The bit-twiddling hacks page has a number of options. Of course, you could argue that iterating over all 32 possible bits is O(N) in that it’s the same cost every time 🙂 For simplicity, I’d consider the lookup-table-per-byte approach, or Brian Kernighan’s neat idea which iterates as many times as there are bits set, which … 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
I think you’ve got yourself confused between arrays and numbers, specifically what it means to manipulate binary numbers. I’ll go about this by example. Say you have a number of error messages and you want to return them in a return value from a function. Now, you might label your errors 1,2,3,4… which makes sense … Read more
bool is a built-in basic type in C#. Any underlying representation would be an implementation detail. The C# 4.0 Language Specification states in section 4.1.8: The bool type represents boolean logical quantities. The possible values of type bool are true and false. No standard conversions exist between bool and other types. In particular, the bool … Read more
You’d have to write your own implementation of Iterable<Boolean> which took an array of bytes, and then created Iterator<Boolean> values which remembered the current index into the byte array and the current index within the current byte. Then a utility method like this would come in handy: private static Boolean isBitSet(byte b, int bit) { … Read more
from bitarray import bitarray a = bitarray(2**20) You can check out more info about this module at http://pypi.python.org/pypi/bitarray/
From Bit Twiddling Hacks Update Test program Live On Coliru #include <utility> #include <iostream> #include <bitset> using I = uint8_t; auto dump(I v) { return std::bitset<sizeof(I) * __CHAR_BIT__>(v); } I bit_twiddle_permute(I v) { I t = v | (v – 1); // t gets v’s least significant 0 bits set to 1 // Next set … Read more
Yes, a byte is always 8 bits in modern computing. The book uses Words, not bytes In the book, the word and the size of the word is explicitly mentioned, while there is not a word (haha) about bytes. Look at the phrase ..is represented in RAM by 32 consecutive 16-bit words.. The whole size … Read more
Convert.ToString(MyVeryOwnByte, 2).PadLeft(8, ‘0’); This will fill the empty space to the left with ‘0’ for a total of 8 characters in the string
First remember that machine words are of fixed size. Say 4, and that your input is: +—+—+—+—+ | a | b | c | d | +—+—+—+—+ Then pushing everything one position to the left gives: +—+—+—+—+ | b | c | d | X | +—+—+—+—+ Question what to put as X? with a … Read more