c - 是否有更优化的方法来处理其中一些功能？

Question

最近完成了一些课本上的位操作练习，牢牢掌握了位操作背后的一些核心思想。我写这篇文章的主要目的是优化我当前的代码。我有预感，有些功能我可以更好地处理。您对以下代码有什么建议吗？

#include <stdio.h>
#include "funcs.h"

// basically sizeof(int) using bit manipulation
unsigned int int_size(){
    int size = 0;
    for(unsigned int i = ~00u; i > 0; i >>= 1, size++);
    return size;
}

// get a bit at a specific nth index
// index starts with 0 on the most significant bit
unsigned int bit_get(unsigned int data, unsigned int n){
    return (data >> (int_size() - n - 1)) & 1;
}

// set a bit at a specific nth index
// index starts with 0 on the most significant bit
unsigned int bit_set(unsigned int data, unsigned int n){
    return data | (1 << (int_size() - n - 1));
}

// gets the bit width of the data (<32)
unsigned int bit_width(unsigned int data){
    int width = int_size();
    for(; width > 0; width--)
        if((data & (1 << width)) != 0)
            break;
    return width + 1;
}

// print the data contained in an unsigned int
void print_data(unsigned int data){
    printf("%016X = ",data);
    for(int i = 0; i < int_size(); i++)
        printf("%X",bit_get(data,i));
    putchar('\n');
}

// search for pattern in source (where pattern is n wide)
unsigned int bitpat_search(unsigned int source, unsigned int pattern,
        unsigned int n){
    int right = int_size() - n;
    unsigned int mask = 0;
    for(int i = 0; i < n; i++)
        mask |= 1 << i;
    for(int i = 0; i < right; i++)
        if(((source & (mask << (right - i))) >> (right - i) ^ pattern) == 0)
            return i - bit_width(source);
    return -1;
}

// extract {count} bits from data starting at {start}
unsigned int bitpat_get(unsigned int data, int start, int count){
    if(start < 0 || count < 0 || int_size() <= start || int_size() <= count || bit_width(data) != count)
        return -1;
    unsigned int mask = 1;
    for(int i = 0; i < count; i++)
        mask |= 1 << i;
    mask <<= int_size() - start - count;
    return (data & mask) >> (int_size() - start - count);
}

// set {count} bits (basically width of {replace}) in {*data} starting at {start}
void bitpat_set(unsigned int *data, unsigned int replace, int start, int count){
    if(start < 0 || count < 0 || int_size() <= start || int_size() <= count || bit_width(replace) != count)
        return;
    unsigned int mask = 1;
    for(int i = 0; i < count; i++)
        mask |= 1 << i;
    *data = ((*data | (mask << (int_size() - start - count))) & ~(mask << (int_size() - start - count))) | (replace << (int_size() - start - count));
}

Answer 1

因为您的 int_size() 函数每次都返回相同的值，您可以在那里节省一些时间:

unsigned int int_size(){
    static unsigned int size = 0;
    if (size == 0)
         for(unsigned int i = ~00u; i > 0; i >>= 1, size++);
    return size;
}

所以它只会计算一次值。但是用 sizeof(int)*8 替换此函数的所有调用会好得多。