public async Task WriteUsingSingleBuffer(bool asyncOperation, bool asyncHandle)
{
string filePath = GetTestFilePath();
int bufferSize = Environment.SystemPageSize;
int fileSize = bufferSize * 10;
byte[] content = RandomNumberGenerator.GetBytes(fileSize);
using (SafeFileHandle handle = File.OpenHandle(filePath, FileMode.CreateNew, FileAccess.Write, FileShare.None, GetFileOptions(asyncHandle)))
using (SectorAlignedMemory <byte> buffer = SectorAlignedMemory <byte> .Allocate(bufferSize))
{
int total = 0;
while (total != fileSize)
{
int take = Math.Min(content.Length - total, bufferSize);
content.AsSpan(total, take).CopyTo(buffer.GetSpan());
if (asyncOperation)
{
await RandomAccess.WriteAsync(handle, buffer.Memory, fileOffset : total);
}
else
{
RandomAccess.Write(handle, buffer.GetSpan(), fileOffset: total);
}
total += buffer.Memory.Length;
}
}
Assert.Equal(content, File.ReadAllBytes(filePath));
}
public async Task ReadWriteAsyncUsingNonPageSizedMultipleBuffers()
{
string filePath = GetTestFilePath();
// The Windows scatter/gather APIs accept segments that are exactly one page long.
// Combined with the FILE_FLAG_NO_BUFFERING's requirements, the segments must also
// be aligned at page size boundaries and have a size of a multiple of the page size.
// Using segments with a length of twice the page size adheres to the second requirement
// but not the first. The RandomAccess implementation will see it and issue sequential
// read/write syscalls per segment, instead of one scatter/gather syscall.
// This test verifies that fallback behavior.
int bufferSize = Environment.SystemPageSize * 2;
int fileSize = bufferSize * 2;
byte[] content = RandomNumberGenerator.GetBytes(fileSize);
using (SafeFileHandle handle = File.OpenHandle(filePath, FileMode.CreateNew, FileAccess.ReadWrite, FileShare.None, FileOptions.Asynchronous | NoBuffering))
using (SectorAlignedMemory <byte> buffer = SectorAlignedMemory <byte> .Allocate(fileSize))
{
Memory <byte> firstHalf = buffer.Memory.Slice(0, bufferSize);
Memory <byte> secondHalf = buffer.Memory.Slice(bufferSize);
content.AsSpan().CopyTo(buffer.GetSpan());
await RandomAccess.WriteAsync(handle, new ReadOnlyMemory <byte>[] { firstHalf, secondHalf }, 0);
buffer.GetSpan().Clear();
await RandomAccess.ReadAsync(handle, new Memory <byte>[] { firstHalf, secondHalf }, 0);
}
Assert.Equal(content, await File.ReadAllBytesAsync(filePath));
}
public async Task ReadUsingSingleBuffer(bool asyncOperation, bool asyncHandle)
{
const int fileSize = 1_000_000; // 1 MB
string filePath = GetTestFilePath();
byte[] expected = RandomNumberGenerator.GetBytes(fileSize);
File.WriteAllBytes(filePath, expected);
using (SafeFileHandle handle = File.OpenHandle(filePath, FileMode.Open, options: GetFileOptions(asyncHandle)))
using (SectorAlignedMemory <byte> buffer = SectorAlignedMemory <byte> .Allocate(Environment.SystemPageSize))
{
int current = 0;
int total = 0;
do
{
current = asyncOperation
? await RandomAccess.ReadAsync(handle, buffer.Memory, fileOffset : total)
: RandomAccess.Read(handle, buffer.GetSpan(), fileOffset: total);
Assert.True(expected.AsSpan(total, current).SequenceEqual(buffer.GetSpan().Slice(0, current)));
total += current;
}while (current != 0);
Assert.Equal(fileSize, total);
}
}
public async Task ReadShouldReturnZeroForEndOfFile(bool asyncOperation, bool asyncHandle)
{
int fileSize = Environment.SystemPageSize + 1; // it MUST NOT be a multiple of it (https://github.com/dotnet/runtime/issues/62851)
string filePath = GetTestFilePath();
byte[] expected = RandomNumberGenerator.GetBytes(fileSize);
File.WriteAllBytes(filePath, expected);
using FileStream fileStream = new (filePath, FileMode.Open, FileAccess.Read, FileShare.None, 0, GetFileOptions(asyncHandle));
using SectorAlignedMemory <byte> buffer = SectorAlignedMemory <byte> .Allocate(Environment.SystemPageSize);
int current = 0;
int total = 0;
do
{
current = asyncOperation
? await fileStream.ReadAsync(buffer.Memory)
: fileStream.Read(buffer.GetSpan());
Assert.True(expected.AsSpan(total, current).SequenceEqual(buffer.GetSpan().Slice(0, current)));
total += current;
}while (current != 0);
Assert.Equal(fileSize, total);
}
public async Task ReadWriteAsyncUsingMultipleBuffers(bool memoryPageSized)
{
string filePath = GetTestFilePath();
// We test with buffers both one and two memory pages long. In the former case,
// the I/O operations will issue one scatter/gather API call, and in the latter
// case they will issue multiple calls; one per buffer. The buffers must still
// be aligned to comply with FILE_FLAG_NO_BUFFERING's requirements.
int bufferSize = Environment.SystemPageSize * (memoryPageSized ? 1 : 2);
int fileSize = bufferSize * 2;
byte[] content = RandomNumberGenerator.GetBytes(fileSize);
using (SafeFileHandle handle = File.OpenHandle(filePath, FileMode.CreateNew, FileAccess.ReadWrite, FileShare.None, FileOptions.Asynchronous | NoBuffering))
using (SectorAlignedMemory <byte> buffer = SectorAlignedMemory <byte> .Allocate(fileSize))
{
Memory <byte> firstHalf = buffer.Memory.Slice(0, bufferSize);
Memory <byte> secondHalf = buffer.Memory.Slice(bufferSize);
content.AsSpan().CopyTo(buffer.GetSpan());
await RandomAccess.WriteAsync(handle, new ReadOnlyMemory <byte>[] { firstHalf, secondHalf }, 0);
buffer.GetSpan().Clear();
long nRead = await RandomAccess.ReadAsync(handle, new Memory <byte>[] { firstHalf, secondHalf }, 0);
Assert.Equal(buffer.GetSpan().Length, nRead);
AssertExtensions.SequenceEqual(buffer.GetSpan(), content.AsSpan());
}
}
public async Task WriteAsyncUsingMultipleBuffers(bool async)
{
string filePath = GetTestFilePath();
int bufferSize = Environment.SystemPageSize;
int fileSize = bufferSize * 10;
byte[] content = RandomNumberGenerator.GetBytes(fileSize);
using (SafeFileHandle handle = File.OpenHandle(filePath, FileMode.CreateNew, FileAccess.Write, FileShare.None, FileOptions.Asynchronous | NoBuffering))
using (SectorAlignedMemory <byte> buffer_1 = SectorAlignedMemory <byte> .Allocate(bufferSize))
using (SectorAlignedMemory <byte> buffer_2 = SectorAlignedMemory <byte> .Allocate(bufferSize))
{
long total = 0;
IReadOnlyList <ReadOnlyMemory <byte> > buffers = new ReadOnlyMemory <byte>[]
{
buffer_1.Memory,
buffer_2.Memory,
};
while (total != fileSize)
{
content.AsSpan((int)total, bufferSize).CopyTo(buffer_1.GetSpan());
content.AsSpan((int)total + bufferSize, bufferSize).CopyTo(buffer_2.GetSpan());
total += async
? await RandomAccess.WriteAsync(handle, buffers, fileOffset : total)
: RandomAccess.Write(handle, buffers, fileOffset: total);
}
}
Assert.Equal(content, File.ReadAllBytes(filePath));
}
public async Task ReadAsyncUsingSingleBuffer()
{
const int fileSize = 1_000_000; // 1 MB
string filePath = GetTestFilePath();
byte[] expected = RandomNumberGenerator.GetBytes(fileSize);
File.WriteAllBytes(filePath, expected);
using (SafeFileHandle handle = File.OpenHandle(filePath, FileMode.Open, options: FileOptions.Asynchronous | NoBuffering))
using (SectorAlignedMemory <byte> buffer = SectorAlignedMemory <byte> .Allocate(Environment.SystemPageSize))
{
int current = 0;
int total = 0;
// From https://docs.microsoft.com/en-us/windows/win32/fileio/file-buffering:
// "File access sizes, including the optional file offset in the OVERLAPPED structure,
// if specified, must be for a number of bytes that is an integer multiple of the volume sector size."
// So if buffer and physical sector size is 4096 and the file size is 4097:
// the read from offset=0 reads 4096 bytes
// the read from offset=4096 reads 1 byte
// the read from offset=4097 THROWS (Invalid argument, offset is not a multiple of sector size!)
// That is why we stop at the first incomplete read (the next one would throw).
// It's possible to get 0 if we are lucky and file size is a multiple of physical sector size.
do
{
current = await RandomAccess.ReadAsync(handle, buffer.Memory, fileOffset : total);
Assert.True(expected.AsSpan(total, current).SequenceEqual(buffer.GetSpan().Slice(0, current)));
total += current;
}while (current == buffer.Memory.Length);
Assert.Equal(fileSize, total);
}
}
public async Task ReadAsyncUsingMultipleBuffers(bool asyncOperation, bool asyncHandle)
{
const int fileSize = 1_000_000; // 1 MB
string filePath = GetTestFilePath();
byte[] expected = RandomNumberGenerator.GetBytes(fileSize);
File.WriteAllBytes(filePath, expected);
using (SafeFileHandle handle = File.OpenHandle(filePath, FileMode.Open, options: GetFileOptions(asyncHandle)))
using (SectorAlignedMemory <byte> buffer_1 = SectorAlignedMemory <byte> .Allocate(Environment.SystemPageSize))
using (SectorAlignedMemory <byte> buffer_2 = SectorAlignedMemory <byte> .Allocate(Environment.SystemPageSize))
{
long current = 0;
long total = 0;
IReadOnlyList <Memory <byte> > buffers = new Memory <byte>[]
{
buffer_1.Memory,
buffer_2.Memory,
};
do
{
current = asyncOperation
? await RandomAccess.ReadAsync(handle, buffers, fileOffset : total)
: RandomAccess.Read(handle, buffers, fileOffset: total);
int takeFromFirst = Math.Min(buffer_1.Memory.Length, (int)current);
Assert.True(expected.AsSpan((int)total, takeFromFirst).SequenceEqual(buffer_1.GetSpan().Slice(0, takeFromFirst)));
int takeFromSecond = (int)current - takeFromFirst;
Assert.True(expected.AsSpan((int)total + takeFromFirst, takeFromSecond).SequenceEqual(buffer_2.GetSpan().Slice(0, takeFromSecond)));
total += current;
} while (current == buffer_1.Memory.Length + buffer_2.Memory.Length);
Assert.Equal(fileSize, total);
}
}