text: // Copyright (c) 2012 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  // This file declares HttpCache::Transaction, a private class of HttpCache so
  // it should only be included by http_cache.cc
  
  #ifndef NET_HTTP_HTTP_CACHE_TRANSACTION_H_
  #define NET_HTTP_HTTP_CACHE_TRANSACTION_H_
  
  #include <string>
  
  #include "base/time/time.h"
  #include "net/base/completion_callback.h"
  #include "net/base/net_log.h"
  #include "net/base/request_priority.h"
  #include "net/http/http_cache.h"
  #include "net/http/http_request_headers.h"
  #include "net/http/http_response_headers.h"
  #include "net/http/http_response_info.h"
  #include "net/http/http_transaction.h"
  
  namespace net {
  
  class PartialData;
  struct HttpRequestInfo;
  struct LoadTimingInfo;
  
  // This is the transaction that is returned by the HttpCache transaction
  // factory.
  class HttpCache::Transaction : public HttpTransaction {
   public:
    // The transaction has the following modes, which apply to how it may access
    // its cache entry.
    //
    //  o If the mode of the transaction is NONE, then it is in "pass through"
    //    mode and all methods just forward to the inner network transaction.
    //
    //  o If the mode of the transaction is only READ, then it may only read from
    //    the cache entry.
    //
    //  o If the mode of the transaction is only WRITE, then it may only write to
    //    the cache entry.
    //
    //  o If the mode of the transaction is READ_WRITE, then the transaction may
    //    optionally modify the cache entry (e.g., possibly corresponding to
    //    cache validation).
    //
    //  o If the mode of the transaction is UPDATE, then the transaction may
    //    update existing cache entries, but will never create a new entry or
    //    respond using the entry read from the cache.
    enum Mode {
      NONE            = 0,
      READ_META       = 1 << 0,
      READ_DATA       = 1 << 1,
      READ            = READ_META | READ_DATA,
      WRITE           = 1 << 2,
      READ_WRITE      = READ | WRITE,
      UPDATE          = READ_META | WRITE,  // READ_WRITE & ~READ_DATA
    };
  
    Transaction(RequestPriority priority,
                HttpCache* cache);
    ~Transaction() override;
  
    Mode mode() const { return mode_; }
  
    const std::string& key() const { return cache_key_; }
  
    // Writes |buf_len| bytes of meta-data from the provided buffer |buf|. to the
    // HTTP cache entry that backs this transaction (if any).
    // Returns the number of bytes actually written, or a net error code. If the
    // operation cannot complete immediately, returns ERR_IO_PENDING, grabs a
    // reference to the buffer (until completion), and notifies the caller using
    // the provided |callback| when the operation finishes.
    //
    // The first time this method is called for a given transaction, previous
    // meta-data will be overwritten with the provided data, and subsequent
    // invocations will keep appending to the cached entry.
    //
    // In order to guarantee that the metadata is set to the correct entry, the
    // response (or response info) must be evaluated by the caller, for instance
    // to make sure that the response_time is as expected, before calling this
    // method.
    int WriteMetadata(IOBuffer* buf,
                      int buf_len,
                      const CompletionCallback& callback);
  
    // This transaction is being deleted and we are not done writing to the cache.
    // We need to indicate that the response data was truncated.  Returns true on
    // success. Keep in mind that this operation may have side effects, such as
    // deleting the active entry.
    bool AddTruncatedFlag();
  
    HttpCache::ActiveEntry* entry() { return entry_; }
  
    // Returns the LoadState of the writer transaction of a given ActiveEntry. In
    // other words, returns the LoadState of this transaction without asking the
    // http cache, because this transaction should be the one currently writing
    // to the cache entry.
    LoadState GetWriterLoadState() const;
  
    const CompletionCallback& io_callback() { return io_callback_; }
  
    const BoundNetLog& net_log() const;
  
    // Bypasses the cache lock whenever there is lock contention.
    void BypassLockForTest() {
      bypass_lock_for_test_ = true;
    }
  
    // Generates a failure when attempting to conditionalize a network request.
    void FailConditionalizationForTest() {
      fail_conditionalization_for_test_ = true;
    }
  
    // HttpTransaction methods:
    int Start(const HttpRequestInfo* request_info,
              const CompletionCallback& callback,
              const BoundNetLog& net_log) override;
    int RestartIgnoringLastError(const CompletionCallback& callback) override;
    int RestartWithCertificate(X509Certificate* client_cert,
                               const CompletionCallback& callback) override;
    int RestartWithAuth(const AuthCredentials& credentials,
                        const CompletionCallback& callback) override;
    bool IsReadyToRestartForAuth() override;
    int Read(IOBuffer* buf,
             int buf_len,
             const CompletionCallback& callback) override;
    void StopCaching() override;
    bool GetFullRequestHeaders(HttpRequestHeaders* headers) const override;
    int64 GetTotalReceivedBytes() const override;
    void DoneReading() override;
    const HttpResponseInfo* GetResponseInfo() const override;
    LoadState GetLoadState() const override;
    UploadProgress GetUploadProgress(void) const override;
    void SetQuicServerInfo(QuicServerInfo* quic_server_info) override;
    bool GetLoadTimingInfo(LoadTimingInfo* load_timing_info) const override;
    void SetPriority(RequestPriority priority) override;
    void SetWebSocketHandshakeStreamCreateHelper(
        net::WebSocketHandshakeStreamBase::CreateHelper* create_helper) override;
    void SetBeforeNetworkStartCallback(
        const BeforeNetworkStartCallback& callback) override;
    void SetBeforeProxyHeadersSentCallback(
        const BeforeProxyHeadersSentCallback& callback) override;
    int ResumeNetworkStart() override;
  
   private:
    static const size_t kNumValidationHeaders = 2;
    // Helper struct to pair a header name with its value, for
    // headers used to validate cache entries.
    struct ValidationHeaders {
      ValidationHeaders() : initialized(false) {}
  
      std::string values[kNumValidationHeaders];
      bool initialized;
    };
  
    enum State {
      STATE_NONE,
      STATE_GET_BACKEND,
      STATE_GET_BACKEND_COMPLETE,
      STATE_SEND_REQUEST,
      STATE_SEND_REQUEST_COMPLETE,
      STATE_SUCCESSFUL_SEND_REQUEST,
      STATE_NETWORK_READ,
      STATE_NETWORK_READ_COMPLETE,
      STATE_INIT_ENTRY,
      STATE_OPEN_ENTRY,
      STATE_OPEN_ENTRY_COMPLETE,
      STATE_CREATE_ENTRY,
      STATE_CREATE_ENTRY_COMPLETE,
      STATE_DOOM_ENTRY,
      STATE_DOOM_ENTRY_COMPLETE,
      STATE_ADD_TO_ENTRY,
      STATE_ADD_TO_ENTRY_COMPLETE,
      STATE_START_PARTIAL_CACHE_VALIDATION,
      STATE_COMPLETE_PARTIAL_CACHE_VALIDATION,
      STATE_UPDATE_CACHED_RESPONSE,
      STATE_UPDATE_CACHED_RESPONSE_COMPLETE,
      STATE_OVERWRITE_CACHED_RESPONSE,
      STATE_TRUNCATE_CACHED_DATA,
      STATE_TRUNCATE_CACHED_DATA_COMPLETE,
      STATE_TRUNCATE_CACHED_METADATA,
      STATE_TRUNCATE_CACHED_METADATA_COMPLETE,
      STATE_PARTIAL_HEADERS_RECEIVED,
      STATE_CACHE_READ_RESPONSE,
      STATE_CACHE_READ_RESPONSE_COMPLETE,
      STATE_CACHE_WRITE_RESPONSE,
      STATE_CACHE_WRITE_TRUNCATED_RESPONSE,
      STATE_CACHE_WRITE_RESPONSE_COMPLETE,
      STATE_CACHE_READ_METADATA,
      STATE_CACHE_READ_METADATA_COMPLETE,
      STATE_CACHE_QUERY_DATA,
      STATE_CACHE_QUERY_DATA_COMPLETE,
      STATE_CACHE_READ_DATA,
      STATE_CACHE_READ_DATA_COMPLETE,
      STATE_CACHE_WRITE_DATA,
      STATE_CACHE_WRITE_DATA_COMPLETE
    };
  
    // Used for categorizing transactions for reporting in histograms. Patterns
    // cover relatively common use cases being measured and considered for
    // optimization. Many use cases that are more complex or uncommon are binned
    // as PATTERN_NOT_COVERED, and details are not reported.
    // NOTE: This enumeration is used in histograms, so please do not add entries
    // in the middle.
    enum TransactionPattern {
      PATTERN_UNDEFINED,
      PATTERN_NOT_COVERED,
      PATTERN_ENTRY_NOT_CACHED,
      PATTERN_ENTRY_USED,
      PATTERN_ENTRY_VALIDATED,
      PATTERN_ENTRY_UPDATED,
      PATTERN_ENTRY_CANT_CONDITIONALIZE,
      PATTERN_MAX,
    };
  
    // This is a helper function used to trigger a completion callback.  It may
    // only be called if callback_ is non-null.
    void DoCallback(int rv);
  
    // This will trigger the completion callback if appropriate.
    int HandleResult(int rv);
  
    // Runs the state transition loop.
    int DoLoop(int result);
  
    // Each of these methods corresponds to a State value.  If there is an
    // argument, the value corresponds to the return of the previous state or
    // corresponding callback.
    int DoGetBackend();
    int DoGetBackendComplete(int result);
    int DoSendRequest();
    int DoSendRequestComplete(int result);
    int DoSuccessfulSendRequest();
    int DoNetworkRead();
    int DoNetworkReadComplete(int result);
    int DoInitEntry();
    int DoOpenEntry();
    int DoOpenEntryComplete(int result);
    int DoCreateEntry();
    int DoCreateEntryComplete(int result);
    int DoDoomEntry();
    int DoDoomEntryComplete(int result);
    int DoAddToEntry();
    int DoAddToEntryComplete(int result);
    int DoStartPartialCacheValidation();
    int DoCompletePartialCacheValidation(int result);
    int DoUpdateCachedResponse();
    int DoUpdateCachedResponseComplete(int result);
    int DoOverwriteCachedResponse();
    int DoTruncateCachedData();
    int DoTruncateCachedDataComplete(int result);
    int DoTruncateCachedMetadata();
    int DoTruncateCachedMetadataComplete(int result);
    int DoPartialHeadersReceived();
    int DoCacheReadResponse();
    int DoCacheReadResponseComplete(int result);
    int DoCacheWriteResponse();
    int DoCacheWriteTruncatedResponse();
    int DoCacheWriteResponseComplete(int result);
    int DoCacheReadMetadata();
    int DoCacheReadMetadataComplete(int result);
    int DoCacheQueryData();
    int DoCacheQueryDataComplete(int result);
    int DoCacheReadData();
    int DoCacheReadDataComplete(int result);
    int DoCacheWriteData(int num_bytes);
    int DoCacheWriteDataComplete(int result);
  
    // These functions are involved in a field trial testing storing certificates
    // in seperate entries from the HttpResponseInfo.
    void ReadCertChain();
    void WriteCertChain();
  
    // Sets request_ and fields derived from it.
    void SetRequest(const BoundNetLog& net_log, const HttpRequestInfo* request);
  
    // Returns true if the request should be handled exclusively by the network
    // layer (skipping the cache entirely).
    bool ShouldPassThrough();
  
    // Called to begin reading from the cache.  Returns network error code.
    int BeginCacheRead();
  
    // Called to begin validating the cache entry.  Returns network error code.
    int BeginCacheValidation();
  
    // Called to begin validating an entry that stores partial content.  Returns
    // a network error code.
    int BeginPartialCacheValidation();
  
    // Validates the entry headers against the requested range and continues with
    // the validation of the rest of the entry.  Returns a network error code.
    int ValidateEntryHeadersAndContinue();
  
    // Called to start requests which were given an "if-modified-since" or
    // "if-none-match" validation header by the caller (NOT when the request was
    // conditionalized internally in response to LOAD_VALIDATE_CACHE).
    // Returns a network error code.
    int BeginExternallyConditionalizedRequest();
  
    // Called to restart a network transaction after an error.  Returns network
    // error code.
    int RestartNetworkRequest();
  
    // Called to restart a network transaction with a client certificate.
    // Returns network error code.
    int RestartNetworkRequestWithCertificate(X509Certificate* client_cert);
  
    // Called to restart a network transaction with authentication credentials.
    // Returns network error code.
    int RestartNetworkRequestWithAuth(const AuthCredentials& credentials);
  
    // Called to determine if we need to validate the cache entry before using it,
    // and whether the validation should be synchronous or asynchronous.
    ValidationType RequiresValidation();
  
    // Called to make the request conditional (to ask the server if the cached
    // copy is valid).  Returns true if able to make the request conditional.
    bool ConditionalizeRequest();
  
    // Makes sure that a 206 response is expected.  Returns true on success.
    // On success, handling_206_ will be set to true if we are processing a
    // partial entry.
    bool ValidatePartialResponse();
  
    // Handles a response validation error by bypassing the cache.
    void IgnoreRangeRequest();
  
    // Removes content-length and byte range related info if needed.
    void FixHeadersForHead();
  
    // Launches an asynchronous revalidation based on this transaction.
    void TriggerAsyncValidation();
  
    // Changes the response code of a range request to be 416 (Requested range not
    // satisfiable).
    void FailRangeRequest();
  
    // Setups the transaction for reading from the cache entry.
    int SetupEntryForRead();
  
    // Reads data from the network.
    int ReadFromNetwork(IOBuffer* data, int data_len);
  
    // Reads data from the cache entry.
    int ReadFromEntry(IOBuffer* data, int data_len);
  
    // Called to write data to the cache entry.  If the write fails, then the
    // cache entry is destroyed.  Future calls to this function will just do
    // nothing without side-effect.  Returns a network error code.
    int WriteToEntry(int index, int offset, IOBuffer* data, int data_len,
                     const CompletionCallback& callback);
  
    // Called to write response_ to the cache entry. |truncated| indicates if the
    // entry should be marked as incomplete.
    int WriteResponseInfoToEntry(bool truncated);
  
    // Called to append response data to the cache entry.  Returns a network error
    // code.
    int AppendResponseDataToEntry(IOBuffer* data, int data_len,
                                  const CompletionCallback& callback);
  
    // Called when we are done writing to the cache entry.
    void DoneWritingToEntry(bool success);
  
    // Returns an error to signal the caller that the current read failed. The
    // current operation |result| is also logged. If |restart| is true, the
    // transaction should be restarted.
    int OnCacheReadError(int result, bool restart);
  
    // Called when the cache lock timeout fires.
    void OnAddToEntryTimeout(base::TimeTicks start_time);
  
    // Deletes the current partial cache entry (sparse), and optionally removes
    // the control object (partial_).
    void DoomPartialEntry(bool delete_object);
  
    // Performs the needed work after receiving data from the network, when
    // working with range requests.
    int DoPartialNetworkReadCompleted(int result);
  
    // Performs the needed work after receiving data from the cache, when
    // working with range requests.
    int DoPartialCacheReadCompleted(int result);
  
    // Restarts this transaction after deleting the cached data. It is meant to
    // be used when the current request cannot be fulfilled due to conflicts
    // between the byte range request and the cached entry.
    int DoRestartPartialRequest();
  
    // Resets the relavant internal state to remove traces of internal processing
    // related to range requests. Deletes |partial_| if |delete_object| is true.
    void ResetPartialState(bool delete_object);
  
    // Resets |network_trans_|, which must be non-NULL.  Also updates
    // |old_network_trans_load_timing_|, which must be NULL when this is called.
    void ResetNetworkTransaction();
  
    // Returns true if we should bother attempting to resume this request if it
    // is aborted while in progress. If |has_data| is true, the size of the stored
    // data is considered for the result.
    bool CanResume(bool has_data);
  
    void UpdateTransactionPattern(TransactionPattern new_transaction_pattern);
    void RecordHistograms();
  
    // Called to signal completion of asynchronous IO.
    void OnIOComplete(int result);
  
    State next_state_;
    const HttpRequestInfo* request_;
    RequestPriority priority_;
    BoundNetLog net_log_;
    scoped_ptr<HttpRequestInfo> custom_request_;
    HttpRequestHeaders request_headers_copy_;
    // If extra_headers specified a "if-modified-since" or "if-none-match",
    // |external_validation_| contains the value of those headers.
    ValidationHeaders external_validation_;
    base::WeakPtr<HttpCache> cache_;
    HttpCache::ActiveEntry* entry_;
    HttpCache::ActiveEntry* new_entry_;
    scoped_ptr<HttpTransaction> network_trans_;
    CompletionCallback callback_;  // Consumer's callback.
    HttpResponseInfo response_;
    HttpResponseInfo auth_response_;
    const HttpResponseInfo* new_response_;
    std::string cache_key_;
    Mode mode_;
    State target_state_;
    bool reading_;  // We are already reading. Never reverts to false once set.
    bool invalid_range_;  // We may bypass the cache for this request.
    bool truncated_;  // We don't have all the response data.
    bool is_sparse_;  // The data is stored in sparse byte ranges.
    bool range_requested_;  // The user requested a byte range.
    bool handling_206_;  // We must deal with this 206 response.
    bool cache_pending_;  // We are waiting for the HttpCache.
    bool done_reading_;  // All available data was read.
    bool vary_mismatch_;  // The request doesn't match the stored vary data.
    bool couldnt_conditionalize_request_;
    bool bypass_lock_for_test_;  // A test is exercising the cache lock.
    bool fail_conditionalization_for_test_;  // Fail ConditionalizeRequest.
    scoped_refptr<IOBuffer> read_buf_;
    int io_buf_len_;
    int read_offset_;
    int effective_load_flags_;
    int write_len_;
    scoped_ptr<PartialData> partial_;  // We are dealing with range requests.
    UploadProgress final_upload_progress_;
    CompletionCallback io_callback_;
  
    // Members used to track data for histograms.
    TransactionPattern transaction_pattern_;
    base::TimeTicks entry_lock_waiting_since_;
    base::TimeTicks first_cache_access_since_;
    base::TimeTicks send_request_since_;
  
    int64 total_received_bytes_;
  
    // Load timing information for the last network request, if any.  Set in the
    // 304 and 206 response cases, as the network transaction may be destroyed
    // before the caller requests load timing information.
    scoped_ptr<LoadTimingInfo> old_network_trans_load_timing_;
  
    // The helper object to use to create WebSocketHandshakeStreamBase
    // objects. Only relevant when establishing a WebSocket connection.
    // This is passed to the underlying network transaction. It is stored here in
    // case the transaction does not exist yet.
    WebSocketHandshakeStreamBase::CreateHelper*
        websocket_handshake_stream_base_create_helper_;
  
    BeforeNetworkStartCallback before_network_start_callback_;
    BeforeProxyHeadersSentCallback before_proxy_headers_sent_callback_;
  
    base::WeakPtrFactory<Transaction> weak_factory_;
  
    DISALLOW_COPY_AND_ASSIGN(Transaction);
  };
  
  }  // namespace net
  
  #endif  // NET_HTTP_HTTP_CACHE_TRANSACTION_H_
  