Find most significant bit (left-most) that is set in a bit array

Posted by Claudiu on Stack Overflow See other posts from Stack Overflow or by Claudiu
Published on 2010-04-06T23:42:59Z Indexed on 2010/04/06 23:53 UTC
Read the original article Hit count: 210

Filed under:

bit-manipulation

|

32bit

|

c

I have a bit array implementation where the 0th index is the MSB of the first byte in an array, the 8th index is the MSB of the second byte, etc...

What's a fast way to find the first bit that is set in this bit array? All the related solutions I have looked up find the first least significant bit, but I need the first most significant one. So, given 0x00A1, I want 9.

© Stack Overflow or respective owner

Related posts about bit-manipulation

Find three numbers appeared only once using bit manipulation

as seen on Stack Overflow - Search for 'Stack Overflow'
In a sequence of length n, where n=2k+3, that is there are k unique numbers appeared twice, how to find the three unique numbers that appeared only once using bit manipulation? for example, in sequence 1 1 2 6 3 6 5 7 7 the three unique numbers are 2 3 5. >>> More
Learning C bit manipulation

as seen on Stack Overflow - Search for 'Stack Overflow'
I didn't know any better name for a title of the question. For ex: on one of my previous questions one answered ((a)-(b))&0x80000000) 31 - this is kind of a too advanced for me and i can't really get what it means. I am not looking just for an answer of that, but i need someone to tell me some… >>> More
Bit manipulation, permutate bits

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi. I am trying to make a loop that loops through all different integers where exactly 10 of the last 40 bits are set high, the rest set low. The reason is that I have a map with 40 different values, and I want to sum all different ways ten of these values can be multiplied. (This is just out of… >>> More
bit manipulation in java

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a fragment of bytes in a byte[]. The total size of the array is 4 and I want to convert this into a positive long number. For example if the byte array is having four bytes 101, 110, 10, 1 then i want to get the long number represented by binary sequence 00000000 00000000 00000000 00000000… >>> More
Doing 64 bit manipulation using 32 bit data in Fixed point arithmetic using C.

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I am stuck with a problem. I am working on a hardware which only does support 32 bit operations. sizeof(int64_t) is 4. Sizeof(int) is 4. and I am porting an application which assumes size of int64_t to be 8 bytes. The problem is it has this macro BIG_MULL(a,b) ( (int64_t)(a) *… >>> More

Related posts about 32bit

32bit 64bit referenced library

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I am developing an application that has two DLLs one is a 32bit version another is 64bit version, Client is 32bit Server is 64bit My question is is there a way I can say use the 32bit dll when doing Debug/Release and use 64bit dll when I perform a publish. I realize I can solve this problem… >>> More
how to find if the machine is 32bit or 64bit

as seen on Stack Overflow - Search for 'Stack Overflow'
Is there anyway from a C prog to find whether the OS is currently running in 32bit or 64bit mode. I am using a simple program as below int main(void){ switch(sizeof(void*)){ case 4: printf("32\n"); break; case 8: printf("64\n"); break; } } Is this a correct… >>> More
MapViewOfFile shared between 32bit and 64bit processes

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I'm trying to use MapViewOfFile in a 64 bit process on a file that is already mapped to memory of another 32 bit process. It fails and gives me an "access denied" error. Is this a known Windows limitation or am I doing something wrong? Same code works fine with 2 32bit processes. The code… >>> More
Windows 7 license - move from 32bit to 64bit with OEM key with Lenovo

as seen on Super User - Search for 'Super User'
http://superuser.com/questions/73327/can-i-use-a-windows-7-professional-32-bit-oem-licence-to-install-the-64-bit-versi This questions asks it generically, but does anybody know specifically about Lenovo outlet computers? I want to buy an outlet computer with Windows 7 Home Premium 32, but I would… >>> More
Crash when attempting to install 32bit delphi service on 2008 r2

as seen on Server Fault - Search for 'Server Fault'
I have an old 32bit delphi application (with no source code), that is used as a windows service. It runs fine on windows 2003 32bit. I do not know if it has been created as a service originally, or converted to one later on. It is supposed to get installed to the server using a /install flag on the… >>> More