X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Flib%2Fkernel%2Fbitmap.c;h=77edf2270b35435538fbbb5adeec52096403f50b;hb=468f548e6848498767eb6ac7b55ab9bca06de462;hp=95d689034617917f9cd23ef7b5423978fa774cec;hpb=fc637378f55d2e5d39ef4ebd58e3a3b1a13a4fa9;p=pintos-anon

diff --git a/src/lib/kernel/bitmap.c b/src/lib/kernel/bitmap.c
index 95d6890..77edf22 100644
--- a/src/lib/kernel/bitmap.c
+++ b/src/lib/kernel/bitmap.c
@@ -1,6 +1,7 @@
 #include "bitmap.h"
 #include <debug.h>
 #include <limits.h>
+#include <random.h>
 #include <round.h>
 #include <stdio.h>
 #include "threads/malloc.h"
@@ -46,18 +47,18 @@ bit_mask (size_t bit_idx)
   return (elem_type) 1 << (bit_idx % ELEM_BITS);
 }
 
-/* Returns the number of elements required for B's bits. */
+/* Returns the number of elements required for BIT_CNT bits. */
 static inline size_t
-elem_cnt (const struct bitmap *b) 
+elem_cnt (size_t bit_cnt)
 {
-  return DIV_ROUND_UP (b->bit_cnt, ELEM_BITS);
+  return DIV_ROUND_UP (bit_cnt, ELEM_BITS);
 }
 
-/* Returns the number of bytes required by B's elements. */
+/* Returns the number of bytes required for BIT_CNT bits. */
 static inline size_t
-byte_cnt (const struct bitmap *b) 
+byte_cnt (size_t bit_cnt)
 {
-  return sizeof (elem_type) * elem_cnt (b);
+  return sizeof (elem_type) * elem_cnt (bit_cnt);
 }
 
 /* Returns a bit mask in which the bits actually used in the last
@@ -69,6 +70,8 @@ last_mask (const struct bitmap *b)
   return last_bits ? ((elem_type) 1 << last_bits) - 1 : (elem_type) -1;
 }
 
+/* Creation and destruction. */
+
 /* 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
@@ -80,7 +83,7 @@ bitmap_create (size_t bit_cnt)
   if (b != NULL)
     {
       b->bit_cnt = bit_cnt;
-      b->bits = malloc (byte_cnt (b));
+      b->bits = malloc (byte_cnt (bit_cnt));
       if (b->bits != NULL || bit_cnt == 0)
         {
           bitmap_set_all (b, false);
@@ -91,6 +94,30 @@ bitmap_create (size_t bit_cnt)
   return NULL;
 }
 
+/* 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_in_buf (size_t bit_cnt, void *block, size_t block_size UNUSED)
+{
+  struct bitmap *b = block;
+  
+  ASSERT (block_size >= bitmap_buf_size (bit_cnt));
+
+  b->bit_cnt = bit_cnt;
+  b->bits = (elem_type *) (b + 1);
+  bitmap_set_all (b, false);
+  return b;
+}
+
+/* Returns the number of bytes required to accomodate a bitmap
+   with BIT_CNT bits (for use with bitmap_create_in_buf()). */
+size_t
+bitmap_buf_size (size_t bit_cnt) 
+{
+  return sizeof (struct bitmap) + byte_cnt (bit_cnt);
+}
+
 /* Destroys bitmap B, freeing its storage.
    Not for use on bitmaps created by
    bitmap_create_preallocated(). */
@@ -103,6 +130,8 @@ bitmap_destroy (struct bitmap *b)
       free (b);
     }
 }
+
+/* Bitmap size. */
 
 /* Returns the number of bits in B. */
 size_t
@@ -110,72 +139,60 @@ bitmap_size (const struct bitmap *b)
 {
   return b->bit_cnt;
 }
+
+/* Setting and testing single bits. */
 
-/* Sets the bit numbered IDX in B to VALUE. */
+/* Atomically sets the bit numbered IDX in B to VALUE. */
 void
 bitmap_set (struct bitmap *b, size_t idx, bool value) 
 {
   ASSERT (b != NULL);
   ASSERT (idx < b->bit_cnt);
   if (value)
-    b->bits[elem_idx (idx)] |= bit_mask (idx);
+    bitmap_mark (b, idx);
   else
-    b->bits[elem_idx (idx)] &= ~bit_mask (idx);
-}
-
-/* Sets all bits in B to VALUE. */
-void
-bitmap_set_all (struct bitmap *b, bool value) 
-{
-  ASSERT (b != NULL);
-
-  bitmap_set_multiple (b, 0, bitmap_size (b), value);
+    bitmap_reset (b, idx);
 }
 
-/* Sets the bits numbered START through END, exclusive, in B to
-   VALUE. */
+/* Atomically sets the bit numbered BIT_IDX in B to true. */
 void
-bitmap_set_multiple (struct bitmap *b, size_t start, size_t end, bool value) 
+bitmap_mark (struct bitmap *b, size_t bit_idx) 
 {
-  size_t idx;
-  
-  ASSERT (b != NULL);
-  ASSERT (start <= end);
-  ASSERT (end <= b->bit_cnt);
+  size_t idx = elem_idx (bit_idx);
+  elem_type mask = bit_mask (bit_idx);
 
-  for (idx = start; idx < end; idx++)
-    bitmap_set (b, idx, value);
+  /* This is equivalent to `b->bits[idx] |= mask' except that it
+     is guaranteed to be atomic on a uniprocessor machine.  See
+     the description of the OR instruction in [IA32-v2b]. */
+  asm ("orl %1, %0" : "=m" (b->bits[idx]) : "r" (mask) : "cc");
 }
 
-/* Atomically sets the bit numbered IDX in B to true. */
+/* Atomically sets the bit numbered BIT_IDX in B to false. */
 void
-bitmap_mark (struct bitmap *b, size_t idx) 
+bitmap_reset (struct bitmap *b, size_t bit_idx) 
 {
-  asm ("orl %1, %0"
-       : "=m" (b->bits[elem_idx (idx)])
-       : "r" (bit_mask (idx)));
-}
+  size_t idx = elem_idx (bit_idx);
+  elem_type mask = bit_mask (bit_idx);
 
-/* Atomically sets the bit numbered IDX in B to false. */
-void
-bitmap_reset (struct bitmap *b, size_t idx) 
-{
-  asm ("andl %1, %0"
-       : "=m" (b->bits[elem_idx (idx)])
-       : "r" (~bit_mask (idx)));
+  /* This is equivalent to `b->bits[idx] &= ~mask' except that it
+     is guaranteed to be atomic on a uniprocessor machine.  See
+     the description of the AND instruction in [IA32-v2a]. */
+  asm ("andl %1, %0" : "=m" (b->bits[idx]) : "r" (~mask) : "cc");
 }
 
 /* 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
-bitmap_flip (struct bitmap *b, size_t idx) 
+bitmap_flip (struct bitmap *b, size_t bit_idx) 
 {
-  ASSERT (b != NULL);
-  ASSERT (idx < b->bit_cnt);
-  asm ("xorl %1, %0"
-       : "=m" (b->bits[elem_idx (idx)])
-       : "r" (bit_mask (idx)));
+  size_t idx = elem_idx (bit_idx);
+  elem_type mask = bit_mask (bit_idx);
+
+  /* This is equivalent to `b->bits[idx] ^= mask' except that it
+     is guaranteed to be atomic on a uniprocessor machine.  See
+     the description of the XOR instruction in [IA32-v2b]. */
+  asm ("xorl %1, %0" : "=m" (b->bits[idx]) : "r" (mask) : "cc");
 }
 
 /* Returns the value of the bit numbered IDX in B. */
@@ -186,156 +203,176 @@ bitmap_test (const struct bitmap *b, size_t idx)
   ASSERT (idx < b->bit_cnt);
   return (b->bits[elem_idx (idx)] & bit_mask (idx)) != 0;
 }
+
+/* Setting and testing multiple bits. */
 
-/* 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) 
+/* Sets all bits in B to VALUE. */
+void
+bitmap_set_all (struct bitmap *b, bool value) 
 {
-  size_t idx;
-  
   ASSERT (b != NULL);
-  ASSERT (start <= end);
-  ASSERT (end <= b->bit_cnt);
 
-  for (idx = start; idx < end; idx++)
-    if (bitmap_test (b, idx) == value)
-      return true;
-  return false;
+  bitmap_set_multiple (b, 0, bitmap_size (b), value);
 }
 
-/* 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_scan (const struct bitmap *b, size_t start, size_t cnt, bool value) 
+/* Sets the CNT bits starting at START in B to VALUE. */
+void
+bitmap_set_multiple (struct bitmap *b, size_t start, size_t cnt, bool value) 
 {
-  size_t idx, last;
+  size_t i;
   
   ASSERT (b != NULL);
   ASSERT (start <= b->bit_cnt);
+  ASSERT (start + cnt <= b->bit_cnt);
 
-  if (cnt <= 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;
+  for (i = 0; i < cnt; i++)
+    bitmap_set (b, start + i, value);
 }
 
-/* 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. */
+/* Returns the number of bits in B between START and START + CNT,
+   exclusive, that are set to VALUE. */
 size_t
-bitmap_scan_and_flip (struct bitmap *b, size_t start, size_t cnt, bool value)
+bitmap_count (const struct bitmap *b, size_t start, size_t cnt, bool value) 
 {
-  size_t idx = bitmap_scan (b, start, cnt, value);
-  if (idx != BITMAP_ERROR) 
-    bitmap_set_multiple (b, idx, idx + cnt, !value);
-  return idx;
+  size_t i, value_cnt;
+
+  ASSERT (b != NULL);
+  ASSERT (start <= b->bit_cnt);
+  ASSERT (start + cnt <= b->bit_cnt);
+
+  value_cnt = 0;
+  for (i = 0; i < cnt; i++)
+    if (bitmap_test (b, start + i) == value)
+      value_cnt++;
+  return value_cnt;
 }
 
-/* Returns the number of bits in B between START and END,
-   exclusive, that are set to VALUE. */
-size_t
-bitmap_count (const struct bitmap *b, size_t start, size_t end, bool value) 
+/* Returns true if any bits in B between START and START + CNT,
+   exclusive, are set to VALUE, and false otherwise. */
+bool
+bitmap_contains (const struct bitmap *b, size_t start, size_t cnt, bool value) 
 {
-  size_t idx, cnt;
-
+  size_t i;
+  
   ASSERT (b != NULL);
-  ASSERT (start <= end);
-  ASSERT (end <= b->bit_cnt);
+  ASSERT (start <= b->bit_cnt);
+  ASSERT (start + cnt <= b->bit_cnt);
 
-  cnt = 0;
-  for (idx = start; idx < end; idx++)
-    cnt += bitmap_test (b, idx) == value;
-  return cnt;
+  for (i = 0; i < cnt; i++)
+    if (bitmap_test (b, start + i) == value)
+      return true;
+  return false;
 }
 
-/* Returns true if any bits in B between START and END,
+/* Returns true if any bits in B between START and START + CNT,
    exclusive, are set to true, and false otherwise.*/
 bool
-bitmap_any (const struct bitmap *b, size_t start, size_t end) 
+bitmap_any (const struct bitmap *b, size_t start, size_t cnt) 
 {
-  return contains (b, start, end, true);
+  return bitmap_contains (b, start, cnt, true);
 }
 
-/* Returns true if no bits in B between START and END, exclusive,
-   are set to true, and false otherwise.*/
+/* Returns true if no bits in B between START and START + CNT,
+   exclusive, are set to true, and false otherwise.*/
 bool
-bitmap_none (const struct bitmap *b, size_t start, size_t end) 
+bitmap_none (const struct bitmap *b, size_t start, size_t cnt) 
 {
-  return !contains (b, start, end, true);
+  return !bitmap_contains (b, start, cnt, true);
 }
 
-/* Returns true if every bit in B between START and END,
+/* Returns true if every bit in B between START and START + CNT,
    exclusive, is set to true, and false otherwise. */
 bool
-bitmap_all (const struct bitmap *b, size_t start, size_t end) 
+bitmap_all (const struct bitmap *b, size_t start, size_t cnt) 
+{
+  return !bitmap_contains (b, start, cnt, false);
+}
+
+/* Finding set or unset bits. */
+
+/* Finds and returns the starting index of a 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_scan (const struct bitmap *b, size_t start, size_t cnt, bool value) 
+{
+  ASSERT (b != NULL);
+  ASSERT (start <= b->bit_cnt);
+
+  if (cnt <= b->bit_cnt) 
+    {
+      size_t last = b->bit_cnt - cnt;
+      size_t middle = start + random_ulong () % (last - start + 1); 
+      size_t i = middle;
+      do
+        {
+          if (!bitmap_contains (b, i, cnt, !value))
+            return i; 
+          i = i != last ? i + 1 : start;
+        }
+      while (i != middle);
+    }
+  return BITMAP_ERROR;
+}
+
+/* Finds a 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.
+   If CNT is zero, returns 0.
+   Bits are set atomically, but testing bits is not atomic with
+   setting them. */
+size_t
+bitmap_scan_and_flip (struct bitmap *b, size_t start, size_t cnt, bool value)
 {
-  return !contains (b, start, end, false);
+  size_t idx = bitmap_scan (b, start, cnt, value);
+  if (idx != BITMAP_ERROR) 
+    bitmap_set_multiple (b, idx, cnt, !value);
+  return idx;
 }
+
+/* File input and output. */
 
 #ifdef FILESYS
 /* Returns the number of bytes needed to store B in a file. */
 size_t
 bitmap_file_size (const struct bitmap *b) 
 {
-  return byte_cnt (b);
+  return byte_cnt (b->bit_cnt);
 }
 
-/* Reads FILE into B, ignoring errors. */
-void
+/* Reads B from FILE.  Returns true if successful, false
+   otherwise. */
+bool
 bitmap_read (struct bitmap *b, struct file *file) 
 {
+  bool success = true;
   if (b->bit_cnt > 0) 
     {
-      file_read_at (file, b->bits, byte_cnt (b), 0);
-      b->bits[elem_cnt (b) - 1] &= last_mask (b);
+      off_t size = byte_cnt (b->bit_cnt);
+      success = file_read_at (file, b->bits, size, 0) == size;
+      b->bits[elem_cnt (b->bit_cnt) - 1] &= last_mask (b);
     }
+  return success;
 }
 
-/* Writes FILE to B, ignoring errors. */
-void
+/* Writes B to FILE.  Return true if successful, false
+   otherwise. */
+bool
 bitmap_write (const struct bitmap *b, struct file *file)
 {
-  file_write_at (file, b->bits, byte_cnt (b), 0);
+  off_t size = byte_cnt (b->bit_cnt);
+  return file_write_at (file, b->bits, size, 0) == size;
 }
 #endif /* FILESYS */
+
+/* Debugging. */
 
 /* Dumps the contents of B to the console as hexadecimal. */
 void
 bitmap_dump (const struct bitmap *b) 
 {
-  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;
+  hex_dump (0, b->bits, byte_cnt (b->bit_cnt), false);
 }