPLE_H
int add(int a, int b);
void print_message(const char *message);
#endif

#include <stdio.h>
#include "example.h"
int add(int a, int b) {
    return a + b;
}
void print_message(const char *message) {
    printf("Message: %s\n", message);
}

gcc -shared -o libexample.so -fPIC example.c

from cffi import FFI
ffi = FFI()
ffi.cdef("""
    int add(int a, int b);
    void print_message(const char *message);
""")
lib = ffi.dlopen("./libexample.so")
print("Add result:", lib.add(5, 7))
lib.print_message(b"Hello from Python!")

from cffi import FFI
ffi = FFI()
ffi.cdef("""
    typedef struct {
        int x;
        int y;
    } Point;
    double distance(Point p1, Point p2);
""")
ffi.set_source("_geometry",
"""
    #include <math.h>
    typedef struct {
        int x;
        int y;
    } Point;
    double distance(Point p1, Point p2) {
        int dx = p1.x - p2.x;
        int dy = p1.y - p2.y;
        return sqrt(dx*dx + dy*dy);
    }
""")
if __name__ == "__main__":
    ffi.compile()

from _geometry import ffi, lib
p1 = ffi.new("Point *", [1, 2])
p2 = ffi.new("Point *", [4, 6])
distance = lib.distance(p1[0], p2[0])
print("Distance:", distance)  # 输出: 5.0

from cffi import FFI
ffi = FFI()
ffi.cdef("""
    typedef struct {
        char *name;
        int age;
    } Person;
    Person *create_person(char *name, int age);
    void free_person(Person *p);
""")
# 假设这是与C库交互的部分
ffi.set_source("_person", "")
if __name__ == "__main__":
    ffi.compile()
from _person import ffi, lib
# 自动内存管理
person = ffi.new("Person *")
person.name = ffi.new("char[]", b"Alice")
person.age = 30
# 手动内存管理
p = lib.create_person(b"Bob", 25)
try:
    print(ffi.string(p.name), p.age)
finally:
    lib.free_person(p)

import numpy as np
from cffi import FFI
ffi = FFI()
ffi.cdef("""
    void square_array(double *array, int length);
""")
ffi.set_source("_numpy_example",
"""
    void square_array(double *array, int length) {
        for (int i = 0; i < length; i++) {
            array[i] = array[i] * array[i];
        }
    }
""")
if __name__ == "__main__":
    ffi.compile()
from _numpy_example import ffi, lib
arr = np.array([1.0, 2.0, 3.0, 4.0], dtype=np.float64)
ptr = ffi.cast("double *", arr.ctypes.data)
lib.square_array(ptr, len(arr))
print(arr)  # 输出: [ 1.  4.  9. 16.]