I writing Hash Table with Double Hashing. This Code working ONLY with ASCII text files and finding the number of occurrences of each word in Input File! I hope you look at my code and point out mistakes and shortcomings. Thanks in Advance :)

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define STRINGSIZE 50 
#define EXP 2 
#define TABLESIZE 100 

struct hashtable {
    int amount; 
    char string[50]; 
};

struct hastable *insert(char *str, struct hashtable *table, int *psize, int *pbusy);
unsigned int hash(const char *str);
unsigned int hash2(const char *str);
int get(char *str, struct hashtable *table, int size);

struct hashtable *rehash(struct hashtable *table, int *size, int *pbusy) {
    int i = 0;
    int size2 = 0;
    int psize2 = *size;
    int result = 0;
    (*size) *= EXP; 
    struct hashtable *temp = (struct hashtable*)calloc(sizeof(struct hashtable), *size);
    *pbusy = 0;

    while (i < psize2) {
        temp = insert(table[i].string, temp, size, pbusy, table[i].amount);
        i++;
    }

    free(table);
    return temp;
}

int get(char *str, struct hashtable *table, int size) {
    unsigned int value = hash(str) % size; 
    int i = 0;

    while (value < size) {
        
        if (!strcmp(table[value].string, str)) {
            return table[value].amount;
        } 

        value = (hash(str) + i + hash2(str)) % size;
        i++;
        
        if (value == (size - 1)) 
            break;
    }

    return 0;
}

unsigned int hash2(const char *str) {  
    unsigned int hash = 0;

    for(; *str; str++) {
        hash += (unsigned char)(*str);
        hash -= (hash << 13) | (hash >> 19);
    }

    return hash;
}

unsigned int hash(const char *str) {
    static const unsigned int b = 378551;
    unsigned int a = 63689;
    unsigned int hash = 0;

    for (; *str; str++) {
        hash = hash * a + (unsigned char)(*str);
        a *= b;
    }

    return hash;
}

struct hastable *insert(char *str, struct hashtable *table, int *psize, int *pbusy, int amount) {
    unsigned long long int value = 0;

    if ((*pbusy) > ((2 * (*psize)) / 3)) { 
        printf("Rehash... ");
        printf("Table Size = %d", *psize);
        table = rehash(table, psize, pbusy, str);
        printf(" [OK]\n");
    }
    
    value = hash(str) % (*psize);

    if (!strcmp(table[value].string, str)) { 
        (table[value].amount)++;
    } else if (!strlen(table[value].string)) { 
        strcpy(table[value].string, str); 
        
        if (!amount){
            table[value].amount++;  
        } else {
            table[value].amount = amount;
        }

        (*pbusy)++; 
    } else if ((strcmp(table[value].string, str)) && (strlen(table[value].string))) { 
        value = (hash(str) + hash2(str)) % (*psize); 
        int i = 0;

        while (value < *psize) {
            
            if (!strcmp(table[value].string, str)) {
                table[value].amount++;
                break;

            } else if (!strlen(table[value].string)) {
                strcpy(table[value].string, str);
                
                if (!amount){
                    table[value].amount++; 
                } else {
                    table[value].amount = amount;
                }

                (*pbusy)++; 
                break;
            }

            value = (hash(str) + (i + hash2(str))) % (*psize);
            i++;

        }
    } 

    return table;
}

void WorkWithFile(char *argv[]) {   
    FILE *text = fopen(argv[1], "r"); 
    
    if (NULL == text) { 
        printf("Error! You was opened empty file or file doesn't exist!\n");
        return;
    } else {
        printf("File was opened\n");
        char string[STRINGSIZE] = { 0 }; 
        int size = TABLESIZE;
        int busy = 0; 
        int *psize = &size;
        int *pbusy = &busy;
        int i = 0;
        struct hashtable *table = (struct hashtable*)calloc(size, sizeof(struct hashtable)); 
        
        printf("Building HashTable...\n");
        while (fscanf(text, "%s", string) == 1) { 
            table = insert(string, table, psize, pbusy, 0);
        }

        fclose(text); 
        printf("[OK]\n\n");

        while (!strstr(string, "EOF")) {
            printf("Enter Substring : ");
            scanf("%s", string);
            printf("The Number of Occurrences ");
            printf("%d\n\n", get(string, table, size));
        }

        free(table);
    }
}

int main(int argc, char *argv[]) {
    printf("Welcome to HashTable Program!\n");

    if (1 < argc) {
        printf("Argument has been Received\n");
        srand(time(NULL));
        WorkWithFile(argv);
    } else {
        printf("The program requires an argument on the command line!\nPlease run this program from console with any arguments.\n");
        return 1;
    }

    return 0;
}