精简版的sprintf

1.先说一下为什么要封装这个精简版的sprintf。是在做一个RF解码器时，使用到IIC的oled屏，使用到C库的sprintf。小用量的单片机（现在用到的单片机是STM8S003F3）一调用C库的sprintf，rom的容量直接满了......所以有了这个精简版的sprintf。嵌入式用到的地方还挺多的，收藏一下吧。废话不多说，上代码。

2.sprintf.c

//#include 
#include 

 
#define PADDING_RIGHT   1
#define PADDING_ZERO    2
#define PRINTI_BUF_LEN  12      //for 32bit signed integer
 
static int print2(char **out, int ch)
{
    int count = 1;
 
    if(ch == '\n')
        count += print2(out, '\r');
 
    if(out)
        *(*out)++ = ch;
    else
        putchar(ch);
 
    return count;
}
 
 
static int prints2(char **out, const char *str, int width, int pad)
{
    int count = 0, padChar = ' ';
 
    if(width > 0)
    {
        int len = 0;
        const char *ptr;
 
        for(ptr = str; *ptr; ++ptr)
            len++;
 
        if(len >= width)
            width = 0;
        else
            width -= len;
 
        if(pad & PADDING_ZERO)
            padChar = '0';
    }
 
    if(!(pad & PADDING_RIGHT))
    {
        for(; width > 0; width--)
        {
            count += print2(out, padChar);
        }
    }
 
    while(*str)
    {
        count += print2(out, *str++);
    }
 
    while(width--)
    {
        count += print2(out, padChar);
    }
 
    return count;
}
 
 
static int printi2(char **out, int val, int base, int sign, int width, int pad, int alphaBase)
{
    char buf[PRINTI_BUF_LEN];
    char *ptr;
    int t, neg = 0, count = 0;
    unsigned int uval = (unsigned int)val;
 
    if(val == 0)
    {
        buf[0] = '0';
        buf[1] = '\0';
        return prints2(out, buf, width, pad);
    }
 
    if(sign && base == 10 && val < 0)
    {
        neg = 1;
        uval = (unsigned int)-val;
    }
 
    ptr = buf + PRINTI_BUF_LEN - 1;
    *ptr = '\0';
 
    while(uval)
    {
        t = uval % base;
        if(t >= 10)
            t += alphaBase - '0' - 10;
        *--ptr = t + '0';
        uval /= base;
    }
 
    if(neg)
    {
        if(width && (pad & PADDING_ZERO))
        {
            count += print2(out, '-');
            width--;
        }
        else
        {
            *--ptr = '-';
        }
    }
 
    return count + prints2(out, ptr, width, pad);
}
 
static int vprintf2(char **out, const char *fmt, va_list args)
{
    int count = 0;
 
    while(*fmt)
    {
        if(*fmt == '%')
        {
            int width = 0, pad = 0;
            int type;
            char *str, tmp[2];
 
            fmt++;
 
            if(!*fmt)
                break;
 
            if(*fmt == '%')
                goto _out;
 
            if(*fmt == '-')
            {
                pad = PADDING_RIGHT;
                fmt++;
            }
 
            if(*fmt == '0')
            {
                pad = PADDING_ZERO;
                fmt++;
            }
 
            for(; *fmt >= '0' && *fmt <= '9'; fmt++)
                width = width * 10 + *fmt - '0';
 
            type = *fmt;
            switch(type)
            {
            case 's':
                str = va_arg(args, char *);
                str = str ? str : "(null)";
                count += prints2(out, str, width, pad);
                break;
 
            case 'd':
                count += printi2(out, va_arg(args, int), 10, 1, width, pad, 0);
                break;
 
            case 'u':
                count += printi2(out, va_arg(args, int), 10, 0, width, pad, 0);
                break;
 
            case 'x':
                count += printi2(out, va_arg(args, int), 16, 0, width, pad, 'a');
                break;
 
            case 'p':
                count += prints2(out, "0x", 0, 0);
                width = 8;
                pad = PADDING_ZERO;
            case 'X':
                count += printi2(out, va_arg(args, int), 16, 0, width, pad, 'A');
                break;
 
            case 'c':
                tmp[0] = (char)va_arg(args, int);
                tmp[1] = 0;
                count += prints2(out, tmp, width, pad);
                break;
            }
        }
        else
        {
_out:
            count += print2(out, *fmt);
        }
 
        fmt++;
    }
 
    if(out)
        **out = '\0';
 
    va_end(args);
    return count;
}
 
int printf2(const char *fmt, ...)
{
    va_list va;
 
    va_start(va, fmt);
    return vprintf2(0, fmt, va);
}
 
int sprintf2(char *buf, const char *fmt, ...)
{
    va_list va;
 
    va_start(va, fmt);
    return vprintf2(&buf, fmt, va);
}

3.sprintf.h

#ifndef __SPRINTF_H
#define __SPRINTF_H

#include 
#include 
extern int putchar(int ch);

static int print2(char **out, int ch);
static int prints2(char **out, const char *str, int width, int pad);
static int printi2(char **out, int val, int base, int sign, int width, int pad, int alphaBase);
static int vprintf2(char **out, const char *fmt, va_list args);
int printf2(const char *fmt, ...);
int sprintf2(char *buf, const char *fmt, ...);

#endif 

 

4.最后上一下解码器的效果。