cdecl程序—将C语言的声明翻译成通俗易懂的语言

用法：运行该程序后，输入一个C语言声明，即可翻译成通俗易懂的语言

#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()
{
    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,"lone"))
        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()
{
    char *p=this.string;

    while((*p=getchar())==' ');/*skip over the ' '*/

    if(isalnum(*p))
    {
        while(isalnum(*++p=getchar()))/*read the next identifier starting with a-Z or 0-9*/
            ;
        ungetc(*p,stdin);
        *p='\0';
        this.type=classify_string();
        return;/*return to void function*/
    }

    if(*p=='*')
    {
        strcpy(this.string," pointer to ");
        this.type='*';
        return;
    }

    this.string[1]='\0';
    this.type=*p;
    return;
}

/*understand all the code stack in the analysis*/
read_to_first_identifier()
{
    gettoken();
    while(this.type!=IDENTIFIER)
        {
            push(this);/*stack[++top]=this*/
            gettoken();
        }
    printf(" %s is ",this.string);
    gettoken();
}

deal_with_arrays()
{
    while(this.type=='[')
    {
        printf(" array ");
        gettoken();/*read a number or ']'*/
        if(isdigit(this.string[0]))
        {
            printf(" 0..%d ",atoi(this.string)-1);
            gettoken();
        }
        gettoken();
        printf(" of ");
    }
}

deal_with_function_args()
{
    while(this.
        gettoken();

    gettoken();
    printf(" function returing ");
}

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

deal_with_declarator()
{
    switch(this.type)
    {
        case '[':
            deal_with_arrays();
            break;
        case '(':
            deal_with_function_args();
    }

    deal_with_pointers();

    while(top>=0)
    {
        if(stack[top].type=='(')
        {
            pop;
            gettoken();
            deal_with_declarator();
        }
        else
            printf("%s ",pop.string);
    }
}

int main()
{
    read_to_first_identifier();
    deal_with_declarator();
    printf("\n");
    return 0;
}