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Best practices for circular shift (rotate) operations in C++
...dapted it to rotate by the width of the type (using fixed-width types like uint32_t).
#include <stdint.h> // for uint32_t
#include <limits.h> // for CHAR_BIT
// #define NDEBUG
#include <assert.h>
static inline uint32_t rotl32 (uint32_t n, unsigned int c)
{
const unsigned in...
What is Bit Masking?
...01b
Result: 00000101b
Masking is implemented using AND, so in C we get:
uint8_t stuff(...) {
uint8_t mask = 0x0f; // 00001111b
uint8_t value = 0x55; // 01010101b
return mask & value;
}
Here is a fairly common use-case: Extracting individual bytes from a larger word. We define the ...
error: ‘uint16_t’ does not name a type - c++1y / stl - 清泛IT社区，为创新赋能！
...ger types */
typedef signed char int8_t;
typedef unsigned char uint8_t;
typedef short int16_t;
typedef unsigned short uint16_t;
typedef int int32_t;
typedef unsigned uint32_t;
typedef long long int64_t;
typedef unsigned long long&nb...
'uint32_t' identifier not found error
...ted by C. For example:
typedef __int32 int32_t;
typedef unsigned __int32 uint32_t;
/* ... etc. ... */
Hope this helps!
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Why do people say there is modulo bias when using a random number generator?
...u_int32_t)-upper_bound % upper_bound) (assuming u_int32_t is a BSD-ism for uint32_t).
– Ian Abbott
Aug 15 '19 at 17:13
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Rounding up to next power of 2
...y at that time?). From : jameshfisher.com/2018/03/30/round-up-power-2.html uint64_t next_pow2(uint64_t x) { return x == 1 ? 1 : 1<<(64-__builtin_clzl(x-1)); } And for 32 bit : uint32_t next_pow2(uint32_t x) { return x == 1 ? 1 : 1<<(32-__builtin_clz(x-1)); } That is if you use GCC (and...
Hash function that produces short hashes?
...o.h>
#include <string.h>
#include <stdint.h> // for uint32_t
uint32_t fletcher32_1(const uint16_t *data, size_t len)
{
uint32_t c0, c1;
unsigned int i;
for (c0 = c1 = 0; len >= 360; len -= 360) {
for (i = 0; ...
Pick a random element from an array
..."Frodo", "sam", "wise", "gamgee"]
let randomIndex = Int(arc4random_uniform(UInt32(array.count)))
print(array[randomIndex])
The castings are ugly, but I believe they're required unless someone else has another way.
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Swift Beta performance: sorting arrays
...x_swift[i] = CInt(random())
x_c[i] = CInt(random())
}
let swift_start:UInt64 = mach_absolute_time();
quicksort_swift(&x_swift, 0, x_swift.count)
let swift_stop:UInt64 = mach_absolute_time();
let c_start:UInt64 = mach_absolute_time();
quicksort_c(&x_c, CInt(x_c.count))
let c_stop:UInt64...
Why does the C preprocessor interpret the word “linux” as the constant “1”?
... OS X 10.8.5, I got the output:
#define __DBL_MIN_EXP__ (-1021)
#define __UINT_LEAST16_MAX__ 65535
#define __ATOMIC_ACQUIRE 2
#define __FLT_MIN__ 1.17549435082228750797e-38F
#define __UINT_LEAST8_TYPE__ unsigned char
#define __INTMAX_C(c) c ## L
#define __CHAR_BIT__ 8
#define __UINT8_MAX__ 255
#def...