如何：使用指標複製位元組陣列 (C# 程式設計手冊)
下列範例會使用指標在陣列之間複製位元組。
這個範例使用 unsafe 關鍵字，可讓您在 Copy 方法中使用指標。 fixed 陳述式是用於宣告指向來源和目標陣列的指標。 這會「固定」(Pin) 來源和目的地陣列在記憶體中的位置，如此一來就不會因記憶體回收而移動。 陣列的記憶體區塊會在 fixed 區塊完成時解除固定狀態。 由於這個範例中的 Copy 方法使用 unsafe 關鍵字，因此必須使用 /unsafe 編譯器選項進行編譯。 若要在 Visual Studio 中設定選項，以滑鼠右鍵按一下專案名稱，然後按一下 [屬性]。 在 [建置] 索引標籤上，選取 [容許 Unsafe 程式碼]。
範例
// compile with: /unsafe
class TestCopy
{
// The unsafe keyword allows pointers to be used in the following method.
static unsafe void Copy(byte[] source, int sourceOffset, byte[] target,
int targetOffset, int count)
{
// If either array is not instantiated, you cannot complete the copy.
if ((source == null) || (target == null))
{
throw new System.ArgumentException();
}
// If either offset, or the number of bytes to copy, is negative, you
// cannot complete the copy.
if ((sourceOffset < 0) || (targetOffset < 0) || (count < 0))
{
throw new System.ArgumentException();
}
// If the number of bytes from the offset to the end of the array is
// less than the number of bytes you want to copy, you cannot complete
// the copy.
if ((source.Length - sourceOffset < count) ||
(target.Length - targetOffset < count))
{
throw new System.ArgumentException();
}
// The following fixed statement pins the location of the source and
// target objects in memory so that they will not be moved by garbage
// collection.
fixed (byte* pSource = source, pTarget = target)
{
// Set the starting points in source and target for the copying.
byte* ps = pSource + sourceOffset;
byte* pt = pTarget + targetOffset;
// Copy the specified number of bytes from source to target.
for (int i = 0; i < count; i++)
{
*pt = *ps;
pt++;
ps++;
}
}
}
static void Main()
{
// Create two arrays of the same length.
int length = 100;
byte[] byteArray1 = new byte[length];
byte[] byteArray2 = new byte[length];
// Fill byteArray1 with 0 - 99.
for (int i = 0; i < length; ++i)
{
byteArray1[i] = (byte)i;
}
// Display the first 10 elements in byteArray1.
System.Console.WriteLine("The first 10 elements of the original are:");
for (int i = 0; i < 10; ++i)
{
System.Console.Write(byteArray1[i] + " ");
}
System.Console.WriteLine("\n");
// Copy the contents of byteArray1 to byteArray2.
Copy(byteArray1, 0, byteArray2, 0, length);
// Display the first 10 elements in the copy, byteArray2.
System.Console.WriteLine("The first 10 elements of the copy are:");
for (int i = 0; i < 10; ++i)
{
System.Console.Write(byteArray2[i] + " ");
}
System.Console.WriteLine("\n");
// Copy the contents of the last 10 elements of byteArray1 to the
// beginning of byteArray2.
// The offset specifies where the copying begins in the source array.
int offset = length - 10;
Copy(byteArray1, offset, byteArray2, 0, length - offset);
// Display the first 10 elements in the copy, byteArray2.
System.Console.WriteLine("The first 10 elements of the copy are:");
for (int i = 0; i < 10; ++i)
{
System.Console.Write(byteArray2[i] + " ");
}
System.Console.WriteLine("\n");
}
}
/* Output:
The first 10 elements of the original are:
0 1 2 3 4 5 6 7 8 9
The first 10 elements of the copy are:
0 1 2 3 4 5 6 7 8 9
The first 10 elements of the copy are:
90 91 92 93 94 95 96 97 98 99
*/