--- /dev/null
+/*
+ * Copyright (C) 2010 Apple Inc. 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 APPLE INC. ``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 APPLE INC. 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.
+ */
+
+#ifndef PageReservation_h
+#define PageReservation_h
+
+#include <wtf/PageAllocation.h>
+
+namespace WTF {
+
+/*
+ PageReservation
+
+ Like PageAllocation, the PageReservation class provides a cross-platform memory
+ allocation interface, but with a set of capabilities more similar to that of
+ VirtualAlloc than posix mmap. PageReservation can be used to allocate virtual
+ memory without committing physical memory pages using PageReservation::reserve.
+ Following a call to reserve all memory in the region is in a decommited state,
+ in which the memory should not be used (accessing the memory may cause a fault).
+
+ Before using memory it must be committed by calling commit, which is passed start
+ and size values (both of which require system page size granularity). One the
+ committed memory is no longer needed 'decommit' may be called to return the
+ memory to its devommitted state. Commit should only be called on memory that is
+ currently decommitted, and decommit should only be called on memory regions that
+ are currently committed. All memory should be decommited before the reservation
+ is deallocated. Values in memory may not be retained accross a pair of calls if
+ the region of memory is decommitted and then committed again.
+
+ Memory protection should not be changed on decommitted memory, and if protection
+ is changed on memory while it is committed it should be returned to the orignal
+ protection before decommit is called.
+*/
+
+class PageReservation : private PageBlock {
+public:
+ PageReservation()
+ : m_committed(0)
+ , m_writable(false)
+ , m_executable(false)
+ {
+ }
+
+ using PageBlock::base;
+ using PageBlock::size;
+
+#ifndef __clang__
+ using PageBlock::operator bool;
+#else
+ // FIXME: This is a workaround for <rdar://problem/8876150>, wherein Clang incorrectly emits an access
+ // control warning when a client tries to use operator bool exposed above via "using PageBlock::operator bool".
+ operator bool() const { return PageBlock::operator bool(); }
+#endif
+
+ void commit(void* start, size_t size)
+ {
+ ASSERT(*this);
+ ASSERT(isPageAligned(start));
+ ASSERT(isPageAligned(size));
+ ASSERT(contains(start, size));
+
+ m_committed += size;
+ OSAllocator::commit(start, size, m_writable, m_executable);
+ }
+
+ void decommit(void* start, size_t size)
+ {
+ ASSERT(*this);
+ ASSERT(isPageAligned(start));
+ ASSERT(isPageAligned(size));
+ ASSERT(contains(start, size));
+
+ m_committed -= size;
+ OSAllocator::decommit(start, size);
+ }
+
+ size_t committed()
+ {
+ return m_committed;
+ }
+
+ static PageReservation reserve(size_t size, OSAllocator::Usage usage = OSAllocator::UnknownUsage, bool writable = true, bool executable = false)
+ {
+ ASSERT(isPageAligned(size));
+ return PageReservation(OSAllocator::reserveUncommitted(size, usage, writable, executable), size, writable, executable, false);
+ }
+
+ static PageReservation reserveWithGuardPages(size_t size, OSAllocator::Usage usage = OSAllocator::UnknownUsage, bool writable = true, bool executable = false)
+ {
+ ASSERT(isPageAligned(size));
+ return PageReservation(OSAllocator::reserveUncommitted(size + pageSize() * 2, usage, writable, executable, true), size, writable, executable, true);
+ }
+
+ void deallocate()
+ {
+ ASSERT(!m_committed);
+
+ // Clear base & size before calling release; if this is *inside* allocation
+ // then we won't be able to clear then after deallocating the memory.
+ PageReservation tmp;
+ std::swap(tmp, *this);
+
+ ASSERT(tmp);
+ ASSERT(!*this);
+
+ OSAllocator::releaseDecommitted(tmp.base(), tmp.size());
+ }
+
+private:
+ PageReservation(void* base, size_t size, bool writable, bool executable, bool hasGuardPages)
+ : PageBlock(base, size, hasGuardPages)
+ , m_committed(0)
+ , m_writable(writable)
+ , m_executable(executable)
+ {
+ }
+
+ size_t m_committed;
+ bool m_writable;
+ bool m_executable;
+};
+
+}
+
+using WTF::PageReservation;
+
+#endif // PageReservation_h
projects / apple / javascriptcore.git / blobdiff