Threadsafe bitmap class

src/xenia/base/bit_map.cc

@@ -0,0 +1,96 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2015 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/base/bit_map.h"
+
+#include "xenia/base/assert.h"
+#include "xenia/base/atomic.h"
+#include "xenia/base/math.h"
+
+namespace xe {
+
+BitMap::BitMap() = default;
+
+BitMap::BitMap(size_t size) { Resize(size); }
+
+BitMap::BitMap(uint32_t* data, size_t size) {
+  assert_true(size % 4 == 0);
+
+  data_.resize(size / 4);
+  std::memcpy(data_.data(), data, size);
+}
+
+size_t BitMap::Acquire() {
+  for (size_t i = 0; i < data_.size(); i++) {
+    uint32_t entry = 0;
+    uint32_t new_entry = 0;
+    int acquired_idx = -1;
+
+    do {
+      entry = data_[i];
+      uint8_t index = lzcnt(entry);
+      if (index == kDataSizeBits) {
+        // None free.
+        acquired_idx = -1;
+        break;
+      }
+
+      // Entry has a free bit. Acquire it.
+      uint32_t bit = 1 << (kDataSizeBits - index - 1);
+      new_entry = entry & ~bit;
+      assert_not_zero(entry & bit);
+
+      acquired_idx = index;
+    } while (!atomic_cas(entry, new_entry, &data_[i]));
+
+    if (acquired_idx != -1) {
+      // Acquired.
+      return (i * kDataSizeBits) + acquired_idx;
+    }
+  }
+
+  return -1;
+}
+
+void BitMap::Release(size_t index) {
+  auto slot = index / kDataSizeBits;
+  index -= slot * kDataSizeBits;
+
+  uint32_t bit = 1 << (kDataSizeBits - index - 1);
+
+  uint32_t entry = 0;
+  uint32_t new_entry = 0;
+  do {
+    entry = data_[slot];
+    assert_zero(entry & bit);
+
+    new_entry = entry | bit;
+  } while (!atomic_cas(entry, new_entry, &data_[slot]));
+}
+
+void BitMap::Resize(size_t new_size) {
+  auto old_size = data_.size();
+  assert_true(new_size % 4 == 0);
+  data_.resize(new_size / 4);
+
+  // Initialize new entries.
+  if (data_.size() > old_size) {
+    for (size_t i = old_size; i < data_.size(); i++) {
+      data_[i] = -1;
+    }
+  }
+}
+
+void BitMap::Reset() {
+  for (size_t i = 0; i < data_.size(); i++) {
+    data_[i] = -1;
+  }
+}
+
+}  // namespace xe