Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Buffer.cs / 1 / Buffer.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== namespace System { //Only contains static methods. Does not require serialization using System; using System.Runtime.CompilerServices; [System.Runtime.InteropServices.ComVisible(true)] public static class Buffer { // Copies from one primitive array to another primitive array without // respecting types. This calls memmove internally. [MethodImplAttribute(MethodImplOptions.InternalCall)] public static extern void BlockCopy(Array src, int srcOffset, Array dst, int dstOffset, int count); // A very simple and efficient array copy that assumes all of the // parameter validation has already been done. All counts here are // in bytes. [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern void InternalBlockCopy(Array src, int srcOffset, Array dst, int dstOffset, int count); // This is ported from the optimized CRT assembly in memchr.asm. The JIT generates // pretty good code here and this ends up being within a couple % of the CRT asm. // It is however cross platform as the CRT hasn't ported their fast version to 64-bit // platforms. // internal unsafe static int IndexOfByte(byte* src, byte value, int index, int count) { BCLDebug.Assert(src != null, "src should not be null"); byte* pByte = src + index; // Align up the pointer to sizeof(int). while (((int)pByte & 3) != 0) { if (count == 0) return -1; else if (*pByte == value) return (int) (pByte - src); count--; pByte++; } // Fill comparer with value byte for comparisons // // comparer = 0/0/value/value uint comparer = (((uint)value << 8) + (uint)value); // comparer = value/value/value/value comparer = (comparer << 16) + comparer; // Run through buffer until we hit a 4-byte section which contains // the byte we're looking for or until we exhaust the buffer. while (count > 3) { // Test the buffer for presence of value. comparer contains the byte // replicated 4 times. uint t1 = *(uint*)pByte; t1 = t1 ^ comparer; uint t2 = 0x7efefeff + t1; t1 = t1 ^ 0xffffffff; t1 = t1 ^ t2; t1 = t1 & 0x81010100; // if t1 is zero then these 4-bytes don't contain a match if (t1 != 0) { // We've found a match for value, figure out which position it's in. int foundIndex = (int) (pByte - src); if (pByte[0] == value) return foundIndex; else if (pByte[1] == value) return foundIndex + 1; else if (pByte[2] == value) return foundIndex + 2; else if (pByte[3] == value) return foundIndex + 3; } count -= 4; pByte += 4; } // Catch any bytes that might be left at the tail of the buffer while (count > 0) { if (*pByte == value) return (int) (pByte - src); count--; pByte++; } // If we don't have a match return -1; return -1; } // Gets a particular byte out of the array. The array must be an // array of primitives. // // This essentially does the following: // return ((byte*)array) + index. // [MethodImplAttribute(MethodImplOptions.InternalCall)] public static extern byte GetByte(Array array, int index); // Sets a particular byte in an the array. The array must be an // array of primitives. // // This essentially does the following: // *(((byte*)array) + index) = value. // [MethodImplAttribute(MethodImplOptions.InternalCall)] public static extern void SetByte(Array array, int index, byte value); // Gets a particular byte out of the array. The array must be an // array of primitives. // // This essentially does the following: // return array.length * sizeof(array.UnderlyingElementType). // [MethodImplAttribute(MethodImplOptions.InternalCall)] public static extern int ByteLength(Array array); internal unsafe static void ZeroMemory(byte* src, long len) { while(len-- > 0) *(src + len) = 0; } internal unsafe static void memcpy(byte* src, int srcIndex, byte[] dest, int destIndex, int len) { BCLDebug.Assert( (srcIndex >= 0) && (destIndex >= 0) && (len >= 0), "Index and length must be non-negative!"); BCLDebug.Assert(dest.Length - destIndex >= len, "not enough bytes in dest"); // If dest has 0 elements, the fixed statement will throw an // IndexOutOfRangeException. Special-case 0-byte copies. if (len==0) return; fixed(byte* pDest = dest) { memcpyimpl(src+srcIndex, pDest+destIndex, len); } } internal unsafe static void memcpy(byte[] src, int srcIndex, byte* pDest, int destIndex, int len) { BCLDebug.Assert( (srcIndex >= 0) && (destIndex >= 0) && (len >= 0), "Index and length must be non-negative!"); BCLDebug.Assert(src.Length - srcIndex >= len, "not enough bytes in src"); // If dest has 0 elements, the fixed statement will throw an // IndexOutOfRangeException. Special-case 0-byte copies. if (len==0) return; fixed(byte* pSrc = src) { memcpyimpl(pSrc+srcIndex, pDest+destIndex, len); } } internal unsafe static void memcpy(char* pSrc, int srcIndex, char* pDest, int destIndex, int len) { BCLDebug.Assert( (srcIndex >= 0) && (destIndex >= 0) && (len >= 0), "Index and length must be non-negative!"); // No boundary check for buffer overruns - dangerous if (len==0) return; memcpyimpl((byte*)(char*)(pSrc+srcIndex), (byte*)(char*)(pDest+destIndex), len*2); } // Note - using a long instead of an int for the length parameter // slows this method down by ~18%. internal unsafe static void memcpyimpl(byte* src, byte* dest, int len) { BCLDebug.Assert(len >= 0, "Negative length in memcopy!"); #if FEATURE_PAL // Portable naive implementation while (len-- > 0) *dest++ = *src++; #else // It turns out that on AMD64 it is faster to not be careful of alignment issues. // On IA64 it is necessary to be careful... Oh well. When we do the IA64 push we // can work on this implementation. #if IA64 long dstAlign = 8 - (((long)dest) & 7); // number of bytes to copy before dest is 8-byte aligned while ((dstAlign > 0) && (len > 0)) { *dest++ = *src++; len--; dstAlign--; } long srcAlign = 8 - (((long)src) & 7); if (len > 0) { if (srcAlign != 8) { if (4 == srcAlign) { while (len >= 4) { ((int*)dest)[0] = ((int*)src)[0]; dest += 4; src += 4; len -= 4; } srcAlign = 2; // fall through to 2-byte copies } if ((2 == srcAlign) || (6 == srcAlign)) { while (len >= 2) { ((short*)dest)[0] = ((short*)src)[0]; dest += 2; src += 2; len -= 2; } } while (len-- > 0) { *dest++ = *src++; } } else { if (len >= 16) { do { ((long*)dest)[0] = ((long*)src)[0]; ((long*)dest)[1] = ((long*)src)[1]; dest += 16; src += 16; } while ((len -= 16) >= 16); } if (len > 0) // protection against negative len and optimization for len==16*N { if ((len & 8) != 0) { ((long*)dest)[0] = ((long*)src)[0]; dest += 8; src += 8; } if ((len & 4) != 0) { ((int*)dest)[0] = ((int*)src)[0]; dest += 4; src += 4; } if ((len & 2) != 0) { ((short*)dest)[0] = ((short*)src)[0]; dest += 2; src += 2; } if ((len & 1) != 0) { *dest++ = *src++; } } } } #else // AMD64 implementation uses longs instead of ints where possible // //This is a faster memcpy implementation, from // COMString.cpp. For our strings, this beat the processor's // repeat & move single byte instruction, which memcpy expands into. // (You read that correctly.) // This is 3x faster than a simple while loop copying byte by byte, // for large copies. if (len >= 16) { do { #if AMD64 ((long*)dest)[0] = ((long*)src)[0]; ((long*)dest)[1] = ((long*)src)[1]; #else ((int*)dest)[0] = ((int*)src)[0]; ((int*)dest)[1] = ((int*)src)[1]; ((int*)dest)[2] = ((int*)src)[2]; ((int*)dest)[3] = ((int*)src)[3]; #endif dest += 16; src += 16; } while ((len -= 16) >= 16); } if(len > 0) // protection against negative len and optimization for len==16*N { if ((len & 8) != 0) { #if AMD64 ((long*)dest)[0] = ((long*)src)[0]; #else ((int*)dest)[0] = ((int*)src)[0]; ((int*)dest)[1] = ((int*)src)[1]; #endif dest += 8; src += 8; } if ((len & 4) != 0) { ((int*)dest)[0] = ((int*)src)[0]; dest += 4; src += 4; } if ((len & 2) != 0) { ((short*)dest)[0] = ((short*)src)[0]; dest += 2; src += 2; } if ((len & 1) != 0) *dest++ = *src++; } #endif // IA64 #endif // FEATURE_PAL } } }
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