Method SwapToAnotherFile

src/DownloadClient.cpp:1431–1540

// toFile = Try to swap to this partfile only

bool CUpDownClient::SwapToAnotherFile(bool bIgnoreNoNeeded, bool ignoreSuspensions, bool bRemoveCompletely, CPartFile* toFile)
{
	// Fail if m_reqfile is invalid
	if ( m_reqfile == NULL ) {
		return false;
	}

	// It would be stupid to swap away a downloading source
	if (GetDownloadState() == DS_DOWNLOADING) {
		return false;
	}

	// The iterator of the final target
	A4AFList::iterator target = m_A4AF_list.end();

	// Do we want to swap to a specific file?
	if ( toFile != NULL ) {
		A4AFList::iterator it = m_A4AF_list.find( toFile );
		if ( it != m_A4AF_list.end() ) {

			// We force ignoring of timestamps
			if ( IsValidSwapTarget( it, bIgnoreNoNeeded, true ) ) {
				// Set the target
				target = it;
			}
		}
	} else {
		// We want highest priority possible, but need to start with
		// a value less than any other priority
		char priority = -1;

		A4AFList::iterator it = m_A4AF_list.begin();
		for ( ; it != m_A4AF_list.end(); ++it ) {
			if ( IsValidSwapTarget( it, bIgnoreNoNeeded, ignoreSuspensions ) ) {
				char cur_priority = it->first->GetDownPriority();

				// We would prefer to get files with needed parts, thus rate them higher.
				// However, this really only matters if bIgnoreNoNeeded is true.
				if ( it->second.NeededParts )
						cur_priority += 10;

				// Change target if the current file has a higher rate than the previous
				if ( cur_priority > priority ) {
					priority = cur_priority;

					// Set the new target
					target = it;

					// Break on the first High-priority file with needed parts
					if ( priority == PR_HIGH + 10 ) {
						break;
					}
				}
			}
		}
	}

	// Try to swap if we found a valid target