input.cpp

一个小型C语言编译器

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <assert.h>
#include <string.h>

#define        MAXLINE        512
#define        BUFSIZE        4096

int  lineno = 0;
long bsize  = -1;
FILE* file  = NULL;

unsigned char* cp    = NULL;
unsigned char* limit = NULL;
unsigned char* line  = NULL;

unsigned char  buffer[MAXLINE + 1 + BUFSIZE + 1] = {0};


int fillbuf(void);
void nextline(void);
void inputInit(void);

void nextline() {
	do {
		if (cp >= limit) {
			fillbuf();
			if (cp >= limit)
				cp = limit;
			if (cp == limit)
				return;
		} else
			lineno++;
		for (line = cp; *cp==' ' || *cp=='\t'; cp++)
			;
	} while (*cp == '\n' && cp == limit);
	if (*cp == '#') {
        //resynch();      //预处理
		//for(; *cp != '\n' && cp < limit; ++cp);
		//nextline();

        printf("don't support the preprocess now!!!! sorry\r\n");
        exit(0);
	}
}

void inputInit() {
	limit = cp = &buffer[MAXLINE+1];
	bsize = -1;
	lineno = 0;
	fillbuf();
	if (cp >= limit)
		cp = limit;
	nextline();
}





int fillbuf()
{
	if (bsize == 0)
		return 0;
	if (cp >= limit)
		cp = &buffer[MAXLINE+1];
	else {
        int n = limit - cp;
		unsigned char *s = &buffer[MAXLINE+1] - n;
		assert(s >= buffer);
		line = s - (cp - line);
		while (cp < limit)
			*s++ = *cp++;
		cp = &buffer[MAXLINE+1] - n;
	}
    assert(file);//assue that file has been initialized
	//bsize = fread(file, &buffer[MAXLINE+1], BUFSIZE);
    bsize = fread ((void*)&buffer[MAXLINE +1], 1, BUFSIZE, file);
	if (bsize < 0) {
		printf("read error\n");
		exit(1);
	}
	limit = &buffer[MAXLINE+1+bsize];
	*limit = '\n';
	return bsize;
}



void display()
{
    char* disp = NULL;
    int n = limit - cp;

    if(n == 0) {
        printf("the display content is empty\r\n");
        return ;
    }
    disp = (char*)malloc(n+1);

    memcpy(disp, cp, n);
    disp[n] = '\0';

    printf("%s", disp);

    free(disp);
    cp += n;
}