C#•2y ago

BinaryReader and BinaryWriter api behaviour incompatibility

BinaryReader read(span<byte>) does not call read(byte[], int, int) but BinaryWriter write(span<byte>) DOES call write(byte[], int, int) is this expected behaviour?

2 Replies

Klarth•2y ago

https://github.com/dotnet/runtime/blob/215b39abf947da7a40b0cb137eab4bceb24ad3e3/src/libraries/System.Private.CoreLib/src/System/IO/BinaryWriter.cs#L386 https://github.com/dotnet/runtime/blob/38ca26b27b9e7a867e6ff69eec3cabbfb4e9e1cf/src/libraries/System.Private.CoreLib/src/System/IO/BinaryReader.cs#L336 Write seems to write directly to the underlying stream...unless you've derived from it? In that case, it copies to a rented array and uses the array-writing overload. It seems a bit odd of an implementation to me, but maybe it's there for some backwards compatibility reasons.

androidui•2y ago

hmm alright im using a MemoryStream for both output and input

class MemoryWriter : TypeCheckingBinaryWriter
{
    public long Position { get => BaseStream.Position; set => BaseStream.Position = value; }
    public long Length => BaseStream.Length;

    public MemoryWriter(Stream output) : base(output)
    {
    }

    public MemoryWriter(Stream output, bool leaveOpen) : base(output, Encoding.UTF8, leaveOpen)
    {
    }

    public MemoryWriter() : this(new MemoryStream(), false)
    {
    }

class MemoryWriter : TypeCheckingBinaryWriter
{
    public long Position { get => BaseStream.Position; set => BaseStream.Position = value; }
    public long Length => BaseStream.Length;

    public MemoryWriter(Stream output) : base(output)
    {
    }

    public MemoryWriter(Stream output, bool leaveOpen) : base(output, Encoding.UTF8, leaveOpen)
    {
    }

    public MemoryWriter() : this(new MemoryStream(), false)
    {
    }

MemoryWriter memory = new();

var old = memory.BaseStream.Position;
memory.BaseStream.Position = 0;

// keep open
MemoryReader reader = new(memory.BaseStream, true);

while (reader.BaseStream.Position != reader.BaseStream.Length)
{
    // ...
}
reader.Dispose();
memory.BaseStream.Position = old;

MemoryWriter memory = new();

var old = memory.BaseStream.Position;
memory.BaseStream.Position = 0;

// keep open
MemoryReader reader = new(memory.BaseStream, true);

while (reader.BaseStream.Position != reader.BaseStream.Length)
{
    // ...
}
reader.Dispose();
memory.BaseStream.Position = old;

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BinaryReader and BinaryWriter api behaviour incompatibility