/************************************************************************
*                                                                       *    
*  Copyright Digital Equipment Corporation 1998. All rights reserved.   *
*                                                                       *    
*  Restricted Rights: Use, duplication, or disclosure by the U.S.       *    
*  Government is subject to restrictions as set forth in subparagraph   *    
*  (c) (1) (ii) of DFARS 252.227-7013, or in FAR 52.227-19, or in FAR   *    
*  52.227-14 Alt. III, as applicable.                                   *    
*                                                                       *    
*  This software is proprietary to and embodies the confidential        *    
*  technology of Digital Equipment Corporation. Possession, use, or     *    
*  copying of this software and media is authorized only pursuant to a  *    
*  valid written license from Digital or an authorized sublicensor.     *    
*                                                                       *    
************************************************************************/

/*      chap_8_mem_management.c         */

/* This example takes lines of input from the terminal until    */
/* it encounters a Ctrl/Z, it places the strings into an        */
/* allocated buffer, copies the strings to memory allocated for */
/* structures, prints the lines back to the screen, and then    */
/* deallocates all the memory used for the structures.          */

#include  <stdlib.h>
#include  <stdio.h>
#define   MAX_LINE_LENGTH  80

struct line_rec {               /*  Declare the structure.   */
    struct line_rec *next;      /*  Pointer to next line.    */
    char *data;                 /*  A line from terminal.    */
};

int main(void)
{
    char *buffer;
     
    /* Define pointers to        */
    /*  structure (input lines). */

    struct line_rec *first_line = NULL,
            *next_line,
            *last_line = NULL;

    /* Buffer points to memory.  */
    buffer = malloc(MAX_LINE_LENGTH);

    if (buffer == NULL) {       /* If error ...  */
        perror("malloc");
        exit(EXIT_FAILURE);
    }

    while (gets(buffer) != NULL) {      /* While not Ctrl/Z ...  */
        /* Allocate for input line.  */
        next_line = calloc(1, sizeof (struct line_rec));

        if (next_line == NULL) {
            perror("calloc");
            exit(EXIT_FAILURE);
        }

        /* Put line in data area.    */
        next_line->data = buffer;

        if (last_line == NULL)  /* Reset pointers.   */
            first_line = next_line;
        else
            last_line->next = next_line;

        last_line = next_line;
        /* Allocate space for the     */
        /*  next input line.          */
        buffer = malloc(MAX_LINE_LENGTH);

        if (buffer == NULL) {
            perror("malloc");
            exit(EXIT_FAILURE);
        }
    }
    free(buffer);       /* Last buffer always unused. */
    next_line = first_line;     /* Pointer to beginning.  */

    while (next_line != NULL) {
        puts(next_line->data);  /* Write line to screen.  */
        free(next_line->data);  /* Deallocate a line.     */
        last_line = next_line;
        next_line = next_line->next;
        free(last_line);
    }

    exit(EXIT_SUCCESS);
}