Golang C.cupsLastError类(方法)实例源码

// connect calls C.httpConnect2 to create a new, open connection to
// the CUPS server specified by environment variables, client.conf, etc.
//
// connect also acquires the connection semaphore and locks the OS
// thread to allow the CUPS API to use thread-local storage cleanly.
//
// The caller is responsible to close the connection when finished
// using cupsCore.disconnect.
func (cc *cupsCore) connect() (*C.http_t, error) {
	cc.connectionSemaphore.Acquire()

	// Lock the OS thread so that thread-local storage is available to
	// cupsLastError() and cupsLastErrorString().
	runtime.LockOSThread()

	var http *C.http_t

	select {
	case h := <-cc.connectionPool:
		// Reuse another connection.
		http = h
	default:
		// No connection available for reuse; create a new one.
		http = C.httpConnect2(cc.host, cc.port, nil, C.AF_UNSPEC, cc.encryption, 1, cc.connectTimeout, nil)
		if http == nil {
			defer cc.disconnect(http)
			return nil, fmt.Errorf("Failed to connect to CUPS server %s:%d because %d %s",
				C.GoString(cc.host), int(cc.port), int(C.cupsLastError()), C.GoString(C.cupsLastErrorString()))
		}
	}

	return http, nil
}

// getPPD gets the filename of the PPD for a printer by calling
// C.cupsGetPPD3. If the PPD hasn't changed since the time indicated
// by modtime, then the returned filename is a nil pointer.
//
// Note that modtime is a pointer whose value is changed by this
// function.
//
// The caller is responsible to C.free the returned *C.char filename
// if the returned filename is not nil.
func (cc *cupsCore) getPPD(printername *C.char, modtime *C.time_t) (*C.char, error) {
	bufsize := C.size_t(filePathMaxLength)
	buffer := (*C.char)(C.malloc(bufsize))
	if buffer == nil {
		return nil, errors.New("Failed to malloc; out of memory?")
	}
	C.memset(unsafe.Pointer(buffer), 0, bufsize)

	var http *C.http_t
	if !cc.hostIsLocal {
		// Don't need a connection or corresponding semaphore if the PPD
		// is on the local filesystem.
		// Still need OS thread lock; see else.
		var err error
		http, err = cc.connect()
		if err != nil {
			return nil, err
		}
		defer cc.disconnect(http)

	} else {
		// Lock the OS thread so that thread-local storage is available to
		// cupsLastError() and cupsLastErrorString().
		runtime.LockOSThread()
		defer runtime.UnlockOSThread()
	}

	httpStatus := C.cupsGetPPD3(http, printername, modtime, buffer, bufsize)

	switch httpStatus {
	case C.HTTP_STATUS_NOT_MODIFIED:
		// Cache hit.
		if len(C.GoString(buffer)) > 0 {
			os.Remove(C.GoString(buffer))
		}
		C.free(unsafe.Pointer(buffer))
		return nil, nil

	case C.HTTP_STATUS_OK:
		// Cache miss.
		return buffer, nil

	default:
		if len(C.GoString(buffer)) > 0 {
			os.Remove(C.GoString(buffer))
		}
		C.free(unsafe.Pointer(buffer))
		cupsLastError := C.cupsLastError()
		if cupsLastError != C.IPP_STATUS_OK {
			return nil, fmt.Errorf("Failed to call cupsGetPPD3(): %d %s",
				int(cupsLastError), C.GoString(C.cupsLastErrorString()))
		}

		return nil, fmt.Errorf("Failed to call cupsGetPPD3(); HTTP status: %d", int(httpStatus))
	}
}

// printFile prints by calling C.cupsPrintFile2().
// Returns the CUPS job ID, which is 0 (and meaningless) when err
// is not nil.
func (cc *cupsCore) printFile(user, printername, filename, title *C.char, numOptions C.int, options *C.cups_option_t) (C.int, error) {
	http, err := cc.connect()
	if err != nil {
		return 0, err
	}
	defer cc.disconnect(http)

	C.cupsSetUser(user)
	jobID := C.cupsPrintFile2(http, printername, filename, title, numOptions, options)
	if jobID == 0 {
		return 0, fmt.Errorf("Failed to call cupsPrintFile2() for file %s: %d %s",
			C.GoString(filename), int(C.cupsLastError()), C.GoString(C.cupsLastErrorString()))
	}

	return jobID, nil
}

// CreateTempFile calls cupsTempFd() to create a new file that (1) lives in a
// "temporary" location (like /tmp) and (2) is readable by CUPS. The caller
// is responsible for deleting the file.
func CreateTempFile() (*os.File, error) {
	length := C.size_t(filePathMaxLength)
	filename := (*C.char)(C.malloc(length))
	if filename == nil {
		return nil, errors.New("Failed to malloc(); out of memory?")
	}
	defer C.free(unsafe.Pointer(filename))

	createTempFileLock.Lock()
	defer createTempFileLock.Unlock()

	runtime.LockOSThread()
	defer runtime.UnlockOSThread()

	fd := C.cupsTempFd(filename, C.int(length))
	if fd == C.int(-1) {
		err := fmt.Errorf("Failed to call cupsTempFd(): %d %s",
			int(C.cupsLastError()), C.GoString(C.cupsLastErrorString()))
		return nil, err
	}

	return os.NewFile(uintptr(fd), C.GoString(filename)), nil
}

// doRequest calls cupsDoRequest().
func (cc *cupsCore) doRequest(request *C.ipp_t, acceptableStatusCodes []C.ipp_status_t) (*C.ipp_t, error) {
	http, err := cc.connect()
	if err != nil {
		return nil, err
	}
	defer cc.disconnect(http)

	if C.ippValidateAttributes(request) != 1 {
		return nil, fmt.Errorf("Bad IPP request: %s", C.GoString(C.cupsLastErrorString()))
	}

	response := C.cupsDoRequest(http, request, C.POST_RESOURCE)
	if response == nil {
		return nil, fmt.Errorf("cupsDoRequest failed: %d %s", int(C.cupsLastError()), C.GoString(C.cupsLastErrorString()))
	}
	statusCode := C.getIPPRequestStatusCode(response)
	for _, sc := range acceptableStatusCodes {
		if statusCode == sc {
			return response, nil
		}
	}

	return nil, fmt.Errorf("IPP status code %d", int(statusCode))
}