lr/sprint.c

#include<stdio.h>
#include<stdbool.h>
#include<unistd.h>
#include<stdint.h>

#define __rbp(x) asm("movq %%rbp,%0":"=m"(x))
#define __rdi(x) asm("movq %%rdi,%0":"=m"(x))
#define __rsi(x) asm("movq %%rsi,%0":"=m"(x))
#define __rdx(x) asm("movq %%rdx,%0":"=m"(x))
#define __rcx(x) asm("movq %%rcx,%0":"=m"(x))
#define __r8(x) asm("movq %%r8,%0":"=m"(x))
#define __r9(x) asm("movq %%r9,%0":"=m"(x))

static int sprinti(char*s,int d);
static int sprinti16(char*s,int d);
typedef union sprint_type {int64_t i64;int32_t i32;char c;char*s;}sprint_type;

// Print formatted string with variable number
// of arguments into destination string dest
int sprint(char*dest,char*fmt,...)
{
	bool special=false;
	int bpos=0;
	int curarg=2;
	sprint_type args[6];
	sprint_type rdi,rsi,rdx,rcx,r8,r9;

	__rdi(rdi);
	__rsi(rsi);
	__rdx(rdx);
	__rcx(rcx);
	__r8(r8);
	__r9(r9);

	args[0]=rdi;
	args[1]=rsi;
	args[2]=rdx;
	args[3]=rcx;
	args[4]=r8;
	args[5]=r9;

	for(int i=0;fmt[i];++i)
	{
		switch(fmt[i])
		{

			case '%':
				if(special)
				{
					dest[bpos++]=fmt[i];
					special=false;
				}
				else
					special=true;
				break;

			default:
				if(special)
				{

					switch(fmt[i])
					{

						case 'd':
						case 'i':
						case 'u':
							{
								char tmp[1024];
								int n;
								n=sprinti(tmp,args[curarg++].i32);
								for(int k=0;tmp[k]&&k<=n;++k)
									dest[bpos++]=tmp[k];
							}
							break;

						case 'x':
						case 'p':
							{
								char tmp[1024];
								int n;
								n=sprinti16(tmp,args[curarg++].i32);
								for(int k=0;tmp[k]&&k<=n;++k)
									dest[bpos++]=tmp[k];
							}
							break;

						case 's':
							{
								for(int k=0;args[curarg].s[k];++k)
									dest[bpos++]=args[curarg].s[k];
								++curarg;
							}
							break;

						case 'c':
							dest[bpos++]=args[curarg++].c;
							break;

					}

					special=false;
				}
				else
					dest[bpos++]=fmt[i];
				break;

		}
	}

	dest[bpos]=0;
	return bpos;
}

static int sprinti16(char*s,int d)
{
	static char g[]={'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'};
	char b[32]={0};
	int bp=0;
	int i=0;

	if(!s)return 0;

	if(d<0)
	{
		b[bp++]='-';
		d=-d;
	}

	// Get each digit as character
	while(d>0)
	{
		int m=d%16;
		d/=16;
		b[i++]=g[m];
	}
	b[i]=0;

	int max=i-1;

	// Print reversed string
	for(;i>=0;--i)
	{
		if(b[i]>31)
			s[max-i]=b[i];
	}
	s[max+1]=0;

	return max;
}

static int sprinti(char*s,int d)
{
	char b[32]={0};
	int bp=0;
	int i=0;

	if(!s)return 0;

	if(d<0)
	{
		b[bp++]='-';
		d=-d;
	}

	// Get each digit as character
	while(d>0)
	{
		int m=d%10;
		d/=10;
		if(m+'0'>31)
			b[i++]=m+'0';
	}
	b[i]=0;

	int max=i-1;

	// Print reversed string
	for(;i>=0;--i)
	{
		if(b[i]>31)
			s[max-i]=b[i];
	}
	s[max+1]=0;

	return max;
}