Numeric literals in C# are int, not byte (and the bit shift will be evaluated by the compiler, hence only the 510 remains). You are therefore trying to assign a value to a byte which does not fit. You can mask with 255: byte b = (255 << 1) & 0xFF to reduce the result … Read more
A mask defines which bits you want to keep, and which bits you want to clear. Masking is the act of applying a mask to a value. This is accomplished by doing: Bitwise ANDing in order to extract a subset of the bits in the value Bitwise ORing in order to set a subset of … Read more
I still write code for systems that do not have floating point support in hardware. In these systems you need bit-shifting for nearly all your arithmetic. Also you need shifts to generate hashes. Polynomial arithmetic (CRC, Reed-Solomon Codes are the mainstream applications) or uses shifts as well. However, shifts are just used because they are … Read more
To get a bit mask: var mask = 1 << 5; // gets the 6th bit To test if a bit is set: if ((n & mask) != 0) { // bit is set } else { // bit is not set } To set a bit: n |= mask; To clear a bit: n … Read more
(n & (n – 1)) == 0 is best. However, note that it will incorrectly return true for n=0, so if that is possible, you will want to check for it explicitly. http://www.graphics.stanford.edu/~seander/bithacks.html has a large collection of clever bit-twiddling algorithms, including this one.
First, a paper you should consider reading, if you want to understand floating point foibles better: “What Every Computer Scientist Should Know About Floating Point Arithmetic,” http://www.validlab.com/goldberg/paper.pdf And now to some meat. The following code is bare bones, and attempts to produce an IEEE-754 single precision float from an unsigned int in the range 0 … Read more
According to JavaScript Performance for Madmen Wrapping integer arithmetic expressions in ( ) | 0 allows the runtime to be sure that you’re doing integer arithmetic instead of floating-point arithmetic. This allows it to avoid checking for overflow and produce faster code in many cases. and according to the page, it’s true for “most” Javascript … Read more
Think about how you multiply in decimal using pencil and paper: 12 x 26 —- 72 24 —- 312 What does multiplication look like in binary? 0111 x 0101 ——- 0111 0000 0111 ——- 100011 Notice anything? Unlike multiplication in decimal, where you need to memorize the “times table,” when multiplying in binary, you are … Read more
C standard allows compiler to put bit-fields in any order. There is no reliable and portable way to determine the order. If you need to know the exact bit positions, it is better use plain unsigned variable and bit masking. Here’s one possible alternative to using bit-fields: #include <stdio.h> #define MASK_A 0x00FF #define MASK_B 0x3F00 … Read more
From http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel unsigned int v; // count bits set in this (32-bit value) unsigned int c; // store the total here c = v – ((v >> 1) & 0x55555555); c = ((c >> 2) & 0x33333333) + (c & 0x33333333); c = ((c >> 4) + c) & 0x0F0F0F0F; c = ((c >> 8) … Read more