/// <summary>
/// Reads the preamble, the ranges, and the names of the rest of the buffers.
/// </summary>
public static BFastHeader ReadBFastHeader(this Stream stream)
{
var r = new BFastHeader();
var br = new BinaryReader(stream);
r.Preamble = new BFastPreamble
{
Magic = br.ReadInt64(),
DataStart = br.ReadInt64(),
DataEnd = br.ReadInt64(),
NumArrays = br.ReadInt64(),
}
.Validate();
r.Ranges = stream.ReadArray <BFastRange>((int)r.Preamble.NumArrays);
var padding = ComputePadding(r.Ranges);
br.ReadBytes((int)padding);
CheckAlignment(br.BaseStream);
var nameBytes = br.ReadBytes((int)r.Ranges[0].Count);
r.Names = UnpackStrings(nameBytes);
padding = ComputePadding(r.Ranges[0].End);
br.ReadBytes((int)padding);
CheckAlignment(br.BaseStream);
return(r.Validate());
}
/// <summary>
/// Creates a BFAST structure, without any actual data buffers, from a list of sizes of buffers (not counting the name buffer).
/// Used as an intermediate step to create a BFAST.
/// </summary>
public static BFastHeader CreateBFastHeader(this long[] bufferSizes, string[] bufferNames)
{
if (bufferNames.Length != bufferSizes.Length)
{
throw new Exception($"The number of buffer sizes {bufferSizes.Length} is not equal to the number of buffer names {bufferNames.Length}");
}
var header = new BFastHeader
{
Names = bufferNames
};
header.Preamble.Magic = Constants.Magic;
header.Preamble.NumArrays = bufferSizes.Length + 1;
// Allocate the data for the ranges
header.Ranges = new BFastRange[header.Preamble.NumArrays];
header.Preamble.DataStart = ComputeNextAlignment(header.Preamble.RangesEnd);
var nameBufferLength = PackStrings(bufferNames).LongLength;
var sizes = (new[] { nameBufferLength }).Concat(bufferSizes).ToArray();
// Compute the offsets for the data buffers
var curIndex = header.Preamble.DataStart;
var i = 0;
foreach (var size in sizes)
{
curIndex = ComputeNextAlignment(curIndex);
Debug.Assert(IsAligned(curIndex));
header.Ranges[i].Begin = curIndex;
curIndex += size;
header.Ranges[i].End = curIndex;
i++;
}
// Finish with the header
// Each buffer we contain is padded to ensure the next one
// starts on alignment, so we pad our DataEnd to reflect this reality
header.Preamble.DataEnd = ComputeNextAlignment(curIndex);
// Check that everything adds up
return(header.Validate());
}