DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Mercurial (d09edbe2abfe)

VCS Links

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/Attributes.h"
#include "mozilla/UniquePtrExtensions.h"
#include "mozilla/UniquePtr.h"

#include "nsIIncrementalDownload.h"
#include "nsIRequestObserver.h"
#include "nsIProgressEventSink.h"
#include "nsIChannelEventSink.h"
#include "nsIAsyncVerifyRedirectCallback.h"
#include "nsIInterfaceRequestor.h"
#include "nsIObserverService.h"
#include "nsIObserver.h"
#include "nsIStreamListener.h"
#include "nsIFile.h"
#include "nsITimer.h"
#include "nsIURI.h"
#include "nsIInputStream.h"
#include "nsNetUtil.h"
#include "nsWeakReference.h"
#include "prio.h"
#include "prprf.h"
#include <algorithm>
#include "nsIContentPolicy.h"
#include "nsContentUtils.h"
#include "mozilla/UniquePtr.h"

// Default values used to initialize a nsIncrementalDownload object.
#define DEFAULT_CHUNK_SIZE (4096 * 16)  // bytes
#define DEFAULT_INTERVAL 60             // seconds

#define UPDATE_PROGRESS_INTERVAL PRTime(100 * PR_USEC_PER_MSEC)  // 100ms

// Number of times to retry a failed byte-range request.
#define MAX_RETRY_COUNT 20

using namespace mozilla;
using namespace mozilla::net;

//-----------------------------------------------------------------------------

static nsresult WriteToFile(nsIFile* lf, const char* data, uint32_t len,
                            int32_t flags) {
  PRFileDesc* fd;
  int32_t mode = 0600;
  nsresult rv;
  rv = lf->OpenNSPRFileDesc(flags, mode, &fd);
  if (NS_FAILED(rv)) return rv;

  if (len)
    rv = PR_Write(fd, data, len) == int32_t(len) ? NS_OK : NS_ERROR_FAILURE;

  PR_Close(fd);
  return rv;
}

static nsresult AppendToFile(nsIFile* lf, const char* data, uint32_t len) {
  int32_t flags = PR_WRONLY | PR_CREATE_FILE | PR_APPEND;
  return WriteToFile(lf, data, len, flags);
}

// maxSize may be -1 if unknown
static void MakeRangeSpec(const int64_t& size, const int64_t& maxSize,
                          int32_t chunkSize, bool fetchRemaining,
                          nsCString& rangeSpec) {
  rangeSpec.AssignLiteral("bytes=");
  rangeSpec.AppendInt(int64_t(size));
  rangeSpec.Append('-');

  if (fetchRemaining) return;

  int64_t end = size + int64_t(chunkSize);
  if (maxSize != int64_t(-1) && end > maxSize) end = maxSize;
  end -= 1;

  rangeSpec.AppendInt(int64_t(end));
}

//-----------------------------------------------------------------------------

class nsIncrementalDownload final : public nsIIncrementalDownload,
                                    public nsIStreamListener,
                                    public nsIObserver,
                                    public nsIInterfaceRequestor,
                                    public nsIChannelEventSink,
                                    public nsSupportsWeakReference,
                                    public nsIAsyncVerifyRedirectCallback {
 public:
  NS_DECL_ISUPPORTS
  NS_DECL_NSIREQUEST
  NS_DECL_NSIINCREMENTALDOWNLOAD
  NS_DECL_NSIREQUESTOBSERVER
  NS_DECL_NSISTREAMLISTENER
  NS_DECL_NSIOBSERVER
  NS_DECL_NSIINTERFACEREQUESTOR
  NS_DECL_NSICHANNELEVENTSINK
  NS_DECL_NSIASYNCVERIFYREDIRECTCALLBACK

  nsIncrementalDownload();

 private:
  ~nsIncrementalDownload() = default;
  nsresult FlushChunk();
  void UpdateProgress();
  nsresult CallOnStartRequest();
  void CallOnStopRequest();
  nsresult StartTimer(int32_t interval);
  nsresult ProcessTimeout();
  nsresult ReadCurrentSize();
  nsresult ClearRequestHeader(nsIHttpChannel* channel);

  nsCOMPtr<nsIRequestObserver> mObserver;
  nsCOMPtr<nsISupports> mObserverContext;
  nsCOMPtr<nsIProgressEventSink> mProgressSink;
  nsCOMPtr<nsIURI> mURI;
  nsCOMPtr<nsIURI> mFinalURI;
  nsCOMPtr<nsIFile> mDest;
  nsCOMPtr<nsIChannel> mChannel;
  nsCOMPtr<nsITimer> mTimer;
  mozilla::UniquePtr<char[]> mChunk;
  int32_t mChunkLen;
  int32_t mChunkSize;
  int32_t mInterval;
  int64_t mTotalSize;
  int64_t mCurrentSize;
  uint32_t mLoadFlags;
  int32_t mNonPartialCount;
  nsresult mStatus;
  bool mIsPending;
  bool mDidOnStartRequest;
  PRTime mLastProgressUpdate;
  nsCOMPtr<nsIAsyncVerifyRedirectCallback> mRedirectCallback;
  nsCOMPtr<nsIChannel> mNewRedirectChannel;
  nsCString mPartialValidator;
  bool mCacheBust;
};

nsIncrementalDownload::nsIncrementalDownload()
    : mChunkLen(0),
      mChunkSize(DEFAULT_CHUNK_SIZE),
      mInterval(DEFAULT_INTERVAL),
      mTotalSize(-1),
      mCurrentSize(-1),
      mLoadFlags(LOAD_NORMAL),
      mNonPartialCount(0),
      mStatus(NS_OK),
      mIsPending(false),
      mDidOnStartRequest(false),
      mLastProgressUpdate(0),
      mRedirectCallback(nullptr),
      mNewRedirectChannel(nullptr),
      mCacheBust(false) {}

nsresult nsIncrementalDownload::FlushChunk() {
  NS_ASSERTION(mTotalSize != int64_t(-1), "total size should be known");

  if (mChunkLen == 0) return NS_OK;

  nsresult rv = AppendToFile(mDest, mChunk.get(), mChunkLen);
  if (NS_FAILED(rv)) return rv;

  mCurrentSize += int64_t(mChunkLen);
  mChunkLen = 0;

  return NS_OK;
}

void nsIncrementalDownload::UpdateProgress() {
  mLastProgressUpdate = PR_Now();

  if (mProgressSink)
    mProgressSink->OnProgress(this, mObserverContext, mCurrentSize + mChunkLen,
                              mTotalSize);
}

nsresult nsIncrementalDownload::CallOnStartRequest() {
  if (!mObserver || mDidOnStartRequest) return NS_OK;

  mDidOnStartRequest = true;
  return mObserver->OnStartRequest(this);
}

void nsIncrementalDownload::CallOnStopRequest() {
  if (!mObserver) return;

  // Ensure that OnStartRequest is always called once before OnStopRequest.
  nsresult rv = CallOnStartRequest();
  if (NS_SUCCEEDED(mStatus)) mStatus = rv;

  mIsPending = false;

  mObserver->OnStopRequest(this, mStatus);
  mObserver = nullptr;
  mObserverContext = nullptr;
}

nsresult nsIncrementalDownload::StartTimer(int32_t interval) {
  return NS_NewTimerWithObserver(getter_AddRefs(mTimer), this, interval * 1000,
                                 nsITimer::TYPE_ONE_SHOT);
}

nsresult nsIncrementalDownload::ProcessTimeout() {
  NS_ASSERTION(!mChannel, "how can we have a channel?");

  // Handle existing error conditions
  if (NS_FAILED(mStatus)) {
    CallOnStopRequest();
    return NS_OK;
  }

  // Fetch next chunk

  nsCOMPtr<nsIChannel> channel;
  nsresult rv = NS_NewChannel(getter_AddRefs(channel), mFinalURI,
                              nsContentUtils::GetSystemPrincipal(),
                              nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_DATA_IS_NULL,
                              nsIContentPolicy::TYPE_OTHER,
                              nullptr,  // nsICookieSettings
                              nullptr,  // PerformanceStorage
                              nullptr,  // loadGroup
                              this,     // aCallbacks
                              mLoadFlags);

  if (NS_FAILED(rv)) return rv;

  nsCOMPtr<nsIHttpChannel> http = do_QueryInterface(channel, &rv);
  if (NS_FAILED(rv)) return rv;

  NS_ASSERTION(mCurrentSize != int64_t(-1),
               "we should know the current file size by now");

  rv = ClearRequestHeader(http);
  if (NS_FAILED(rv)) return rv;

  // Don't bother making a range request if we are just going to fetch the
  // entire document.
  if (mInterval || mCurrentSize != int64_t(0)) {
    nsAutoCString range;
    MakeRangeSpec(mCurrentSize, mTotalSize, mChunkSize, mInterval == 0, range);

    rv = http->SetRequestHeader(NS_LITERAL_CSTRING("Range"), range, false);
    if (NS_FAILED(rv)) return rv;

    if (!mPartialValidator.IsEmpty()) {
      rv = http->SetRequestHeader(NS_LITERAL_CSTRING("If-Range"),
                                  mPartialValidator, false);
      if (NS_FAILED(rv)) {
        LOG(
            ("nsIncrementalDownload::ProcessTimeout\n"
             "    failed to set request header: If-Range\n"));
      }
    }

    if (mCacheBust) {
      rv = http->SetRequestHeader(NS_LITERAL_CSTRING("Cache-Control"),
                                  NS_LITERAL_CSTRING("no-cache"), false);
      if (NS_FAILED(rv)) {
        LOG(
            ("nsIncrementalDownload::ProcessTimeout\n"
             "    failed to set request header: If-Range\n"));
      }
      rv = http->SetRequestHeader(NS_LITERAL_CSTRING("Pragma"),
                                  NS_LITERAL_CSTRING("no-cache"), false);
      if (NS_FAILED(rv)) {
        LOG(
            ("nsIncrementalDownload::ProcessTimeout\n"
             "    failed to set request header: If-Range\n"));
      }
    }
  }

  rv = channel->AsyncOpen(this);
  if (NS_FAILED(rv)) return rv;

  // Wait to assign mChannel when we know we are going to succeed.  This is
  // important because we don't want to introduce a reference cycle between
  // mChannel and this until we know for a fact that AsyncOpen has succeeded,
  // thus ensuring that our stream listener methods will be invoked.
  mChannel = channel;
  return NS_OK;
}

// Reads the current file size and validates it.
nsresult nsIncrementalDownload::ReadCurrentSize() {
  int64_t size;
  nsresult rv = mDest->GetFileSize((int64_t*)&size);
  if (rv == NS_ERROR_FILE_NOT_FOUND ||
      rv == NS_ERROR_FILE_TARGET_DOES_NOT_EXIST) {
    mCurrentSize = 0;
    return NS_OK;
  }
  if (NS_FAILED(rv)) return rv;

  mCurrentSize = size;
  return NS_OK;
}

// nsISupports

NS_IMPL_ISUPPORTS(nsIncrementalDownload, nsIIncrementalDownload, nsIRequest,
                  nsIStreamListener, nsIRequestObserver, nsIObserver,
                  nsIInterfaceRequestor, nsIChannelEventSink,
                  nsISupportsWeakReference, nsIAsyncVerifyRedirectCallback)

// nsIRequest

NS_IMETHODIMP
nsIncrementalDownload::GetName(nsACString& name) {
  NS_ENSURE_TRUE(mURI, NS_ERROR_NOT_INITIALIZED);

  return mURI->GetSpec(name);
}

NS_IMETHODIMP
nsIncrementalDownload::IsPending(bool* isPending) {
  *isPending = mIsPending;
  return NS_OK;
}

NS_IMETHODIMP
nsIncrementalDownload::GetStatus(nsresult* status) {
  *status = mStatus;
  return NS_OK;
}

NS_IMETHODIMP
nsIncrementalDownload::Cancel(nsresult status) {
  NS_ENSURE_ARG(NS_FAILED(status));

  // Ignore this cancelation if we're already canceled.
  if (NS_FAILED(mStatus)) return NS_OK;

  mStatus = status;

  // Nothing more to do if callbacks aren't pending.
  if (!mIsPending) return NS_OK;

  if (mChannel) {
    mChannel->Cancel(mStatus);
    NS_ASSERTION(!mTimer, "what is this timer object doing here?");
  } else {
    // dispatch a timer callback event to drive invoking our listener's
    // OnStopRequest.
    if (mTimer) mTimer->Cancel();
    StartTimer(0);
  }

  return NS_OK;
}

NS_IMETHODIMP
nsIncrementalDownload::Suspend() { return NS_ERROR_NOT_IMPLEMENTED; }

NS_IMETHODIMP
nsIncrementalDownload::Resume() { return NS_ERROR_NOT_IMPLEMENTED; }

NS_IMETHODIMP
nsIncrementalDownload::GetLoadFlags(nsLoadFlags* loadFlags) {
  *loadFlags = mLoadFlags;
  return NS_OK;
}

NS_IMETHODIMP
nsIncrementalDownload::SetLoadFlags(nsLoadFlags loadFlags) {
  mLoadFlags = loadFlags;
  return NS_OK;
}

NS_IMETHODIMP
nsIncrementalDownload::GetLoadGroup(nsILoadGroup** loadGroup) {
  return NS_ERROR_NOT_IMPLEMENTED;
}

NS_IMETHODIMP
nsIncrementalDownload::SetLoadGroup(nsILoadGroup* loadGroup) {
  return NS_ERROR_NOT_IMPLEMENTED;
}

// nsIIncrementalDownload

NS_IMETHODIMP
nsIncrementalDownload::Init(nsIURI* uri, nsIFile* dest, int32_t chunkSize,
                            int32_t interval) {
  // Keep it simple: only allow initialization once
  NS_ENSURE_FALSE(mURI, NS_ERROR_ALREADY_INITIALIZED);

  mDest = dest;
  NS_ENSURE_ARG(mDest);

  mURI = uri;
  mFinalURI = uri;

  if (chunkSize > 0) mChunkSize = chunkSize;
  if (interval >= 0) mInterval = interval;
  return NS_OK;
}

NS_IMETHODIMP
nsIncrementalDownload::GetURI(nsIURI** result) {
  nsCOMPtr<nsIURI> uri = mURI;
  uri.forget(result);
  return NS_OK;
}

NS_IMETHODIMP
nsIncrementalDownload::GetFinalURI(nsIURI** result) {
  nsCOMPtr<nsIURI> uri = mFinalURI;
  uri.forget(result);
  return NS_OK;
}

NS_IMETHODIMP
nsIncrementalDownload::GetDestination(nsIFile** result) {
  if (!mDest) {
    *result = nullptr;
    return NS_OK;
  }
  // Return a clone of mDest so that callers may modify the resulting nsIFile
  // without corrupting our internal object.  This also works around the fact
  // that some nsIFile impls may cache the result of stat'ing the filesystem.
  return mDest->Clone(result);
}

NS_IMETHODIMP
nsIncrementalDownload::GetTotalSize(int64_t* result) {
  *result = mTotalSize;
  return NS_OK;
}

NS_IMETHODIMP
nsIncrementalDownload::GetCurrentSize(int64_t* result) {
  *result = mCurrentSize;
  return NS_OK;
}

NS_IMETHODIMP
nsIncrementalDownload::Start(nsIRequestObserver* observer,
                             nsISupports* context) {
  NS_ENSURE_ARG(observer);
  NS_ENSURE_FALSE(mIsPending, NS_ERROR_IN_PROGRESS);

  // Observe system shutdown so we can be sure to release any reference held
  // between ourselves and the timer.  We have the observer service hold a weak
  // reference to us, so that we don't have to worry about calling
  // RemoveObserver.  XXX(darin): The timer code should do this for us.
  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
  if (obs) obs->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, true);

  nsresult rv = ReadCurrentSize();
  if (NS_FAILED(rv)) return rv;

  rv = StartTimer(0);
  if (NS_FAILED(rv)) return rv;

  mObserver = observer;
  mObserverContext = context;
  mProgressSink = do_QueryInterface(observer);  // ok if null

  mIsPending = true;
  return NS_OK;
}

// nsIRequestObserver

NS_IMETHODIMP
nsIncrementalDownload::OnStartRequest(nsIRequest* request) {
  nsresult rv;

  nsCOMPtr<nsIHttpChannel> http = do_QueryInterface(request, &rv);
  if (NS_FAILED(rv)) return rv;

  // Ensure that we are receiving a 206 response.
  uint32_t code;
  rv = http->GetResponseStatus(&code);
  if (NS_FAILED(rv)) return rv;
  if (code != 206) {
    // We may already have the entire file downloaded, in which case
    // our request for a range beyond the end of the file would have
    // been met with an error response code.
    if (code == 416 && mTotalSize == int64_t(-1)) {
      mTotalSize = mCurrentSize;
      // Return an error code here to suppress OnDataAvailable.
      return NS_ERROR_DOWNLOAD_COMPLETE;
    }
    // The server may have decided to give us all of the data in one chunk.  If
    // we requested a partial range, then we don't want to download all of the
    // data at once.  So, we'll just try again, but if this keeps happening then
    // we'll eventually give up.
    if (code == 200) {
      if (mInterval) {
        mChannel = nullptr;
        if (++mNonPartialCount > MAX_RETRY_COUNT) {
          NS_WARNING("unable to fetch a byte range; giving up");
          return NS_ERROR_FAILURE;
        }
        // Increase delay with each failure.
        StartTimer(mInterval * mNonPartialCount);
        return NS_ERROR_DOWNLOAD_NOT_PARTIAL;
      }
      // Since we have been asked to download the rest of the file, we can deal
      // with a 200 response.  This may result in downloading the beginning of
      // the file again, but that can't really be helped.
    } else {
      NS_WARNING("server response was unexpected");
      return NS_ERROR_UNEXPECTED;
    }
  } else {
    // We got a partial response, so clear this counter in case the next chunk
    // results in a 200 response.
    mNonPartialCount = 0;

    // confirm that the content-range response header is consistent with
    // expectations on each 206. If it is not then drop this response and
    // retry with no-cache set.
    if (!mCacheBust) {
      nsAutoCString buf;
      int64_t startByte = 0;
      bool confirmedOK = false;

      rv = http->GetResponseHeader(NS_LITERAL_CSTRING("Content-Range"), buf);
      if (NS_FAILED(rv))
        return rv;  // it isn't a useful 206 without a CONTENT-RANGE of some
                    // sort

      // Content-Range: bytes 0-299999/25604694
      int32_t p = buf.Find("bytes ");

      // first look for the starting point of the content-range
      // to make sure it is what we expect
      if (p != -1) {
        char* endptr = nullptr;
        const char* s = buf.get() + p + 6;
        while (*s && *s == ' ') s++;
        startByte = strtol(s, &endptr, 10);

        if (*s && endptr && (endptr != s) && (mCurrentSize == startByte)) {
          // ok the starting point is confirmed. We still need to check the
          // total size of the range for consistency if this isn't
          // the first chunk
          if (mTotalSize == int64_t(-1)) {
            // first chunk
            confirmedOK = true;
          } else {
            int32_t slash = buf.FindChar('/');
            int64_t rangeSize = 0;
            if (slash != kNotFound &&
                (PR_sscanf(buf.get() + slash + 1, "%lld",
                           (int64_t*)&rangeSize) == 1) &&
                rangeSize == mTotalSize) {
              confirmedOK = true;
            }
          }
        }
      }

      if (!confirmedOK) {
        NS_WARNING("unexpected content-range");
        mCacheBust = true;
        mChannel = nullptr;
        if (++mNonPartialCount > MAX_RETRY_COUNT) {
          NS_WARNING("unable to fetch a byte range; giving up");
          return NS_ERROR_FAILURE;
        }
        // Increase delay with each failure.
        StartTimer(mInterval * mNonPartialCount);
        return NS_ERROR_DOWNLOAD_NOT_PARTIAL;
      }
    }
  }

  // Do special processing after the first response.
  if (mTotalSize == int64_t(-1)) {
    // Update knowledge of mFinalURI
    rv = http->GetURI(getter_AddRefs(mFinalURI));
    if (NS_FAILED(rv)) return rv;
    Unused << http->GetResponseHeader(NS_LITERAL_CSTRING("Etag"),
                                      mPartialValidator);
    if (StringBeginsWith(mPartialValidator, NS_LITERAL_CSTRING("W/")))
      mPartialValidator.Truncate();  // don't use weak validators
    if (mPartialValidator.IsEmpty()) {
      rv = http->GetResponseHeader(NS_LITERAL_CSTRING("Last-Modified"),
                                   mPartialValidator);
      if (NS_FAILED(rv)) {
        LOG(
            ("nsIncrementalDownload::OnStartRequest\n"
             "    empty validator\n"));
      }
    }

    if (code == 206) {
      // OK, read the Content-Range header to determine the total size of this
      // download file.
      nsAutoCString buf;
      rv = http->GetResponseHeader(NS_LITERAL_CSTRING("Content-Range"), buf);
      if (NS_FAILED(rv)) return rv;
      int32_t slash = buf.FindChar('/');
      if (slash == kNotFound) {
        NS_WARNING("server returned invalid Content-Range header!");
        return NS_ERROR_UNEXPECTED;
      }
      if (PR_sscanf(buf.get() + slash + 1, "%lld", (int64_t*)&mTotalSize) != 1)
        return NS_ERROR_UNEXPECTED;
    } else {
      rv = http->GetContentLength(&mTotalSize);
      if (NS_FAILED(rv)) return rv;
      // We need to know the total size of the thing we're trying to download.
      if (mTotalSize == int64_t(-1)) {
        NS_WARNING("server returned no content-length header!");
        return NS_ERROR_UNEXPECTED;
      }
      // Need to truncate (or create, if it doesn't exist) the file since we
      // are downloading the whole thing.
      WriteToFile(mDest, nullptr, 0, PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE);
      mCurrentSize = 0;
    }

    // Notify observer that we are starting...
    rv = CallOnStartRequest();
    if (NS_FAILED(rv)) return rv;
  }

  // Adjust mChunkSize accordingly if mCurrentSize is close to mTotalSize.
  int64_t diff = mTotalSize - mCurrentSize;
  if (diff <= int64_t(0)) {
    NS_WARNING("about to set a bogus chunk size; giving up");
    return NS_ERROR_UNEXPECTED;
  }

  if (diff < int64_t(mChunkSize)) mChunkSize = uint32_t(diff);

  mChunk = mozilla::MakeUniqueFallible<char[]>(mChunkSize);
  if (!mChunk) rv = NS_ERROR_OUT_OF_MEMORY;

  return rv;
}

NS_IMETHODIMP
nsIncrementalDownload::OnStopRequest(nsIRequest* request, nsresult status) {
  // Not a real error; just a trick to kill off the channel without our
  // listener having to care.
  if (status == NS_ERROR_DOWNLOAD_NOT_PARTIAL) return NS_OK;

  // Not a real error; just a trick used to suppress OnDataAvailable calls.
  if (status == NS_ERROR_DOWNLOAD_COMPLETE) status = NS_OK;

  if (NS_SUCCEEDED(mStatus)) mStatus = status;

  if (mChunk) {
    if (NS_SUCCEEDED(mStatus)) mStatus = FlushChunk();

    mChunk = nullptr;  // deletes memory
    mChunkLen = 0;
    UpdateProgress();
  }

  mChannel = nullptr;

  // Notify listener if we hit an error or finished
  if (NS_FAILED(mStatus) || mCurrentSize == mTotalSize) {
    CallOnStopRequest();
    return NS_OK;
  }

  return StartTimer(mInterval);  // Do next chunk
}

// nsIStreamListener

NS_IMETHODIMP
nsIncrementalDownload::OnDataAvailable(nsIRequest* request,
                                       nsIInputStream* input, uint64_t offset,
                                       uint32_t count) {
  while (count) {
    uint32_t space = mChunkSize - mChunkLen;
    uint32_t n, len = std::min(space, count);

    nsresult rv = input->Read(&mChunk[mChunkLen], len, &n);
    if (NS_FAILED(rv)) return rv;
    if (n != len) return NS_ERROR_UNEXPECTED;

    count -= n;
    mChunkLen += n;

    if (mChunkLen == mChunkSize) {
      rv = FlushChunk();
      if (NS_FAILED(rv)) return rv;
    }
  }

  if (PR_Now() > mLastProgressUpdate + UPDATE_PROGRESS_INTERVAL)
    UpdateProgress();

  return NS_OK;
}

// nsIObserver

NS_IMETHODIMP
nsIncrementalDownload::Observe(nsISupports* subject, const char* topic,
                               const char16_t* data) {
  if (strcmp(topic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0) {
    Cancel(NS_ERROR_ABORT);

    // Since the app is shutting down, we need to go ahead and notify our
    // observer here.  Otherwise, we would notify them after XPCOM has been
    // shutdown or not at all.
    CallOnStopRequest();
  } else if (strcmp(topic, NS_TIMER_CALLBACK_TOPIC) == 0) {
    mTimer = nullptr;
    nsresult rv = ProcessTimeout();
    if (NS_FAILED(rv)) Cancel(rv);
  }
  return NS_OK;
}

// nsIInterfaceRequestor

NS_IMETHODIMP
nsIncrementalDownload::GetInterface(const nsIID& iid, void** result) {
  if (iid.Equals(NS_GET_IID(nsIChannelEventSink))) {
    NS_ADDREF_THIS();
    *result = static_cast<nsIChannelEventSink*>(this);
    return NS_OK;
  }

  nsCOMPtr<nsIInterfaceRequestor> ir = do_QueryInterface(mObserver);
  if (ir) return ir->GetInterface(iid, result);

  return NS_ERROR_NO_INTERFACE;
}

nsresult nsIncrementalDownload::ClearRequestHeader(nsIHttpChannel* channel) {
  NS_ENSURE_ARG(channel);

  // We don't support encodings -- they make the Content-Length not equal
  // to the actual size of the data.
  return channel->SetRequestHeader(NS_LITERAL_CSTRING("Accept-Encoding"),
                                   NS_LITERAL_CSTRING(""), false);
}

// nsIChannelEventSink

NS_IMETHODIMP
nsIncrementalDownload::AsyncOnChannelRedirect(
    nsIChannel* oldChannel, nsIChannel* newChannel, uint32_t flags,
    nsIAsyncVerifyRedirectCallback* cb) {
  // In response to a redirect, we need to propagate the Range header.  See bug
  // 311595.  Any failure code returned from this function aborts the redirect.

  nsCOMPtr<nsIHttpChannel> http = do_QueryInterface(oldChannel);
  NS_ENSURE_STATE(http);

  nsCOMPtr<nsIHttpChannel> newHttpChannel = do_QueryInterface(newChannel);
  NS_ENSURE_STATE(newHttpChannel);

  NS_NAMED_LITERAL_CSTRING(rangeHdr, "Range");

  nsresult rv = ClearRequestHeader(newHttpChannel);
  if (NS_FAILED(rv)) return rv;

  // If we didn't have a Range header, then we must be doing a full download.
  nsAutoCString rangeVal;
  Unused << http->GetRequestHeader(rangeHdr, rangeVal);
  if (!rangeVal.IsEmpty()) {
    rv = newHttpChannel->SetRequestHeader(rangeHdr, rangeVal, false);
    NS_ENSURE_SUCCESS(rv, rv);
  }

  // A redirection changes the validator
  mPartialValidator.Truncate();

  if (mCacheBust) {
    rv =
        newHttpChannel->SetRequestHeader(NS_LITERAL_CSTRING("Cache-Control"),
                                         NS_LITERAL_CSTRING("no-cache"), false);
    if (NS_FAILED(rv)) {
      LOG(
          ("nsIncrementalDownload::AsyncOnChannelRedirect\n"
           "    failed to set request header: Cache-Control\n"));
    }
    rv = newHttpChannel->SetRequestHeader(
        NS_LITERAL_CSTRING("Pragma"), NS_LITERAL_CSTRING("no-cache"), false);
    if (NS_FAILED(rv)) {
      LOG(
          ("nsIncrementalDownload::AsyncOnChannelRedirect\n"
           "    failed to set request header: Pragma\n"));
    }
  }

  // Prepare to receive callback
  mRedirectCallback = cb;
  mNewRedirectChannel = newChannel;

  // Give the observer a chance to see this redirect notification.
  nsCOMPtr<nsIChannelEventSink> sink = do_GetInterface(mObserver);
  if (sink) {
    rv = sink->AsyncOnChannelRedirect(oldChannel, newChannel, flags, this);
    if (NS_FAILED(rv)) {
      mRedirectCallback = nullptr;
      mNewRedirectChannel = nullptr;
    }
    return rv;
  }
  (void)OnRedirectVerifyCallback(NS_OK);
  return NS_OK;
}

NS_IMETHODIMP
nsIncrementalDownload::OnRedirectVerifyCallback(nsresult result) {
  NS_ASSERTION(mRedirectCallback, "mRedirectCallback not set in callback");
  NS_ASSERTION(mNewRedirectChannel, "mNewRedirectChannel not set in callback");

  // Update mChannel, so we can Cancel the new channel.
  if (NS_SUCCEEDED(result)) mChannel = mNewRedirectChannel;

  mRedirectCallback->OnRedirectVerifyCallback(result);
  mRedirectCallback = nullptr;
  mNewRedirectChannel = nullptr;
  return NS_OK;
}

extern nsresult net_NewIncrementalDownload(nsISupports* outer, const nsIID& iid,
                                           void** result) {
  if (outer) return NS_ERROR_NO_AGGREGATION;

  RefPtr<nsIncrementalDownload> d = new nsIncrementalDownload();
  return d->QueryInterface(iid, result);
}