buffer.cs

// ==++==
// 
//   Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// ==--==

// For code consistency between.NET Framework and .NET Core
#if WIN64
    #define BIT64
#elif WIN32
    #define BIT32
#else
    #error Unknown architecture
#endif
#if !PLATFORM_UNIX
    #define PLATFORM_WINDOWS
#endif

#if AMD64 || ARM64 || (BIT32 && !ARM)
#define HAS_CUSTOM_BLOCKS
#endif

namespace System {
    
    //Only contains static methods.  Does not require serialization
    
    using System;
    using System.Runtime.CompilerServices;
    using System.Runtime.ConstrainedExecution;
    using System.Runtime.InteropServices;
    using System.Runtime.Versioning;
    using System.Diagnostics.Contracts;
    using System.Security;
    using System.Runtime;

#if BIT64
    using nuint = System.UInt64;
#else // BIT64
    using nuint = System.UInt32;
#endif // BIT64

[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.  The count and 
        // offset parameters here are in bytes.  If you want to use traditional
        // array element indices and counts, use Array.Copy.
        [System.Security.SecuritySafeCritical]  // auto-generated
        [ResourceExposure(ResourceScope.None)]
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        public static extern void BlockCopy(Array src, int srcOffset,
            Array dst, int dstOffset, int count);

        // A very simple and efficient memmove that assumes all of the
        // parameter validation has already been done.  The count and offset
        // parameters here are in bytes.  If you want to use traditional
        // array element indices and counts, use Array.Copy.
        [System.Security.SecuritySafeCritical]  // auto-generated
        [ResourceExposure(ResourceScope.None)]
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        internal static extern void InternalBlockCopy(Array src, int srcOffsetBytes,
            Array dst, int dstOffsetBytes, int byteCount);

        // 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.
        //
        [System.Security.SecurityCritical]  // auto-generated
        internal unsafe static int IndexOfByte(byte* src, byte value, int index, int count)
        {
            Contract.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;
        }
        
        // Returns a bool to indicate if the array is of primitive data types
        // or not.
        [System.Security.SecurityCritical]  // auto-generated
        [ResourceExposure(ResourceScope.None)]
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern bool IsPrimitiveTypeArray(Array array);

        // 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.
        //
        [System.Security.SecurityCritical]  // auto-generated
        [ResourceExposure(ResourceScope.None)]
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern byte _GetByte(Array array, int index);

        [System.Security.SecuritySafeCritical]  // auto-generated
        public static byte GetByte(Array array, int index)
        {
            // Is the array present?
            if (array == null)
                throw new ArgumentNullException("array");

            // Is it of primitive types?
            if (!IsPrimitiveTypeArray(array))
                throw new ArgumentException(Environment.GetResourceString("Arg_MustBePrimArray"), "array");

            // Is the index in valid range of the array?
            if (index < 0 || index >= _ByteLength(array))
                throw new ArgumentOutOfRangeException("index");

            return _GetByte(array, 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.
        //
        [System.Security.SecurityCritical]  // auto-generated
        [ResourceExposure(ResourceScope.None)]
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern void _SetByte(Array array, int index, byte value);

        [System.Security.SecuritySafeCritical]  // auto-generated
        public static void SetByte(Array array, int index, byte value)
        {
            // Is the array present?
            if (array == null)
                throw new ArgumentNullException("array");

            // Is it of primitive types?
            if (!IsPrimitiveTypeArray(array))
                throw new ArgumentException(Environment.GetResourceString("Arg_MustBePrimArray"), "array");

            // Is the index in valid range of the array?
            if (index < 0 || index >= _ByteLength(array))
                throw new ArgumentOutOfRangeException("index");

            // Make the FCall to do the work
            _SetByte(array, index, 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).
        //
        [System.Security.SecurityCritical]  // auto-generated
        [ResourceExposure(ResourceScope.None)]
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        private static extern int _ByteLength(Array array);

        [System.Security.SecuritySafeCritical]  // auto-generated
        public static int ByteLength(Array array)
        {
            // Is the array present?
            if (array == null)
                throw new ArgumentNullException("array");

            // Is it of primitive types?
            if (!IsPrimitiveTypeArray(array))
                throw new ArgumentException(Environment.GetResourceString("Arg_MustBePrimArray"), "array");

            return _ByteLength(array);
        }

        [System.Security.SecurityCritical]  // auto-generated
        internal unsafe static void ZeroMemory(byte* src, long len)
        {
            while(len-- > 0)
                *(src + len) = 0;
        }

        [System.Security.SecurityCritical]  // auto-generated
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        internal unsafe static void Memcpy(byte[] dest, int destIndex, byte* src, int srcIndex, int len) {
            Contract.Assert( (srcIndex >= 0) && (destIndex >= 0) && (len >= 0), "Index and length must be non-negative!");
            Contract.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) {
                Memcpy(pDest + destIndex, src + srcIndex, len);
            }
        }

        [SecurityCritical]
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        internal unsafe static void Memcpy(byte* pDest, int destIndex, byte[] src, int srcIndex, int len)
        {
            Contract.Assert( (srcIndex >= 0) && (destIndex >= 0) && (len >= 0), "Index and length must be non-negative!");        
            Contract.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) {
                Memcpy(pDest + destIndex, pSrc + srcIndex, len);
            }
        }

        // This is tricky to get right AND fast, so lets make it useful for the whole Fx.
        // E.g. System.Runtime.WindowsRuntime!WindowsRuntimeBufferExtensions.MemCopy uses it.

        // This method has a slightly different behavior on arm and other platforms.
        // On arm this method behaves like memcpy and does not handle overlapping buffers.
        // While on other platforms it behaves like memmove and handles overlapping buffers.
        // This behavioral difference is unfortunate but intentional because
        // 1. This method is given access to other internal dlls and this close to release we do not want to change it.
        // 2. It is difficult to get this right for arm and again due to release dates we would like to visit it later.
        [FriendAccessAllowed]
        [System.Security.SecurityCritical]
        [ResourceExposure(ResourceScope.None)] 
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
#if ARM
        [MethodImplAttribute(MethodImplOptions.InternalCall)]
        internal unsafe static extern void Memcpy(byte* dest, byte* src, int len);
#else // ARM
        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
        internal unsafe static void Memcpy(byte* dest, byte* src, int len) {
            Contract.Assert(len >= 0, "Negative length in memcopy!");
            Memmove(dest, src, (uint)len);
        }
#endif // ARM

        // This method has different signature for x64 and other platforms and is done for performance reasons.
        [System.Security.SecurityCritical]
        [ResourceExposure(ResourceScope.None)]
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        internal unsafe static void Memmove(byte* dest, byte* src, nuint len)
        {
#if AMD64 || (BIT32 && !ARM)
            const nuint CopyThreshold = 2048;
#elif ARM64
#if PLATFORM_WINDOWS
            // 

            const nuint CopyThreshold = 2048;
#else // PLATFORM_WINDOWS
            // Managed code is currently faster than glibc unoptimized memmove
            // 

            const nuint CopyThreshold = UInt64.MaxValue;
#endif // PLATFORM_WINDOWS
#else
            const nuint CopyThreshold = 512;
#endif // AMD64 || (BIT32 && !ARM)

            // P/Invoke into the native version when the buffers are overlapping.

            if (((nuint)dest - (nuint)src < len) || ((nuint)src - (nuint)dest < len)) goto PInvoke;

            byte* srcEnd = src + len;
            byte* destEnd = dest + len;

            if (len <= 16) goto MCPY02;
            if (len > 64) goto MCPY05;

            MCPY00:
            // Copy bytes which are multiples of 16 and leave the remainder for MCPY01 to handle.
            Contract.Assert(len > 16 && len <= 64);
#if HAS_CUSTOM_BLOCKS
            *(Block16*)dest = *(Block16*)src;                   // [0,16]
#elif BIT64
            *(long*)dest = *(long*)src;
            *(long*)(dest + 8) = *(long*)(src + 8);             // [0,16]
#else
            *(int*)dest = *(int*)src;
            *(int*)(dest + 4) = *(int*)(src + 4);
            *(int*)(dest + 8) = *(int*)(src + 8);
            *(int*)(dest + 12) = *(int*)(src + 12);             // [0,16]
#endif
            if (len <= 32) goto MCPY01;
#if HAS_CUSTOM_BLOCKS
            *(Block16*)(dest + 16) = *(Block16*)(src + 16);     // [0,32]
#elif BIT64
            *(long*)(dest + 16) = *(long*)(src + 16);
            *(long*)(dest + 24) = *(long*)(src + 24);           // [0,32]
#else
            *(int*)(dest + 16) = *(int*)(src + 16);
            *(int*)(dest + 20) = *(int*)(src + 20);
            *(int*)(dest + 24) = *(int*)(src + 24);
            *(int*)(dest + 28) = *(int*)(src + 28);             // [0,32]
#endif
            if (len <= 48) goto MCPY01;
#if HAS_CUSTOM_BLOCKS
            *(Block16*)(dest + 32) = *(Block16*)(src + 32);     // [0,48]
#elif BIT64
            *(long*)(dest + 32) = *(long*)(src + 32);
            *(long*)(dest + 40) = *(long*)(src + 40);           // [0,48]
#else
            *(int*)(dest + 32) = *(int*)(src + 32);
            *(int*)(dest + 36) = *(int*)(src + 36);
            *(int*)(dest + 40) = *(int*)(src + 40);
            *(int*)(dest + 44) = *(int*)(src + 44);             // [0,48]
#endif

            MCPY01:
            // Unconditionally copy the last 16 bytes using destEnd and srcEnd and return.
            Contract.Assert(len > 16 && len <= 64);
#if HAS_CUSTOM_BLOCKS
            *(Block16*)(destEnd - 16) = *(Block16*)(srcEnd - 16);
#elif BIT64
            *(long*)(destEnd - 16) = *(long*)(srcEnd - 16);
            *(long*)(destEnd - 8) = *(long*)(srcEnd - 8);
#else
            *(int*)(destEnd - 16) = *(int*)(srcEnd - 16);
            *(int*)(destEnd - 12) = *(int*)(srcEnd - 12);
            *(int*)(destEnd - 8) = *(int*)(srcEnd - 8);
            *(int*)(destEnd - 4) = *(int*)(srcEnd - 4);
#endif
            return;

            MCPY02:
            // Copy the first 8 bytes and then unconditionally copy the last 8 bytes and return.
            if ((len & 24) == 0) goto MCPY03;
            Contract.Assert(len >= 8 && len <= 16);
#if BIT64
            *(long*)dest = *(long*)src;
            *(long*)(destEnd - 8) = *(long*)(srcEnd - 8);
#else
            *(int*)dest = *(int*)src;
            *(int*)(dest + 4) = *(int*)(src + 4);
            *(int*)(destEnd - 8) = *(int*)(srcEnd - 8);
            *(int*)(destEnd - 4) = *(int*)(srcEnd - 4);
#endif
            return;

            MCPY03:
            // Copy the first 4 bytes and then unconditionally copy the last 4 bytes and return.
            if ((len & 4) == 0) goto MCPY04;
            Contract.Assert(len >= 4 && len < 8);
            *(int*)dest = *(int*)src;
            *(int*)(destEnd - 4) = *(int*)(srcEnd - 4);
            return;

            MCPY04:
            // Copy the first byte. For pending bytes, do an unconditionally copy of the last 2 bytes and return.
            Contract.Assert(len < 4);
            if (len == 0) return;
            *dest = *src;
            if ((len & 2) == 0) return;
            *(short*)(destEnd - 2) = *(short*)(srcEnd - 2);
            return;

            MCPY05:
            // PInvoke to the native version when the copy length exceeds the threshold.
            if (len > CopyThreshold)
            {
                goto PInvoke;
            }
            // Copy 64-bytes at a time until the remainder is less than 64.
            // If remainder is greater than 16 bytes, then jump to MCPY00. Otherwise, unconditionally copy the last 16 bytes and return.
            Contract.Assert(len > 64 && len <= CopyThreshold);
            nuint n = len >> 6;

            MCPY06:
#if HAS_CUSTOM_BLOCKS
            *(Block64*)dest = *(Block64*)src;
#elif BIT64
            *(long*)dest = *(long*)src;
            *(long*)(dest + 8) = *(long*)(src + 8);
            *(long*)(dest + 16) = *(long*)(src + 16);
            *(long*)(dest + 24) = *(long*)(src + 24);
            *(long*)(dest + 32) = *(long*)(src + 32);
            *(long*)(dest + 40) = *(long*)(src + 40);
            *(long*)(dest + 48) = *(long*)(src + 48);
            *(long*)(dest + 56) = *(long*)(src + 56);
#else
            *(int*)dest = *(int*)src;
            *(int*)(dest + 4) = *(int*)(src + 4);
            *(int*)(dest + 8) = *(int*)(src + 8);
            *(int*)(dest + 12) = *(int*)(src + 12);
            *(int*)(dest + 16) = *(int*)(src + 16);
            *(int*)(dest + 20) = *(int*)(src + 20);
            *(int*)(dest + 24) = *(int*)(src + 24);
            *(int*)(dest + 28) = *(int*)(src + 28);
            *(int*)(dest + 32) = *(int*)(src + 32);
            *(int*)(dest + 36) = *(int*)(src + 36);
            *(int*)(dest + 40) = *(int*)(src + 40);
            *(int*)(dest + 44) = *(int*)(src + 44);
            *(int*)(dest + 48) = *(int*)(src + 48);
            *(int*)(dest + 52) = *(int*)(src + 52);
            *(int*)(dest + 56) = *(int*)(src + 56);
            *(int*)(dest + 60) = *(int*)(src + 60);
#endif
            dest += 64;
            src += 64;
            n--;
            if (n != 0) goto MCPY06;

            len %= 64;
            if (len > 16) goto MCPY00;
#if HAS_CUSTOM_BLOCKS
            *(Block16*)(destEnd - 16) = *(Block16*)(srcEnd - 16);
#elif BIT64
            *(long*)(destEnd - 16) = *(long*)(srcEnd - 16);
            *(long*)(destEnd - 8) = *(long*)(srcEnd - 8);
#else
            *(int*)(destEnd - 16) = *(int*)(srcEnd - 16);
            *(int*)(destEnd - 12) = *(int*)(srcEnd - 12);
            *(int*)(destEnd - 8) = *(int*)(srcEnd - 8);
            *(int*)(destEnd - 4) = *(int*)(srcEnd - 4);
#endif
            return;

            PInvoke:
            _Memmove(dest, src, len);
        }

        // Non-inlinable wrapper around the QCall that avoids poluting the fast path
        // with P/Invoke prolog/epilog.
        [SecurityCritical]
        [ResourceExposure(ResourceScope.None)]
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        [MethodImplAttribute(MethodImplOptions.NoInlining)]
        private unsafe static void _Memmove(byte* dest, byte* src, nuint len)
        {
            __Memmove(dest, src, len);
        }

        [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]
        [SuppressUnmanagedCodeSecurity]
        [SecurityCritical]
        [ResourceExposure(ResourceScope.None)]        
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        extern private unsafe static void __Memmove(byte* dest, byte* src, nuint len);

        // The attributes on this method are chosen for best JIT performance. 
        // Please do not edit unless intentional.
        [System.Security.SecurityCritical]
        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
        [CLSCompliant(false)]
        public static unsafe void MemoryCopy(void* source, void* destination, long destinationSizeInBytes, long sourceBytesToCopy)
        {
            if (sourceBytesToCopy > destinationSizeInBytes)
            {
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.sourceBytesToCopy);
            }
            Memmove((byte*)destination, (byte*)source, checked((nuint)sourceBytesToCopy));
        }


        // The attributes on this method are chosen for best JIT performance. 
        // Please do not edit unless intentional.
        [System.Security.SecurityCritical]
        [MethodImplAttribute(MethodImplOptions.AggressiveInlining)]
        [CLSCompliant(false)]
        public static unsafe void MemoryCopy(void* source, void* destination, ulong destinationSizeInBytes, ulong sourceBytesToCopy)
        {
            if (sourceBytesToCopy > destinationSizeInBytes)
            {
                ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.sourceBytesToCopy);
            }
#if BIT64
            Memmove((byte*)destination, (byte*)source, sourceBytesToCopy);
#else // BIT64
            Memmove((byte*)destination, (byte*)source, checked((uint)sourceBytesToCopy));
#endif // BIT64
        }
        
#if HAS_CUSTOM_BLOCKS        
        [StructLayout(LayoutKind.Sequential, Size = 16)]
        private struct Block16 { }

        [StructLayout(LayoutKind.Sequential, Size = 64)]
        private struct Block64 { } 
#endif // HAS_CUSTOM_BLOCKS         
    }
}