[模板] 字串賦值

2019-08-30

模板

setInt()

inline char* setInt(register char buffer[], register int src, const char suffix)
{
    static char tmp[13];
    register char* st = tmp + 12;
    register unsigned int div;
    *st = 0;
    if (src < 0)
    {
        src = ~src + 1;
        *(--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
        while (src = div)
            * (--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
        *(--st) = '-';
    }
    else
    {
        do
        {
            *(--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
        } while (src = div);
    }
    while (*buffer++ = *st++)
        ;
    *buffer++ = suffix;
    return buffer;
}

setUInt()

inline char* setUInt(register char buffer[], register unsigned int src, const char suffix)
{
    static char tmp[11];
    register char* st = tmp + 10;
    register unsigned int div;
    *st = 0;
    do
    {
        *(--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
    } while (src = div);
    while (*buffer++ = *st++)
        ;
    *buffer++ = suffix;
    return buffer;
}

setLongLong()

inline char* setLongLong(register char buffer[], register long long src, const char suffix)
{
    static char tmp[22];
    register char * st = tmp + 21;
    register unsigned long long div;
    *st = 0;
    if (src < 0)
    {
        src = ~src + 1;
        *(--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
        while (src = div)
            * (--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
        *(--st) = '-';
    }
    else
    {
        do
        {
            *(--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
        } while (src = div);
    }
    while (*buffer++ = *st++)
        ;
    *buffer++ = suffix;
    return buffer;
}

setULongLong()

inline char* setULongLong(register char buffer[], register unsigned long long src, const char suffix)
{
    static char tmp[22];
    register char *st = tmp + 21;
    register unsigned long long div;
    *st = 0;
    do
    {
        *(--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
    } while (src = div);
    while (*buffer++ = *st++)
        ;
    *buffer++ = suffix;
    return buffer;
}

概述

本組模板為整數轉字串模板，使用此模板取代 sprintf() 可以大幅將整數打印到字串的時間，此外本模板內建指針偏移，可以節省使用 strlen() 偏移指針的開銷。

參數

buffer

本字串用來接收字串化後的數值。

src

本參數為要輸出的整數

suffix

本參數為串接在整數後面的一個後綴字元，若無後墜請輸入 0 (或 '\0')

返回值

該函數返回最後一個格式化數字的下一位元指標，如果含有後綴則在後綴的下一位。

實例

#include <stdio.h>

inline char* setUInt(register char buffer[], register unsigned int src, const char suffix)
{
    static char tmp[11];
    register char* st = tmp + 10;
    register unsigned int div;
    *st = 0;
    do
    {
        *(--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
    } while (src = div);
    while (*buffer++ = *st++)
        ;
    *buffer++ = suffix;
    return buffer;
}

inline char* setInt(register char buffer[], register int src, const char suffix)
{
    static char tmp[13];
    register char* st = tmp + 12;
    register unsigned int div;
    *st = 0;
    if (src < 0)
    {
        src = ~src + 1;
        *(--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
        while (src = div)
            * (--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
        *(--st) = '-';
    }
    else
    {
        do
        {
            *(--st) = (src - ((div = src / 10) << 3) - (div << 1)) | '0';
        } while (src = div);
    }
    while (*buffer++ = *st++)
        ;
    *buffer++ = suffix;
    return buffer;
}

char input[10000], * st = input;

int main()
{
    unsigned long long v = 1LL << 31;
    st = setInt(st, 2147483647, ' ');
    st = setInt(st, v, '\n');
    st = setInt(st, -2147483647, ' ');
    puts(input);
    return 0;
}

編譯運行結果

2147483647 -2147483648
-2147483647

注意事項

在 32 位元架構下的編譯器，由於不需要做右移處理所以 int 的速度一般會比 short 來的更快 (或至少一樣快)，所以在記憶體空間足夠的請況下，保持使用 int 是比較好的選擇。

更新紀錄

2019-9-6

將轉正移至單獨一行避免 ZJ 編譯器出錯
整數轉字元用 '|' 取代 '+' 提升效率
buffer 改成靜態減少宣告時間