Eclipse ADT: 'Unable to open sync connection!'

Sometimes, you get this wierd looking error on eclipse while working/developing on your phone.

[2010-10-12 09:36:48 - myapp] java.io.IOException: Unable to open sync connection!
[2010-10-12 09:36:48 - myapp] Launch canceled!

You have tried the following (but in vain!):
1. Disconnecting/connecting the USB cable.
2. Restarting eclipse.
3. Restarting adb daemon.
4. Restarting your computer!


Even after this if the problem persists. Just disable/enable 'USB debugging' on your phone.
This should most of the times solve this issue.

A short perl code to find union of 2 arrays in perl

Using slices on hash variable :)

sub array_union {
    my ($arrRef1, $arrRef2) = @_;
    my %hash;
    @hash{@$arrRef1} = undef;
    @hash{@$arrRef2} = undef;
    return keys %hash;
}

Upgrading CM7 on LG O2X

If you are planning to upgrade CM7 on your LG O2X, please make sure you have done the following!
Upgrade clockworkmod to a version >= 5. (You can do this from 'ROM Manager' itself)

ARFF file-reader in C++

Long time ago I had written a C++ library to parse ARFF files for one of my Machine-Learning projects. Today, I'm making the code open-source! Here's the link to the code hosted on github: https://github.com/teju85/ARFF. This also comes with doxygen documentation for the API exposed by this library and also has unit-tests (written using google-test) for CYA.

Iterator for templated STL containers in C++

I realized this today! The following code almost always will give compilation error.

std::vector::const_iterator itr;

And the compilation error (with g++ version 3.4.6) will be as vague as:

error: expected `;' before "itr"

The solution is to just do the following:

typename std::vector::const_iterator itr;

Getting (approx?) memory usage information on linux

Here's the code for doing so: (Tested on Ubuntu 10.10)

#include <unistd.h>
#include <stdio.h>
int processMemUsage() {
    int vm = 0;
    FILE* fp = fopen("/proc/self/stat", "r");
    if(fp == NULL) {
        return vm;
    }
    int dummy;
    char cmd[128], state[8];
    fscanf(fp, "%d%s%s%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d%d",
           &dummy, cmd, state, &dummy, &dummy, &dummy, &dummy,
           &dummy, &dummy, &dummy, &dummy, &dummy, &dummy,
           &dummy, &dummy, &dummy, &dummy, &dummy, &dummy,
           &dummy, &dummy, &dummy);
    unsigned long vmSize;
    fscanf(fp, "%lu", &vmSize);
    fclose(fp);
    vm = (int) (vmSize >> 10);
    return vm;
}

Hope this helps!

How to request 'super user' permission from your app?

NOTE: This blog assumes that you have installed Superuser application installed on your device! Also, I'm not responsible for any bricked devices!

Process p;
try {
    p = Runtime.getRuntime().exec("su");
}
catch(IOException e) {
    e.printStackTrace();
}

This will pop up a window from 'Superuser' application which will ask user to whether allow your app to be given 'su' permissions or not. Users can either 'Allow' or 'Deny' and also set 'Remember this option' on this window.

Hope this helps!