Implemented Region. Arena allocator now uses Region for OS specific allocation and page management.

src/region.cpp

@@ -0,0 +1,153 @@
+//
+//  region.cpp
+//  Kraken Engine
+//
+//  Copyright 2026 Kearwood Gilbert. All rights reserved.
+//
+//  Redistribution and use in source and binary forms, with or without modification, are
+//  permitted provided that the following conditions are met:
+//
+//  1. Redistributions of source code must retain the above copyright notice, this list of
+//  conditions and the following disclaimer.
+//
+//  2. Redistributions in binary form must reproduce the above copyright notice, this list
+//  of conditions and the following disclaimer in the documentation and/or other materials
+//  provided with the distribution.
+//
+//  THIS SOFTWARE IS PROVIDED BY KEARWOOD GILBERT ''AS IS'' AND ANY EXPRESS OR IMPLIED
+//  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+//  FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL KEARWOOD GILBERT OR
+//  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+//  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+//  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+//  ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+//  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+//  ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+//  The views and conclusions contained in the software and documentation are those of the
+//  authors and should not be interpreted as representing official policies, either expressed
+//  or implied, of Kearwood Gilbert.
+//
+
+#include "../include/mimir.h"
+#include "mimir_impl.h"
+
+#include <cassert>
+#include <cstring>
+#include <bit>
+
+namespace mimir {
+
+Region::Region()
+  : m_data(nullptr)
+  , m_committedSize(0)
+  , m_maxSize(0)
+{
+
+}
+
+Region::~Region()
+{
+  if (m_data) {
+#if defined(_WIN32) || defined(_WIN64)
+    if (!VirtualFree((void*)m_data, 0, MEM_RELEASE)) {
+      ReportWindowsLastError("VirtualAlloc");
+    }
+#elif defined(__unix__) || defined(__APPLE__) || defined(ANDROID)
+    munmap(m_data, KRAKEN_MEM_ROUND_UP_PAGE(m_maxSize));
+#else
+    static_assert(false, "Not Implemented");
+#endif
+  }
+}
+
+bool Region::init(size_t maxSize)
+{
+  assert(m_data == nullptr);
+  assert(m_committedSize == 0);
+
+  m_maxSize = KRAKEN_MEM_ROUND_UP_PAGE(maxSize);
+
+#if defined(_WIN32) || defined(_WIN64)
+  m_data = (std::byte*)VirtualAlloc(NULL, KRAKEN_MEM_ROUND_UP_PAGE(m_maxSize), MEM_RESERVE, PAGE_NOACCESS);
+  if (m_data == nullptr) {
+    ReportWindowsLastError("VirtualAlloc");
+    return false;
+  }
+#elif defined(__unix__) || defined(__APPLE__) || defined(ANDROID)
+  m_data = (std::byte*)mmap(NULL, KRAKEN_MEM_ROUND_UP_PAGE(m_maxSize), PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+  if (m_data == MAP_FAILED) {
+    return false;
+  }
+#else
+  static_assert(false, "Not Implemented");
+#endif
+  return true;
+}
+ 
+bool Region::resize(size_t size)
+{
+  size_t newSize = KRAKEN_MEM_ROUND_UP_PAGE(size);
+
+  if (newSize == m_committedSize) {
+    return true;
+  }
+
+  if (newSize > m_committedSize) {
+    // ---- Growing ----
+#if defined(_WIN32) || defined(_WIN64)
+    if (VirtualAlloc(m_data + m_committedSize, newSize - m_committedSize, MEM_COMMIT, PAGE_READWRITE) == nullptr) {
+      ReportWindowsLastError("VirtualAlloc");
+      return false;
+    }
+#elif defined(__unix__) || defined(__APPLE__) || defined(ANDROID)
+    if (mprotect(m_data + m_committedSize, newSize - m_committedSize, PROT_READ | PROT_WRITE) != 0) {
+      return false;
+    }
+#else
+    static_assert(false, "Not Implemented");
+#endif
+    m_committedSize = newSize;
+    return true;
+  } // if (newSize > m_committedSize)
+
+  // ---- Shrinking ----
+  std::byte* rangeStart = m_data + newSize;
+  size_t rangeLen = m_committedSize - newSize;
+#if defined(_WIN32) || defined(_WIN64)
+  if (!VirtualAlloc(rangeStart, rangeLen, MEM_RESET, PAGE_NOACCESS)) {
+    ReportWindowsLastError("VirtualAlloc");
+  } else {
+    m_committedSize = newSize;
+  }
+#elif defined(__unix__) || defined(__APPLE__) || defined(ANDROID)
+  if (madvise(rangeStart, rangeLen, MADV_DONTNEED) != 0) {
+    // TODO - Log Error or debug build assert
+  }
+  if (mprotect(rangeStart, rangeLen, PROT_NONE) != 0) {
+    // TODO - Log Error or debug build assert
+  }
+#else
+  static_assert(false, "Not Implemented");
+#endif
+  m_committedSize = newSize;
+
+  return true;
+}
+
+size_t Region::getSize() const
+{
+  return m_committedSize;
+}
+
+size_t Region::getMaxSize() const
+{
+  return m_maxSize;
+}
+
+std::byte* Region::getAddress() const
+{
+  return m_data;
+}
+
+};