Variable block descriptor size in bitmap_alloc

.gitignore

@@ -17,3 +17,4 @@ autom4te.cache
 include/config.h*
 missing
 stamp-h1
+tests/test_bitmapalloc

include/libmalloc/bitmap_alloc.h

@@ -8,7 +8,7 @@
  * @brief 
  * 
  */
-typedef struct
+typedef struct bitmap_heap_descriptor_t
 {
     /**
      * @brief The underlying bitmap representing the availability of chunks of
@@ -60,6 +60,42 @@ typedef struct
      */
     unsigned long free_block_count;
 
+    /**
+     * @brief Bitmask used to isolate only those bits which indicate the
+     * availability of a block. Useful when several bits are used to represent
+     * the state of a single block. See `block_bits`.
+     * 
+     */
+    unsigned long mask;
+
+    /**
+     * @brief The number of bits required to represent the state of each block.
+     * 
+     * If the value is greater than 1, the most significant bit describing each 
+     * block shall indicate its availability. Less significant bits shall 
+     * represent other aspects of the block's state. The number of trailing 
+     * zeroes in `mask` shall be used to calculate this quantity.
+     * 
+     * This qualtity is assumed to be a power of 2, and less than or equal to
+     * the number of bits in an unsigned long. Therefore, acceptable values for
+     * this quantity are as follows: 1, 2, 4, 8, 16, 32[, 64].
+     * 
+     */
+    unsigned long block_bits;
+
+    /**
+     * @brief The number of blocks described by a single unsigned long contained
+     * in `bitmap`. Equal to (8 * sizeof(unsigned long)) / block_bits.
+     * 
+     */
+    unsigned long blocks_in_word;
+
+    /**
+     * @brief Memory will be allocated relative to this location.
+     * 
+     */
+    unsigned long offset;
+
 } bitmap_heap_descriptor_t;
 
 /**
@@ -73,7 +109,8 @@ typedef struct
  * @param size 
  * @return unsigned long 
  */
-unsigned long reserve_region(bitmap_heap_descriptor_t *heap, unsigned long size);
+unsigned long reserve_region(bitmap_heap_descriptor_t *heap, 
+    unsigned long size);
 
 /**
  * @brief Marks the region of memory indicated by `location` and `size` as
@@ -97,13 +134,12 @@ void free_region(bitmap_heap_descriptor_t *heap, unsigned long location,
  * @param block_size The minimum unit of allocation
  * @return unsigned long 
  */
-unsigned long bitmap_size(const memory_map_t *map, unsigned long block_size);
+unsigned long bitmap_size(const memory_map_t *map, unsigned long block_size, unsigned long block_bits);
 
 /**
  * @brief Builds the heap's internal structures according to the memory
- * layout provided in `map`. Assumes that the layout in `map` refers to the
+ * layout provided in `map`. All locations in `map` are relative to the `offset`
- * caller's virtual address space, and utilizes some of the memory marked as
+ * field in `heap`.
- * 'available' to store the heap's internal structures.
  * 
  * A callback function `mmap` may be provided, which will be used to map the
  * space required by the heap to store its internal bitmaps. If `mmap` is NULL,
@@ -111,43 +147,34 @@ unsigned long bitmap_size(const memory_map_t *map, unsigned long block_size);
  * 
  * There are several requirements for the initial state of the `heap` structure:
  * 
- * - The `cache` field must be defined, and point to an array of unsigned longs
+ * - The `bitmap` field may point to a pre-allocated region of memory which will
- * of sufficient size.
+ * be used to store the heap's internal bitmap. If this field is NULL, part of
+ * the heap will be used to store the bitmap, and `mmap`, if not NULL, will be
+ * called to map that region of memory.
  * 
- * - The `block_size` field must be set to the desired smallest unit of allocation.
+ * - The `cache` field may point to an array of unsigned longs of sufficient 
- * 
+ * size, which will be used to speed up memory allocation. If this field is
- * @param heap A pointer to the structure describing the heap
+ * NULL, caching will not be performed.
- * @param map A pointer to the structure providing an initial memory layout
- * @param mmap A callback function used to map memory in the virtual address space
- * @return int 
- */
-int initialize_virtual_heap(bitmap_heap_descriptor_t *heap, const memory_map_t *map, 
-    int (*mmap)(void *location, unsigned long size));
-
-/**
- * @brief Builds the heap's internal structures according to the memory
- * layout provided in `map`. Assumes that physical memory space is being alocated,
- * and therefore does not make assumptions about the caller's address space or
- * attempt to utilize the memory inside the heap. The caller is responsible for
- * providing space to store the heap's internal structures.
- * 
- * There are several requirements for the initial state of the `heap` structure:
- * 
- * - The `bitmap` field must be defined, and sufficient memory reserved at that
- * location to contain the heap's bitmap.
- * 
- * - The `cache` field must be defined, and point to an array of unsigned longs
- * of sufficient size.
  * 
  * - The `cache_capacity` field must be set to the size of the array pointed to
- * by `cache`
+ * by `cache`.
  * 
- * - The `block_size` field must be set to the desired smallest unit of allocation.
+ * - The `block_size` field must be set to the desired smallest unit of 
+ * allocation.
+ * 
+ * - The `block_bits` field must be set to the number of bits required to store
+ * a block's metadata.
+ * 
+ * - The `offset` field must be set to the first location to allocate memory
+ * from. Locations in `map` will be interpreted as relative to `offset`.
  * 
  * @param heap A pointer to the structure describing the heap
  * @param map A pointer to the structure providing an initial memory layout
- * @return int 0 upon success; nonzero upon failure
+ * @param mmap A callback function used to map memory in the virtual address 
+ * space
+ * @return int 0 upon success, nonzero upon failure.
  */
-int initialize_physical_heap(bitmap_heap_descriptor_t *heap, const memory_map_t *map);
+int initialize_heap(bitmap_heap_descriptor_t *heap, memory_map_t *map, 
+    int (*mmap)(void *location, unsigned long size));
 
 #endif

include/libmalloc/common.h

@@ -8,6 +8,6 @@
  * NOMEM shall be returned by any malloc-like function upon failure, rather than
  * NULL.
  */
-#define NOMEM ~0
+#define NOMEM ((unsigned long)~0)
 
 #endif

src/bitmap_alloc.c

@@ -2,17 +2,19 @@
 #include "libmalloc/common.h"
 #include "util.h"
 
-/*
+static const int BIT_AVAIL = 0;
- * The number of bits contained in a single integer inside the heap's bitmap.
+static const int BIT_USED = 1;
- * Should be either 32 or 64 depending on the host machine.
- */
-static const int bitmap_word_size = 8 * sizeof(unsigned long);
 
 /*
  * Sets all elements in the cache's underlying array to 0.
  */
 static inline void clear_cache(bitmap_heap_descriptor_t *heap)
 {
+    if(heap->cache == (unsigned long*)0)
+    {
+        return;
+    }
+
     for(int i = 0; i < heap->cache_capacity; i++)
     {
         heap->cache[i] = 0;
@@ -34,22 +36,48 @@ static inline void clear_bitmap(bitmap_heap_descriptor_t *heap)
  * Sets bit `index` in the heap's bitmap, marking the underlying block as
  * available.
  */
-static inline void set_bit(bitmap_heap_descriptor_t *heap, int index)
+static inline void set_bit(bitmap_heap_descriptor_t *heap, int index, int bit)
 {
-    int bitmap_index = index / bitmap_word_size;
+    if(bit < heap->block_bits)
-    int bitmap_offset = index % bitmap_word_size;
+    {
-    heap->bitmap[bitmap_index] |= (unsigned long)1 << bitmap_offset;
+        int bitmap_index = index / heap->blocks_in_word;
+        int bitmap_offset = index % heap->blocks_in_word;
+        unsigned long mask = (unsigned long)1 << (heap->block_bits * (bitmap_offset + 1) - 1 - bit);
+        heap->bitmap[bitmap_index] |= mask;
+    }
 }
 
 /*
  * Clears bit `index` in the heap's bitmap, marking the underlying block as
  * reserved.
  */
-static inline void clear_bit(bitmap_heap_descriptor_t *heap, int index)
+static inline void clear_bit(bitmap_heap_descriptor_t *heap, int index, int bit)
 {
-    int bitmap_index = index / bitmap_word_size;
+    if(bit < heap->block_bits)
-    int bitmap_offset = index % bitmap_word_size;
+    {
-    heap->bitmap[bitmap_index] &= ~((unsigned long)1 << bitmap_offset);
+        int bitmap_index = index / heap->blocks_in_word;
+        int bitmap_offset = index % heap->blocks_in_word;
+        unsigned long mask = ~((unsigned long)1 
+            << (heap->block_bits * (bitmap_offset + 1) - 1 - bit));
+        heap->bitmap[bitmap_index] &= mask;
+    }
+}
+
+/*
+ * Tests whether the block at bit `index` is available. If so, returns nonzero,
+ * else returns 0.
+ */
+static inline int test_bit(bitmap_heap_descriptor_t *heap, int index, int bit)
+{
+    if(bit > (heap->block_bits - 1))
+    {
+        return 1;
+    }
+    unsigned long mask = ((unsigned long)1 
+            << (heap->block_bits * ((index % heap->blocks_in_word) + 1) 
+                - 1 
+                - bit));
+    return (heap->bitmap[index / heap->blocks_in_word] & mask) != 0;
 }
 
 /*
@@ -57,33 +85,57 @@ static inline void clear_bit(bitmap_heap_descriptor_t *heap, int index)
  * blocks as available. Operation is used while spltting a block to reserve one
  * of its child blocks.
  */
-static inline void set_pair(bitmap_heap_descriptor_t *heap, int index)
+static inline void set_pair(bitmap_heap_descriptor_t *heap, int index, int bit)
 {
-    int bitmap_index = index / bitmap_word_size;
+    if(bit < heap->block_bits)
-    int bitmap_offset = index % bitmap_word_size;
+    {
-    heap->bitmap[bitmap_index] |= (unsigned long)1 << bitmap_offset;
+        int bitmap_index = index / heap->blocks_in_word;
-    heap->bitmap[bitmap_index] |= (unsigned long)1 << (bitmap_offset ^ 1);
+        int bitmap_offset = index % heap->blocks_in_word;
+
+        unsigned long mask_a = (unsigned long)1 << (heap->block_bits * (bitmap_offset + 1) - 1 - bit);
+        unsigned long mask_b = (unsigned long)1 << (heap->block_bits * ((bitmap_offset ^ 1) + 1) - 1 - bit);
+
+        heap->bitmap[bitmap_index] |= mask_a;
+        heap->bitmap[bitmap_index] |= mask_b;
+    } 
 }
 
 /*
  * Clears bit `index` and its buddy in the heap's bitmap, marking the underlying
- * blocks as reserved. Used when merging two child blocks into a single parent block.
+ * blocks as reserved. Used when merging two child blocks into a single parent 
+ * block.
  */
-static inline void clear_pair(bitmap_heap_descriptor_t *heap, int index)
+static inline void clear_pair(bitmap_heap_descriptor_t *heap, int index, int bit)
 {
-    int bitmap_index = index / bitmap_word_size;
+    if(bit < heap->block_bits)
-    int bitmap_offset = index % bitmap_word_size;
+    {
-    heap->bitmap[bitmap_index] &= ~((unsigned long)1 << bitmap_offset);
+        int bitmap_index = index / heap->blocks_in_word;
-    heap->bitmap[bitmap_index] &= ~((unsigned long)1 << (bitmap_offset ^ 1));
+        int bitmap_offset = index % heap->blocks_in_word;
+
+        unsigned long mask_a = ~((unsigned long)1 << (heap->block_bits * (bitmap_offset + 1) - 1 - bit));
+        unsigned long mask_b = ~((unsigned long)1 << (heap->block_bits * ((bitmap_offset ^ 1) + 1) - 1 - bit));
+
+        heap->bitmap[bitmap_index] &= mask_a;
+        heap->bitmap[bitmap_index] &= mask_b;
+    }
 }
 
 /*
  * Computes the location in the cache that `index` would be stored at, if it
  * were cached.
  */
-static inline int cache_location_from_index(int index)
+static inline int cache_location_from_index(bitmap_heap_descriptor_t *heap, int index)
 {
-    return llog2(index + 1) - llog2(bitmap_word_size) - 1;
+    return llog2(index + 1) - llog2(heap->blocks_in_word) - 1;
+}
+
+/*
+ * Computes the location in the cache that blocks at the indicated height are
+ * cached at.
+ */
+static inline int cache_location_from_height(bitmap_heap_descriptor_t *heap, int height)
+{
+    return heap->height - height - llog2(heap->blocks_in_word);
 }
 
 /*
@@ -92,10 +144,18 @@ static inline int cache_location_from_index(int index)
  */
 static inline int check_cache(bitmap_heap_descriptor_t *heap, int height)
 {
-    unsigned long n = heap->cache[heap->height - height - llog2(bitmap_word_size)];
+    if(heap->cache != (unsigned long*)0)
-    heap->cache[heap->height - height - llog2(bitmap_word_size)] = 0;
+    {
+        int loc = cache_location_from_height(heap, height);
+        unsigned long n = heap->cache[loc];
+        heap->cache[loc] = 0;
         return n;
     }
+    else
+    {
+        return 0;
+    }
+}
 
 /*
  * If space in the cache exists, stores the provided index at the appropriate
@@ -103,12 +163,19 @@ static inline int check_cache(bitmap_heap_descriptor_t *heap, int height)
  */
 static inline void store_cache(bitmap_heap_descriptor_t *heap, int index)
 {
-    int level = cache_location_from_index(index);
+    if(heap->cache != (unsigned long*)0)
+    {
+        int level = cache_location_from_index(heap, index);
         if(level >= 0 && heap->cache[level] == 0)
         {
             heap->cache[level] = index;
         }
     }
+    else
+    {
+        return 0;
+    }
+}
 
 /*
  * If `index` is stored in the cache, remove it. Otherwise, leave the cache
@@ -116,12 +183,19 @@ static inline void store_cache(bitmap_heap_descriptor_t *heap, int index)
  */
 static inline void uncache(bitmap_heap_descriptor_t *heap, int index)
 {
-    int level = cache_location_from_index(index);
+    if(heap->cache != (unsigned long*)0)
+    {
+        int level = cache_location_from_index(heap, index);
         if(level >= 0 && heap->cache[level] == index)
         {
             heap->cache[level] = 0;
         }
     }
+    else
+    {
+        return 0;
+    }
+}
 
 /*
  * Marks the indicated block as unavailable, and marks its children as both
@@ -133,9 +207,9 @@ static inline int split_block(bitmap_heap_descriptor_t *heap, int index)
 {
     if(index)
     {
-        clear_bit(heap, index);
+        clear_bit(heap, index, BIT_AVAIL);
         index *= 2;
-        set_pair(heap, index);
+        set_pair(heap, index, BIT_AVAIL);
         store_cache(heap, index + 1);
     }
     return index;
@@ -152,12 +226,12 @@ static inline int split_block(bitmap_heap_descriptor_t *heap, int index)
  */
 static int merge_block(bitmap_heap_descriptor_t *heap, int index)
 {
-    while(index > 1 && (heap->bitmap[index / bitmap_word_size] & ((unsigned long)1 << ((index % bitmap_word_size) ^ 1))))
+    while(index > 1 && test_bit(heap, index ^ 1, BIT_AVAIL))
     {
         uncache(heap, index ^ 1);
-        clear_pair(heap, index);
+        clear_pair(heap, index, BIT_AVAIL);
         index /= 2;
-        set_bit(heap, index);
+        set_bit(heap, index, BIT_AVAIL);
     }
     return index;
 }
@@ -174,20 +248,21 @@ static int find_free_region(bitmap_heap_descriptor_t *heap, int height)
     {
         return 0;
     }
-    else if (height <= heap->height - ilog2(bitmap_word_size))
+    else if (height <= heap->height - ilog2(heap->blocks_in_word))
     {
         unsigned long cached_index = check_cache(heap, height);
         if(cached_index)
         {
             return cached_index;
         }
-        unsigned long start = (1 << (heap->height - height)) / bitmap_word_size;
+        unsigned long start = (1 << (heap->height - height)) / heap->blocks_in_word;
-        unsigned long end = ((1 << (heap->height - height + 1)) / bitmap_word_size);
+        unsigned long end = ((1 << (heap->height - height + 1)) / heap->blocks_in_word);
         for (int index = start; index < end; index++)
         {
-            if (heap->bitmap[index] != 0)
+            unsigned long avail_mask = heap->bitmap[index] & heap->mask;
+            if (avail_mask != 0)
             {
-                return bitmap_word_size * index + __builtin_ctzl(heap->bitmap[index]);
+                return heap->blocks_in_word * index + (__builtin_ctzl(avail_mask) / heap->block_bits);
             }
         }
     }
@@ -198,25 +273,144 @@ static int find_free_region(bitmap_heap_descriptor_t *heap, int height)
 #else
         static const unsigned long bitmasks[] = {0x00000002, 0x0000000C, 0x000000F0, 0x0000FF00, 0xFFFF0000};
 #endif
-        int depth = heap->height - height;
+        int bitmask_index = heap->height - height + llog2(heap->block_bits);
-        if (heap->bitmap[0] & bitmasks[depth])
+        if (heap->bitmap[0] & bitmasks[bitmask_index] & heap->mask)
         {
-            return __builtin_ctzl(heap->bitmap[0] & bitmasks[depth]);
+            return __builtin_ctzl(heap->bitmap[0] & bitmasks[bitmask_index] & heap->mask) / heap->block_bits;
         }
     }
     return split_block(heap, find_free_region(heap, height + 1));
 }
 
+static unsigned long compute_memory_size(const memory_map_t *map)
+{
+    // Find the last available region in the memory map.
+    int map_index = map->size - 1;
+    while(map->array[map_index].type != M_AVAILABLE)
+    {
+        map_index--;
+    }
+
+    return map->array[map_index].location + map->array[map_index].size;
+}
+
+static unsigned long generate_mask(unsigned long block_bits)
+{
+    unsigned long blocks_in_word = 8 * sizeof(unsigned long) / block_bits;
+    unsigned long mask = 0;
+    for(unsigned long i = 1; i <= blocks_in_word; i++)
+    {
+        mask |= 1UL << (i * block_bits - 1UL);
+    }
+    return mask;
+}
+
+static int construct_heap_desc(bitmap_heap_descriptor_t *heap, const memory_map_t *map)
+{
+    if(heap->block_bits == 0 || heap->block_bits > (8 * sizeof(*heap->bitmap)))
+    {
+        return -1;
+    }
+    else if(heap->block_size == 0)
+    {
+        return -1;
+    }
+    else if((1 << llog2(heap->block_bits)) != heap->block_bits)
+    {
+        return -1;
+    }
+
+    unsigned long memory_size = compute_memory_size(map);
+    heap->blocks_in_word = 8 * sizeof(*heap->bitmap) / heap->block_bits;
+    heap->bitmap_size = heap->block_bits * (memory_size / heap->block_size) / 4;
+    heap->bitmap_size = 1 << llog2(heap->bitmap_size);
+    heap->height = llog2(memory_size / heap->block_size);
+    heap->free_block_count = 0;
+    heap->mask = generate_mask(heap->block_bits);
+
+    if(heap->bitmap_size <= sizeof(*heap->bitmap))
+    {
+        return -1;
+    }
+    else if(heap->bitmap_size >= memory_size && heap->bitmap == (unsigned long*)0)
+    {
+        return -1;
+    }
+    return 0;
+}
+
+static void initialize_bitmap(bitmap_heap_descriptor_t *heap, const memory_map_t *map)
+{
+    clear_bitmap(heap);
+    for(int i = 0; i < map->size; i++)
+    {
+        if(map->array[i].type != M_AVAILABLE)
+        {
+            continue;
+        }
+
+        unsigned long location = (map->array[i].location + heap->block_size - 1);// & ~(heap->block_size - 1);
+        location -= location % heap->block_size;
+        unsigned long region_end = map->array[i].location + map->array[i].size;
+
+        while(location + heap->block_size <= region_end)
+        {
+            int bit_offset = (location / heap->block_size) % heap->blocks_in_word;
+            int bitmap_index = ((1UL << (heap->height - 0)) / heap->blocks_in_word) + (location / heap->block_size) / heap->blocks_in_word;
+            unsigned long chunk_size = (heap->blocks_in_word - bit_offset) * heap->block_size;
+            if(bit_offset == 0 && (region_end - location) >= chunk_size)
+            {
+                // Set all bits in the word
+                heap->bitmap[bitmap_index] = heap->mask & ~0;
+                heap->free_block_count += heap->blocks_in_word;
+            }
+            else if(bit_offset == 0)
+            {
+                // Set the first 'count' bits
+                int count = (region_end - location) / heap->block_size;
+                heap->bitmap[bitmap_index] |= heap->mask & ((1UL << (heap->block_bits * count)) - 1);
+                heap->free_block_count += count;
+            }
+            else if((region_end - location) >= chunk_size)
+            {
+                // Set all bits starting at 'bit_offset'
+                heap->bitmap[bitmap_index] |= heap->mask & ~((1UL << (heap->block_bits * bit_offset)) - 1);
+                heap->free_block_count += heap->blocks_in_word - bit_offset;
+            }
+            else
+            {
+                // Set all bits starting at 'bit_offset' up to 'count'
+                int count = (region_end - location) / heap->block_size;
+                heap->bitmap[bitmap_index] |= heap->mask & ((1UL << (heap->block_bits * count)) - 1) & ~((1UL << (heap->block_bits * bit_offset)) - 1);
+                heap->free_block_count += count - bit_offset;
+            }
+
+            // Merge 'buddies' when both available
+            unsigned long mask = ((1UL << (2 * heap->block_bits)) - 1) & heap->mask;
+            for(int j = 0; j < heap->blocks_in_word / 2; j++)
+            {
+                if((heap->bitmap[bitmap_index] & mask) == mask)
+                {
+                    merge_block(heap, bitmap_index * heap->blocks_in_word + j * 2);
+                }
+                mask <<= 2 * heap->block_bits;
+            }
+            
+            location += chunk_size;
+        }
+    }
+}
 
 unsigned long reserve_region(bitmap_heap_descriptor_t *heap, unsigned long size)
 {
-    int height = llog2(size / heap->block_size);
+    int height = llog2((size - 1) / heap->block_size + 1);
     int index = find_free_region(heap, height);
     if(index)
     {
-        clear_bit(heap, index);
+        clear_bit(heap, index, BIT_AVAIL);
+        set_bit(heap, index, BIT_USED);
         heap->free_block_count -= 1 << height;
-        return (heap->block_size << height) * (index - ((unsigned long)1 << (heap->height - height)));
+        return heap->offset + (heap->block_size << height) * (index - ((unsigned long)1 << (heap->height - height)));
     }
     else
     {
@@ -226,107 +420,54 @@ unsigned long reserve_region(bitmap_heap_descriptor_t *heap, unsigned long size)
 
 void free_region(bitmap_heap_descriptor_t *heap, unsigned long location, unsigned long size)
 {
+    location -= heap->offset;
     int height = llog2(size / heap->block_size);
     int index = (location / (heap->block_size * ((unsigned long)1 << height))) + (1 << (heap->height - height));
-    set_bit(heap, index);
+    while(!test_bit(heap, index, BIT_USED))
+    {
+        height++;
+        index /= 2;
+    }
+    set_bit(heap, index, BIT_AVAIL);
+    clear_bit(heap, index, BIT_USED);
     index = merge_block(heap, index);
     store_cache(heap, index);
     heap->free_block_count += 1 << height;
 }
 
-unsigned long bitmap_size(const memory_map_t *map, unsigned long block_size)
+unsigned long bitmap_size(const memory_map_t *map, unsigned long block_size, unsigned long block_bits)
 {
-    // Find the last available region in the memory map.
+    return 1UL << llog2((block_bits * compute_memory_size(map) / block_size) / 4);
-    int map_index = map->size - 1;
-    while(map->array[map_index].type != M_AVAILABLE)
-    {
-        map_index--;
 }
 
-    // Take memory_size to be the last available location in the memory map.
+int initialize_heap(bitmap_heap_descriptor_t *heap, memory_map_t *map, int (*mmap)(void *location, unsigned long size))
-    // Round memory_size up to nearest power of 2
+{
-    unsigned long memory_size = 1 << llog2(map->array[map_index].location + map->array[map_index].size);
+    if(construct_heap_desc(heap, map))
-    return (memory_size / block_size) / 4;
-}
-
-int initialize_virtual_heap(bitmap_heap_descriptor_t *heap, const memory_map_t *map, int (*mmap)(void *location, unsigned long size))
     {
-    /* Not yet implemented */
         return -1;
     }
 
-int initialize_physical_heap(bitmap_heap_descriptor_t *heap, const memory_map_t *map)
+    if(heap->bitmap == (unsigned long*)0)
     {
-    // Find the last available region in the memory map.
+        int map_index = 0;
-    int map_index = map->size - 1;
+        while(map->array[map_index].size < heap->bitmap_size)
-    while(map->array[map_index].type != M_AVAILABLE)
         {
-        map_index--;
+            map_index++;
+            if(map_index >= map->size)
+            {
+                return -1;
+            }
         }
 
-    // Take memory_size to be the last available location in the memory map.
+        heap->bitmap = (unsigned long*)(heap->offset + map->array[map_index].location);
-    // Round memory_size up to nearest power of 2
+        memmap_insert_region(map, map->array[map_index].location, heap->bitmap_size, M_UNAVAILABLE);
-    unsigned long memory_size = 1 << llog2(map->array[map_index].location + map->array[map_index].size);
+        if(mmap && mmap(heap->bitmap, heap->bitmap_size))
-    heap->bitmap_size = (memory_size / heap->block_size) / 4;
-    heap->height = llog2(memory_size / heap->block_size);
-    heap->free_block_count = 0;
-    clear_bitmap(heap);
-    for(int i = 0; i < map->size; i++)
         {
-        if(map->array[i].type != M_AVAILABLE)
+            return -1;
-        {
+        }
-            continue;
     }
     
-        unsigned long location = (map->array[i].location + heap->block_size - 1) & ~(heap->block_size - 1);
+    initialize_bitmap(heap, map);
-        unsigned long region_end = map->array[i].location + map->array[i].size;
-
-        while(location + heap->block_size <= region_end)
-        {
-            int bit_offset = (location / heap->block_size) % bitmap_word_size;
-            int bitmap_index = ((1 << (heap->height - 0)) / bitmap_word_size) + (location / heap->block_size) / bitmap_word_size;
-            unsigned long chunk_size = (bitmap_word_size - bit_offset) * heap->block_size;
-            if(bit_offset == 0 && (region_end - location) >= chunk_size)
-            {
-                // Set all bits in the word
-                heap->bitmap[bitmap_index] = ~0;
-                heap->free_block_count += bitmap_word_size;
-            }
-            else if(bit_offset == 0)
-            {
-                // Set the first 'count' bits
-                int count = (region_end - location) / heap->block_size;
-                heap->bitmap[bitmap_index] |= (1 << count) - 1;
-                heap->free_block_count += count;
-            }
-            else if((region_end - location) >= chunk_size)
-            {
-                // Set all bits starting at 'bit_offset'
-                heap->bitmap[bitmap_index] |= ~((1 << bit_offset) - 1);
-                heap->free_block_count += bitmap_word_size - bit_offset;
-            }
-            else
-            {
-                // Set all bits starting at 'bit_offset' up to 'count'
-                int count = (region_end - location) / heap->block_size;
-                heap->bitmap[bitmap_index] |= ((1 << count) - 1) & ~((1 << bit_offset) - 1);
-                heap->free_block_count += count - bit_offset;
-            }
-
-            // Merge 'buddies' when both available
-            unsigned long mask = 3;
-            for(int j = 0; j < bitmap_word_size / 2; j++)
-            {
-                if((heap->bitmap[bitmap_index] & mask) == mask)
-                {
-                    merge_block(heap, bitmap_index * bitmap_word_size + j * 2);
-                }
-                mask <<= 2;
-            }
-            
-            location += chunk_size;
-        }
-    }
     clear_cache(heap);
     return 0;
 }

tests/Makefile.am

@@ -1,6 +1,6 @@
 if BUILD_TESTS
-    noinst_PROGRAMS = test_buddyalloc
+    noinst_PROGRAMS = test_bitmapalloc
 
-    test_buddyalloc_SOURCES = test_buddyalloc.c
+    test_bitmapalloc_SOURCES = test_bitmapalloc.c
-    test_buddyalloc_LDADD = ../src/libmalloc.a
+    test_bitmapalloc_LDADD = ../src/libmalloc.a
 endif

tests/test_bitmapalloc.c

@@ -0,0 +1,160 @@
+#include "libmalloc/bitmap_alloc.h"
+#include "util.h"
+#include <stdlib.h>
+#include <assert.h>
+#include <stdio.h>
+#include <time.h>
+
+typedef struct memblock_t
+{
+    unsigned long size;
+    unsigned long location;
+} memblock_t;
+
+void print_heap_desc(bitmap_heap_descriptor_t *heap)
+{
+    printf("heap = {\n"
+        "\t.bitmap = %p\n"
+        "\t.bitmap_size = %i\n"
+        "\t.cache = %p\n"
+        "\t.cache_capacity = %i\n"
+        "\t.block_size = %i\n"
+        "\t.height = %i\n"
+        "\t.free_block_count = %i\n"
+        "\t.mask = %lX\n"
+        "\t.block_bits = %i\n"
+        "\t.blocks_in_word = %i\n"
+        "\t.offset = %p\n"
+        "}\n",
+        heap->bitmap, 
+        heap->bitmap_size, 
+        heap->cache, 
+        heap->cache_capacity,
+        heap->block_size,
+        heap->height,
+        heap->free_block_count,
+        heap->mask,
+        heap->block_bits,
+        heap->blocks_in_word,
+        heap->offset);
+}
+
+void print_memory_map(memory_map_t *map)
+{
+    printf("map = {\n"
+        "\t.size = %i\n"
+        "\t.capacity = %i\n"
+        "\t.array = {",
+        map->size,
+        map->capacity);
+    for(int i = 0; i < map->size; i++)
+    {
+        printf("{.type = %i, .location = %lX, .size = %i} ", \
+            map->array[i].type, 
+            map->array[i].location, 
+            map->array[i].size);
+    }
+    printf("}\n}\n");
+}
+
+void test_heap(unsigned long size, unsigned long block_size, unsigned long bits, int result)
+{
+    printf("[TEST] Bitmap allocator: memory=%lX, block_size=%lu, block_bits=%lu\n", size, block_size, bits);
+    const int memory_map_capacity = 32;
+    const int cache_capacity = 20;
+    memory_region_t arr[memory_map_capacity];
+    unsigned long heap_cache[cache_capacity];
+    void *heap_data = malloc(size);
+
+    memory_map_t memory_map = {
+        .array = arr,
+        .capacity = memory_map_capacity,
+        .size = 0
+    };
+
+    bitmap_heap_descriptor_t heap = {
+        .bitmap = NULL,
+        .block_size = block_size,
+        .cache = heap_cache,
+        .cache_capacity = cache_capacity,
+        .block_bits = bits,
+        .offset = (unsigned long)heap_data
+    };
+
+    memmap_insert_region(&memory_map, 0, size, M_AVAILABLE);
+    int status = initialize_heap(&heap, &memory_map, NULL);
+    assert(!(!status != !result));
+    if(status)
+    {
+        return;
+    }
+
+    print_heap_desc(&heap);
+    print_memory_map(&memory_map);
+
+    unsigned long total_blocks = heap.free_block_count;
+
+    memblock_t *reserved_blocks = malloc(sizeof(memblock_t) * size / heap.block_size);
+    unsigned long count = 0;
+    while(1)
+    {
+        memblock_t next_block;
+        next_block.size = heap.block_size * (rand() % 8 + 1);
+        next_block.location = reserve_region(&heap, next_block.size);
+        if(next_block.location != NOMEM)
+        {
+            char *s = (char*)next_block.location;
+            for(int i = 0; i < next_block.size; i++)
+            {
+                s[i] = (char)rand();
+            }
+            reserved_blocks[count] = next_block;
+            count++;
+        }
+        else
+        {
+            printf("\tOut of memory: %i free blocks left, %i total blocks, %i allocations. Tried to allocate %i bytes.\n", heap.free_block_count, total_blocks, count, next_block.size);
+            break;
+        }
+    }
+
+    for(int i = 0; i < count; i++)
+    {
+        assert(reserved_blocks[i].location >= heap.offset);
+        assert(reserved_blocks[i].location + reserved_blocks[i].size <= heap.offset + size);
+        for(int j = i + 1; j < count; j++)
+        {
+            assert((reserved_blocks[j].location + reserved_blocks[j].size) <= reserved_blocks[i].location
+                || reserved_blocks[j].location >= (reserved_blocks[i].location + reserved_blocks[i].size));
+        }
+    }
+
+    for(int i = 0; i < count; i++)
+    {
+        free_region(&heap, reserved_blocks[i].location, bits < 2 ? reserved_blocks[i].size : 0);
+    }
+
+    assert(heap.free_block_count == total_blocks);
+    free(reserved_blocks);
+    free(heap_data);
+}
+
+int main(int argc, char **args)
+{
+    srand(time(0));
+    test_heap(32, 1, 1, 1);
+    test_heap(256, 0, 1, 1);
+    test_heap(256, 1, 0, 1);
+    test_heap(256, 1, 3, 1);
+    test_heap(256, 1, 128, 1);
+    test_heap(256, 1, 4, 1);
+
+    for(int bs = 1; bs <= 32; bs++)
+    {
+        unsigned long n = (8 * sizeof(unsigned long)) - 1 - __builtin_clzl((unsigned long) bs);
+        for(int bits = 1; bits <= (8 * sizeof(unsigned long)) && (2 * bits) < (8 * (1 << n)); bits <<= 1)
+        {
+            test_heap(1024, bs, bits, 0);
+        }
+    }
+}

tests/test_buddyalloc.c

@@ -1,51 +0,0 @@
-#include "libmalloc/bitmap_alloc.h"
-#include "util.h"
-#include <stdlib.h>
-#include <assert.h>
-#include <stdio.h>
-
-int main(int argc, char **args)
-{
-    const int memory_map_capacity = 32;
-    const int heap_size = 1 << 20;
-    const int cache_capacity = 20;
-    memory_region_t arr[memory_map_capacity];
-    unsigned long heap_cache[cache_capacity];
-
-    memory_map_t memory_map = {
-        .array = arr,
-        .capacity = memory_map_capacity,
-        .size = 0
-    };
-
-    bitmap_heap_descriptor_t heap = {
-        .bitmap = malloc(heap_size / 4),
-        .block_size = 1,
-        .cache = heap_cache,
-        .cache_capacity = cache_capacity
-    };
-
-    memmap_insert_region(&memory_map, 0, heap_size, M_AVAILABLE);
-    initialize_physical_heap(&heap, &memory_map);
-
-    unsigned long *reserved_blocks = malloc(sizeof(unsigned long) * heap_size);
-    for(int i = 0; i < heap_size; i++)
-    {
-        reserved_blocks[i] = reserve_region(&heap, 1);
-    }
-
-    /*for(int i = 0; i < heap_size; i++)
-    {
-        for(int j = i + 1; j < heap_size; j++)
-        {
-            assert(reserved_blocks[i] != reserved_blocks[j]);
-        }
-    }*/
-
-    for(int i = 0; i < heap_size; i++)
-    {
-        free_region(&heap, reserved_blocks[i], 1);
-    }
-
-    assert(heap.free_block_count == heap_size);
-}