/// <summary>
/// Takes bytes starting from an offset in an array segment and appends as many as possible to the buffer.
/// </summary>
/// <remarks>
/// This method will append a maximum of <paramref name="count"/> elements to the end of the buffer, starting at <paramref name="offset"/> in <paramref name="buffer"/>.
/// <para>If there is not enough space for <paramref name="count"/> elements, it will fill the remaining space with bytes from the start of <paramref name="buffer"/>.</para>
/// </remarks>
/// <param name="buffer">The array to read from.</param>
/// <param name="offset">The start of the segment.</param>
/// <param name="count">The number of bytes to append.</param>
/// <inheritdoc cref="ThrowIfDisposed()" select="exception[@cref='ObjectDisposedException']" />
/// <exception cref="ArgumentNullException">Thrown if <paramref name="buffer" /> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentOutOfRangeException">Thrown if <paramref name="offset"/> is negative or <paramref name="count"/> is non-positive.</exception>
/// <exception cref="ArraySegmentException">Thrown if the array segment given by the <paramref name="offset"/> and <paramref name="count"/> parameters falls outside of the given array's bounds.</exception>
/// <returns>the number of bytes that were stored.</returns>
public int AppendFill(byte[] buffer, int offset, int count)
{
ThrowIfDisposed();
Guard.NotNull(() => buffer, buffer);
if (offset < 0)
{
throw GetOffsetIsNegativeException(offset);
}
if (count <= 0)
{
throw GetCountIsNonPositiveException(count);
}
if (buffer.Length < offset || offset + count > buffer.Length)
{
throw ArraySegmentException.GetByStartAndLength(offset, count);
}
int stored = AppendInternal(buffer, offset, count);
return(stored);
}
/// <summary>
/// Initializes a new instance of the <see cref="PacketReader"/> class using the given byte array segment as a buffer.
/// </summary>
/// <param name="buffer">The byte array to use as a buffer.</param>
/// <param name="offset">The start of the buffer segment.</param>
/// <param name="length">The length of the buffer segment.</param>
/// <exception cref="ArgumentNullException">
/// Thrown if <paramref name="buffer"/> is <see langword="null"/>.
/// </exception>
/// <exception cref="ArgumentOutOfRangeException">
/// Thrown if <paramref name="offset"/> or <paramref name="length"/> are negative.
/// </exception>
/// <exception cref="ArraySegmentException">
/// Thrown if the array segment given by the <paramref name="offset"/> and
/// <paramref name="length"/> parameters falls outside of the array's bounds.
/// </exception>
public PacketReader(byte[] buffer, int offset, int length)
{
Guard.NotNull(() => buffer, buffer);
if (offset < 0)
{
throw new ArgumentOutOfRangeException(nameof(offset), offset, CommonStrings.OffsetMustBeNonNegative);
}
if (length < 0)
{
throw new ArgumentOutOfRangeException(nameof(length), length, CommonStrings.LengthMustBeNonNegative);
}
if (buffer.Length < offset || offset + length > buffer.Length)
{
throw ArraySegmentException.GetByStartAndLength(offset, length);
}
_buffer = buffer;
_currentOffset = _segmentStart = offset;
_segmentEnd = offset + length;
}
/// <summary>
/// Returns an integer by reading bytes in little-endian byte order.
/// </summary>
/// <param name="buffer">The buffer to read bytes from.</param>
/// <param name="offset">The index of the start of the segment.</param>
/// <param name="count">The number of bytes to read.</param>
/// <exception cref="ArgumentNullException">
/// Thrown if <paramref name="buffer"/> is <see langword="null"/>.
/// </exception>
/// <exception cref="ArgumentOutOfRangeException">
/// <para>Thrown if <paramref name="offset"/> falls outside the bounds of <paramref name="buffer"/>, </para>
/// <para>OR, </para>
/// <para>if <paramref name="count"/> is such that the segment's end falls outside the bounds of <paramref name="buffer"/>.</para>
/// </exception>
/// <returns>an integer constructed by reading bytes in little-endian byte order.</returns>
private static long FromBytes(byte[] buffer, int offset, int count)
{
Guard.NotNull(() => buffer, buffer);
if (offset < 0)
{
throw new ArgumentOutOfRangeException(nameof(offset), offset, CommonStrings.OffsetMustBeNonNegative);
}
if (offset > buffer.Length || offset + count > buffer.Length)
{
throw ArraySegmentException.GetByStartAndLength(offset, count);
}
long result = 0;
int end = offset + count;
for (int position = end - 1; position >= offset; position--)
{
result = unchecked ((result << 8) | buffer[position]);
}
return(result);
}
