Initial version

code/userprog/bitmap.cc

@@ -0,0 +1,172 @@
+// bitmap.c 
+//      Routines to manage a bitmap -- an array of bits each of which
+//      can be either on or off.  Represented as an array of integers.
+//
+// Copyright (c) 1992-1993 The Regents of the University of California.
+// All rights reserved.  See copyright.h for copyright notice and limitation 
+// of liability and disclaimer of warranty provisions.
+
+#include "copyright.h"
+#include "bitmap.h"
+
+// Definitions helpful for representing a bitmap as an array of integers
+#define BitsInByte 	8
+#define BitsInWord 	32
+
+//----------------------------------------------------------------------
+// BitMap::BitMap
+//      Initialize a bitmap with "nitems" bits, so that every bit is clear.
+//      it can be added somewhere on a list.
+//
+//      "nitems" is the number of bits in the bitmap.
+//----------------------------------------------------------------------
+
+BitMap::BitMap (int nitems)
+{
+    numBits = nitems;
+    numWords = divRoundUp (numBits, BitsInWord);
+    map = new unsigned int[numWords];
+    for (int i = 0; i < numBits; i++)
+	Clear (i);
+}
+
+//----------------------------------------------------------------------
+// BitMap::~BitMap
+//      De-allocate a bitmap.
+//----------------------------------------------------------------------
+
+BitMap::~BitMap ()
+{
+  delete [] map;
+  map = NULL;
+}
+
+//----------------------------------------------------------------------
+// BitMap::Mark
+//      Set the "nth" bit in a bitmap.
+//
+//      "which" is the number of the bit to be set.
+//----------------------------------------------------------------------
+
+void
+BitMap::Mark (int which)
+{
+    ASSERT (which >= 0 && which < numBits);
+    map[which / BitsInWord] |= 1 << (which % BitsInWord);
+}
+
+//----------------------------------------------------------------------
+// BitMap::Clear
+//      Clear the "nth" bit in a bitmap.
+//
+//      "which" is the number of the bit to be cleared.
+//----------------------------------------------------------------------
+
+void
+BitMap::Clear (int which)
+{
+    ASSERT (which >= 0 && which < numBits);
+    map[which / BitsInWord] &= ~(1 << (which % BitsInWord));
+}
+
+//----------------------------------------------------------------------
+// BitMap::Test
+//      Return TRUE if the "nth" bit is set.
+//
+//      "which" is the number of the bit to be tested.
+//----------------------------------------------------------------------
+
+bool
+BitMap::Test (int which)
+{
+    ASSERT (which >= 0 && which < numBits);
+
+    if (map[which / BitsInWord] & (1 << (which % BitsInWord)))
+	return TRUE;
+    else
+	return FALSE;
+}
+
+//----------------------------------------------------------------------
+// BitMap::Find
+//      Return the number of the first bit which is clear.
+//      As a side effect, set the bit (mark it as in use).
+//      (In other words, find and allocate a bit.)
+//
+//      If no bits are clear, return -1.
+//----------------------------------------------------------------------
+
+int
+BitMap::Find ()
+{
+    for (int i = 0; i < numBits; i++)
+	if (!Test (i))
+	  {
+	      Mark (i);
+	      return i;
+	  }
+    return -1;
+}
+
+//----------------------------------------------------------------------
+// BitMap::NumClear
+//      Return the number of clear bits in the bitmap.
+//      (In other words, how many bits are unallocated?)
+//----------------------------------------------------------------------
+
+int
+BitMap::NumClear ()
+{
+    int count = 0;
+
+    for (int i = 0; i < numBits; i++)
+	if (!Test (i))
+	    count++;
+    return count;
+}
+
+//----------------------------------------------------------------------
+// BitMap::Print
+//      Print the contents of the bitmap, for debugging.
+//
+//      Could be done in a number of ways, but we just print the #'s of
+//      all the bits that are set in the bitmap.
+//----------------------------------------------------------------------
+
+void
+BitMap::Print ()
+{
+    printf ("Bitmap set:\n");
+    for (int i = 0; i < numBits; i++)
+	if (Test (i))
+	    printf ("%d, ", i);
+    printf ("\n");
+}
+
+// These aren't needed until the FILESYS assignment
+
+//----------------------------------------------------------------------
+// BitMap::FetchFromFile
+//      Initialize the contents of a bitmap from a Nachos file.
+//
+//      "file" is the place to read the bitmap from
+//----------------------------------------------------------------------
+
+void
+BitMap::FetchFrom (OpenFile * file)
+{
+    file->ReadAt (map, numWords * sizeof (unsigned), 0);
+}
+
+//----------------------------------------------------------------------
+// BitMap::WriteBack
+//      Store the contents of a bitmap to a Nachos file.
+//
+//      "file" is the place to write the bitmap to
+//----------------------------------------------------------------------
+
+void
+BitMap::WriteBack (OpenFile * file)
+{
+    file->WriteAt (map, numWords * sizeof (unsigned), 0);
+}