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HttpLocalCache.h (2956B)

      1 // Copyright (c) Microsoft Corporation.
      2 // Licensed under the MIT License.
      3 
      4 #pragma once
      5 
      6 #include "HttpClientWrapper.h"
      7 
      8 namespace AppInstaller::Utility::HttpStream
      9 {
     10     // Represents an entry in the cache.
     11     struct CachedPage
     12     {
     13         int lastAccessCounter = 0;
     14         winrt::Windows::Storage::Streams::IBuffer buffer;
     15     };
     16 
     17     // A cache used internally by the custom HttpRandomAccessStream to reduce round-trips
     18     class HttpLocalCache
     19     {
     20     public:
     21         static constexpr UINT32 PAGE_SIZE = 2 << 16;   // each entry in the cache is 64 KB
     22         static constexpr UINT32 MAX_PAGES = 200;       // cache size capped at 12.5 MB (200 * 64KB)
     23 
     24         // Returns a buffer matching the requested range by reading the parts of the range that are cached
     25         // and downloading the rest using the provided httpClientWrapper object
     26         std::future<winrt::Windows::Storage::Streams::IBuffer> ReadFromCacheAndDownloadIfNecessaryAsync(
     27             const ULONG64 requestedPosition,
     28             const UINT32 requestedSize,
     29             HttpClientWrapper* httpClientWrapper,
     30             winrt::Windows::Storage::Streams::InputStreamOptions httpInputStreamOptions);
     31 
     32     private:
     33         std::map<ULONG64, CachedPage> m_localCache;
     34         UINT32 m_accessCounter = 0U;
     35 
     36         // Returns a vector of all pages corresponding to a range, and another (subset)
     37         // vector of the pages missing from the cache.
     38         void FindCachePages(
     39             const ULONG64 requestedPosition,
     40             const UINT32 requestedSize,
     41             std::vector<ULONG64>& allPages,
     42             std::vector<ULONG64>& unsatisfiablePages);
     43 
     44         void SaveBufferToCache(const winrt::Windows::Storage::Streams::IBuffer& buffer, const ULONG64 firstPageOffset);
     45 
     46         winrt::Windows::Storage::Streams::IBuffer ReadPageFromCache(const ULONG64 pageOffset);
     47 
     48         void VacateStaleEntriesFromCache();
     49 
     50         std::future<void> DownloadAndSaveToCacheAsync(
     51             const std::vector<ULONG64> unsatisfiablePages,
     52             HttpClientWrapper* httpClientWrapper,
     53             const winrt::Windows::Storage::Streams::InputStreamOptions httpInputStreamOptions);
     54 
     55         winrt::Windows::Storage::Streams::IBuffer TrimBufferToSatisfyRequest(
     56             const winrt::Windows::Storage::Streams::IBuffer& constructedBuffer,
     57             const ULONG64 requestedPosition,
     58             const UINT32 requestedSize,
     59             const std::vector<ULONG64> allPages);
     60 
     61         winrt::Windows::Storage::Streams::IBuffer CreateTrimmedBuffer(
     62             const winrt::Windows::Storage::Streams::IBuffer& originalBuffer,
     63             UINT32 trimStartIndex,
     64             UINT32 size);
     65 
     66         winrt::Windows::Storage::Streams::IBuffer ConcatenateBuffers(
     67             const winrt::Windows::Storage::Streams::IBuffer& buffer1,
     68             const winrt::Windows::Storage::Streams::IBuffer& buffer2);
     69     };
     70 }