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libsst-os/SST_SysMem_Win32.c

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+/*
+	SST_SysMem_Win32.c
+	Author: Patrick Baggett <ptbaggett@762studios.com>
+	Created: 12/23/2011
+
+	Purpose: 
+
+	libsst-os system memory allocation functions for Win32 platforms (Windows 7 or later)
+
+	License:
+
+	This program is free software. It comes without any warranty, to
+	the extent permitted by applicable law. You can redistribute it
+	and/or modify it under the terms of the Do What The Fuck You Want
+	To Public License, Version 2, as published by Sam Hocevar. See
+	http://sam.zoy.org/wtfpl/COPYING for more details.
+
+*/
+
+#include "Win32Private.h"
+#include <SST/SST_SysMem.h>
+#include <SST/SST_Assert.h>
+
+static uint32_t cached_pagesize;
+
+void __libsst_init_pagesize()
+{
+	SYSTEM_INFO info;
+	GetNativeSystemInfo(&info);
+
+	cached_pagesize = (uint32_t)info.dwPageSize;
+}
+
+/* Round an allocation of 'amount' bytes to be a multiple of 'pageSize' */
+static size_t roundToPage(uint32_t pageSize, size_t amount)
+{
+	size_t rounded;
+
+	/* ASSUMPTION: pageSize is a power of two */
+	
+	/*
+		Algorithm: Round up allocation to the nearest page.
+		
+		[1] x & (pageSize-1)    = Bytes that are extra parts of a page
+		[2] x & (~(pageSize-1)) = Bytes that are whole pages.
+
+		Start with [2] bytes. If [1] is non-zero, then add page size.
+	*/
+	rounded = amount & (~(pageSize-1));
+	if(amount & (pageSize-1))
+		rounded += pageSize;
+
+	return rounded;
+}
+
+/*************************************************************************/
+
+uint64_t SST_OS_GetMemorySize()
+{
+	ULONGLONG mem = 0;
+
+	if(GetPhysicallyInstalledSystemMemory(&mem))
+		return (uint64_t)mem;
+
+	return 0;
+}
+
+/*************************************************************************/
+
+uint32_t SST_OS_GetPageSize()
+{
+	return cached_pagesize;
+}
+
+/*************************************************************************/
+
+void* SST_OS_AllocPages(size_t allocBytes)
+{
+	SST_OS_DebugAssert(allocBytes > 0, "Allocating 0 bytes is not allowed");
+
+	return VirtualAllocEx(GetCurrentProcess(), NULL, roundToPage(SST_OS_GetPageSize(), allocBytes), MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
+}
+
+/*************************************************************************/
+
+int SST_OS_FreePages(void* pageBase, size_t nrBytes)
+{
+	uintptr_t addr;
+	uint32_t pageSize;
+
+	SST_OS_DebugAssert(pageBase != NULL, "Base address may not be NULL");
+	SST_OS_DebugAssert(nrBytes > 0, "The number of bytes to free may not be zero");
+
+	addr = (uintptr_t)pageBase;
+	pageSize = SST_OS_GetPageSize();
+
+	/* Check if address is aligned to page boundary */
+	if(addr & (pageSize-1))
+		return -1;
+
+	/* Free the pages */
+	if(VirtualFreeEx(GetCurrentProcess(), pageBase, roundToPage(pageSize, nrBytes), MEM_DECOMMIT | MEM_RELEASE) != 0)
+		return 1;
+
+	return 0;
+}
+
+/*************************************************************************/
+
+int SST_OS_ProtectPages(void* pageBase, size_t nrBytes, int protectFlags)
+{
+	uintptr_t addr;
+	uint32_t pageSize;
+	DWORD newFlags = PAGE_NOACCESS;
+
+	SST_OS_DebugAssert(pageBase != NULL, "Base address may not be NULL");
+	SST_OS_DebugAssert(nrBytes > 0, "The number of bytes to free may not be zero");
+
+
+	addr = (uintptr_t)pageBase;
+	pageSize = SST_OS_GetPageSize();
+
+	/* Check if address is aligned to page boundary */
+	if(addr & (pageSize-1))
+		return -1;
+
+	/* Microsoft doesn't believe in bitfields. This switch brought to you by a poor design decision */
+	switch(protectFlags)
+	{
+		/* r/o  */
+		case SST_PROTECT_READ: newFlags = PAGE_READONLY; break;
+
+		/* r/w, w/o */
+		case SST_PROTECT_READ | SST_PROTECT_WRITE:
+		case SST_PROTECT_WRITE: newFlags = PAGE_READWRITE; break; /* Win32 doesn't have w/o */
+
+		/* x/o */
+		case SST_PROTECT_EXEC: newFlags = PAGE_EXECUTE; break;
+
+		/* w/x */
+		case SST_PROTECT_WRITE | SST_PROTECT_EXEC: newFlags = PAGE_EXECUTE_READWRITE; break;
+
+		/* r/x */
+		case SST_PROTECT_READ | SST_PROTECT_EXEC: newFlags = PAGE_EXECUTE_READ; break;
+
+		/* r/w/x */
+		case SST_PROTECT_READ | SST_PROTECT_WRITE | SST_PROTECT_EXEC: newFlags = PAGE_EXECUTE_READWRITE; break;
+	}
+	
+	if(VirtualProtectEx(GetCurrentProcess(), (void*)addr, roundToPage(pageSize, nrBytes), newFlags, NULL) != 0)
+		return 1;
+
+	return 0;
+}
+