getting the number of files in a directory using python

 python -c "import os; print len(os.listdir('.'))"

getting current time as double

linux, mac :

#include <sys/time.h>

static double now_ms(void) 
{ 
struct timeval tv; 
gettimeofday(&tv, NULL); 
return tv.tv_sec*1000. + tv.tv_usec/1000.; 
}

windows

static double now_ms(void) 
{ 
static LARGE_INTEGER frequency;
static bool dummy = QueryPerformanceFrequency(&frequency);

LARGE_INTEGER count;
QueryPerformanceCounter(&count);
if(frequency.QuadPart == 0) return 0;

return (double)count.QuadPart/(double)frequency.QuadPart;
}

A C++ way of tokenizing string

#include <string>
#include <sstream>
#include <iostream>
#include <iterator>
#include <vector>

std::string str("quick brown fox jumps into something that I have forgot");
std::stringstream ss(str);
std::istream_iterator<std::string> it(ss), end;
std::vector<std::string> tokens(it,end);
for(std::vector<std::string>::iterator token=tokens.begin(); token!=tokens.end(); ++token) {
    std::cout << *token << std::endl;
}

Getting Internal Storage Directory in Android NDK

The function name should be changed to your package name and activity class name.

Writtin in C++.

JNIEXPORT void JNICALL Java_com_jongwook_test_TestActivity_test(JNIEnv * env, jobject obj)
{
 jclass cls = env->GetObjectClass(obj);
 jmethodID getFilesDir = env->GetMethodID(cls, "getFilesDir", "()Ljava/io/File;");
 jobject dirobj = env->CallObjectMethod(obj,getFilesDir);
 jclass dir = env->GetObjectClass(dirobj);
 jmethodID getStoragePath =
                       env->GetMethodID(dir, "getAbsolutePath", "()Ljava/lang/String;");
 jstring path=(jstring)env->CallObjectMethod(dirobj, getStoragePath);
 const char *pathstr=env->GetStringUTFChars(path, 0);
 chdir(pathstr);
 env->ReleaseStringUTFChars(path, pathstr);
}

Finding the greatest power of 2 less than given integer

assuming that n is a 32-bit integer

if((n&(n-1))!=0) {
 n |= n >> 1; 
 n |= n >> 2; 
 n |= n >> 4; 
 n |= n >> 8; 
 n |= n >> 16;
 n=n+1;
}

Efficiently calculating integer powers of float

 static float pow(float base, int exp) {
  float result = 1;
  if(exp<0) return 1.0f/pow(base,-exp);
  while (exp!=0) {
   if ((exp & 1)!=0) result *= base;
   exp >>= 1;
   base *= base;
  }
  return result;
 }

Displaying fraction in HTML

Showing something like this : ²²⁄₇

function fraction(a, b) {
     return "<span style=\"font-size:80%;letter-spacing:-1px;\"><sup>"+a+"</sup>⁄<sub>"+b+"</sub> </span>";
}