X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Flib%2Fkernel%2Fbitmap.c;h=9dfded55b64578dce328c53ea6fd2da7275777ff;hb=9818aeac330907b5b314ac58c861d3dba8b15e5e;hp=ea6ce5f9f82103cbea2ad09004cfa602c888627d;hpb=b2c7a704c963f5379280ae336c117e549f40f207;p=pintos-anon

diff --git a/src/lib/kernel/bitmap.c b/src/lib/kernel/bitmap.c
index ea6ce5f..9dfded5 100644
--- a/src/lib/kernel/bitmap.c
+++ b/src/lib/kernel/bitmap.c
@@ -46,18 +46,18 @@ 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
@@ -80,7 +80,7 @@ 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);
@@ -111,16 +111,16 @@ bitmap_size (const struct bitmap *b)
   return b->bit_cnt;
 }
 
-/* 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);
+    bitmap_reset (b, idx);
 }
 
 /* Sets all bits in B to VALUE. */
@@ -132,50 +132,59 @@ bitmap_set_all (struct bitmap *b, bool value)
   bitmap_set_multiple (b, 0, bitmap_size (b), value);
 }
 
-/* Sets the bits numbered START through END, exclusive, in B to
-   VALUE. */
+/* Sets the CNT bits starting at START in B to VALUE. */
 void
-bitmap_set_multiple (struct bitmap *b, size_t start, size_t end, bool value) 
+bitmap_set_multiple (struct bitmap *b, size_t start, size_t cnt, bool value) 
 {
-  size_t idx;
+  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);
 
-  for (idx = start; idx < end; idx++)
-    bitmap_set (b, idx, value);
+  for (i = 0; i < cnt; i++)
+    bitmap_set (b, start + i, value);
 }
 
-/* Atomically sets the bit numbered IDX in B to true. */
+/* Atomically sets the bit numbered BIT_IDX in B to true. */
 void
-bitmap_mark (struct bitmap *b, size_t idx) 
+bitmap_mark (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);
+
+  /* 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 false. */
+/* Atomically sets the bit numbered BIT_IDX in B to false. */
 void
-bitmap_reset (struct bitmap *b, size_t idx) 
+bitmap_reset (struct bitmap *b, size_t bit_idx) 
 {
-  asm ("andl %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 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. */
@@ -187,19 +196,19 @@ bitmap_test (const struct bitmap *b, size_t idx)
   return (b->bits[elem_idx (idx)] & bit_mask (idx)) != 0;
 }
 
-/* Returns true if any bit from START to END, exclusive, is set
+/* Returns true if any of the CNT bits starting at START is set
    to VALUE. */
 static bool
-contains (const struct bitmap *b, size_t start, size_t end, bool value) 
+contains (const struct bitmap *b, size_t start, size_t cnt, bool value) 
 {
-  size_t idx;
+  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);
 
-  for (idx = start; idx < end; idx++)
-    if (bitmap_test (b, idx) == value)
+  for (i = 0; i < cnt; i++)
+    if (bitmap_test (b, start + i) == value)
       return true;
   return false;
 }
@@ -211,15 +220,17 @@ contains (const struct bitmap *b, size_t start, size_t end, bool value)
 size_t
 bitmap_scan (const struct bitmap *b, size_t start, size_t cnt, bool value) 
 {
-  size_t idx, last;
-  
   ASSERT (b != NULL);
   ASSERT (start <= 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;
+  if (cnt <= b->bit_cnt) 
+    {
+      size_t last = b->bit_cnt - cnt;
+      size_t i;
+      for (i = start; i <= last; i++)
+        if (!contains (b, i, cnt, !value))
+          return i; 
+    }
   return BITMAP_ERROR;
 }
 
@@ -235,49 +246,50 @@ bitmap_scan_and_flip (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);
+    bitmap_set_multiple (b, idx, cnt, !value);
   return idx;
 }
 
-/* Returns the number of bits in B between START and END,
+/* Returns the number of bits in B between START and START + CNT,
    exclusive, that are set to VALUE. */
 size_t
-bitmap_count (const struct bitmap *b, size_t start, size_t end, bool value) 
+bitmap_count (const struct bitmap *b, size_t start, size_t cnt, bool value) 
 {
-  size_t idx, cnt;
+  size_t i, value_cnt;
 
   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;
+  value_cnt = 0;
+  for (i = 0; i < cnt; i++)
+    if (bitmap_test (b, start + i) == value)
+      value_cnt++;
+  return value_cnt;
 }
 
-/* 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 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 !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 !contains (b, start, end, false);
+  return !contains (b, start, cnt, false);
 }
 
 #ifdef FILESYS
@@ -285,7 +297,7 @@ bitmap_all (const struct bitmap *b, size_t start, size_t end)
 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. */
@@ -294,8 +306,8 @@ bitmap_read (struct bitmap *b, struct file *file)
 {
   if (b->bit_cnt > 0) 
     {
-      file_read_at (file, b->bits, byte_cnt (b), 0);
-      b->bits[elem_cnt (b) - 1] &= last_mask (b);
+      file_read_at (file, b->bits, byte_cnt (b->bit_cnt), 0);
+      b->bits[elem_cnt (b->bit_cnt) - 1] &= last_mask (b);
     }
 }
 
@@ -303,7 +315,7 @@ bitmap_read (struct bitmap *b, struct file *file)
 void
 bitmap_write (const struct bitmap *b, struct file *file)
 {
-  file_write_at (file, b->bits, byte_cnt (b), 0);
+  file_write_at (file, b->bits, byte_cnt (b->bit_cnt), 0);
 }
 #endif /* FILESYS */
 
@@ -311,7 +323,7 @@ bitmap_write (const struct bitmap *b, struct file *file)
 void
 bitmap_dump (const struct bitmap *b) 
 {
-  hex_dump (0, b->bits, byte_cnt (b), false);
+  hex_dump (0, b->bits, byte_cnt (b->bit_cnt), false);
 }
 
 /* Returns the number of bytes required to accomodate a bitmap
@@ -319,9 +331,7 @@ bitmap_dump (const struct bitmap *b)
 size_t
 bitmap_needed_bytes (size_t bit_cnt) 
 {
-  struct bitmap b;
-  b.bit_cnt = bit_cnt;
-  return byte_cnt (&b) + sizeof b;
+  return sizeof (struct bitmap) + byte_cnt (bit_cnt);
 }
 
 /* Creates and returns a bitmap with BIT_CNT bits in the