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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #include "content/browser/loader/redirect_to_file_resource_handler.h"
      6 
      7 #include "base/bind.h"
      8 #include "base/logging.h"
      9 #include "base/threading/thread_restrictions.h"
     10 #include "content/browser/loader/resource_request_info_impl.h"
     11 #include "content/browser/loader/temporary_file_stream.h"
     12 #include "content/public/browser/resource_controller.h"
     13 #include "content/public/common/resource_response.h"
     14 #include "net/base/file_stream.h"
     15 #include "net/base/io_buffer.h"
     16 #include "net/base/mime_sniffer.h"
     17 #include "net/base/net_errors.h"
     18 #include "storage/common/blob/shareable_file_reference.h"
     19 
     20 using storage::ShareableFileReference;
     21 
     22 namespace {
     23 
     24 // This class is similar to identically named classes in AsyncResourceHandler
     25 // and BufferedResourceHandler, but not quite.
     26 // TODO(ncbray) generalize and unify these cases?
     27 // In general, it's a bad idea to point to a subbuffer (particularly with
     28 // GrowableIOBuffer) because the backing IOBuffer may realloc its data.  In this
     29 // particular case we know RedirectToFileResourceHandler will not realloc its
     30 // buffer while a write is occurring, so we should be safe.  This property is
     31 // somewhat fragile, however, and depending on it is dangerous.  A more
     32 // principled approach would require significant refactoring, however, so for
     33 // the moment we're relying on fragile properties.
     34 class DependentIOBuffer : public net::WrappedIOBuffer {
     35  public:
     36   DependentIOBuffer(net::IOBuffer* backing, char* memory)
     37       : net::WrappedIOBuffer(memory),
     38         backing_(backing) {
     39   }
     40  private:
     41   virtual ~DependentIOBuffer() {}
     42 
     43   scoped_refptr<net::IOBuffer> backing_;
     44 };
     45 
     46 }  // namespace
     47 
     48 namespace content {
     49 
     50 static const int kInitialReadBufSize = 32768;
     51 static const int kMaxReadBufSize = 524288;
     52 
     53 // A separate IO thread object to manage the lifetime of the net::FileStream and
     54 // the ShareableFileReference. When the handler is destroyed, it asynchronously
     55 // closes net::FileStream after all pending writes complete. Only after the
     56 // stream is closed is the ShareableFileReference released, to ensure the
     57 // temporary is not deleted before it is closed.
     58 class RedirectToFileResourceHandler::Writer {
     59  public:
     60   Writer(RedirectToFileResourceHandler* handler,
     61          scoped_ptr<net::FileStream> file_stream,
     62          ShareableFileReference* deletable_file)
     63       : handler_(handler),
     64         file_stream_(file_stream.Pass()),
     65         is_writing_(false),
     66         deletable_file_(deletable_file) {
     67     DCHECK(!deletable_file_->path().empty());
     68   }
     69 
     70   bool is_writing() const { return is_writing_; }
     71   const base::FilePath& path() const { return deletable_file_->path(); }
     72 
     73   int Write(net::IOBuffer* buf, int buf_len) {
     74     DCHECK(!is_writing_);
     75     DCHECK(handler_);
     76     int result = file_stream_->Write(
     77         buf, buf_len,
     78         base::Bind(&Writer::DidWriteToFile, base::Unretained(this)));
     79     if (result == net::ERR_IO_PENDING)
     80       is_writing_ = true;
     81     return result;
     82   }
     83 
     84   void Close() {
     85     handler_ = NULL;
     86     if (!is_writing_)
     87       CloseAndDelete();
     88   }
     89 
     90  private:
     91   // Only DidClose can delete this.
     92   ~Writer() {
     93   }
     94 
     95   void DidWriteToFile(int result) {
     96     DCHECK(is_writing_);
     97     is_writing_ = false;
     98     if (handler_) {
     99       handler_->DidWriteToFile(result);
    100     } else {
    101       CloseAndDelete();
    102     }
    103   }
    104 
    105   void CloseAndDelete() {
    106     DCHECK(!is_writing_);
    107     int result = file_stream_->Close(base::Bind(&Writer::DidClose,
    108                                                 base::Unretained(this)));
    109     if (result != net::ERR_IO_PENDING)
    110       DidClose(result);
    111   }
    112 
    113   void DidClose(int result) {
    114     delete this;
    115   }
    116 
    117   RedirectToFileResourceHandler* handler_;
    118 
    119   scoped_ptr<net::FileStream> file_stream_;
    120   bool is_writing_;
    121 
    122   // We create a ShareableFileReference that's deletable for the temp file
    123   // created as a result of the download.
    124   scoped_refptr<storage::ShareableFileReference> deletable_file_;
    125 
    126   DISALLOW_COPY_AND_ASSIGN(Writer);
    127 };
    128 
    129 RedirectToFileResourceHandler::RedirectToFileResourceHandler(
    130     scoped_ptr<ResourceHandler> next_handler,
    131     net::URLRequest* request)
    132     : LayeredResourceHandler(request, next_handler.Pass()),
    133       buf_(new net::GrowableIOBuffer()),
    134       buf_write_pending_(false),
    135       write_cursor_(0),
    136       writer_(NULL),
    137       next_buffer_size_(kInitialReadBufSize),
    138       did_defer_(false),
    139       completed_during_write_(false),
    140       weak_factory_(this) {
    141 }
    142 
    143 RedirectToFileResourceHandler::~RedirectToFileResourceHandler() {
    144   // Orphan the writer to asynchronously close and release the temporary file.
    145   if (writer_) {
    146     writer_->Close();
    147     writer_ = NULL;
    148   }
    149 }
    150 
    151 void RedirectToFileResourceHandler::
    152     SetCreateTemporaryFileStreamFunctionForTesting(
    153         const CreateTemporaryFileStreamFunction& create_temporary_file_stream) {
    154   create_temporary_file_stream_ = create_temporary_file_stream;
    155 }
    156 
    157 bool RedirectToFileResourceHandler::OnResponseStarted(
    158     ResourceResponse* response,
    159     bool* defer) {
    160   DCHECK(writer_);
    161   response->head.download_file_path = writer_->path();
    162   return next_handler_->OnResponseStarted(response, defer);
    163 }
    164 
    165 bool RedirectToFileResourceHandler::OnWillStart(const GURL& url, bool* defer) {
    166   DCHECK(!writer_);
    167 
    168   // Defer starting the request until we have created the temporary file.
    169   // TODO(darin): This is sub-optimal.  We should not delay starting the
    170   // network request like this.
    171   will_start_url_ = url;
    172   did_defer_ = *defer = true;
    173   if (create_temporary_file_stream_.is_null()) {
    174     CreateTemporaryFileStream(
    175         base::Bind(&RedirectToFileResourceHandler::DidCreateTemporaryFile,
    176                    weak_factory_.GetWeakPtr()));
    177   } else {
    178     create_temporary_file_stream_.Run(
    179         base::Bind(&RedirectToFileResourceHandler::DidCreateTemporaryFile,
    180                    weak_factory_.GetWeakPtr()));
    181   }
    182   return true;
    183 }
    184 
    185 bool RedirectToFileResourceHandler::OnWillRead(
    186     scoped_refptr<net::IOBuffer>* buf,
    187     int* buf_size,
    188     int min_size) {
    189   DCHECK_EQ(-1, min_size);
    190 
    191   if (buf_->capacity() < next_buffer_size_)
    192     buf_->SetCapacity(next_buffer_size_);
    193 
    194   // We should have paused this network request already if the buffer is full.
    195   DCHECK(!BufIsFull());
    196 
    197   *buf = buf_.get();
    198   *buf_size = buf_->RemainingCapacity();
    199 
    200   buf_write_pending_ = true;
    201   return true;
    202 }
    203 
    204 bool RedirectToFileResourceHandler::OnReadCompleted(int bytes_read,
    205                                                     bool* defer) {
    206   DCHECK(buf_write_pending_);
    207   buf_write_pending_ = false;
    208 
    209   // We use the buffer's offset field to record the end of the buffer.
    210   int new_offset = buf_->offset() + bytes_read;
    211   DCHECK(new_offset <= buf_->capacity());
    212   buf_->set_offset(new_offset);
    213 
    214   if (BufIsFull()) {
    215     did_defer_ = *defer = true;
    216 
    217     if (buf_->capacity() == bytes_read) {
    218       // The network layer has saturated our buffer in one read. Next time, we
    219       // should give it a bigger buffer for it to fill.
    220       next_buffer_size_ = std::min(next_buffer_size_ * 2, kMaxReadBufSize);
    221     }
    222   }
    223 
    224   return WriteMore();
    225 }
    226 
    227 void RedirectToFileResourceHandler::OnResponseCompleted(
    228     const net::URLRequestStatus& status,
    229     const std::string& security_info,
    230     bool* defer) {
    231   if (writer_ && writer_->is_writing()) {
    232     completed_during_write_ = true;
    233     completed_status_ = status;
    234     completed_security_info_ = security_info;
    235     did_defer_ = true;
    236     *defer = true;
    237     return;
    238   }
    239   next_handler_->OnResponseCompleted(status, security_info, defer);
    240 }
    241 
    242 void RedirectToFileResourceHandler::DidCreateTemporaryFile(
    243     base::File::Error error_code,
    244     scoped_ptr<net::FileStream> file_stream,
    245     ShareableFileReference* deletable_file) {
    246   DCHECK(!writer_);
    247   if (error_code != base::File::FILE_OK) {
    248     controller()->CancelWithError(net::FileErrorToNetError(error_code));
    249     return;
    250   }
    251 
    252   writer_ = new Writer(this, file_stream.Pass(), deletable_file);
    253 
    254   // Resume the request.
    255   DCHECK(did_defer_);
    256   bool defer = false;
    257   if (!next_handler_->OnWillStart(will_start_url_, &defer)) {
    258     controller()->Cancel();
    259   } else if (!defer) {
    260     ResumeIfDeferred();
    261   } else {
    262     did_defer_ = false;
    263   }
    264   will_start_url_ = GURL();
    265 }
    266 
    267 void RedirectToFileResourceHandler::DidWriteToFile(int result) {
    268   bool failed = false;
    269   if (result > 0) {
    270     next_handler_->OnDataDownloaded(result);
    271     write_cursor_ += result;
    272     failed = !WriteMore();
    273   } else {
    274     failed = true;
    275   }
    276 
    277   if (failed) {
    278     DCHECK(!writer_->is_writing());
    279     // TODO(davidben): Recover the error code from WriteMore or |result|, as
    280     // appropriate.
    281     if (completed_during_write_ && completed_status_.is_success()) {
    282       // If the request successfully completed mid-write, but the write failed,
    283       // convert the status to a failure for downstream.
    284       completed_status_.set_status(net::URLRequestStatus::CANCELED);
    285       completed_status_.set_error(net::ERR_FAILED);
    286     }
    287     if (!completed_during_write_)
    288       controller()->CancelWithError(net::ERR_FAILED);
    289   }
    290 
    291   if (completed_during_write_ && !writer_->is_writing()) {
    292     // Resume shutdown now that all data has been written to disk. Note that
    293     // this should run even in the |failed| case above, otherwise a failed write
    294     // leaves the handler stuck.
    295     bool defer = false;
    296     next_handler_->OnResponseCompleted(completed_status_,
    297                                        completed_security_info_,
    298                                        &defer);
    299     if (!defer) {
    300       ResumeIfDeferred();
    301     } else {
    302       did_defer_ = false;
    303     }
    304   }
    305 }
    306 
    307 bool RedirectToFileResourceHandler::WriteMore() {
    308   DCHECK(writer_);
    309   for (;;) {
    310     if (write_cursor_ == buf_->offset()) {
    311       // We've caught up to the network load, but it may be in the process of
    312       // appending more data to the buffer.
    313       if (!buf_write_pending_) {
    314         if (BufIsFull())
    315           ResumeIfDeferred();
    316         buf_->set_offset(0);
    317         write_cursor_ = 0;
    318       }
    319       return true;
    320     }
    321     if (writer_->is_writing())
    322       return true;
    323     DCHECK(write_cursor_ < buf_->offset());
    324 
    325     // Create a temporary buffer pointing to a subsection of the data buffer so
    326     // that it can be passed to Write.  This code makes some crazy scary
    327     // assumptions about object lifetimes, thread sharing, and that buf_ will
    328     // not realloc durring the write due to how the state machine in this class
    329     // works.
    330     // Note that buf_ is also shared with the code that writes data into the
    331     // cache, so modifying it can cause some pretty subtle race conditions:
    332     // https://code.google.com/p/chromium/issues/detail?id=152076
    333     // We're using DependentIOBuffer instead of DrainableIOBuffer to dodge some
    334     // of these issues, for the moment.
    335     // TODO(ncbray) make this code less crazy scary.
    336     // Also note that Write may increase the refcount of "wrapped" deep in the
    337     // bowels of its implementation, the use of scoped_refptr here is not
    338     // spurious.
    339     scoped_refptr<DependentIOBuffer> wrapped = new DependentIOBuffer(
    340         buf_.get(), buf_->StartOfBuffer() + write_cursor_);
    341     int write_len = buf_->offset() - write_cursor_;
    342 
    343     int rv = writer_->Write(wrapped.get(), write_len);
    344     if (rv == net::ERR_IO_PENDING)
    345       return true;
    346     if (rv <= 0)
    347       return false;
    348     next_handler_->OnDataDownloaded(rv);
    349     write_cursor_ += rv;
    350   }
    351 }
    352 
    353 bool RedirectToFileResourceHandler::BufIsFull() const {
    354   // This is a hack to workaround BufferedResourceHandler's inability to
    355   // deal with a ResourceHandler that returns a buffer size of less than
    356   // 2 * net::kMaxBytesToSniff from its OnWillRead method.
    357   // TODO(darin): Fix this retardation!
    358   return buf_->RemainingCapacity() <= (2 * net::kMaxBytesToSniff);
    359 }
    360 
    361 void RedirectToFileResourceHandler::ResumeIfDeferred() {
    362   if (did_defer_) {
    363     did_defer_ = false;
    364     controller()->Resume();
    365   }
    366 }
    367 
    368 }  // namespace content
    369