Translate the C Declaration into Engilish

cdecl.c

#include <stdio.h>
#include <stdint.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)
{
    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)
{
    char *p = this.string;

    while ((*p = getchar()) == ' ');

    if (isalnum(*p)) {
        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;
}

void
read_to_first_identifier()
{
    gettoken();

    while (this.type != IDENTIFIER) {
        push(this);
        gettoken();
    }

    printf("%s is ", this.string);
    gettoken();
}


void
deal_with_arrays()
{
    while (this.type == '[') {
        printf("array ");
        gettoken();
        if (isdigit(this.string[0])) {
            printf("0...%d ", atoi(this.string) - 1);
            gettoken();
        }

        gettoken();
        printf("of ");
    }
}


void
deal_with_function_args()
{
    while (this.type != ')') {
              gettoken();
    }

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


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


void
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;
}