/// <summary><inheritDoc/></summary>
public virtual int Get(long position, byte[] bytes, int off, int len)
{
GroupedRandomAccessSource.SourceEntry entry = GetSourceEntryForOffset(position);
// if true, we have run out of data to read from
if (entry == null)
{
return(-1);
}
long offN = entry.OffsetN(position);
int remaining = len;
while (remaining > 0)
{
// if true, we have run out of data to read from
if (entry == null)
{
break;
}
if (offN > entry.source.Length())
{
break;
}
int count = entry.source.Get(offN, bytes, off, remaining);
if (count == -1)
{
break;
}
off += count;
position += count;
remaining -= count;
offN = 0;
entry = GetSourceEntryForOffset(position);
}
return(remaining == len ? -1 : len - remaining);
}
/// <summary>
/// Returns the SourceEntry that contains the byte at the specified offset
/// sourceReleased is called as a notification callback so subclasses can take care of cleanup
/// when the source is no longer the active source
/// </summary>
/// <param name="offset">the offset of the byte to look for</param>
/// <returns>the SourceEntry that contains the byte at the specified offset</returns>
private GroupedRandomAccessSource.SourceEntry GetSourceEntryForOffset(long offset)
{
if (offset >= size)
{
return(null);
}
if (offset >= currentSourceEntry.firstByte && offset <= currentSourceEntry.lastByte)
{
return(currentSourceEntry);
}
// hook to allow subclasses to release resources if necessary
SourceReleased(currentSourceEntry.source);
int startAt = GetStartingSourceIndex(offset);
for (int i = startAt; i < sources.Length; i++)
{
if (offset >= sources[i].firstByte && offset <= sources[i].lastByte)
{
currentSourceEntry = sources[i];
SourceInUse(currentSourceEntry.source);
return(currentSourceEntry);
}
}
return(null);
}
// by default, do nothing
/// <summary>
/// <inheritDoc/>
/// The source that contains the byte at position is retrieved, the correct offset into that source computed, then the value
/// from that offset in the underlying source is returned.
/// </summary>
public virtual int Get(long position)
{
GroupedRandomAccessSource.SourceEntry entry = GetSourceEntryForOffset(position);
// if true, we have run out of data to read from
if (entry == null)
{
return(-1);
}
return(entry.source.Get(entry.OffsetN(position)));
}
/// <summary>
/// Constructs a new
/// <see cref="GroupedRandomAccessSource"/>
/// based on the specified set of sources
/// </summary>
/// <param name="sources">the sources used to build this group</param>
public GroupedRandomAccessSource(IRandomAccessSource[] sources)
{
this.sources = new GroupedRandomAccessSource.SourceEntry[sources.Length];
long totalSize = 0;
for (int i = 0; i < sources.Length; i++)
{
this.sources[i] = new GroupedRandomAccessSource.SourceEntry(i, sources[i], totalSize);
totalSize += sources[i].Length();
}
size = totalSize;
currentSourceEntry = this.sources[sources.Length - 1];
SourceInUse(currentSourceEntry.source);
}
