// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;
using System.IO;
using System.Text;
using System.Diagnostics;


// This abstract base class represents a writer that can write
// primitives to an arbitrary stream. A subclass can override methods to
// give unique encodings.
//
internal class BinaryWriter : IDisposable
{
    public static readonly BinaryWriter Null = new BinaryWriter();

    protected Stream OutStream;
    private byte[] _buffer;    // temp space for writing primitives to.
    private Encoding _encoding;
    private Encoder _encoder;

    private bool _leaveOpen;

    // Perf optimization stuff
    private byte[] _largeByteBuffer;  // temp space for writing chars.
    private int _maxChars;   // max # of chars we can put in _largeByteBuffer
                             // Size should be around the max number of chars/string * Encoding's max bytes/char
    private const int LargeByteBufferSize = 256;

    // Protected default constructor that sets the output stream
    // to a null stream (a bit bucket).
    protected BinaryWriter()
    {
        OutStream = Stream.Null;
        _buffer = new byte[16];
        _encoding = new UTF8Encoding(false, true);
        _encoder = _encoding.GetEncoder();
    }

    public BinaryWriter(Stream output) : this(output, new UTF8Encoding(false, true), false)
    {
    }

    public BinaryWriter(Stream output, Encoding encoding) : this(output, encoding, false)
    {
    }

    public BinaryWriter(Stream output, Encoding encoding, bool leaveOpen)
    {
        if (output == null)
        {
            throw new ArgumentNullException("output");
        }
        if (encoding == null)
        {
            throw new ArgumentNullException("encoding");
        }
        if (!output.CanWrite)
        {
            throw new ArgumentException("StreamNotWritable");
        }

        OutStream = output;
        _buffer = new byte[16];
        _encoding = encoding;
        _encoder = _encoding.GetEncoder();
        _leaveOpen = leaveOpen;
    }

    protected virtual void Dispose(bool disposing)
    {
        if (disposing)
        {
            if (_leaveOpen)
            {
                OutStream.Flush();
            }
            else
            {
                OutStream.Dispose();
            }
        }
    }

    public void Dispose()
    {
        Dispose(true);
    }

    /*
     * Returns the stream associate with the writer. It flushes all pending
     * writes before returning. All subclasses should override Flush to
     * ensure that all buffered data is sent to the stream.
     */
    public virtual Stream BaseStream
    {
        get
        {
            Flush();
            return OutStream;
        }
    }

    // Clears all buffers for this writer and causes any buffered data to be
    // written to the underlying device. 
    public virtual void Flush()
    {
        OutStream.Flush();
    }

    public virtual long Seek(int offset, SeekOrigin origin)
    {
        return OutStream.Seek(offset, origin);
    }

    // Writes a boolean to this stream. A single byte is written to the stream
    // with the value 0 representing false or the value 1 representing true.
    // 
    public virtual void Write(bool value)
    {
        _buffer[0] = (byte)(value ? 1 : 0);
        OutStream.Write(_buffer, 0, 1);
    }

    // Writes a byte to this stream. The current position of the stream is
    // advanced by one.
    // 
    public virtual void Write(byte value)
    {
        OutStream.WriteByte(value);
    }

    // Writes a signed byte to this stream. The current position of the stream 
    // is advanced by one.
    // 
#pragma warning disable 3019, 3021
    [CLSCompliant(false)]
    public virtual void Write(sbyte value)
    {
        OutStream.WriteByte((byte)value);
    }
#pragma warning restore 3019, 3021

    // Writes a byte array to this stream.
    // 
    // This default implementation calls the Write(Object, int, int)
    // method to write the byte array.
    // 
    public virtual void Write(byte[] buffer)
    {
        if (buffer == null)
        {
            throw new ArgumentNullException("buffer");
        }

        OutStream.Write(buffer, 0, buffer.Length);
    }

    // Writes a section of a byte array to this stream.
    //
    // This default implementation calls the Write(Object, int, int)
    // method to write the byte array.
    // 
    public virtual void Write(byte[] buffer, int index, int count)
    {
        OutStream.Write(buffer, index, count);
    }


    // Writes a character to this stream. The current position of the stream is
    // advanced by two.
    // Note this method cannot handle surrogates properly in UTF-8.
    // 
    public unsafe virtual void Write(char ch)
    {
        if (char.IsSurrogate(ch))
        {
            throw new ArgumentException("SurrogatesNotAllowedAsSingleChar");
        }

        Debug.Assert(_encoding.GetMaxByteCount(1) <= 16, "_encoding.GetMaxByteCount(1) <= 16)");
        int numBytes = 0;
        char[] chBuf = new char[] { ch };
        numBytes = _encoder.GetBytes(chBuf, 0, 1, _buffer, 0, true);
        OutStream.Write(_buffer, 0, numBytes);
    }

    // Writes a character array to this stream.
    // 
    // This default implementation calls the Write(Object, int, int)
    // method to write the character array.
    // 
    public virtual void Write(char[] chars)
    {
        if (chars == null)
        {
            throw new ArgumentNullException("chars");
        }

        byte[] bytes = _encoding.GetBytes(chars, 0, chars.Length);
        OutStream.Write(bytes, 0, bytes.Length);
    }

    // Writes a section of a character array to this stream.
    //
    // This default implementation calls the Write(Object, int, int)
    // method to write the character array.
    // 
    public virtual void Write(char[] chars, int index, int count)
    {
        byte[] bytes = _encoding.GetBytes(chars, index, count);
        OutStream.Write(bytes, 0, bytes.Length);
    }


    // Writes a double to this stream. The current position of the stream is
    // advanced by eight.
    // 
    public unsafe virtual void Write(double value)
    {
        ulong TmpValue = *(ulong*)&value;
        _buffer[0] = (byte)TmpValue;
        _buffer[1] = (byte)(TmpValue >> 8);
        _buffer[2] = (byte)(TmpValue >> 16);
        _buffer[3] = (byte)(TmpValue >> 24);
        _buffer[4] = (byte)(TmpValue >> 32);
        _buffer[5] = (byte)(TmpValue >> 40);
        _buffer[6] = (byte)(TmpValue >> 48);
        _buffer[7] = (byte)(TmpValue >> 56);
        OutStream.Write(_buffer, 0, 8);
    }

    public virtual void Write(decimal value)
    {
        int[] bits = decimal.GetBits(value);
        Debug.Assert(bits.Length == 4);

        int lo = bits[0];
        _buffer[0] = (byte)lo;
        _buffer[1] = (byte)(lo >> 8);
        _buffer[2] = (byte)(lo >> 16);
        _buffer[3] = (byte)(lo >> 24);

        int mid = bits[1];
        _buffer[4] = (byte)mid;
        _buffer[5] = (byte)(mid >> 8);
        _buffer[6] = (byte)(mid >> 16);
        _buffer[7] = (byte)(mid >> 24);

        int hi = bits[2];
        _buffer[8] = (byte)hi;
        _buffer[9] = (byte)(hi >> 8);
        _buffer[10] = (byte)(hi >> 16);
        _buffer[11] = (byte)(hi >> 24);

        int flags = bits[3];
        _buffer[12] = (byte)flags;
        _buffer[13] = (byte)(flags >> 8);
        _buffer[14] = (byte)(flags >> 16);
        _buffer[15] = (byte)(flags >> 24);

        OutStream.Write(_buffer, 0, 16);
    }

    // Writes a two-byte signed integer to this stream. The current position of
    // the stream is advanced by two.
    // 
    public virtual void Write(short value)
    {
        _buffer[0] = (byte)value;
        _buffer[1] = (byte)(value >> 8);
        OutStream.Write(_buffer, 0, 2);
    }

    // Writes a two-byte unsigned integer to this stream. The current position
    // of the stream is advanced by two.
    // 
    //[CLSCompliant(false)]
    public virtual void Write(ushort value)
    {
        _buffer[0] = (byte)value;
        _buffer[1] = (byte)(value >> 8);
        OutStream.Write(_buffer, 0, 2);
    }

    // Writes a four-byte signed integer to this stream. The current position
    // of the stream is advanced by four.
    // 
    public virtual void Write(int value)
    {
        _buffer[0] = (byte)value;
        _buffer[1] = (byte)(value >> 8);
        _buffer[2] = (byte)(value >> 16);
        _buffer[3] = (byte)(value >> 24);
        OutStream.Write(_buffer, 0, 4);
    }

    // Writes a four-byte unsigned integer to this stream. The current position
    // of the stream is advanced by four.
    // 
    //[CLSCompliant(false)]
    public virtual void Write(uint value)
    {
        _buffer[0] = (byte)value;
        _buffer[1] = (byte)(value >> 8);
        _buffer[2] = (byte)(value >> 16);
        _buffer[3] = (byte)(value >> 24);
        OutStream.Write(_buffer, 0, 4);
    }

    // Writes an eight-byte signed integer to this stream. The current position
    // of the stream is advanced by eight.
    // 
    public virtual void Write(long value)
    {
        _buffer[0] = (byte)value;
        _buffer[1] = (byte)(value >> 8);
        _buffer[2] = (byte)(value >> 16);
        _buffer[3] = (byte)(value >> 24);
        _buffer[4] = (byte)(value >> 32);
        _buffer[5] = (byte)(value >> 40);
        _buffer[6] = (byte)(value >> 48);
        _buffer[7] = (byte)(value >> 56);
        OutStream.Write(_buffer, 0, 8);
    }

    // Writes an eight-byte unsigned integer to this stream. The current 
    // position of the stream is advanced by eight.
    // 
    //[CLSCompliant(false)]
    public virtual void Write(ulong value)
    {
        _buffer[0] = (byte)value;
        _buffer[1] = (byte)(value >> 8);
        _buffer[2] = (byte)(value >> 16);
        _buffer[3] = (byte)(value >> 24);
        _buffer[4] = (byte)(value >> 32);
        _buffer[5] = (byte)(value >> 40);
        _buffer[6] = (byte)(value >> 48);
        _buffer[7] = (byte)(value >> 56);
        OutStream.Write(_buffer, 0, 8);
    }

    // Writes a float to this stream. The current position of the stream is
    // advanced by four.
    // 
    public unsafe virtual void Write(float value)
    {
        uint TmpValue = *(uint*)&value;
        _buffer[0] = (byte)TmpValue;
        _buffer[1] = (byte)(TmpValue >> 8);
        _buffer[2] = (byte)(TmpValue >> 16);
        _buffer[3] = (byte)(TmpValue >> 24);
        OutStream.Write(_buffer, 0, 4);
    }


    // Writes a length-prefixed string to this stream in the BinaryWriter's
    // current Encoding. This method first writes the length of the string as 
    // a four-byte unsigned integer, and then writes that many characters 
    // to the stream.
    // 
    public unsafe virtual void Write(string value)
    {
        if (value == null)
        {
            throw new ArgumentNullException("value");
        }

        int len = _encoding.GetByteCount(value);
        Write7BitEncodedInt(len);

        if (_largeByteBuffer == null)
        {
            _largeByteBuffer = new byte[LargeByteBufferSize];
            _maxChars = LargeByteBufferSize / _encoding.GetMaxByteCount(1);
        }

        if (len <= LargeByteBufferSize)
        {
            _encoding.GetBytes(value, 0, value.Length, _largeByteBuffer, 0);
            OutStream.Write(_largeByteBuffer, 0, len);
        }
        else
        {
            // Aggressively try to not allocate memory in this loop for
            // runtime performance reasons.  Use an Encoder to write out 
            // the string correctly (handling surrogates crossing buffer
            // boundaries properly).  
            int charStart = 0;
            int numLeft = value.Length;
#if DEBUG
            int totalBytes = 0;
#endif
            while (numLeft > 0)
            {
                // Figure out how many chars to process this round.
                int charCount = (numLeft > _maxChars) ? _maxChars : numLeft;
                int byteLen;
                byteLen = _encoder.GetBytes(value.ToCharArray(), charStart, charCount, _largeByteBuffer, 0, charCount == numLeft);
#if DEBUG
                totalBytes += byteLen;
                Debug.Assert(totalBytes <= len && byteLen <= LargeByteBufferSize, "BinaryWriter::Write(String) - More bytes encoded than expected!");
#endif
                OutStream.Write(_largeByteBuffer, 0, byteLen);
                charStart += charCount;
                numLeft -= charCount;
            }
#if DEBUG
            Debug.Assert(totalBytes == len, "BinaryWriter::Write(String) - Didn't write out all the bytes!");
#endif
        }
    }

    protected void Write7BitEncodedInt(int value)
    {
        // Write out an int 7 bits at a time.  The high bit of the byte,
        // when on, tells reader to continue reading more bytes.
        uint v = (uint)value;   // support negative numbers
        while (v >= 0x80)
        {
            Write((byte)(v | 0x80));
            v >>= 7;
        }
        Write((byte)v);
    }
}