From 7208221ed45d1b4fddf876ac6f072f0c36cab270 Mon Sep 17 00:00:00 2001
From: David Phillips <david@sighup.nz>
Date: Thu, 6 Apr 2017 15:26:27 +1200
Subject: Improve documentation, add comamnd line arguments

---
 hist-sort.c | 48 +++++++++++++++++++++++++++---------------------
 1 file changed, 27 insertions(+), 21 deletions(-)

diff --git a/hist-sort.c b/hist-sort.c
index cf7a0dd..423f026 100644
--- a/hist-sort.c
+++ b/hist-sort.c
@@ -19,9 +19,6 @@
 #include <stdlib.h>
 #include <time.h>
 
-#define RANGE 10000
-#define COUNT 10000000
-
 int
 is_sorted(unsigned int *data, size_t length) {
 	size_t i = 0;
@@ -52,32 +49,43 @@ sort(unsigned int *data, size_t length, unsigned int max) {
 		return;
 	}
 
-	for (i = 0; i < length; i++) {
+	/* build the histogram */
+	for (i = 0; i < length; i++)
 		hist[data[i]]++;
-	}
 
+	/* expand histogram to form sorted set */
 	j = 0;
-	for (i = 0; i < max+1; i++) {
+	for (i = 0; i < max+1; i++)
 		for (; hist[i]; hist[i]--, j++)
 			data[j] = i;
-	}
 }
 
 void
-dump_data(unsigned int *data, size_t length) {
-	size_t i = 0;
-
-	for (i = 0; i < length; i++)
-		printf("%d, ", data[i]);
-
-	fputc('\n', stdout);
+show_usage(const char *argv0) {
+	fprintf(stderr, "usage: %s <item_count> <max_value>\n", argv0);
 }
 
 int
 main(int argc, char **argv) {
 	clock_t start, end;
-	unsigned int *data = calloc(COUNT, sizeof(unsigned int));
+	unsigned int *data = NULL;
+	int range = 0;
+	int count = 0;
+
+	if (argc != 3) {
+		show_usage(argv[0]);
+		return 1;
+	}
+
+	count = atoi(argv[1]);
+	range = atoi(argv[2]);
+
+	if (count <= 0 || range <= 0) {
+		show_usage(argv[0]);
+		return 1;
+	}
 
+	data = calloc(count, sizeof(unsigned int));
 	if (!data) {
 		perror("calloc");
 		return 1;
@@ -85,18 +93,16 @@ main(int argc, char **argv) {
 
 	srand(time(NULL));
 
-	fill_random(data, COUNT, RANGE);
+	fill_random(data, count, range);
 
-	//dump_data(data, COUNT);
 	start = clock();
-	sort(data, COUNT, RANGE);
+	sort(data, count, range);
 	end = clock();
-	//dump_data(data, COUNT);
 
-	printf("Time elapsed to sort: %.4f\n",
+	printf("Time taken to sort: %.4f\n",
 			((double)(end-start))/CLOCKS_PER_SEC);
 
-	if (!is_sorted(data, COUNT)) {
+	if (!is_sorted(data, count)) {
 		fprintf(stderr, "Failed: out of order\n");
 	} else {
 		printf("Success.\n");
-- 
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