get_string.c

/*
 * get_string.c
 *
 *
 * Read a string from stdin, store it in an array,
 * and print it back to the user.
 */

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

#define INITIAL_BUFFER_SIZE 16

/*
 * Input:   @buffer: buffer to increse memory
 *          @buffer_size: the size of the buffer(pointer)
 * Output:  the double sized buffer
 * Summary: This function doubles the capacity of your buffer by
 *          creating a new one and cleaning up the old one.
 */
char* IncreaseBuffer(char* buffer, int* buffer_size);

int main(int argc, char *argv[])
{
    // alloc memory for the initial buffer
    char *buffer = (char *)malloc(INITIAL_BUFFER_SIZE * sizeof(char));
    int input_ch;
    int buffer_len = INITIAL_BUFFER_SIZE;
    int char_len = 0;
    int increase_time = 0;

    // promote user to input
    printf("Enter a string: ");
    while((input_ch = getchar()) != '\n') {
        if(input_ch == EOF) {
            break;
        }
        if(char_len == buffer_len - 1) {
            // not enough space, malloc memory
            buffer = IncreaseBuffer(buffer, &buffer_len);
            increase_time++;
        }
        buffer[char_len++] = input_ch;
    }

    // the strings should be end with '\0'
    buffer[char_len] = '\0';

    // some print
    printf("String size: %d\n", char_len);
    printf("Buffer increases: %d\n", increase_time);
    printf("You entered: %s\n", buffer);

    free(buffer);

    return 0;
}

char* IncreaseBuffer(char* buffer, int* buffer_size) {
    // malloc the memory for the new space
    char *new_buffer = (char *)malloc(*buffer_size * 2 * sizeof(char));
    *buffer_size *= 2;

    // copy staff
    char *head_new = new_buffer;
    char *head_old = buffer;
    while(*head_old != '\0') {
        *head_new = *head_old;
        head_old++;
        head_new++;
    }

    // earse the old space
    free(buffer);

    return new_buffer;
}