typedef char *string;
typedef struct
{
 
     string fieldName;
     string value;
 
}oneField;
 
/* this starts the function*/
 
link tokenize (string input_string)
{
int numOfSpaces;
string next, temp;
oneField thisRecord;
/* used for head of linked list */
link head;
int field, counter = 0;
void insert(link*, oneField);
head = 0;
while(1)
{
numOfSpaces = 0;
next = next_word(input_string, &numOfSpaces);
/* next = the word which we will work with here */
if(counter == 0){
strcpy(thisRecord.fieldName, next);
}
if(counter == 1){
strcpy(thisRecord.value, next);
} 
 
/* if the word returned by next_word was the last word
in the input string, then the element at that length
should be the null character, in which case we will
break from the loop */
counter++;
if(input_string[strlen(next)] == '\0')
break;
input_string += strlen(next) + numOfSpaces;
}
return head;
}

thisRecord.fieldName =next

/**************************
* cgilib.h *
***************************/
typedef char *string;
typedef struct
{
 string fieldName;
 string value;
}oneField;
struct element {
 oneField       data;
 struct element *next;
};
typedef struct element   node;
typedef node             *link;
link tokenize(string input_string);
string cgi_val(link head, string field);
void print_table(link head);
string next_word(char *, int *);
 
 
 
/**************************
* cgilib.c *
***************************/
#include "cgilib.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
/*
 *  Used to parse an input string, and returns a linked
 *  list of tokens.  Maintained by alphabetical order of
 *  the field name, and the data stored in each node
 *  is a record representing one field
 */
link tokenize (string input_string)
{
 int numOfSpaces;
 string next;
 oneField thisRecord;
 /* used for head of linked list */
 link head;
 int counter = 0;
 void insert(link*, oneField);
 head = 0;
 while(1)
 {
  numOfSpaces = 0;
  next = next_word(input_string, &numOfSpaces);
  /* next = the word which we will work with here */
  if(counter == 0){
   thisRecord.fieldName = (char *) calloc(strlen(next), sizeof(char));
   strcpy(thisRecord.fieldName, next);
  }else if(counter == 1){
   thisRecord.value = (char *) calloc(strlen(next), sizeof(char));
   strcpy(thisRecord.value, next);
   insert(&head, thisRecord);
  }else if(counter % 2 == 0){
   thisRecord.fieldName = (char *) calloc(strlen(next), sizeof(char));
   strcpy(thisRecord.fieldName, next);
  }else{
   thisRecord.value = (char *) calloc(strlen(next), sizeof(char));
   strcpy(thisRecord.value, next);
   insert(&head, thisRecord);
  }
  /* if the word returned by next_word was the last word
     in the input string, then the element at that length
     should be the null character, in which case we will
     break from the loop */
  counter++;
  if(input_string[strlen(next)] == '\0')
   break;
  input_string += strlen(next) + numOfSpaces;
 }
 return head;
}
/*
 *  Steps through the linked list pointed to by the head
 *  and finds the node pointed to by the given field
 */
string cgi_val(link head, string field)
{
 void toUpper(string);
 link start = head;
 while(head)
 {
  toUpper(head->data.fieldName);
  toUpper(field);
  if(!strcmp(head->data.fieldName, field))
  {
   return head->data.value;
  }
  head = head->next;
 }
 head = start;
 return "ERROR!  FIELD NAME NOT FOUND!";
}
/*
 *  Used to print the table
 *  Given: head of linked list
 */
void print_table(link head)
{
 link start = head;
 printf("\n%s%26s\n%s\n", "Field Name", "Value", 
     "----------------------------------------------");
 while(head)
 {
  printf("%-20s%-40s\n", head->data.fieldName, head->data.value);
  head = head -> next;
 }
 printf("----------------------------------------------\n");
 head = start;
}
/*  
 *  Used in order to put strings of any length in
 *  the linked list (dynamically generates the string)
 */
string next_word(char * pos, int *numOfSpaces){
 /* count is the number of total characters in the string,
    whereas trueCount counts special 3-digit characters as
    only one 'true' character*/
 int count = 0, trueCount = 0, i;
 char * b = pos;
 int forConvert;
 string a;
 char current;
 if(pos[0] == '\0')
  return NULL;
 /* still check for spec. char in input */
 while(((current = *b) != '=') && (current != '&') && (current != '\0')){
  trueCount++;
  count++;
  b++;
  if(current == '%')
   trueCount = trueCount - 2;
 }
 a = (char *) calloc(trueCount + 1, sizeof(char));
 /* check for spec chars */
 for(i = 0; i < trueCount; i++)
 {
  if(*pos == '%')
  {
   pos++;
   switch(*pos)
   {
    case '0': forConvert = 16*0;
         break;
    case '1': forConvert = 16*1;
         break;
    case '2': forConvert = 16*2;
         break;
    case '3': forConvert = 16*3;
         break;
    case '4': forConvert = 16*4;
         break;
    case '5': forConvert = 16*5;
         break;
    case '6': forConvert = 16*6;
         break;
    case '7': forConvert = 16*7;
         break;
    case '8': forConvert = 16*8;
         break;
    case '9': forConvert = 16*9;
         break;
    case 'A':
    case 'a': forConvert = 16*10;
         break;
    case 'B': 
    case 'b': forConvert = 16*11;
         break;
    case 'C':
    case 'c': forConvert = 16*12;
         break;
    case 'D':
    case 'd': forConvert = 16*13;
         break;
    case 'E':
    case 'e': forConvert = 16*14;
         break;
    case 'F':
    case 'f': forConvert = 16*15;
         break;
    default:
      printf("%c is not a proper hex number!\n", *pos);
      exit(1);
   }
   pos++;
   switch(*pos)
   {
    case '0': forConvert += 0;
         break;
    case '1': forConvert += 1;
         break;
    case '2': forConvert += 2;
         break;
    case '3': forConvert += 3;
         break;
    case '4': forConvert += 4;
         break;
    case '5': forConvert += 5;
         break;
    case '6': forConvert += 6;
         break;
    case '7': forConvert += 7;
         break;
    case '8': forConvert += 8;
         break;
    case '9': forConvert += 9;
         break;
    case 'A':
    case 'a': forConvert += 10;
         break;
    case 'B': 
    case 'b': forConvert += 11;
         break;
    case 'C':
    case 'c': forConvert += 12;
         break;
    case 'D':
    case 'd': forConvert += 13;
         break;
    case 'E':
    case 'e': forConvert += 14;
         break;
    case 'F':
    case 'f': forConvert += 15;
         break;
    default:
      printf("%c is not a proper hex number!(2)\n", *pos);
      exit(1);
   }
   *numOfSpaces = *numOfSpaces + 2;
   a[i] = forConvert;
  }else if(*pos == '+'){
   a[i] = ' ';
  }else{
   a[i] = *pos;
  }
  pos++;
 }
 a[trueCount] = '\0';
 *numOfSpaces = *numOfSpaces + 1;
 return a;
}
 
/***************************************************
****************************************************
****************************************************
***************************************************/
void insert(link *list_head, oneField a){
 link p = *list_head, prev = NULL, new_node;
 while(p && strcmp(a.fieldName, p->data.fieldName) > 0)
 {
  prev = p;
  p = p->next;
 }
 new_node = malloc(sizeof(node));
 new_node -> data = a;
 new_node -> next = p;
 if(prev)
  prev -> next = new_node;
 else
  *list_head = new_node;
}
void toUpper(string a){
 int i;
 
 for(i = 0; i < strlen(a); i++){
  a[i] = toupper(a[i]);
 }
}
 
 
/**************************
* mainProgram.c *
***************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "cgilib.h"  /*  It contains the function prototype of
                           "exit".  */
string get_input(void)
{
 string a;
 int c;
 int count = 0;
 char file_name[20];
 FILE *text;
 printf("\n\nEnter the file name -->  ");
 gets(file_name);
 text = fopen(file_name, "r");  /*  open the file for reading  */
 if (!text)
 {
  printf("\n\nError: The file \"%s\" does not exist.\n",
                                       file_name);
  exit(1);        /*  terminate the program with an error  */
 }
 
 while ((c = getc(text)) != EOF)
  count++;
 
 fclose(text);
 a = (char *)calloc(count+1, sizeof(char));
 text = fopen(file_name, "r");
 if(!text)
 {
  printf("file not found!!!!\n");
  exit(1);
 }
 fgets(a, count+1, text);
 return a;
}
void main()
{
 link a;
 char inputField[31];
 string inputString;
 inputString = get_input();
 a = tokenize(inputString);
 print_table(a);
 while(1){
  printf("Enter a field name(Enter exit to Quit): ");
  gets(inputField);
  if(!strcmp(inputField, "exit")){
   break;
  }
  printf("Value for specified field: %s\n", cgi_val(a,inputField));
 }
}