Blake3.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Containers/StringFwd.h"
#include "Containers/StringView.h"
#include "Containers/UnrealString.h"
#include "HAL/Platform.h"
#include "HAL/PlatformString.h"
#include "HAL/UnrealMemory.h"
#include "Memory/MemoryFwd.h"
#include "Memory/MemoryView.h"
#include "Misc/AssertionMacros.h"
#include "Serialization/Archive.h"
#include "String/BytesToHex.h"
#include "String/HexToBytes.h"
#include "Templates/TypeCompatibleBytes.h"
 
class FArchive;
class FCompositeBuffer;
template <typename CharType> class TStringBuilderBase;
 
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
/** Stores a BLAKE3 hash. */
struct FBlake3Hash
{
public:
    using ByteArray = uint8[32];
 
    /** Construct a zero hash. */
    FBlake3Hash() = default;
 
    /** Construct a hash from an array of 32 bytes. */
    inline explicit FBlake3Hash(const ByteArray& Hash);
 
    /** Construct a hash from a 64-character hex string. */
    inline explicit FBlake3Hash(FAnsiStringView HexHash);
    inline explicit FBlake3Hash(FWideStringView HexHash);
    inline explicit FBlake3Hash(FUtf8StringView HexHash);
 
    /** Construct a hash from a view of 32 bytes. */
    inline static FBlake3Hash FromView(FMemoryView Hash);
 
    /** Reset this to a zero hash. */
    inline void Reset() { *this = FBlake3Hash(); }
 
    /** Returns whether this is a zero hash. */
    inline bool IsZero() const;
 
    /** Returns a reference to the raw byte array for the hash. */
    inline ByteArray& GetBytes() { return Hash; }
    inline const ByteArray& GetBytes() const { return Hash; }
 
    /** A zero hash. */
    static const FBlake3Hash Zero;
 
    inline bool operator==(const FBlake3Hash& B) const
    {
        return FMemory::Memcmp(GetBytes(), B.GetBytes(), sizeof(decltype(GetBytes()))) == 0;
    }
 
    inline bool operator!=(const FBlake3Hash& B) const
    {
        return FMemory::Memcmp(GetBytes(), B.GetBytes(), sizeof(decltype(GetBytes()))) != 0;
    }
 
    inline bool operator<(const FBlake3Hash& B) const
    {
        return FMemory::Memcmp(GetBytes(), B.GetBytes(), sizeof(decltype(GetBytes()))) < 0;
    }
 
    friend inline FArchive& operator<<(FArchive& Ar, FBlake3Hash& Value)
    {
        Ar.Serialize(Value.GetBytes(), sizeof(decltype(Value.GetBytes())));
        return Ar;
    }
 
    friend inline uint32 GetTypeHash(const FBlake3Hash& Value)
    {
        return *reinterpret_cast<const uint32*>(Value.GetBytes());
    }
 
private:
    alignas(uint32) ByteArray Hash{};
};
 
inline const FBlake3Hash FBlake3Hash::Zero;
 
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
/** Calculates a BLAKE3 hash. */
class FBlake3
{
public:
    inline FBlake3() { Reset(); }
 
    FBlake3(const FBlake3&) = delete;
    FBlake3& operator=(const FBlake3&) = delete;
 
    /** Reset to the default state in which no input has been written. */
    void Reset();
 
    /** Add the buffer as input to the hash. May be called any number of times. */
    void Update(FMemoryView View);
    void Update(const void* Data, uint64 Size);
    void Update(const FCompositeBuffer& Buffer);
 
    /**
     * Finalize the hash of the input data.
     *
     * May be called any number of times, and more input may be added after.
     */
    [[nodiscard]] FBlake3Hash Finalize() const;
 
    /** Calculate the hash of the buffer. */
    [[nodiscard]] static FBlake3Hash HashBuffer(FMemoryView View);
    [[nodiscard]] static FBlake3Hash HashBuffer(const void* Data, uint64 Size);
    [[nodiscard]] static FBlake3Hash HashBuffer(const FCompositeBuffer& Buffer);
 
private:
    TAlignedBytes<1912, 8> HasherBytes;
};
 
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
inline FBlake3Hash::FBlake3Hash(const ByteArray& InHash)
{
    FMemory::Memcpy(Hash, InHash, sizeof(ByteArray));
}
 
inline FBlake3Hash::FBlake3Hash(const FAnsiStringView HexHash)
{
    check(HexHash.Len() == sizeof(ByteArray) * 2);
    UE::String::HexToBytes(HexHash, Hash);
}
 
inline FBlake3Hash::FBlake3Hash(const FWideStringView HexHash)
{
    check(HexHash.Len() == sizeof(ByteArray) * 2);
    UE::String::HexToBytes(HexHash, Hash);
}
 
inline FBlake3Hash::FBlake3Hash(const FUtf8StringView HexHash)
{
    check(HexHash.Len() == sizeof(ByteArray) * 2);
    UE::String::HexToBytes(HexHash, Hash);
}
 
inline FBlake3Hash FBlake3Hash::FromView(const FMemoryView InHash)
{
    checkf(InHash.GetSize() == sizeof(ByteArray),
        TEXT("FBlake3Hash cannot be constructed from a view of %" UINT64_FMT " bytes."), InHash.GetSize());
    FBlake3Hash NewHash;
    FMemory::Memcpy(NewHash.Hash, InHash.GetData(), sizeof(ByteArray));
    return NewHash;
}
 
inline bool FBlake3Hash::IsZero() const
{
    using UInt32Array = uint32[8];
    static_assert(sizeof(UInt32Array) == sizeof(ByteArray), "Invalid size for UInt32Array");
    for (uint32 Value : reinterpret_cast<const UInt32Array&>(Hash))
    {
        if (Value != 0)
        {
            return false;
        }
    }
    return true;
}
 
template <typename CharType>
inline TStringBuilderBase<CharType>& operator<<(TStringBuilderBase<CharType>& Builder, const FBlake3Hash& Hash)
{
    UE::String::BytesToHexLower(Hash.GetBytes(), Builder);
    return Builder;
}
 
/** Construct a hash from a 64-character hex string. */
inline void LexFromString(FBlake3Hash& OutHash, const TCHAR* Buffer)
{
    OutHash = FBlake3Hash(Buffer);
}
 
/** Convert a hash to a 64-character hex string. */
[[nodiscard]] FString LexToString(const FBlake3Hash& Hash);