/*
Program: BIGARRAY.C
Author : Kim Moser
Date   : 11/17/1991
System : IBM PC / Borland Turbo C 2.0
Descrip: Disk-based arrays
*/

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

#include "bigarray.h"

static int BigArray_seek(BigArray *array, index_type i);
static int BigArray_seek(BigArray *array, index_type i)
{
	if (array->file_pointer_index != i) {
		array->file_pointer_index = i;
		return (fseek(array->fp, i*array->elmt_size, SEEK_SET));
	}
	return (0);
}

BigArray *BigArray_calloc(char *fname, index_type num_elmts, size_t elmt_size)
{
	BigArray *r;
	index_type i;

	if ((r = malloc(sizeof(*r))) != NULL) {
		if ((r->fname = strdup(fname)) == NULL) {
			free(r);
			return (NULL);
		}
		if ((r->fp = fopen(fname, "wb+")) == NULL) {
			free(r->fname);
			free(r);
			return (NULL);
		}
		r->num_elmts = num_elmts;
		r->elmt_size = elmt_size;
		if ((r->last_elmt = calloc((size_t) 1, (size_t) elmt_size)) == NULL) {
			free(r->fname);
			fclose(r->fp);
			free(r);
			return (NULL);
		}
		r->last_elmt_index = -1L;


		for (i=0; i < num_elmts; i++) {
			if (fwrite((void*) r->last_elmt, (size_t) elmt_size, (size_t) 1, r->fp) != (size_t) 1) {
				free(r->fname);
				free(r->last_elmt);
				fclose(r->fp);
				free(r);
				return (NULL);
			}
		}
		if (fseek(r->fp, 0L, SEEK_SET)) {
			free(r->fname);
			fclose(r->fp);
			free(r->last_elmt);
			free(r);
			return (NULL);
		}
		r->last_elmt_index = -1L;
		r->file_pointer_index = 0;
	}
	return (r);
}

int BigArray_free(BigArray *array)
{
	if (fclose(array->fp)) return (0);
	if (unlink(array->fname)) return (0);
	free(array->fname);
	free(array->last_elmt);
	return (1);
}

void *BigArray_element(BigArray *array, index_type i, void *dest)
{
	if (i != array->last_elmt_index) {
		if (BigArray_seek(array, i)) {
			return (NULL);
		}
		if (fread(array->last_elmt, (size_t) array->elmt_size, (size_t) 1, array->fp) != (size_t) 1) {
			return (NULL);
		}
		array->last_elmt_index = i;
		array->file_pointer_index++;
		memcpy(dest, array->last_elmt, array->elmt_size);
	}
	return (dest);
}

int BigArray_assign(BigArray *array, index_type i, void *src)
{
	if (i == array->last_elmt_index) {
		memcpy(array->last_elmt, src, array->elmt_size);
	}

	if (BigArray_seek(array, i)) {
		return (0);
	}
	if (fwrite(src, array->elmt_size, 1, array->fp) != 1) {
		return (0);
	}
	array->file_pointer_index++;
	return (1);
}

#if 0

#define NUM_ELMTS	10
#define ELMT_TYPE	char

void main(void)
{
	index_type i, j;
	ELMT_TYPE e;
	BigArray *array;

	if ((array = BigArray_calloc("f:array.$$$", NUM_ELMTS, sizeof(ELMT_TYPE))) == NULL) {
		fprintf(stderr, "BigArray_calloc() failed.\n");
		exit(-1);
	}

	for (i=0; i < NUM_ELMTS; i++) {
		e = random(255);
		j = random(NUM_ELMTS);
		fprintf(stderr, "%ld'th elmt = %d\n", j, (int) e);
		if (!BigArray_assign(array, j, (void*) &e)) {
			fprintf(stderr, "BigArray_assign() failed for %ld'th elmt.\n", i);
			exit(-1);
		}
	}
	fprintf(stderr, "\n");

	for (i=0; i < NUM_ELMTS; i++) {
		if (BigArray_element(array, i, &e) == NULL) {
			fprintf(stderr, "BigArray_element() failed for %ld'th elmt.\n", i);
			exit(-1);
		}
		fprintf(stderr, "%ld'th elmt = %d.\n", i, (int) e);
	}

	if (!BigArray_free(array)) {
		fprintf(stderr, "BigArray_free() failed.\n");
		exit(-1);
	}
}

#endif