ftoa.c

来自「Rabbit 32Bit RTOS源代码」· C语言 代码 · 共 119 行

/*********************************************************************
*                   Copyright (c) 2011-2012,李士伟
*                     All rights reserved.
*文 件 名：ftoa.c
*描    述：浮点数转化成ascii码
*当前版本：V1.00
*作    者：李士伟
*创建日期：2012.01.15
**********************************************************************/
#include <lib\ftoa.h>

/*********************************************************************
*函 数 名：ftoa
*描    述：浮点数转化成ascii码
*输入参数：f: 浮点数
*          precision: 小数精度
*输出参数：dst: 浮点数字符串
*返 回 值：转化ascii码使用字节数(包含'\0')
*注    意：
**********************************************************************/
unsigned int ftoa(double f, int precision, char *dst)
{
    unsigned long m,n;
    int flag = 0;
    char buf[40];
    char *p = buf + 40;

    *--p = '\0';

    if (f < 0)
    {
        f = -f;
        flag = 1;
    }

    m = (unsigned long)f;
    f = f - m;

    switch (precision)
    {
        case 1:
        {
            n = f * 10;
            break;
        }
        case 2:
        {
            n = f * 100;
            break;
        }
        case 3:
        {
            n = f * 1000;
            break;
        }
        case 4:
        {
            n = f * 10000;
            break;
        }
        case 5:
        {
            n = f * 100000;
            break;
        }
        case 6:
        {
            n = f * 1000000;
            break;
        }
        case 7:
        {
            n = f * 10000000;
            break;
        }
        case 8:
        {
            n = f * 100000000;
            break;
        }
        default:
        {
            n = f * 1000000;
            break;
        }
    }

    do
    {
        *--p = '0' + n % 10;
        n = n / 10;
    }
    while (--precision);

    *--p = '.';

    do
    {
        *--p = '0' + m % 10;
        m = m / 10;
    }
    while (m);

    n = buf + 40 - p + flag;

    if (flag)
    {
        *dst++ = '-';
    }

    do
    {
        *dst++ = *p;
    }
    while (*p++ != '\0');

    return n;
}