X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Flib%2Fkernel%2Fbitmap.c;h=cacc263a200b5fea1dc440afdc3249788681567f;hb=15bd5676b2d0ae5f2e96c33b3b7007dd24105141;hp=7bbc92868ca9fdf908798c919c168c7b3b44732b;hpb=f2f8875638593bd5365cfd6a5ba7c9578e52322f;p=pintos-anon

diff --git a/src/lib/kernel/bitmap.c b/src/lib/kernel/bitmap.c
index 7bbc928..cacc263 100644
--- a/src/lib/kernel/bitmap.c
+++ b/src/lib/kernel/bitmap.c
@@ -8,9 +8,28 @@
 #include "filesys/file.h"
 #endif
 
+/* Element type.
+
+   This must be an unsigned integer type at least as wide as int.
+
+   Each bit represents one bit in the bitmap.
+   If bit 0 in an element represents bit K in the bitmap,
+   then bit 1 in the element represents bit K+1 in the bitmap,
+   and so on. */
+typedef unsigned long elem_type;
+
 /* Number of bits in an element. */
 #define ELEM_BITS (sizeof (elem_type) * CHAR_BIT)
 
+/* From the outside, a bitmap is an array of bits.  From the
+   inside, it's an array of elem_type (defined above) that
+   simulates an array of bits. */
+struct bitmap
+  {
+    size_t bit_cnt;     /* Number of bits. */
+    elem_type *bits;    /* Elements that represent bits. */
+  };
+
 /* Returns the index of the element that contains the bit
    numbered BIT_IDX. */
 static inline size_t
@@ -50,28 +69,39 @@ last_mask (const struct bitmap *b)
   return last_bits ? ((elem_type) 1 << last_bits) - 1 : (elem_type) -1;
 }
 
-/* Initializes B to be a bitmap of BIT_CNT bits.
-   Returns true if successfalse, false if memory allocation
+/* Initializes B to be a bitmap of BIT_CNT bits
+   and sets all of its bits to false.
+   Returns true if success, false if memory allocation
    failed. */
-bool
-bitmap_init (struct bitmap *b, size_t bit_cnt) 
+struct bitmap *
+bitmap_create (size_t bit_cnt) 
 {
-  b->bit_cnt = bit_cnt;
-  b->bits = malloc (byte_cnt (b));
-  if (b->bits == NULL && bit_cnt > 0) 
-    return false;
-
-  bitmap_set_all (b, false);
-  return true;
+  struct bitmap *b = malloc (sizeof *b);
+  if (b != NULL)
+    {
+      b->bit_cnt = bit_cnt;
+      b->bits = malloc (byte_cnt (b));
+      if (b->bits != NULL || bit_cnt == 0)
+        {
+          bitmap_set_all (b, false);
+          return b;
+        }
+      free (b);
+    }
+  return NULL;
 }
 
-/* Destroys bitmap B, freeing its storage. */
+/* Destroys bitmap B, freeing its storage.
+   Not for use on bitmaps created by
+   bitmap_create_preallocated(). */
 void
 bitmap_destroy (struct bitmap *b) 
 {
-  ASSERT (b);
-  
-  free (b->bits);
+  if (b != NULL) 
+    {
+      free (b->bits);
+      free (b);
+    }
 }
 
 /* Returns the number of bits in B. */
@@ -97,33 +127,45 @@ bitmap_set (struct bitmap *b, size_t idx, bool value)
 void
 bitmap_set_all (struct bitmap *b, bool value) 
 {
-  size_t i;
+  ASSERT (b != NULL);
+
+  bitmap_set_multiple (b, 0, bitmap_size (b), value);
+}
+
+/* Sets the bits numbered START through END, exclusive, in B to
+   VALUE. */
+void
+bitmap_set_multiple (struct bitmap *b, size_t start, size_t end, bool value) 
+{
+  size_t idx;
   
   ASSERT (b != NULL);
+  ASSERT (start <= end);
+  ASSERT (end <= b->bit_cnt);
 
-  if (b->bit_cnt > 0)
-    {
-      for (i = 0; i < elem_cnt (b); i++)
-        b->bits[i] = value ? (elem_type) -1 : 0;
-      b->bits[elem_cnt (b) - 1] &= last_mask (b); 
-    }
+  for (idx = start; idx < end; idx++)
+    bitmap_set (b, idx, value);
 }
 
-/* Sets the bit numbered IDX in B to true. */
+/* Atomically sets the bit numbered IDX in B to true. */
 void
 bitmap_mark (struct bitmap *b, size_t idx) 
 {
-  bitmap_set (b, idx, true);
+  asm ("orl %1, %0"
+       : "=m" (b->bits[elem_idx (idx)])
+       : "r" (bit_mask (idx)));
 }
 
-/* Sets the bit numbered IDX in B to false. */
+/* Atomically sets the bit numbered IDX in B to false. */
 void
 bitmap_reset (struct bitmap *b, size_t idx) 
 {
-  bitmap_set (b, idx, false);
+  asm ("andl %1, %0"
+       : "=m" (b->bits[elem_idx (idx)])
+       : "r" (~bit_mask (idx)));
 }
 
-/* Toggles the bit numbered IDX in B;
+/* Atomically toggles the bit numbered IDX in B;
    that is, if it is true, makes it false,
    and if it is false, makes it true. */
 void
@@ -131,7 +173,9 @@ bitmap_flip (struct bitmap *b, size_t idx)
 {
   ASSERT (b != NULL);
   ASSERT (idx < b->bit_cnt);
-  b->bits[elem_idx (idx)] ^= bit_mask (idx);
+  asm ("xorl %1, %0"
+       : "=m" (b->bits[elem_idx (idx)])
+       : "r" (bit_mask (idx)));
 }
 
 /* Returns the value of the bit numbered IDX in B. */
@@ -143,126 +187,95 @@ bitmap_test (const struct bitmap *b, size_t idx)
   return (b->bits[elem_idx (idx)] & bit_mask (idx)) != 0;
 }
 
-/* Returns the smallest index of a bit set to VALUE in B.
-   If no bits in B are set to VALUE, returns BITMAP_ERROR. */
-size_t
-bitmap_scan (const struct bitmap *b, bool value) 
+/* Returns true if any bit from START to END, exclusive, is set
+   to VALUE. */
+static bool
+contains (const struct bitmap *b, size_t start, size_t end, bool value) 
 {
-  elem_type ignore = value ? 0 : (elem_type) -1;
   size_t idx;
   
   ASSERT (b != NULL);
-  for (idx = 0; idx < elem_cnt (b); idx++)
-    {
-      elem_type e = b->bits[idx];
-      if (e != ignore)
-        {
-          idx *= ELEM_BITS;
-
-          while ((e & 1) != value)
-            {
-              e >>= 1;
-              idx++;
-            }
+  ASSERT (start <= end);
+  ASSERT (end <= b->bit_cnt);
 
-          return idx < b->bit_cnt ? idx : BITMAP_ERROR;
-        }
-    }
-  return BITMAP_ERROR;
+  for (idx = start; idx < end; idx++)
+    if (bitmap_test (b, idx) == value)
+      return true;
+  return false;
 }
 
-/* Finds the smallest index of a bit set to false in B,
-   sets it to true, and returns the index.
-   If no bits in B are set to false, changes no bits and
-   returns BITMAP_ERROR. */
+/* Finds and returns the starting index of the first group of CNT
+   consecutive bits in B at or after START that are all set to
+   VALUE.
+   If there is no such group, returns BITMAP_ERROR. */
 size_t
-bitmap_find_and_set (struct bitmap *b) 
+bitmap_scan (const struct bitmap *b, size_t start, size_t cnt, bool value) 
 {
-  size_t idx = bitmap_scan (b, false);
-  if (idx != BITMAP_ERROR) 
-    bitmap_mark (b, idx);
-  return idx;
+  size_t idx, last;
+  
+  ASSERT (b != NULL);
+  ASSERT (start <= b->bit_cnt);
+
+  for (idx = start, last = b->bit_cnt - cnt; idx <= last; idx++)
+    if (!contains (b, idx, idx + cnt, !value))
+      return idx;
+  return BITMAP_ERROR;
 }
 
-/* Finds the smallest index of a bit set to true in B,
-   sets it to false, and returns the index.
-   If no bits in B are set to true, changes no bits and
-   returns BITMAP_ERROR. */
+/* Finds the first group of CNT consecutive bits in B at or after
+   START that are all set to VALUE, flips them all to !VALUE,
+   and returns the index of the first bit in the group.
+   If there is no such group, returns BITMAP_ERROR.
+   Bits are set atomically, but testing bits is not atomic with
+   setting them. */
 size_t
-bitmap_find_and_clear (struct bitmap *b) 
+bitmap_scan_and_flip (struct bitmap *b, size_t start, size_t cnt, bool value)
 {
-  size_t idx = bitmap_scan (b, true);
+  size_t idx = bitmap_scan (b, start, cnt, value);
   if (idx != BITMAP_ERROR) 
-    bitmap_reset (b, idx);
+    bitmap_set_multiple (b, idx, idx + cnt, !value);
   return idx;
 }
 
-/* Returns the number of bits in B set to true. */
+/* Returns the number of bits in B between START and END,
+   exclusive, that are set to VALUE. */
 size_t
-bitmap_set_cnt (const struct bitmap *b) 
+bitmap_count (const struct bitmap *b, size_t start, size_t end, bool value) 
 {
-  size_t cnt;
-  size_t i;
+  size_t idx, cnt;
 
   ASSERT (b != NULL);
+  ASSERT (start <= end);
+  ASSERT (end <= b->bit_cnt);
+
   cnt = 0;
-  for (i = 0; i < elem_cnt (b); i++)
-    {
-      elem_type e = b->bits[i];
-      while (e != 0) 
-        {
-          cnt++;
-          e &= e - 1;
-        }
-    }
+  for (idx = start; idx < end; idx++)
+    cnt += bitmap_test (b, idx) == value;
   return cnt;
 }
 
-/* Returns true if any bits in B are set to true,
-   and false otherwise.*/
-bool
-bitmap_any (const struct bitmap *b) 
-{
-  size_t i;
-
-  ASSERT (b != NULL);
-  for (i = 0; i < elem_cnt (b); i++)
-    if (b->bits[i])
-      return true;
-  return false;
-}
-
-/* Returns the number of bits in B set to false. */
+/* Returns true if any bits in B between START and END,
+   exclusive, are set to true, and false otherwise.*/
 bool
-bitmap_clear_cnt (const struct bitmap *b) 
+bitmap_any (const struct bitmap *b, size_t start, size_t end) 
 {
-  return b->bit_cnt - bitmap_set_cnt (b);
+  return contains (b, start, end, true);
 }
 
-/* Returns true if no bits in B are set to true,
-   and false otherwise.*/
+/* Returns true if no bits in B between START and END, exclusive,
+   are set to true, and false otherwise.*/
 bool
-bitmap_none (const struct bitmap *b) 
+bitmap_none (const struct bitmap *b, size_t start, size_t end) 
 {
-  return !bitmap_any (b); 
+  return !contains (b, start, end, true);
 }
 
-/* Returns true if every bit in B is set to true,
-   and false otherwise. */
+/* Returns true if every bit in B between START and END,
+   exclusive, is set to true, and false otherwise. */
 bool
-bitmap_all (const struct bitmap *b) 
+bitmap_all (const struct bitmap *b, size_t start, size_t end) 
 {
-  size_t i;
-
-  ASSERT (b != NULL);
-
-  if (b->bit_cnt == 0)
-    return true;
-  
-  for (i = 0; i < elem_cnt (b) - 1; i++)
-    if (b->bits[i] != (elem_type) -1)
-      return false;
-  return b->bits[i] == last_mask (b);
+  return !contains (b, start, end, false);
 }
 
 #ifdef FILESYS
@@ -296,5 +309,32 @@ bitmap_write (const struct bitmap *b, struct file *file)
 void
 bitmap_dump (const struct bitmap *b) 
 {
-  hex_dump (b->bits, byte_cnt (b), false);
+  hex_dump (0, b->bits, byte_cnt (b), false);
+}
+
+/* Returns the number of bytes required to accomodate a bitmap
+   with BIT_CNT bits. */
+size_t
+bitmap_needed_bytes (size_t bit_cnt) 
+{
+  struct bitmap b;
+  b.bit_cnt = bit_cnt;
+  return byte_cnt (&b) + sizeof b;
 }
+
+/* Creates and returns a bitmap with BIT_CNT bits in the
+   BLOCK_SIZE bytes of storage preallocated at BLOCK.
+   BLOCK_SIZE must be at least bitmap_needed_bytes(BIT_CNT). */
+struct bitmap *
+bitmap_create_preallocated (size_t bit_cnt, void *block, size_t block_size) 
+{
+  struct bitmap *b = block;
+  
+  ASSERT (block_size >= bitmap_needed_bytes (bit_cnt));
+
+  b->bit_cnt = bit_cnt;
+  b->bits = (elem_type *) (b + 1);
+  bitmap_set_all (b, false);
+  return b;
+}
+