public AvifItemData ReadItemData(ItemLocationEntry entry)
{
if (entry is null)
{
ExceptionUtil.ThrowArgumentNullException(nameof(entry));
}
AvifItemData data;
if (entry.Extents.Count == 1)
{
long offset = CalculateExtentOffset(entry.BaseOffset, entry.ConstructionMethod, entry.Extents[0]);
this.reader.Position = offset;
ulong totalItemSize = entry.TotalItemSize;
if (totalItemSize <= ManagedAvifItemDataMaxSize)
{
ManagedAvifItemData managedItemData = new ManagedAvifItemData((int)totalItemSize, this.arrayPool);
this.reader.ProperRead(managedItemData.GetBuffer(), 0, (int)managedItemData.Length);
data = managedItemData;
}
else
{
UnmanagedAvifItemData unmanagedItemData = new UnmanagedAvifItemData(totalItemSize);
try
{
this.reader.ProperRead(unmanagedItemData.UnmanagedBuffer, 0, totalItemSize);
data = unmanagedItemData;
unmanagedItemData = null;
}
finally
{
unmanagedItemData?.Dispose();
}
}
}
else
{
data = ReadDataFromMultipleExtents(entry);
}
return(data);
}
private AvifItemData ReadDataFromMultipleExtents(ItemLocationEntry entry)
{
AvifItemData data;
IReadOnlyList <ItemLocationExtent> extents = entry.Extents;
ulong totalItemSize = entry.TotalItemSize;
if (totalItemSize <= ManagedAvifItemDataMaxSize)
{
ManagedAvifItemData managedItemData = new ManagedAvifItemData((int)totalItemSize, this.arrayPool);
int offset = 0;
int remainingBytes = (int)managedItemData.Length;
byte[] bytes = managedItemData.GetBuffer();
for (int i = 0; i < extents.Count; i++)
{
ItemLocationExtent extent = extents[i];
long itemOffset = CalculateExtentOffset(entry.BaseOffset, entry.ConstructionMethod, extent);
int length = (int)extent.Length;
if (length > remainingBytes)
{
throw new FormatException("The extent length is greater than the number of bytes remaining for the item.");
}
this.reader.Position = itemOffset;
this.reader.ProperRead(bytes, offset, length);
offset += length;
remainingBytes -= length;
}
if (remainingBytes > 0)
{
// This should never happen, the total item size is the sum of all the extent sizes.
throw new FormatException("The item has more data than was read from the extents.");
}
data = managedItemData;
}
else
{
UnmanagedAvifItemData unmanagedItemData = new UnmanagedAvifItemData(totalItemSize);
try
{
ulong offset = 0;
ulong remainingBytes = totalItemSize;
for (int i = 0; i < extents.Count; i++)
{
ItemLocationExtent extent = extents[i];
long itemOffset = CalculateExtentOffset(entry.BaseOffset, entry.ConstructionMethod, extent);
ulong length = extent.Length;
if (length > remainingBytes)
{
throw new FormatException("The extent length is greater than the number of bytes remaining for the item.");
}
this.reader.Position = itemOffset;
this.reader.ProperRead(unmanagedItemData.UnmanagedBuffer, offset, length);
offset += length;
remainingBytes -= length;
}
if (remainingBytes > 0)
{
// This should never happen, the total item size is the sum of all the extent sizes.
throw new FormatException("The item has more data than was read from the extents.");
}
data = unmanagedItemData;
unmanagedItemData = null;
}
finally
{
unmanagedItemData?.Dispose();
}
}
return(data);
}