python - 使用 Python 脚本在 C 代码中添加行

Question

我需要计算 C 代码中循环的执行时间，为此我需要编写一个 python 脚本，通过检测循环前后的注释在循环前后添加“gettimeofday”。

代码如下:

int main(int argc, char** argv) {
  int i,j;
  int M = argv[0][0] * 10000;
  int res = argc; 

  // loopId = 1; depth = 1; outermost
  for (i=0; i<M; i++) {
    // loopId = 2; depth = 2; innermost 
    for (j=0; j<M; j++) {
      res *= 7 % 71;
    }     
    // end loop (loopId = 2)
    // loopId = 3; depth = 2; innermost
    for (j=0; j<M; j++){ 
      res += 9 % 91;
    }
    // end loop (loopId = 3)
  }
  // end loop (loopId = 1)

  return res;
}

Answer 1

import sys, re

expS=re.compile(r'\s*//\s*loopId = (\d+); depth = \d+; \w+')
expE=re.compile(r'\s*//\s*end loop \(loopId = (\d+)\)')
lines, varcnt = [], 0
with open(sys.argv[1]) as f:
    for line in f:
        line = line.rstrip()
        lines += [ line ]
        m = re.match(expS, line)
        if m:
            varcnt += 1
            loopid = int(m.group(1))
            lines += [ 'gettimeofday(&tv[{}], 0);'.format((loopid-1)*2) ]
            continue
        m = re.match(expE, line)
        if m:
            loopid = int(m.group(1))
            sid, eid = (loopid-1)*2, (loopid-1)*2+1
            lines += [ 'gettimeofday(&tv[{}], 0);'.format(eid) ]
            lines += [ 'printf("Id {}: %ld\\n", tdiff_xxx(&tv[{}],&tv[{}]));'.format(
                loopid, sid, eid) ]

print '#include <sys/time.h>'
print 'struct timeval tv[{}];'.format(varcnt*2)
print 'long tdiff_xxx(struct timeval *t0, struct timeval *t1) {'
print '  return (t1->tv_sec-t0->tv_sec)*1000000 + t1->tv_usec-t0->tv_usec;'
print '}' 
for l in lines: print l