/usr/share/gocode/src/github.com/google/cups-connector/cups/core.go is in google-cloud-print-connector 0.0~git20151105.24.1902938-2.
This file is owned by root:root, with mode 0o644.
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Copyright 2015 Google Inc. All rights reserved.
Use of this source code is governed by a BSD-style
license that can be found in the LICENSE file or at
https://developers.google.com/open-source/licenses/bsd
*/
package cups
/*
#include "cups.h"
*/
import "C"
import (
"errors"
"fmt"
"os"
"runtime"
"strings"
"time"
"unsafe"
"github.com/google/cups-connector/lib"
"github.com/google/cups-connector/log"
)
const (
// jobURIFormat is the string format required by the CUPS API
// to do things like query the state of a job.
jobURIFormat = "/jobs/%d"
// filePathMaxLength varies by operating system and file system.
// This value should be large enough to be useful and small enough
// to work on any platform.
filePathMaxLength = 1024
)
// cupsCore handles CUPS API interaction and connection management.
type cupsCore struct {
host *C.char
port C.int
encryption C.http_encryption_t
connectTimeout C.int
// connectionSemaphore limits the quantity of open CUPS connections.
connectionSemaphore *lib.Semaphore
// connectionPool allows a connection to be reused instead of closed.
connectionPool chan *C.http_t
hostIsLocal bool
}
func newCUPSCore(maxConnections uint, connectTimeout time.Duration) (*cupsCore, error) {
host := C.cupsServer()
port := C.ippPort()
encryption := C.cupsEncryption()
timeout := C.int(connectTimeout / time.Millisecond)
var e string
switch encryption {
case C.HTTP_ENCRYPTION_ALWAYS:
e = "encrypting ALWAYS"
case C.HTTP_ENCRYPTION_IF_REQUESTED:
e = "encrypting IF REQUESTED"
case C.HTTP_ENCRYPTION_NEVER:
e = "encrypting NEVER"
case C.HTTP_ENCRYPTION_REQUIRED:
e = "encryption REQUIRED"
default:
encryption = C.HTTP_ENCRYPTION_REQUIRED
e = "encrypting REQUIRED"
}
var hostIsLocal bool
if h := C.GoString(host); strings.HasPrefix(h, "/") || h == "localhost" {
hostIsLocal = true
}
cs := lib.NewSemaphore(maxConnections)
cp := make(chan *C.http_t)
cc := &cupsCore{host, port, encryption, timeout, cs, cp, hostIsLocal}
// This connection isn't used, just checks that a connection is possible
// before returning from the constructor.
http, err := cc.connect()
if err != nil {
return nil, err
}
cc.disconnect(http)
log.Infof("connected to CUPS server %s:%d %s\n", C.GoString(host), int(port), e)
return cc, nil
}
// 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
}
// getPrinters gets the current list and state of printers by calling
// C.doRequest (IPP_OP_CUPS_GET_PRINTERS).
//
// The caller is responsible to C.ippDelete the returned *C.ipp_t response.
func (cc *cupsCore) getPrinters(attributes **C.char, attrSize C.int) (*C.ipp_t, error) {
// ippNewRequest() returns ipp_t pointer which does not need explicit free.
request := C.ippNewRequest(C.IPP_OP_CUPS_GET_PRINTERS)
C.ippAddStrings(request, C.IPP_TAG_OPERATION, C.IPP_TAG_KEYWORD, C.REQUESTED_ATTRIBUTES,
attrSize, nil, attributes)
response, err := cc.doRequest(request,
[]C.ipp_status_t{C.IPP_STATUS_OK, C.IPP_STATUS_ERROR_NOT_FOUND})
if err != nil {
err = fmt.Errorf("Failed to call cupsDoRequest() [IPP_OP_CUPS_GET_PRINTERS]: %s", err)
return nil, err
}
return response, 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))
}
}
// getJobAttributes gets the requested attributes for a job by calling
// C.doRequest (IPP_OP_GET_JOB_ATTRIBUTES).
//
// The caller is responsible to C.ippDelete the returned *C.ipp_t response.
func (cc *cupsCore) getJobAttributes(jobID C.int, attributes **C.char) (*C.ipp_t, error) {
uri, err := createJobURI(jobID)
if err != nil {
return nil, err
}
defer C.free(unsafe.Pointer(uri))
// ippNewRequest() returns ipp_t pointer does not need explicit free.
request := C.ippNewRequest(C.IPP_OP_GET_JOB_ATTRIBUTES)
C.ippAddString(request, C.IPP_TAG_OPERATION, C.IPP_TAG_URI, C.JOB_URI_ATTRIBUTE, nil, uri)
C.ippAddStrings(request, C.IPP_TAG_OPERATION, C.IPP_TAG_KEYWORD, C.REQUESTED_ATTRIBUTES,
C.int(0), nil, attributes)
response, err := cc.doRequest(request, []C.ipp_status_t{C.IPP_STATUS_OK})
if err != nil {
err = fmt.Errorf("Failed to call cupsDoRequest() [IPP_OP_GET_JOB_ATTRIBUTES]: %s", err)
return nil, err
}
return response, nil
}
// createJobURI creates a uri string for the job-uri attribute, used to get the
// state of a CUPS job.
func createJobURI(jobID C.int) (*C.char, error) {
length := C.size_t(urlMaxLength)
uri := (*C.char)(C.malloc(length))
if uri == nil {
return nil, errors.New("Failed to malloc; out of memory?")
}
resource := C.CString(fmt.Sprintf(jobURIFormat, uint32(jobID)))
defer C.free(unsafe.Pointer(resource))
C.httpAssembleURI(C.HTTP_URI_CODING_ALL,
uri, C.int(length), C.IPP, nil, C.cupsServer(), C.ippPort(), resource)
return uri, 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))
}
// 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
}
// disconnect calls C.httpClose to close an open CUPS connection, then
// unlocks the OS thread and the connection semaphore.
//
// The http argument may be nil; the OS thread and semaphore are still
// treated the same as described above.
func (cc *cupsCore) disconnect(http *C.http_t) {
go func() {
select {
case cc.connectionPool <- http:
// Hand this connection to the next guy who needs it.
case <-time.After(time.Second):
// Don't wait very long; stale connections are no fun.
C.httpClose(http)
}
}()
runtime.UnlockOSThread()
cc.connectionSemaphore.Release()
}
func (cc *cupsCore) connQtyOpen() uint {
return cc.connectionSemaphore.Count()
}
func (cc *cupsCore) connQtyMax() uint {
return cc.connectionSemaphore.Size()
}
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