c_translation.c

C語言聲明翻譯程序very useful

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#define MAXTOKENS 100
#define MAXTOKENLEN 64

enum type_tag{ IDENTIFIER,QUALIFIER,TYPE };

struct token 
{
	char type;
	char string [MAXTOKENLEN];
};

int top = -1;
struct token stack[MAXTOKENS];
struct token this;

#define pop stack[top--]
#define push(s) stack[++top]=s

enum type_tag classify_string(void)
/* 推断标志符的类型 */
{
	char *s = this.string;
	if(!strcmp(s,"const"))
	{
		strcpy(s,"read-only");
		return QUALIFIER;
	}
	if(!strcmp(s,"volatile"))
		return QUALIFIER;
	if(!strcmp(s,"void"))
		return TYPE;
	if(!strcmp(s,"char"))
		return TYPE;
	if(!strcmp(s,"signed"))
		return TYPE;
	if(!strcmp(s,"unsigned"))
		return TYPE;
	if(!strcmp(s,"short"))
		return TYPE;
	if(!strcmp(s,"int"))
		return TYPE;
	if(!strcmp(s,"long"))
		return TYPE;
	if(!strcmp(s,"float"))
		return TYPE;
	if(!strcmp(s,"double"))
		return TYPE;
	if(!strcmp(s,"struct"))
		return TYPE;
	if(!strcmp(s,"union"))
		return TYPE;
	if(!strcmp(s,"enum"))
		return TYPE;

	return IDENTIFIER;
}

void gettoken(void)  /* 读取下一个标记到"this" */
{
	char *p = this.string;

	/* 略过空白字符 */
	while((*p = getchar()) == ' ')
		;
	if(isalnum(*p))
	{
		/* 读入的标志符以A-Z,0-9开头 */
		while( isalnum(*++p=getchar()) )
			;
		ungetc(*p,stdin);
		*p = '\0';
		this.type=classify_string();
		return;
	}

	if(*p=='*')
	{
		strcpy(this.string,"pointer to");
		this.type = '*';
		return;
	}
	this.string[1]='\0';
	this.type = *p;
	return;
}
/* 理解所有分析过程的代码段 */

read_to_first_identifier()
{
	gettoken();
	while(this.type != IDENTIFIER)
	{
		push(this);
		gettoken();
	}
	printf("%s is ",this.string);
	gettoken();
}

deal_with_arrays()
{
	while(this.type == '[')
	{
		printf("array ");
		gettoken();  /* 数字 */
		if(isdigit(this.string[0]))
		{
			printf("0..%d ",atoi(this.string)-1);
			gettoken();  /* 读取'[' */
		}
		gettoken();  /* 读取'['的再一个标记 */
		printf("of ");
	}
}

deal_with_function_args()
{
	while(this.type!=')')
	{
		gettoken();
	}
	gettoken();
	printf("function_on returning ");
}

deal_with_pointers()
{
	while(stack[top].type == '*')
	{
		printf("%s ",pop.string);
	}
}

deal_with_declarator()
{
	/* 处理标志符之后可能存在的数组/函数 */
	switch(this.type)
	{
	case '[':
		deal_with_arrays();
		break;
	case '(':
		deal_with_function_args();
	}

	deal_with_pointers();

	/* 处理在读入到标志符之前压入到堆栈中的符号 */
    while(top>=0)
	{
		if(stack[top].type == '(')
		{
			pop;
			gettoken();  /* 读取')'之后的符号 */
			deal_with_declarator();
		}
		else
		{
			printf("%s ",pop.string);
		}
	}

}

int main()
{
	/* 将标记压入堆栈中，直到遇见标志符 */
	read_to_first_identifier();
	deal_with_declarator();
	printf("\n");
	return 0;
}