python之转换 mmap 对象(mmaps 不支持串联)/将 c 代码转换为 python

大家好，我正在尝试将下面的代码转换为 python(访问树莓派 1Mhz 计时器)，我不知道什么时候要映射对象，我们需要 + TIMER_OFFSET (timer = (long long int *) ((char *)st_base + TIMER_OFFSET);) 当我尝试在 Python 中执行此操作时，我得到了 SystemError: mmaps don't support concatenation。我一直在寻找转换 mmap 对象，但我什么也没找到，我们可以解决这个问题吗？可以将整个代码转换为 python 吗？我的意思是现在我对它有了第二个想法？

#include <stdio.h> 
#include <sys/mman.h> 
#include <sys/types.h> 
#include <sys/stat.h> 
#include <fcntl.h> 
#include <unistd.h> 
 
#define ST_BASE (0x3F003000) 
#define TIMER_OFFSET (4) 
 
int main(int argc, char *argv[]) { 
    long long int t, prev, *timer; // 64 bit timer 
    int fd; 
    void *st_base; // byte ptr to simplify offset math 
 
    // get access to system core memory 
    if (-1 == (fd = open("/dev/mem", O_RDONLY))) { 
        fprintf(stderr, "open() failed.\n"); 
        return 255; 
    } 
 
    // map a specific page into process's address space 
    if (MAP_FAILED == (st_base = mmap(NULL, 4096, 
                        PROT_READ, MAP_SHARED, fd, ST_BASE))) { 
        fprintf(stderr, "mmap() failed.\n"); 
        return 254; 
    } 
 
    // set up pointer, based on mapped page 
    timer = (long long int *)((char *)st_base + TIMER_OFFSET); //<- here is problem 
 
    // read initial timer 
    prev = *timer; 
    // and wait 
    sleep(1); 
 
    while (1==1) { // forever 
        // read new timer 
        t = *timer; 
        printf("Timer diff = %lld    \r", prev); 
        fflush(stdout); 
        // save current timer 
        prev = t; 
        // and wait 
        sleep(1); 
    } 
    // will never get here 
    return 0; 
} 

Python 代码(现在我跳过这个 ifs):

ST_BASE = 0x3F003000 
TIMER_OFFSET = 4 
import struct 
sizeof_long_long = struct.calcsize('q') 
 
def timer(): 
    while True: 
        fd = os.open("/dev/mem",os.O_RDWR | os.O_SYNC) 
        stBase = mmap.mmap(fileno=fd,length=4096,offset=ST_BASE) 
        timer_bytes = stBase[TIMER_OFFSET:TIMER_OFFSET + sizeof_long_long] 
        #print(timer_bytes) 
        timer_value, = struct.unpack('q', timer_bytes) 
        print(timer_value) 
        os.close(fd) 

请您参考如下方法:

差不多好了 :) 只需 unpack_from 而不是 off unpack

import os, mmap, sys 
import struct 
 
ST_BASE = 0x3F003000 
TIMER_OFFSET = 4 
sizeof_long_long = struct.calcsize("Q") 
LENGTH = TIMER_OFFSET + sizeof_long_long 
 
def timer(): 
    fd = os.open("/dev/mem", os.O_RDONLY | os.O_SYNC) 
    stBase = mmap.mmap(fileno=fd, length=4096, access=mmap.ACCESS_COPY, offset=ST_BASE) 
    os.close(fd) 
 
    while True: 
        timer_value = struct.unpack_from("Q", stBase, TIMER_OFFSET)[0] 
        print("timer_value")