libraries/tbs/plugins/tbs_plugin_opentbs.php
function Ext_DeductFormat(&$Ext, $Search) {
		if (strpos(',odt,ods,odg,odf,odp,odm,ott,ots,otg,otp,', ',' . $Ext . ',') !== false) return 'odf';
		if (strpos(',docx,xlsx,xlsm,pptx,', ',' . $Ext . ',') !== false) return 'openxml';
		if (!$Search) return false;
		if ($this->FileExists('content.xml')) {
			// OpenOffice documents
			if ($this->FileExists('META-INF/manifest.xml')) {
				$Ext = '?'; // not needed for processing OpenOffice documents
				return 'odf';
			}
		} elseif ($this->FileExists('[Content_Types].xml')) {
			// Ms Office documents
			if ($this->FileExists('word/document.xml')) {
				$Ext = 'docx';
				return 'openxml';
			} elseif ($this->FileExists('xl/workbook.xml')) {
				$Ext = 'xlsx';
				return 'openxml';
			} elseif ($this->FileExists('ppt/presentation.xml')) {
				$Ext = 'pptx';
				return 'openxml';
			}
		}
		return false;
	}
function Ext_DeductFormat(&$Ext, $Search) {
		if (strpos(',odt,ods,odg,odf,odp,odm,ott,ots,otg,otp,', ',' . $Ext . ',') !== false) return 'odf';
		if (strpos(',docx,xlsx,xlsm,pptx,', ',' . $Ext . ',') !== false) return 'openxml';
		if (!$Search) return false;
		if ($this->FileExists('content.xml')) {
			// OpenOffice documents
			if ($this->FileExists('META-INF/manifest.xml')) {
				$Ext = '?'; // not needed for processing OpenOffice documents
				return 'odf';
			}
		} elseif ($this->FileExists('[Content_Types].xml')) {
			// Ms Office documents
			if ($this->FileExists('word/document.xml')) {
				$Ext = 'docx';
				return 'openxml';
			} elseif ($this->FileExists('xl/workbook.xml')) {
				$Ext = 'xlsx';
				return 'openxml';
			} elseif ($this->FileExists('ppt/presentation.xml')) {
				$Ext = 'pptx';
				return 'openxml';
			}
		}
		return false;
	}
Return the type of document corresponding to the given extension.