src/dawn/native/BlobCache.h

// Copyright 2022 The Dawn & Tint Authors
//
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#ifndef SRC_DAWN_NATIVE_BLOBCACHE_H_
#define SRC_DAWN_NATIVE_BLOBCACHE_H_

#include <algorithm>
#include <mutex>
#include <span>
#include <vector>

#include "src/dawn/common/Sha3.h"
#include "src/dawn/native/Blob.h"
#include "src/dawn/native/CacheResult.h"
#include "src/dawn/native/Error.h"
#include "src/utils/platform.h"

namespace dawn::platform {
class CachingInterface;
}

namespace dawn::native {

class CacheKey;
class InstanceBase;

namespace detail {
std::vector<std::byte> GenerateHashPrefixedPayload(std::span<const std::byte> value);
}  // namespace detail

// This class should always be thread-safe because it may be called asynchronously.
class BlobCache {
  public:
    BlobCache(const dawn::native::DawnCacheDeviceDescriptor& desc, bool enableHashValidation);

    // Returns empty blob if the key is not found in the cache. Returns an internal error if hash
    // validation is enabled and the key is found but the hash validation fails.
    ResultOrError<Blob> Load(const CacheKey& key);

    // Value to store must be non-empty/non-null.
    void Store(const CacheKey& key, std::span<const std::byte> value);
    void Store(const CacheKey& key, const Blob& value);

    // Store a CacheResult into the cache if it isn't cached yet.
    // Calls T::ToBlob which should be defined elsewhere.
    template <typename T>
    void EnsureStored(const CacheResult<T>& cacheResult) {
        if (!cacheResult.IsCached()) {
            Store(cacheResult.GetCacheKey(), cacheResult->ToBlob());
        }
    }

    // Generates a blob that holds the actual stored bytes which may be different depending on
    // whether hash validation is enabled.
    Blob GenerateActualStoredBlobForTesting(std::span<const std::byte> value);

  private:
    // Non-thread safe internal implementations of load and store. Exposed callers that use
    // these helpers need to make sure that these are entered with `mMutex` held.
    // If hash validation enabled:
    //   * StoreInternal insert the hash of |value| as prefix,
    //   * LoadInternal validate that the hash of the content after the prefix matches.
    // This hashing and validation is transparent to the caller.
    void StoreInternal(const CacheKey& cacheKey, std::span<const std::byte> value);
    ResultOrError<Blob> LoadInternal(const CacheKey& key);

    // Validates the cache key for this version of Dawn. At the moment, this is naively checking
    // that the cache key contains the dawn version string in it.
    bool ValidateCacheKey(const CacheKey& key);

    const bool mHashValidation;
    const WGPUDawnLoadCacheDataCallbackInfo mLoadCallbackInfo;
    const WGPUDawnStoreCacheDataCallbackInfo mStoreCallbackInfo;
};

}  // namespace dawn::native

#endif  // SRC_DAWN_NATIVE_BLOBCACHE_H_