Changes in kernel/generic/src/adt/bitmap.c [9d58539:d5f774f6] in mainline

File:

• kernel/generic/src/adt/bitmap.c (modified) (4 diffs)

kernel/generic/src/adt/bitmap.c

@@ -35 +35 @@
  *
  * This file implements bitmap ADT and provides functions for
- * setting and clearing ranges of bits.
+ * setting and clearing ranges of bits and for finding ranges
+ * of unset bits.
+ *
+ * The bitmap ADT can optionally implement a two-level hierarchy
+ * for faster range searches. The second level bitmap (of blocks)
+ * is not precise, but conservative. This means that if the block
+ * bit is set, it guarantees that all bits in the block are set.
+ * But if the block bit is unset, nothing can be said about the
+ * bits in the block.
+ *
  */
 
@@ -44 +53 @@
 #include <macros.h>
 
-#define ALL_ONES        0xff
-#define ALL_ZEROES      0x00
+#define ALL_ONES    0xff
+#define ALL_ZEROES  0x00
+
+/** Get bitmap size
+ *
+ * Return the size (in bytes) required for the bitmap.
+ *
+ * @param elements   Number bits stored in bitmap.
+ * @param block_size Block size of the 2nd level bitmap.
+ *                   If set to zero, no 2nd level is used.
+ *
+ * @return Size (in bytes) required for the bitmap.
+ *
+ */
+size_t bitmap_size(size_t elements, size_t block_size)
+{
+        size_t size = elements / BITMAP_ELEMENT;
+        
+        if ((elements % BITMAP_ELEMENT) != 0)
+                size++;
+        
+        if (block_size > 0) {
+                size += elements / block_size;
+                
+                if ((elements % block_size) != 0)
+                        size++;
+        }
+        
+        return size;
+}
 
 /** Initialize bitmap.
@@ -51 +88 @@
  * No portion of the bitmap is set or cleared by this function.
  *
- * @param bitmap        Bitmap structure.
- * @param map           Address of the memory used to hold the map.
- * @param bits          Number of bits stored in bitmap.
- */
-void bitmap_initialize(bitmap_t *bitmap, uint8_t *map, size_t bits)
-{
-        bitmap->map = map;
-        bitmap->bits = bits;
-}
-
-/** Set range of bits.
- *
- * @param bitmap        Bitmap structure.
- * @param start         Starting bit.
- * @param bits          Number of bits to set.
- */
-void bitmap_set_range(bitmap_t *bitmap, size_t start, size_t bits)
-{
-        size_t i = 0;
-        size_t aligned_start;
-        size_t lub;     /* leading unaligned bits */
-        size_t amb;     /* aligned middle bits */
-        size_t tab;     /* trailing aligned bits */
-        
-        ASSERT(start + bits <= bitmap->bits);
-        
-        aligned_start = ALIGN_UP(start, 8);
-        lub = min(aligned_start - start, bits);
-        amb = bits > lub ? bits - lub : 0;
-        tab = amb % 8;
-        
-        if (!bits)
+ * @param bitmap     Bitmap structure.
+ * @param elements   Number of bits stored in bitmap.
+ * @param block_size Block size of the 2nd level bitmap.
+ *                   If set to zero, no 2nd level is used.
+ * @param data       Address of the memory used to hold the map.
+ *                   The optional 2nd level bitmap follows the 1st
+ *                   level bitmap.
+ *
+ */
+void bitmap_initialize(bitmap_t *bitmap, size_t elements, size_t block_size,
+    void *data)
+{
+        bitmap->elements = elements;
+        bitmap->bits = (uint8_t *) data;
+        
+        if (block_size > 0) {
+                bitmap->block_size = block_size;
+                bitmap->blocks = bitmap->bits +
+                    bitmap_size(elements, 0);
+        } else {
+                bitmap->block_size = 0;
+                bitmap->blocks = NULL;
+        }
+}
+
+static void bitmap_set_range_internal(uint8_t *bits, size_t start, size_t count)
+{
+        if (count == 0)
                 return;
-
-        if (start + bits < aligned_start) {
+        
+        size_t aligned_start = ALIGN_UP(start, BITMAP_ELEMENT);
+        
+        /* Leading unaligned bits */
+        size_t lub = min(aligned_start - start, count);
+        
+        /* Aligned middle bits */
+        size_t amb = (count > lub) ? (count - lub) : 0;
+        
+        /* Trailing aligned bits */
+        size_t tab = amb % BITMAP_ELEMENT;
+        
+        if (start + count < aligned_start) {
                 /* Set bits in the middle of byte. */
-                bitmap->map[start / 8] |= ((1 << lub) - 1) << (start & 7);
+                bits[start / BITMAP_ELEMENT] |=
+                    ((1 << lub) - 1) << (start & BITMAP_REMAINER);
                 return;
         }
@@ -93 +138 @@
         if (lub) {
                 /* Make sure to set any leading unaligned bits. */
-                bitmap->map[start / 8] |= ~((1 << (8 - lub)) - 1);
-        }
-        for (i = 0; i < amb / 8; i++) {
+                bits[start / BITMAP_ELEMENT] |=
+                    ~((1 << (BITMAP_ELEMENT - lub)) - 1);
+        }
+        
+        size_t i;
+        
+        for (i = 0; i < amb / BITMAP_ELEMENT; i++) {
                 /* The middle bits can be set byte by byte. */
-                bitmap->map[aligned_start / 8 + i] = ALL_ONES;
-        }
+                bits[aligned_start / BITMAP_ELEMENT + i] = ALL_ONES;
+        }
+        
         if (tab) {
                 /* Make sure to set any trailing aligned bits. */
-                bitmap->map[aligned_start / 8 + i] |= (1 << tab) - 1;
-        }
-        
-}
-
-/** Clear range of bits.
- *
- * @param bitmap        Bitmap structure.
- * @param start         Starting bit.
- * @param bits          Number of bits to clear.
- */
-void bitmap_clear_range(bitmap_t *bitmap, size_t start, size_t bits)
-{
-        size_t i = 0;
-        size_t aligned_start;
-        size_t lub;     /* leading unaligned bits */
-        size_t amb;     /* aligned middle bits */
-        size_t tab;     /* trailing aligned bits */
-        
-        ASSERT(start + bits <= bitmap->bits);
-        
-        aligned_start = ALIGN_UP(start, 8);
-        lub = min(aligned_start - start, bits);
-        amb = bits > lub ? bits - lub : 0;
-        tab = amb % 8;
-
-        if (!bits)
+                bits[aligned_start / BITMAP_ELEMENT + i] |= (1 << tab) - 1;
+        }
+}
+
+/** Set range of bits.
+ *
+ * @param bitmap Bitmap structure.
+ * @param start  Starting bit.
+ * @param count  Number of bits to set.
+ *
+ */
+void bitmap_set_range(bitmap_t *bitmap, size_t start, size_t count)
+{
+        ASSERT(start + count <= bitmap->elements);
+        
+        bitmap_set_range_internal(bitmap->bits, start, count);
+        
+        if (bitmap->block_size > 0) {
+                size_t aligned_start = ALIGN_UP(start, bitmap->block_size);
+                
+                /* Leading unaligned bits */
+                size_t lub = min(aligned_start - start, count);
+                
+                /* Aligned middle bits */
+                size_t amb = (count > lub) ? (count - lub) : 0;
+                
+                size_t aligned_size = amb / bitmap->block_size;
+                
+                bitmap_set_range_internal(bitmap->blocks, aligned_start,
+                    aligned_size);
+        }
+}
+
+static void bitmap_clear_range_internal(uint8_t *bits, size_t start,
+    size_t count)
+{
+        if (count == 0)
                 return;
-
-        if (start + bits < aligned_start) {
+        
+        size_t aligned_start = ALIGN_UP(start, BITMAP_ELEMENT);
+        
+        /* Leading unaligned bits */
+        size_t lub = min(aligned_start - start, count);
+        
+        /* Aligned middle bits */
+        size_t amb = (count > lub) ? (count - lub) : 0;
+        
+        /* Trailing aligned bits */
+        size_t tab = amb % BITMAP_ELEMENT;
+        
+        if (start + count < aligned_start) {
                 /* Set bits in the middle of byte */
-                bitmap->map[start / 8] &= ~(((1 << lub) - 1) << (start & 7));
+                bits[start / BITMAP_ELEMENT] &=
+                    ~(((1 << lub) - 1) << (start & BITMAP_REMAINER));
                 return;
         }
-
+        
         if (lub) {
                 /* Make sure to clear any leading unaligned bits. */
-                bitmap->map[start / 8] &= (1 << (8 - lub)) - 1;
-        }
-        for (i = 0; i < amb / 8; i++) {
+                bits[start / BITMAP_ELEMENT] &=
+                    (1 << (BITMAP_ELEMENT - lub)) - 1;
+        }
+        
+        size_t i;
+        
+        for (i = 0; i < amb / BITMAP_ELEMENT; i++) {
                 /* The middle bits can be cleared byte by byte. */
-                bitmap->map[aligned_start / 8 + i] = ALL_ZEROES;
-        }
+                bits[aligned_start / BITMAP_ELEMENT + i] = ALL_ZEROES;
+        }
+        
         if (tab) {
                 /* Make sure to clear any trailing aligned bits. */
-                bitmap->map[aligned_start / 8 + i] &= ~((1 << tab) - 1);
-        }
-
+                bits[aligned_start / BITMAP_ELEMENT + i] &= ~((1 << tab) - 1);
+        }
+}
+
+/** Clear range of bits.
+ *
+ * @param bitmap Bitmap structure.
+ * @param start  Starting bit.
+ * @param count  Number of bits to clear.
+ *
+ */
+void bitmap_clear_range(bitmap_t *bitmap, size_t start, size_t count)
+{
+        ASSERT(start + count <= bitmap->elements);
+        
+        bitmap_clear_range_internal(bitmap->bits, start, count);
+        
+        if (bitmap->block_size > 0) {
+                size_t aligned_start = start / bitmap->block_size;
+                
+                size_t aligned_end = (start + count) / bitmap->block_size;
+                
+                if (((start + count) % bitmap->block_size) != 0)
+                        aligned_end++;
+                
+                size_t aligned_size = aligned_end - aligned_start;
+                
+                bitmap_clear_range_internal(bitmap->blocks, aligned_start,
+                    aligned_size);
+        }
 }
 
 /** Copy portion of one bitmap into another bitmap.
  *
- * @param dst           Destination bitmap.
- * @param src           Source bitmap.
- * @param bits          Number of bits to copy.
- */
-void bitmap_copy(bitmap_t *dst, bitmap_t *src, size_t bits)
-{
+ * @param dst   Destination bitmap.
+ * @param src   Source bitmap.
+ * @param count Number of bits to copy.
+ *
+ */
+void bitmap_copy(bitmap_t *dst, bitmap_t *src, size_t count)
+{
+        ASSERT(count <= dst->elements);
+        ASSERT(count <= src->elements);
+        
         size_t i;
         
-        ASSERT(bits <= dst->bits);
-        ASSERT(bits <= src->bits);
-        
-        for (i = 0; i < bits / 8; i++)
-                dst->map[i] = src->map[i];
-        
-        if (bits % 8) {
-                bitmap_clear_range(dst, i * 8, bits % 8);
-                dst->map[i] |= src->map[i] & ((1 << (bits % 8)) - 1);
-        }
+        for (i = 0; i < count / BITMAP_ELEMENT; i++)
+                dst->bits[i] = src->bits[i];
+        
+        if (count % BITMAP_ELEMENT) {
+                bitmap_clear_range(dst, i * BITMAP_ELEMENT,
+                    count % BITMAP_ELEMENT);
+                dst->bits[i] |= src->bits[i] &
+                    ((1 << (count % BITMAP_ELEMENT)) - 1);
+        }
+}
+
+static int constraint_satisfy(size_t index, size_t base, size_t constraint)
+{
+        return (((base + index) & constraint) == 0);
+}
+
+/** Find a continuous zero bit range
+ *
+ * Find a continuous zero bit range in the bitmap. The address
+ * computed as the sum of the index of the first zero bit and
+ * the base argument needs to be compliant with the constraint
+ * (those bits that are set in the constraint cannot be set in
+ * the address).
+ *
+ * If the index argument is non-NULL, the continuous zero range
+ * is set and the index of the first bit is stored to index.
+ * Otherwise the bitmap stays untouched.
+ *
+ * @param bitmap     Bitmap structure.
+ * @param count      Number of continuous zero bits to find.
+ * @param base       Address of the first bit in the bitmap.
+ * @param constraint Constraint for the address of the first zero bit.
+ * @param index      Place to store the index of the first zero
+ *                   bit. Can be NULL (in which case the bitmap
+ *                   is not modified).
+ *
+ * @return Non-zero if a continuous range of zero bits satisfying
+ *         the constraint has been found.
+ * @return Zero otherwise.
+ *
+ */
+int bitmap_allocate_range(bitmap_t *bitmap, size_t count, size_t base,
+    size_t constraint, size_t *index)
+{
+        if (count == 0)
+                return false;
+        
+        /*
+         * This is a trivial implementation that should be
+         * optimized further.
+         */
+        
+        for (size_t i = 0; i < bitmap->elements; i++) {
+                if (!constraint_satisfy(i, base, constraint))
+                        continue;
+                
+                if (!bitmap_get(bitmap, i)) {
+                        bool continuous = true;
+                        
+                        for (size_t j = 1; j < count; j++) {
+                                if ((i + j >= bitmap->elements) ||
+                                    (bitmap_get(bitmap, i + j))) {
+                                        continuous = false;
+                                        break;
+                                }
+                        }
+                        
+                        if (continuous) {
+                                if (index != NULL) {
+                                        bitmap_set_range(bitmap, i, count);
+                                        *index = i;
+                                }
+                                
+                                return true;
+                        }
+                }
+                
+        }
+        
+        return false;
+}
+
+/** Clear range of set bits.
+ *
+ * This is essentially bitmap_clear_range(), but it also
+ * checks whether all the cleared bits are actually set.
+ *
+ * @param bitmap Bitmap structure.
+ * @param start  Starting bit.
+ * @param count  Number of bits to clear.
+ *
+ */
+void bitmap_free_range(bitmap_t *bitmap, size_t start, size_t count)
+{
+        /*
+         * This is a trivial implementation that should be
+         * optimized further.
+         */
+        
+        for (size_t i = 0; i < count; i++) {
+                if (!bitmap_get(bitmap, start + i))
+                        panic("Freeing a bitmap range that is not set");
+        }
+        
+        bitmap_clear_range(bitmap, start, count);
 }