Reuse RandomX hashing context during mining

src/crypto/randomx_hash.cpp

@@ -2,6 +2,77 @@
 
 #include <randomx.h>
 
+struct VextaRandomXHasher::Impl
+{
+    randomx_cache* cache{nullptr};
+    randomx_vm* vm{nullptr};
+
+    Impl(const void* key, std::size_t key_size)
+    {
+        cache = randomx_alloc_cache(RANDOMX_FLAG_DEFAULT);
+        if (cache == nullptr) {
+            return;
+        }
+
+        randomx_init_cache(cache, key, key_size);
+
+        vm = randomx_create_vm(
+            RANDOMX_FLAG_DEFAULT,
+            cache,
+            nullptr);
+
+        if (vm == nullptr) {
+            randomx_release_cache(cache);
+            cache = nullptr;
+        }
+    }
+
+    ~Impl()
+    {
+        if (vm != nullptr) {
+            randomx_destroy_vm(vm);
+        }
+
+        if (cache != nullptr) {
+            randomx_release_cache(cache);
+        }
+    }
+};
+
+VextaRandomXHasher::VextaRandomXHasher(
+    const void* key,
+    std::size_t key_size)
+    : m_impl(std::make_unique<Impl>(key, key_size))
+{
+}
+
+VextaRandomXHasher::~VextaRandomXHasher() = default;
+
+bool VextaRandomXHasher::IsValid() const
+{
+    return m_impl != nullptr &&
+           m_impl->cache != nullptr &&
+           m_impl->vm != nullptr;
+}
+
+bool VextaRandomXHasher::Hash(
+    const void* input,
+    std::size_t input_size,
+    uint8_t output[VEXTA_RANDOMX_HASH_SIZE])
+{
+    if (!IsValid()) {
+        return false;
+    }
+
+    randomx_calculate_hash(
+        m_impl->vm,
+        input,
+        input_size,
+        output);
+
+    return true;
+}
+
 bool VextaRandomXHash(
     const void* input,
     std::size_t input_size,
@@ -9,27 +80,11 @@ bool VextaRandomXHash(
     std::size_t key_size,
     uint8_t output[VEXTA_RANDOMX_HASH_SIZE])
 {
-    randomx_cache* cache = randomx_alloc_cache(RANDOMX_FLAG_DEFAULT);
-    if (cache == nullptr) {
+    VextaRandomXHasher hasher(key, key_size);
+
+    if (!hasher.IsValid()) {
         return false;
     }
 
-    randomx_init_cache(cache, key, key_size);
-
-    randomx_vm* vm = randomx_create_vm(
-        RANDOMX_FLAG_DEFAULT,
-        cache,
-        nullptr);
-
-    if (vm == nullptr) {
-        randomx_release_cache(cache);
-        return false;
-    }
-
-    randomx_calculate_hash(vm, input, input_size, output);
-
-    randomx_destroy_vm(vm);
-    randomx_release_cache(cache);
-
-    return true;
+    return hasher.Hash(input, input_size, output);
 }

src/crypto/randomx_hash.h

@@ -3,9 +3,31 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <memory>
 
 static constexpr std::size_t VEXTA_RANDOMX_HASH_SIZE = 32;
 
+class VextaRandomXHasher
+{
+public:
+    VextaRandomXHasher(const void* key, std::size_t key_size);
+    ~VextaRandomXHasher();
+
+    VextaRandomXHasher(const VextaRandomXHasher&) = delete;
+    VextaRandomXHasher& operator=(const VextaRandomXHasher&) = delete;
+
+    bool IsValid() const;
+
+    bool Hash(
+        const void* input,
+        std::size_t input_size,
+        uint8_t output[VEXTA_RANDOMX_HASH_SIZE]);
+
+private:
+    struct Impl;
+    std::unique_ptr<Impl> m_impl;
+};
+
 /**
  * Calculate a RandomX hash using an explicit key.
  *

src/primitives/block.cpp

@@ -33,15 +33,26 @@ int CBlockHeader::GetAlgo() const
 }
 
 bool CBlockHeader::GetRandomXPoWHash(const uint256& seed, uint256& result) const
+{
+    VextaRandomXHasher hasher(seed.data(), seed.size());
+
+    if (!hasher.IsValid()) {
+        return false;
+    }
+
+    return GetRandomXPoWHash(hasher, result);
+}
+
+bool CBlockHeader::GetRandomXPoWHash(
+    VextaRandomXHasher& hasher,
+    uint256& result) const
 {
     CDataStream stream(SER_GETHASH, PROTOCOL_VERSION);
     stream << *this;
 
-    return VextaRandomXHash(
+    return hasher.Hash(
         stream.data(),
         stream.size(),
-        seed.data(),
-        seed.size(),
         result.begin());
 }
 

src/primitives/block.h

@@ -51,6 +51,8 @@ inline int GetVersionForAlgo(int algo)
  * in the block is a special one that creates a new coin owned by the creator
  * of the block.
  */
+class VextaRandomXHasher;
+
 class CBlockHeader
 {
 public:
@@ -101,6 +103,7 @@ public:
      * The seed is supplied in raw uint256 serialization byte order.
      */
     bool GetRandomXPoWHash(const uint256& seed, uint256& result) const;
+    bool GetRandomXPoWHash(VextaRandomXHasher& hasher, uint256& result) const;
 
     int64_t GetBlockTime() const
     {

src/rpc/mining.cpp

@@ -11,6 +11,7 @@
 #include <consensus/params.h>
 #include <consensus/validation.h>
 #include <core_io.h>
+#include <crypto/randomx_hash.h>
 #include <deploymentinfo.h>
 #include <deploymentstatus.h>
 #include <key_io.h>
@@ -200,6 +201,8 @@ static bool GenerateBlock(ChainstateManager& chainman, CBlock& block, uint64_t&
     const int algo = block.GetAlgo();
 
     uint256 randomx_seed;
+    std::unique_ptr<VextaRandomXHasher> randomx_hasher;
+
     if (algo == ALGO_RANDOMX) {
         if (pindexPrev == nullptr ||
             !GetRandomXSeed(
@@ -211,6 +214,16 @@ static bool GenerateBlock(ChainstateManager& chainman, CBlock& block, uint64_t&
                 RPC_INTERNAL_ERROR,
                 "Failed to resolve RandomX seed");
         }
+
+        randomx_hasher = std::make_unique<VextaRandomXHasher>(
+            randomx_seed.data(),
+            randomx_seed.size());
+
+        if (!randomx_hasher->IsValid()) {
+            throw JSONRPCError(
+                RPC_INTERNAL_ERROR,
+                "Failed to initialize RandomX hasher");
+        }
     } else if (algo != ALGO_SHA256D) {
         throw JSONRPCError(
             RPC_INVALID_PARAMETER,
@@ -225,7 +238,7 @@ static bool GenerateBlock(ChainstateManager& chainman, CBlock& block, uint64_t&
         if (algo == ALGO_SHA256D) {
             pow_hash = block.GetHash();
         } else {
-            if (!block.GetRandomXPoWHash(randomx_seed, pow_hash)) {
+            if (!block.GetRandomXPoWHash(*randomx_hasher, pow_hash)) {
                 throw JSONRPCError(
                     RPC_INTERNAL_ERROR,
                     "Failed to calculate RandomX proof of work hash");