GCC 中与 C / C++ 的库函数名称可能不同了

最新推荐文章于 2023-06-05 11:39:36 发布

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本文介绍在C/C++中如何将整数转换为不同进制的字符串形式，包括使用标准库函数和自定义实现两种方法。示例代码演示了itoa、ltoa及ultoa函数的应用，并提供了一个自定义的整数转字符串库函数实现。

C/C++中使用

    itoa( i, buffer, 10 );
    printf( "String of integer %d (radix 10): %s\n", i, buffer );
    itoa( i, buffer, 16 );
    printf( "String of integer %d (radix 16): 0x%s\n", i, buffer );
    itoa( i, buffer, 2  );
    printf( "String of integer %d (radix 2): %s\n", i, buffer );

    ltoa( l, buffer, 16 );
    printf( "String of long int %ld (radix 16): 0x%s\n", l,
            buffer );

    ultoa( ul, buffer, 16 );
    printf( "String of unsigned long %lu (radix 16): 0x%s\n", ul,
            buffer );

GCC中使用

#include <stdlib.h>
#include <stdio.h>

int main( void )
{
    char buffer[20];
    int  i = 3445;
    long l = -344115L;
    unsigned long ul = 1234567890UL;

    _itoa( i, buffer, 10 );
    printf( "String of integer %d (radix 10): %s\n", i, buffer );
    _itoa( i, buffer, 16 );
    printf( "String of integer %d (radix 16): 0x%s\n", i, buffer );
    _itoa( i, buffer, 2  );
    printf( "String of integer %d (radix 2): %s\n", i, buffer );

    _ltoa( l, buffer, 16 );
    printf( "String of long int %ld (radix 16): 0x%s\n", l,
            buffer );

    _ultoa( ul, buffer, 16 );
    printf( "String of unsigned long %lu (radix 16): 0x%s\n", ul,
            buffer );
}

自己写库函数

EXTERN_C char* ultoa(unsigned long n, char* buffer, int radix)
{
    static const char digital_alphabet[] = "0123456789ABCDEF";
    const int MAX_WIDTH = sizeof(long)*CHAR_BIT;
    char temp_buffer[MAX_WIDTH+1]={0};
    char* p = temp_buffer+MAX_WIDTH;
    do
    {
        *(p--) = digital_alphabet[n%radix];
        n /= radix;
    }while(n);
    p++;
    memcpy(buffer, p, strlen(p)+1);

    return buffer;
}

EXTERN_C char* ltoa(long n, char* buffer, int radix)
{
    unsigned long d = n>0 ? n : -n;
    char * p = buffer;
    if(n<0)
        *(p++) = '-';
    ultoa(d, p, radix);

    return buffer;
}

__inline char* utoa(unsigned n, char* buffer, int radix)
{
    return ultoa(n, buffer, radix);
}

__inline char* itoa(int n, char* buffer, int radix)
{
    return ltoa(n, buffer, radix);
}