From 2fb5ad365949ecff6edf1a4a910428e667233299 Mon Sep 17 00:00:00 2001
From: Stathis Kamperis <ekamperi@gmail.com>
Date: Fri, 11 Jan 2008 20:06:25 +0100
Subject: [PATCH] Initial import of a bitmap implementation as part of a
 filesystem project

---
 homework/bitmap.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 homework/bitmap.c

diff --git a/homework/bitmap.c b/homework/bitmap.c
new file mode 100644
index 0000000..eec9637
--- /dev/null
+++ b/homework/bitmap.c
@@ -0,0 +1,77 @@
+#include <limits.h>    /* for CHAR_BIT */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>    /* for memset() */
+
+int is_blk_free(const unsigned char *array, unsigned int nblk);
+void print_blks(const unsigned char *array, unsigned int nblks);
+void diep(const char *s);
+
+int main(int argc, char *argv[])
+{
+    unsigned char *array;
+    unsigned int i, narr, nblks, u;
+
+    /* Check argument count */
+    if (argc != 2) {
+        fprintf(stderr, "Usage: %s nblocks\n", argv[0]);
+        exit(EXIT_FAILURE);
+    }
+
+    /* Get number of blocks */
+    nblks = (unsigned int) strtoul(argv[1], NULL, 10);
+    u = nblks - CHAR_BIT * (nblks / CHAR_BIT);
+    if (u == 0)
+        narr = nblks / CHAR_BIT;
+    else
+        narr = nblks / CHAR_BIT + 1;
+    printf("nblks = %u\tnarr = %u\n", nblks, narr);
+
+    /* Allocate memory for char bitmap */
+    array = malloc(narr);
+    if (array == NULL)
+        diep("malloc");
+
+    /* Initialize all bits to 0 representing free blocks */
+    memset(array, 0, narr);
+
+    /* Print blocks' status */
+    print_blks(array, nblks);
+
+    /* Flag all blocks as used */
+    for (i = 0; i < narr; i++)
+        array[i] = 0xFF;
+    print_blks(array, nblks);
+
+    /* Free bitmap */
+    free(array);
+
+    return EXIT_SUCCESS;
+}
+
+int is_blk_free(const unsigned char *array, unsigned int nblk)
+{
+    unsigned int idx, u;
+
+    idx = nblk / CHAR_BIT;
+    u = nblk - CHAR_BIT * idx;
+    printf("blk %u is in array %u and bitpos %u\n",
+           nblk, idx, u);
+
+    return ((array[idx] & (1 << u)) == 0);
+}
+
+void print_blks(const unsigned char *array, unsigned int nblks)
+{
+    unsigned int i;
+
+    for (i = 0; i < nblks; i++)
+        printf("blk[%04u] = %s\n",
+               i, is_blk_free(array, i) ? "FREE" : "USED");
+}
+
+void diep(const char *s)
+{
+    perror(s);
+    exit(EXIT_FAILURE);
+}
-- 
2.11.4.GIT