path: root/lookup-incoming.c

#include <assert.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>


#define ROUNDUP(x,y) ((((x)+(y)-1)/(y))*(y))


typedef __uint32_t bitfield_type;
#define BITS_PER_BITFIELD 32
#define BITS_PER_BITFIELD_LOG 5

#define BIT_SET(set, d) \
  ( (void) ( set[d >> BITS_PER_BITFIELD_LOG] |= (1 << (d & (BITS_PER_BITFIELD-1))) ) )
#define BIT_ISSET(set, d) \
  (!(! ( set[d >> BITS_PER_BITFIELD_LOG] & (1 << (d & (BITS_PER_BITFIELD-1))) ) ))

int ANY_BITS_SET(bitfield_type *set, size_t elems)
{
	size_t i;

	for (i = 0; i < elems; i++)
		if (set[i] != 0)
			return 1;

	return 0;
}


typedef __uint32_t art_id;



static int
cmpstring_p_pp(const void *p1, const void *p2)
{
	return strcasecmp((char * const) p1, * (char * const *) p2);
}




int main(int argc, char **argv)
{
	FILE *in_file;
	FILE *out_file;

	char *title_blob;
	size_t title_blob_len;
	char **title = NULL;
	art_id titles;
	art_id titles_read = 0;

	art_id *link_blob;
	size_t link_blob_len;
	art_id **linki;
	art_id *linkis;

	char **cur_title;
	art_id title_id;

	art_id cur_dist;

	art_id i;

	bitfield_type *titles_seen;
	bitfield_type *titles_prev_round;
	bitfield_type *titles_this_round;
	size_t titles_bitfield_elems;
	size_t titles_bitfield_bytes;


	if (argc < 2) {
		printf("Supply article name to look up articles linking to it.\n");
		return 1;
	}


	/*
	 * Read all incoming links into memory
	 */

	in_file = fopen("links-incoming.bin", "rb");
	fseek(in_file, 0, SEEK_END);
	link_blob_len = ftell(in_file);
	rewind(in_file);
	printf("Link blob size: %zd bytes.\n", link_blob_len);

	link_blob = malloc(link_blob_len);
	if (!link_blob) {
		printf("Failed to allocate memory.\n");
		return 1;
	}

	if (link_blob_len != fread(link_blob, 1, link_blob_len, in_file)) {
		printf("Failed to read entire file in one go.\n");
		return 1;
	}
	printf("Link blob read (%zd bytes).\n", ftell(in_file));
	fclose(in_file);

	titles = *link_blob;
	link_blob++;

	linki = malloc(titles * sizeof(art_id*));
	linkis = malloc(titles * sizeof(art_id));

	for (i = 0; i < titles; i++) {
		art_id j;

		linkis[i] = *link_blob;
		link_blob++;

		linki[i] = link_blob;
		link_blob += linkis[i];
	}
	printf("Incoming links prepared.\n");





	/*
	 * Read all titles into memory
	 */



	in_file = fopen("titles-sorted.txt", "r");
	fseek(in_file, 0, SEEK_END);
	title_blob_len = ftell(in_file);
	rewind(in_file);
	printf("Title blob size: %zd bytes.\n", title_blob_len);

	title_blob = malloc(title_blob_len + 1);
	if (!title_blob) {
		printf("Failed to allocate memory.\n");
		return 1;
	}

	if (title_blob_len != fread(title_blob, 1, title_blob_len, in_file)) {
		printf("Failed to read entire file in one go.\n");
		return 1;
	}
	printf("Title blob read (%zd bytes).\n", ftell(in_file));
	fclose(in_file);

	title_blob[title_blob_len] = '\0';

	title = malloc((titles + 1) * sizeof(title[0]));

	title[0] = title_blob;
	titles_read = 1;
	while (title_blob = strchr(title_blob, '\n')) {
		title_blob[0] = '\0';
		title_blob++;
		title[titles_read] = title_blob;
		titles_read++;
	}

	/* Last title will be an empty string, as the file ends with a newline. */
	printf("Titles prepared: %d of %d.\n", titles_read - 1, titles);




	/* Look up article ID */
	cur_title = bsearch(argv[1], title,
				titles, sizeof(title[0]),
				cmpstring_p_pp);

	if (!cur_title) {
		printf("TITLE NOT FOUND: %s\n", argv[1]);
		return 1;
	}

	title_id = cur_title - title;


	#if 0
	/* Print first degree incoming edges */
	printf("Article %zd (%s) is linked from %zd articles:\n", title_id, title[title_id], linkis[title_id]);
	for (i = 0; i < linkis[title_id]; i++) {
		art_id x = linki[title_id][i];
		printf("  %s\n", title[x]);
	}
	#endif



	printf("\n\n\n\nBuilding table of distances...\n\n");

	titles_bitfield_elems = ROUNDUP(titles / BITS_PER_BITFIELD, BITS_PER_BITFIELD);
	titles_bitfield_bytes = titles_bitfield_elems * sizeof(bitfield_type);

	titles_seen = calloc(titles_bitfield_bytes, 1);
	titles_prev_round = NULL;
	titles_this_round = calloc(titles_bitfield_bytes, 1);

	cur_dist = 0;

	BIT_SET(titles_seen, title_id);
	BIT_SET(titles_this_round, title_id);

	while (ANY_BITS_SET(titles_this_round, titles_bitfield_elems)) {
		art_id i;

		cur_dist++;
		printf("Checking distance %d\n", cur_dist);

		free(titles_prev_round); /* free is safe to call on NULL */
		titles_prev_round = titles_this_round;
		titles_this_round = calloc(titles_bitfield_bytes, 1);

		for (i = 0; i < titles; i++) {
			int j;

			if (!BIT_ISSET(titles_prev_round, i))
				continue;

			for (j = 0; j < linkis[i]; j++) {
				art_id x = linki[i][j];
				BIT_SET(titles_this_round, x);
			}
		}

		for (i = 0; i < titles_bitfield_elems; i++) {
			titles_this_round[i] &= ~titles_seen[i];
			titles_seen[i] |= titles_this_round[i];
		}
	}

	/* Result is in titles_prev_round */

	cur_dist -= 1;

	printf("\n\n\nThe articles with the distance of %zd are:\n\n", cur_dist);
	for (i = 0; i < titles; i++) {
		if (BIT_ISSET(titles_prev_round, i)) {
			printf("  %s\n", title[i]);
		}
	}


	return 0;
}