325.8 Dynamic memory allocation

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// Handle for the process heap. This handle is used in all calls to

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// the HeapXXX APIs in the methods below.

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static int ph = GetProcessHeap();

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// Allocates a memory block of the given size. The allocated memory is

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// automatically initialized to zero.

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public static void* Alloc(int size) {

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void* result = HeapAlloc(ph, HEAP_ZERO_MEMORY, size);

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if (result == null) throw new OutOfMemoryException();

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return result;

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}

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// Copies count bytes from src to dst. The source and destination

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// blocks are permitted to overlap.

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public static void Copy(void* src, void* dst, int count) {

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byte* ps = (byte*)src;

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byte* pd = (byte*)dst;

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if (ps > pd) {

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for (; count != 0; count--) *pd++ = *ps++;

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}

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else if (ps < pd) {

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for (ps += count, pd += count; count != 0; count--)

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*--pd = *--ps;

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}

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}

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// Frees a memory block.

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public static void Free(void* block) {

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if (!HeapFree(ph, 0, block)) throw new InvalidOperationException();

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}

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// Re-allocates a memory block. If the reallocation request is for a

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// larger size, the additional region of memory is automatically

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// initialized to zero.

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public static void* ReAlloc(void* block, int size) {

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void* result = HeapReAlloc(ph, HEAP_ZERO_MEMORY, block, size);

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if (result == null) throw new OutOfMemoryException();

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return result;

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}

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// Returns the size of a memory block.

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public static int SizeOf(void* block) {

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int result = HeapSize(ph, 0, block);

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if (result == -1) throw new InvalidOperationException();

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return result;

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}

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// Heap API flags

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const int HEAP_ZERO_MEMORY = 0x00000008;

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// Heap API functions

C# LANGUAGE SPECIFICATION

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[DllImport("kernel32")]

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static extern int GetProcessHeap();

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[DllImport("kernel32")]

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static extern void* HeapAlloc(int hHeap, int flags, int size);

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[DllImport("kernel32")]

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static extern bool HeapFree(int hHeap, int flags, void* block);

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[DllImport("kernel32")]

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static extern void* HeapReAlloc(int hHeap, int flags,

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void* block, int size);

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static void Main() {

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unsafe {

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byte* buffer = (byte*)Memory.Alloc(256);

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for (int i = 0; i < 256; i++) buffer[i] = (byte)i;

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byte[] array = new byte[256];

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fixed (byte* p = array) Memory.Copy(buffer, p, 256);

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Memory.Free(buffer);

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for (int i = 0; i < 256; i++) Console.WriteLine(array[i]);

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}