public RingMemoryPage[] GetPages(long offset, long count)
{
VerifyNotDisposed();
Require.That(count > 0, "Count must be greater than zero", "count");
VerifyCapacityRange(offset, offset + count);
long startPage = GetPage(offset);
long endPage = GetPage(offset + count - 1);
var result = new RingMemoryPage[endPage - startPage + 1];
for (long i = startPage; i <= endPage; i++)
{
long pageOffset =
i == startPage
? offset - GetPageOffset(i)
: 0;
long pageCount =
i == endPage
? (offset + count) - GetPageOffset(i)
: BlockSize - pageOffset;
result[i] = new RingMemoryPage(_pages[i - _pagesOffset], (int)pageOffset, (int)pageCount);
}
return result;
}
/// <summary>
/// Gets a reference to the backing memory pages based on the provided
/// offset and count.
/// </summary>
/// <remarks>
/// <see cref="GetPages"/> provides access to the backing pages of the
/// stream. Reading from or writing to the stream, this method is preferred
/// over <see cref="Read"/> because working with the backing pages limits
/// the number of extra memory allocations that need to be made.
/// </remarks>
/// <param name="offset">The start offset for which to get the backing pages</param>
/// <param name="count">The number of bytes the returned pages must span</param>
/// <returns>The memory pages describing the requested range</returns>
public RingMemoryPage[] GetPages(long offset, long count)
{
VerifyNotDisposed();
Require.That(count > 0, "Count must be greater than zero", "count");
VerifyCapacityRange(offset, offset + count);
// Calculate the complete range of pages based on the data that
// is being read.
long startPage = GetPage(offset);
long endPage = GetPage(offset + count - 1);
var result = new RingMemoryPage[endPage - startPage + 1];
// For all returned memory pages, calculate the offset and count
// for each separate page and return this including a reference to
// the backing memory for that page.
for (long i = startPage; i <= endPage; i++)
{
long pageOffset =
i == startPage
? offset - GetPageOffset(i)
: 0;
long pageCount =
i == endPage
? (offset + count) - GetPageOffset(i)
: BlockSize - pageOffset;
result[i] = new RingMemoryPage(_pages[i - _pagesOffset], (int)pageOffset, (int)pageCount);
}
return result;
}
private bool TryGetSendPage(out RingMemoryPage page)
{
long pageSize = Math.Min(
_sendStream.BlockSize - _sendStream.Head % _sendStream.BlockSize, // Maximum size to stay on the page
_sendStream.Length - _sendStream.Head // Maximum size to send at all
);
if (pageSize == 0)
{
page = new RingMemoryPage();
return false;
}
else
{
page = _sendStream.GetPage(_sendStream.Head, pageSize);
Debug.Assert(_sendStream.Head + pageSize <= _sendStream.Length);
return true;
}
}
