feat: update structure

cs2106/labs/lab4/bitmap/bitmap.c

@@ -0,0 +1,115 @@
+#include "bitmap.h"
+#include <stdio.h>
+
+// IMPLEMENTED FOR YOU
+// Utility function to print out an array of char as bits
+// Print the entire bitmap. Arguments: The bitmap itself, and the length of the
+// bitmap Each bit of the bitmap represents 1 byte of memory. 0 = free, 1 =
+// allocated. map: The bitmap itself, an array of unsigned char.
+//      Each bit of the bitmap represents one byte of memory
+// len: The length of the bitmap array in characters
+//
+// Returns: Nothing
+void print_map(unsigned char *map, int len) {
+  int i, j;
+
+  for (i = 0; i < len; i++) {
+
+    unsigned char mask = 0b10000000;
+    for (j = 0; j < 8; j++) {
+      if (map[i] & mask)
+        printf("1");
+      else
+        printf("0");
+      mask = mask >> 1;
+    }
+    printf(" ");
+  }
+  printf("\n");
+}
+
+// Search the bitmap for the required number of zeroes (representing
+// free bytes of memory). Returns index of first stretch of 0s
+// that meet the criteria. You can use this as an index into
+// an array of char that represents the process heap
+// bitmap = Bitmap declared as an array of unsigned char
+// len = Length of bitmap in characters
+// num_zeroes = Length of string of 0's required
+// Returns: Index to stretch of 0's of required length, -1 if no such stretch
+// can be found
+
+long search_map(unsigned char *bitmap, int len, long num_zeroes) {
+  int count = 0;
+  for (int i = 0; i < len; i++) {
+    unsigned char mask = 0b10000000;
+    for (int j = 0; j < 8; j++) {
+      if ((bitmap[i] & mask) == 0) {
+        count++;
+        if (count == num_zeroes) {
+          return i * 8 + j - num_zeroes + 1;
+        }
+      } else {
+        count = 0;
+      }
+      mask >>= 1;
+    }
+  }
+  return -1;
+} // main
+
+// Set map bits to 0 or 1 depending on whether value is non-zero
+// map = Bitmap, declared as an array of unsigned char
+// start = Starting index to mark as 1 or 0
+// length = Number of bits to mark
+// value = Value to mark the bits as. value = 0 marks the bits
+//          as 0, non-zero marks the bits as 1
+// Returns: Nothing
+// start: 7
+// length: 4
+// value: 1
+
+void set_map(unsigned char *map, long start, long length, int value) {
+  // printf("set_map with start=%ld, length=%ld val=%d\n", start, length,
+  // value);
+  int starting_index = start / 8;
+
+  for (int i = 0; i < length; i++) {
+    int currIdx = (start + i) / 8;
+    int currOffset = (start + i) % 8;
+
+    int mask = 0b10000000;
+    if (value == 0) {
+      map[currIdx] &= ~(mask >> currOffset);
+    } else {
+      map[currIdx] |= (mask >> currOffset);
+    }
+  }
+
+  // the ~(1<< offset) is a nice trick to create, for example
+  // ~(1 << 2) = 1111 1011
+  // By anding this, you can set the value to 0 for that bit
+
+  // map[char_index + length_index] &= ~(1 << length_offset);
+  // the (1<< offset) is a nice trick to create, for example
+  // (1 << 2) = 0000 0100
+  // likewise, set the given bit to 1
+  // map[char_index + length_index] |= (1 << length_offset);
+}
+
+// IMPLEMENTED FOR YOU
+// Marks a stretch of bits as "1", representing allocated memory
+// map = Bitmap declared as array of unsigned char
+// start = Starting index to mark
+// length = Number of bits to mark as "1"
+void allocate_map(unsigned char *map, long start, long length) {
+  set_map(map, start, length, 1);
+}
+
+// IMPLEMENTED FOR YOU
+// Marks a stretch of bits as "0", representing allocated memory
+// map = Bitmap declared as array of unsigned char
+// start = Starting index to mark
+// length = Number of bits to mark as "0"
+void free_map(unsigned char *map, long start, long length) {
+  set_map(map, start, length, 0);
+}