pl0.c

C语言编写的PLO源代码

/*
 * PL/0 complier program for win32 platform (implemented in C)
 *
 * The program has been test on Visual C++ 6.0, Visual C++.NET and
 * Visual C++.NET 2003, on Win98, WinNT, Win2000, WinXP and Win2003
 *
 * 使用方法：
 * 运行后输入PL/0源程序文件?
 * 回答是否输出虚拟机代码
 * 回答是否输出名字表
 * fa.tmp输出虚拟机代码
 * fa1.tmp输出源文件及其各行对应的首地址
 * fa2.tmp输出结?
 * fas.tmp输出名字表
 */

#include <stdio.h>

#include "pl0.h"
#include "string.h"

/* 解释执行时使用的栈 */
#define stacksize 500


int main()
{
    bool nxtlev[symnum];

    printf("Input pl/0 file:");
    scanf("%s", fname);     /* 输入文件名 */

    fin = fopen(fname, "r");

    if (fin)
    {
        printf("List object code?(Y/N)");   /* 是否输出虚拟机代码 */
        scanf("%s", fname);
        listswitch = (fname[0]=='y' || fname[0]=='Y');

        printf("List symbol table?(Y/N)");  /* 是否输出名字表 */
        scanf("%s", fname);
        tableswitch = (fname[0]=='y' || fname[0]=='Y');

        fa1 = fopen("fa1.tmp", "w");
        fprintf(fa1,"Input pl/0 file?   ");
        fprintf(fa1,"%s\n",fname);

        init();     /* 初始化 */

        err = 0;
        cc = cx = ll = 0;
        ch = ' ';

        if(-1 != getsym())
    	{
            fa = fopen("fa.tmp", "w");
            fas = fopen("fas.tmp", "w");
            addset(nxtlev, declbegsys, statbegsys, symnum);
            nxtlev[period] = true;

            if(-1 == block(0, 0, nxtlev))   /* 调用编译程序 */
    		{
                fclose(fa);
                fclose(fa1);
                fclose(fas);
                fclose(fin);
                printf("\n");
                return 0;
    		}
            fclose(fa);
            fclose(fa1);
            fclose(fas);

            if (sym != period)
    		{
                error(9);
    		}

            if (err == 0)
    		{
                fa2 = fopen("fa2.tmp", "w");
                interpret();    /* 调用解释执行程序 */
                fclose(fa2);
    		}
        	else
    		{
                printf("Errors in pl/0 program");
    		}
    	}

        fclose(fin);
    }
    else
    {
        printf("Can't open file!\n");
    }

    printf("\n");
    return 0;
}

/*
* 初始化
*/
void init()
{
    int i;

    /* 设置单字符符号 */
    for (i=0; i<=255; i++)
    {
        ssym[i] = nul;
    }
    ssym['+'] = plus;
    ssym['-'] = minus;
    ssym['*'] = times;
    ssym['/'] = slash;
    ssym['('] = lparen;
    ssym[')'] = rparen;
    ssym['='] = eql;
    ssym[','] = comma;
    ssym['.'] = period;
    ssym['#'] = neq;
    ssym[';'] = semicolon;

    /* 设置保留字名字,按照字母顺序，便于折半查找 */
    strcpy(&(word[0][0]), "begin");
    strcpy(&(word[1][0]), "call");
    strcpy(&(word[2][0]), "const");
    strcpy(&(word[3][0]), "do");
    strcpy(&(word[4][0]), "end");
    strcpy(&(word[5][0]), "if");
    strcpy(&(word[6][0]), "odd");
    strcpy(&(word[7][0]), "procedure");
    strcpy(&(word[8][0]), "read");
    strcpy(&(word[9][0]), "then");
    strcpy(&(word[10][0]), "var");
    strcpy(&(word[11][0]), "while");
    strcpy(&(word[12][0]), "write");

    /* 设置保留字符号 */
    wsym[0] = beginsym;
    wsym[1] = callsym;
    wsym[2] = constsym;
    wsym[3] = dosym;
    wsym[4] = endsym;
    wsym[5] = ifsym;
    wsym[6] = oddsym;
    wsym[7] = procsym;
    wsym[8] = readsym;
    wsym[9] = thensym;
    wsym[10] = varsym;
    wsym[11] = whilesym;
    wsym[12] = writesym;

    /* 设置指令名称 */
    strcpy(&(mnemonic[lit][0]), "lit");
    strcpy(&(mnemonic[opr][0]), "opr");
    strcpy(&(mnemonic[lod][0]), "lod");
    strcpy(&(mnemonic[sto][0]), "sto");
    strcpy(&(mnemonic[cal][0]), "cal");
    strcpy(&(mnemonic[inte][0]), "int");
    strcpy(&(mnemonic[jmp][0]), "jmp");
    strcpy(&(mnemonic[jpc][0]), "jpc");

    /* 设置符号集 */
    for (i=0; i<symnum; i++)
    {
        declbegsys[i] = false;
        statbegsys[i] = false;
        facbegsys[i] = false;
    }

    /* 设置声明开始符号集 */
    declbegsys[constsym] = true;
    declbegsys[varsym] = true;
    declbegsys[procsym] = true;

    /* 设置语句开始符号集 */
    statbegsys[beginsym] = true;
    statbegsys[callsym] = true;
    statbegsys[ifsym] = true;
    statbegsys[whilesym] = true;

    /* 设置因子开始符号集 */
    facbegsys[ident] = true;
    facbegsys[number] = true;
    facbegsys[lparen] = true;
}

/*
* 每次读一行，存入line缓冲区，line被getsym取空后再读一行
*
* 被函数getsym调用。
*/
int getch()
{
    if (cc == ll)
    {
        if (feof(fin))
    	{
            printf("program incomplete");
            return -1;
    	}
        ll=0;
        cc=0;
        printf("%d ", cx);
        fprintf(fa1,"%d ", cx);
        ch = ' ';
        while (ch != 10) //10为换行符
    	{
            if (EOF == fscanf(fin,"%c", &ch))
    		{
                line[ll] = 0;
            	break;
    		}
            printf("%c", ch);
            fprintf(fa1, "%c", ch);
            line[ll] = ch;
        	ll++;
    	}
        printf("\n");
        fprintf(fa1, "\n");
    }
    ch = line[cc];
    cc++;
    return 0;   //0为读取成功
}

/*
* 词法分析，获取一个符号
*/
int getsym()
{
    int i,j,k;

    /* the original version lacks "\r", thanks to foolevery */
    while (ch==' ' || ch==10 || ch==13 || ch==9)  /* 忽略空格、换行、回车和TAB */
    {
        getchdo;
    }
    if (ch>='a' && ch<='z')
    {           /* 名字或保留字以a..z开头 */
        k = 0;
        do {
            if(k<al)
    		{
                a[k] = ch;
        		k++;
    		}
            getchdo;
        } while (ch>='a' && ch<='z' || ch>='0' && ch<='9');
        a[k] = 0;
        strcpy(id, a);
        i = 0;
        j = norw-1;
        do {    /* 搜索当前符号是否为保留字 */
            k = (i+j)/2;
			if (strcmp(id,word[k]) == 0) 
			{
				sym = wsym[k];
				break; 
			}
            if (strcmp(id,word[k]) < 0)
                j = k - 1;    	
            else
                i = k + 1;    		
        } while (i <= j);
        if ( i > j)
    	{
            sym = ident; /* 搜索失败则，是名字或数字 */
    	}
    }
    else
    {
        if (ch>='0' && ch<='9')
        {           /* 检测是否为数字：以0..9开头 */
            k = 0;
            num = 0;
            sym = number;
        	do {
                num = 10*num + ch - '0';
        		k++;
            	getchdo;
            } while (ch>='0' && ch<='9'); /* 获取数字的值 */
        	k--;
            if (k > nmax)
    		{
                error(30);
    		}
    	}
        else
    	{
            if (ch == ':')      /* 检测赋值符号 */
    		{
            	getchdo;
                if (ch == '=')
        		{
                    sym = becomes;
                	getchdo;
        		}
        		else
        		{
                    sym = nul;  /* 不能识别的符号 */
        		}
    		}
        	else
    		{
                if (ch == '<')      /* 检测小于或小于等于符号 */
        		{
                	getchdo;
                    if (ch == '=')
        			{
                		sym = leq;
                		getchdo;
        			}
            		else
        			{
                		sym = lss;
        			}
        		}
        		else
        		{
                    if (ch=='>')        /* 检测大于或大于等于符号 */
        			{
                		getchdo;
                    	if (ch == '=')
        				{
                    		sym = geq;
                			getchdo;
        				}
            			else
        				{
                    		sym = gtr;
        				}
        			}
            		else
        			{
                        sym = ssym[ch];     /* 当符号不满足上述条件时，全部按照单字符符号处理 */
                		if (sym != period)
        				{
                			getchdo;
        				}
        			}
        		}
    		}
    	}
    }
    return 0;
}

/*
* 查找名字的位置.
* 找到则返回在名字表中的位置,否则返回0.
*
* idt:    要查找的名字
* tx:     当前名字表尾指针
*/
int position(char* idt, int tx)
{
    int i;
    strcpy(table[0].name, idt);
    i = tx;
    while (strcmp(table[i].name, idt) != 0)
    {
        i--;
    }
    return i;
}

/*
* 在名字表中加入一项
*
* k:      名字种类constant, variable, procedur
* ptx:    名字表尾指针的指针，为了可以改变名字表尾指针的值
* lev:    名字所在的层次,，以后所有的lev都是这样
* pdx:    dx为当前应分配的变量的相对地址，分配后要增加1
*/
void enter(enum object k, int* ptx, int lev, int* pdx)
{
    (*ptx)++;
    strcpy(table[(*ptx)].name, id); /* 全局变量id中已存有当前名字的名字 */
    table[(*ptx)].kind = k;
    switch (k)
    {
    case constant:  /* 常量名字 */
        if (num > amax)
    	{
            error(31);  /* 数越界 */
            num = 0;
    	}
        table[(*ptx)].val = num;
        break;
    case variable:  /* 变量名字 */
        table[(*ptx)].level = lev;
        table[(*ptx)].adr = (*pdx);
        (*pdx)++;
        break;
    case procedur:  /*　过程名字　*/
        table[(*ptx)].level = lev;
        break;
    }
}

/*
* 用数组实现集合的集合运算
*/
int inset(int e, bool* s)
{
    return s[e];
}

int addset(bool* sr, bool* s1, bool* s2, int n)
{
    int i;
    for (i=0; i<n; i++)
    {
        sr[i] = s1[i]||s2[i];
    }
    return 0;
}

int subset(bool* sr, bool* s1, bool* s2, int n)
{
    int i;
    for (i=0; i<n; i++)
    {
        sr[i] = s1[i]&&(!s2[i]);
    }
    return 0;
}

int mulset(bool* sr, bool* s1, bool* s2, int n)
{
    int i;
    for (i=0; i<n; i++)
    {
        sr[i] = s1[i]&&s2[i];
    }
    return 0;
}

/*
* 测试当前符号是否合法
*
* 在某一部分（如一条语句，一个表达式）将要结束时时我们希望下一个符号属于某集合