git-svn-id: https://profuse.googlecode.com/svn/branches/v2@68 aa027e90-d47c-11dd-86d7-074df07e0730

Bitmap.cpp

@@ -0,0 +1,197 @@
+#include "Bitmap.h"
+#include <cstring>
+
+#include "auto.h"
+
+
+// returns # of 1-bits set (0-8)
+inline static unsigned popCount(uint8_t x)
+{
+    #ifdef __GNUC__
+    return __builtin_popcount(x);
+    #endif
+    
+    // Brian Kernighan / Peter Wegner in CACM 3 (1960), 322.
+    
+    unsigned count;
+    for (count = 0; x; ++count)
+    {
+        x &= x - 1;
+    }
+    return count;
+}
+
+
+
+Bitmap::Bitmap(unsigned blocks)
+{
+    _blocks = _freeBlocks = blocks;
+    
+    _bitmapBlocks = (blocks + 4095) / 4096;
+    _freeIndex = 0;
+    
+    unsigned bitmapSize = _bitmapBlocks * 512;
+    unsigned blockSize = blocks / 8;
+    
+    auto_array bitmap(new uint8_t[bitmapSize]);
+
+    // mark overflow in use, everything else free.
+
+    std::memset(bitmap, 0xff, blocks / 8);
+    std::memset(bitmap + blockSize, 0x00, bitmapSize - blockSize);
+    
+    // edge case
+    unsigned tmp = blocks & 0x07;
+    
+    bitmap[blocks / 8] = ~(0xff >> tmp);
+    
+    _bitmap = bitmap.release();
+    
+    
+}
+
+Bitmap::Bitmap(BlockDevice *device, unsigned keyPointer, unsigned blocks)
+{
+    _blocks = blocks;
+    _freeBlocks = 0;
+    _freeIndex = 0;
+    
+    _bitmapBlocks = (blocks + 4095) / 4096;
+
+    unsigned bitmapSize = _bitmapBlocks * 512;
+    unsigned blockSize = blocks / 8;
+    
+    auto_array bitmap(new uint8_t[bitmapSize]);
+
+    for (unsigned i = 0; i < blockSize; ++i)
+    {
+        device->readBlock(keyPointer + i, bitmap + 512 * i);
+    }
+    
+    // make sure all trailing bits are marked in use.
+
+    // edge case
+    unsigned tmp = blocks & 0x07;
+    
+    bitmap[blocks / 8] &= ~(0xff >> tmp);
+
+    std::memset(bitmap + blockSize, 0x00, bitmapSize - blockSize);
+
+    // set _freeBlocks and _freeIndex;
+    for (unsigned i = 0; i < (blocks + 7) / 8; ++i)
+    {
+        _freeBlocks += popCount(bitmap[i]);
+    } 
+    
+    if (_freeblocks)
+    {
+        for (unsigned i = 0; i < (blocks + 7) / 8; ++i)
+        {
+            if (tmp[i])
+            {
+                _freeIndex = i;
+                break;
+            }
+        }
+    }
+
+    
+    _bitmap = bitmap.release();
+}
+
+Bitmap::~Bitmap()
+{
+    if (_bitmap) delete []_bitmap;
+}
+
+
+void Bitmap::freeBlock(unsigned block)
+{
+    if (block >= _blocks) return;
+    
+    unsigned index = block / 8;
+    unsigned offset = block & 0x07;
+    unsigned mask = 0x80 >> offset;
+    
+    uint8_t tmp = _bitmap[index];
+    
+    if ((tmp & mask) == 0)
+    {
+        ++_freeBlocks;
+        _bitmap[index] = tmp | mask;
+    }
+}
+
+
+int Bitmap::allocBlock(unsigned block)
+{
+    if (block >= _blocks) return -1;
+    
+    
+    unsigned index = block / 8;
+    unsigned offset = block & 0x07;
+    unsigned mask = 0x80 >> offset;
+    
+    uint8_t tmp = _bitmap[index];
+    
+    if ((tmp & mask))
+    {
+        --_freeBlocks;
+        _bitmap[index] = tmp & ~mask;
+        return block;
+    }
+    
+    return -1;
+}
+
+
+int Bitmap::allocBlock()
+{
+    if (!_freeBlocks) return -1;
+    
+    unsigned firstIndex = _firstIndex;
+    unsigned maxIndex = (_blocks + 7) / 8;
+
+
+    for (unsigned index = _firstIndex; index < maxIndex; ++index)
+    {
+        uint8_t tmp = _bitmap[index];
+        if (!tmp) continue;
+        
+        unsigned mask = 0x80;
+        for (unsigned offset = 0; offset < 8; ++offset)
+        {
+            if (tmp & mask)
+            {
+                _firstIndex = index;
+                _bitmap[index] = tmp & ~mask;
+                --_freeBlocks;
+                return index * 8 + offset;
+            }
+            mask = mask >> 1;
+        }
+    }
+
+    for (unsigned index = 0; index < _firstIndex; ++index)
+    {
+        uint8_t tmp = _bitmap[index];
+        if (!tmp) continue;
+        
+        unsigned mask = 0x80;
+        for (unsigned offset = 0; offset < 8; ++offset)
+        {
+            if (tmp & mask)
+            {
+                _firstIndex = index;
+                _bitmap[index] = tmp & ~mask;
+                --_freeBlocks;
+                return index * 8 + offset;
+            }
+            mask = mask >> 1;
+        }
+    }
+
+    
+    // should never happen...
+    return -1;
+}