BigInts, save/load, will make a calculation for block rewards soon

CMakeLists.txt

@@ -124,5 +124,7 @@ target_compile_options(node PRIVATE
     -Wpedantic
     -g
 )
-target_compile_definitions(node PRIVATE)
+target_compile_definitions(node PRIVATE
+    CHAIN_DATA_DIR="${CMAKE_BINARY_DIR}/chain_data"
+)
 set_target_properties(node PROPERTIES OUTPUT_NAME "minicoin_node")

include/block/block.h

@@ -10,13 +10,14 @@
 #include <randomx/librx_wrapper.h>
 
 typedef struct {
-    uint8_t version;
+    uint64_t blockNumber;
-    uint32_t blockNumber;
+    uint64_t timestamp;
+    uint64_t nonce;
     uint8_t prevHash[32];
     uint8_t merkleRoot[32];
-    uint64_t timestamp;
     uint32_t difficultyTarget; // Encoding: [1 byte exponent][3 byte coefficient]; Target = coefficient * 256^(exponent-3)
-    uint64_t nonce; // Higher nonce for RandomX
+    uint8_t version;
+    uint8_t reserved[3];       // 3 bytes (Explicit padding for 8-byte alignment)
 } block_header_t;
 
 typedef struct {

include/block/chain.h

@@ -4,6 +4,9 @@
 #include <block/block.h>
 #include <dynarr.h>
 #include <stdlib.h>
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
 
 typedef struct {
     DynArr* blocks;
@@ -16,5 +19,10 @@ bool Chain_AddBlock(blockchain_t* chain, block_t* block);
 block_t* Chain_GetBlock(blockchain_t* chain, size_t index);
 size_t Chain_Size(blockchain_t* chain);
 bool Chain_IsValid(blockchain_t* chain);
+void Chain_Wipe(blockchain_t* chain);
+
+// I/O
+bool Chain_SaveToFile(blockchain_t* chain, const char* dirpath);
+bool Chain_LoadFromFile(blockchain_t* chain, const char* dirpath);
 
 #endif

include/constants.h

@@ -0,0 +1,37 @@
+#ifndef CONSTANTS_H
+#define CONSTANTS_H
+
+#include <stdint.h>
+#include <uint256.h>
+#include <stdbool.h>
+
+#define DECIMALS 1000000000000ULL
+#define EMISSION_SPEED_FACTOR 20
+const uint64_t M_CAP = 18446744073709551615ULL; // Max uint64
+const uint64_t TAIL_EMISSION = (uint64_t)(1.0 * DECIMALS); // Emission floor is 1.0 coins per block
+// No max supply. Instead of halving, it'll follow a more gradual, Monero-like emission curve.
+
+static inline uint64_t CalculateBlockReward(uint256_t currentSupply, uint64_t height) {
+    // Inclusive of block 0
+
+    if (current_supply.limbs[1] > 0 || 
+        current_supply.limbs[2] > 0 || 
+        current_supply.limbs[3] > 0 || 
+        current_supply.limbs[0] >= M_CAP) {
+        return TAIL_EMISSION;
+    }
+
+    uint64_t supply_64 = current_supply.limbs[0];
+    
+    // Formula: (M - Supply) >> 2^k - lifted from Monero's codebase (thanks guys!)
+    uint64_t reward = (M_CAP - supply_64) >> EMISSION_SPEED_FACTOR;
+
+    // Check if the calculated reward has fallen below the floor
+    if (reward < TAIL_EMISSION) {
+        return TAIL_EMISSION;
+    }
+
+    return reward;
+}
+
+#endif

include/randomx/librx_wrapper.h

@@ -10,7 +10,7 @@
 extern "C" {
 #endif
 
-bool RandomX_Init(const char* key);
+bool RandomX_Init(const char* key, bool preferFullMemory);
 void RandomX_Destroy();
 void RandomX_CalculateHash(const uint8_t* input, size_t inputLen, uint8_t* output);
 

include/uint256.h

@@ -0,0 +1,58 @@
+#ifndef UINT256_H
+#define UINT256_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+
+typedef struct {
+    uint64_t limbs[4]; // 4 * 64 = 256 bits
+} uint256_t;
+
+// Initialize a uint256 with a standard 64-bit value
+static inline uint256_t uint256_from_u64(uint64_t val) {
+    uint256_t res = {{val, 0, 0, 0}};
+    return res;
+}
+
+/**
+ * Adds a uint64_t (transaction amount) to a uint256_t (balance).
+ * Returns true if an overflow occurred (total supply exceeded 256 bits).
+**/
+static inline bool uint256_add_u64(uint256_t* balance, uint64_t amount) {
+    uint64_t old = balance->limbs[0];
+    balance->limbs[0] += amount;
+
+    // Check for carry: if the new value is less than the old, it wrapped around
+    if (balance->limbs[0] < old) {
+        for (int i = 1; i < 4; i++) {
+            balance->limbs[i]++;
+            // If the limb didn't wrap to 0, the carry is fully absorbed
+            if (balance->limbs[i] != 0) return false;
+        }
+        return true; // Overflowed all 256 bits
+    }
+    return false;
+}
+
+/**
+ * Adds two uint256_t values together.
+ * Standard full addition logic.
+**/
+static inline bool uint256_add(uint256_t* a, const uint256_t* b) {
+    uint64_t carry = 0;
+    for (int i = 0; i < 4; i++) {
+        uint64_t old_a = a->limbs[i];
+        a->limbs[i] += b->limbs[i] + carry;
+        
+        // Detect carry: current is less than what we added, or we were at max and had a carry
+        if (carry) {
+            carry = (a->limbs[i] <= old_a);
+        } else {
+            carry = (a->limbs[i] < old_a);
+        }
+    }
+    return carry > 0;
+}
+
+#endif

src/block/block.c

@@ -140,16 +140,17 @@ bool Block_AllTransactionsValid(const block_t* block) {
 
     for (size_t i = 0; i < DynArr_size(block->transactions); i++) {
         signed_transaction_t* tx = (signed_transaction_t*)DynArr_at(block->transactions, i);
-        if (!Transaction_Verify(tx)) {
+        if (tx && Address_IsCoinbase(tx->transaction.senderAddress)) {
-            return false;
-        }
-
-        if (Address_IsCoinbase(tx->transaction.senderAddress)) {
             if (hasCoinbase) {
                 return false; // More than one coinbase transaction
             }
 
             hasCoinbase = true;
+            continue; // Coinbase transactions are valid since the miner has the right to create coins. Only rule is one per block.
+        }
+        
+        if (!Transaction_Verify(tx)) {
+            return false;
         }
     }
 

src/block/chain.c

@@ -1,4 +1,36 @@
 #include <block/chain.h>
+#include <errno.h>
+#include <sys/stat.h>
+
+static bool EnsureDirectoryExists(const char* dirpath) {
+    if (!dirpath || dirpath[0] == '\0') {
+        return false;
+    }
+
+    struct stat st;
+    if (stat(dirpath, &st) == 0) {
+        return S_ISDIR(st.st_mode);
+    }
+
+    if (mkdir(dirpath, 0755) == 0) {
+        return true;
+    }
+
+    if (errno == EEXIST && stat(dirpath, &st) == 0) {
+        return S_ISDIR(st.st_mode);
+    }
+
+    return false;
+}
+
+static bool BuildPath(char* out, size_t outSize, const char* dirpath, const char* filename) {
+    if (!out || outSize == 0 || !dirpath || !filename) {
+        return false;
+    }
+
+    const int written = snprintf(out, outSize, "%s/%s", dirpath, filename);
+    return written > 0 && (size_t)written < outSize;
+}
 
 blockchain_t* Chain_Create() {
     blockchain_t* ptr = (blockchain_t*)malloc(sizeof(blockchain_t));
@@ -24,6 +56,7 @@ void Chain_Destroy(blockchain_t* chain) {
 bool Chain_AddBlock(blockchain_t* chain, block_t* block) {
     if (chain && block && chain->blocks) {
         DynArr_push_back(chain->blocks, block);
+        chain->size++;
         return true;
     }
 
@@ -48,6 +81,217 @@ bool Chain_IsValid(blockchain_t* chain) {
     if (!chain || !chain->blocks) {
         return false;
     }
-    // Add validation logic here
+
+    const size_t chainSize = DynArr_size(chain->blocks);
+    if (chainSize == 0) {
+        return true;
+    }
+
+    for (size_t i = 1; i < chainSize; i++) {
+        block_t* blk = (block_t*)DynArr_at(chain->blocks, i);
+        block_t* prevBlk = (block_t*)DynArr_at(chain->blocks, i - 1);
+        if (!blk || !prevBlk || blk->header.blockNumber != i) { return false; } // NULL blocks or blockNumber != order in chain
+
+        // Verify prevHash is valid
+        uint8_t prevHash[32];
+        Block_CalculateHash(prevBlk, prevHash);
+
+        if (memcmp(blk->header.prevHash, prevHash, 32) != 0) {
+            return false;
+        }
+
+        // A potential issue is verifying PoW, since the chain read might only have header data without transactions.
+        // A potnetial fix is verifying PoW as we go, when getting new blocks from peers, and only accepting blocks
+        //with valid PoW, so that we can assume all blocks in the chain are valid in that regard.
+    }
+    
+    // Genesis needs special handling because the prevHash is always invalid (no previous block)
+    block_t* genesis = (block_t*)DynArr_at(chain->blocks, 0);
+    if (!genesis || genesis->header.blockNumber != 0) { return false; }
+
+    return true;
+}
+
+void Chain_Wipe(blockchain_t* chain) {
+    if (chain && chain->blocks) {
+        DynArr_erase(chain->blocks);
+        chain->size = 0;
+    }
+}
+
+bool Chain_SaveToFile(blockchain_t* chain, const char* dirpath) {
+    // To avoid stalling the chain from peers, write after every block addition (THAT IS VERIFIED)
+
+    if (!chain || !chain->blocks || !EnsureDirectoryExists(dirpath)) {
+        return false;
+    }
+
+    char metaPath[512];
+    if (!BuildPath(metaPath, sizeof(metaPath), dirpath, "chain.meta")) {
+        return false;
+    }
+
+    // Find metadata file (create if not exists) to get the saved chain size (+ other things)
+    FILE* metaFile = fopen(metaPath, "rb+");
+    if (!metaFile) {
+        metaFile = fopen(metaPath, "wb+");
+        if (!metaFile) {
+            return false;
+        }
+
+        // Initialize metadata with size 0
+        size_t initialSize = 0;
+        fwrite(&initialSize, sizeof(size_t), 1, metaFile);
+        // Write last block hash (32 bytes of zeros for now)
+        uint8_t zeroHash[32] = {0};
+        fwrite(zeroHash, sizeof(uint8_t), 32, metaFile);
+
+        // TODO: Potentially some other things here, we'll see
+    }
+
+    // Read
+    size_t savedSize = 0;
+    fread(&savedSize, sizeof(size_t), 1, metaFile);
+    uint8_t lastSavedHash[32];
+    fread(lastSavedHash, sizeof(uint8_t), 32, metaFile);
+
+    // Assume chain saved is valid, and that the chain in memory is valid (as LoadFromFile will verify the saved one)
+    if (savedSize > DynArr_size(chain->blocks)) {
+        // Saved chain is longer than current chain, this should not happen if we are always saving the current chain, but just in case, fail to save to avoid overwriting a potentially valid longer chain with a shorter one.
+        fclose(metaFile);
+        return false;
+    }
+
+    // Filename formart: dirpath/block_{index}.dat
+    // File format: [block_header][num_transactions][transactions...] - since block_header is fixed size, LoadFromFile will only read those by default
+
+    // Save blocks that are not yet saved
+    for (size_t i = savedSize; i < DynArr_size(chain->blocks); i++) {
+        block_t* blk = (block_t*)DynArr_at(chain->blocks, i);
+        if (!blk) {
+            fclose(metaFile);
+            return false;
+        }
+
+        // Construct file path
+        char filePath[256];
+        snprintf(filePath, sizeof(filePath), "%s/block_%zu.dat", dirpath, i);
+
+        FILE* blockFile = fopen(filePath, "wb");
+        if (!blockFile) {
+            fclose(metaFile);
+            return false;
+        }
+
+        // Write block header
+        fwrite(&blk->header, sizeof(block_header_t), 1, blockFile);
+        size_t txSize = DynArr_size(blk->transactions);
+        fwrite(&txSize, sizeof(size_t), 1, blockFile); // Write number of transactions
+        // Write transactions
+        for (size_t j = 0; j < txSize; j++) {
+            signed_transaction_t* tx = (signed_transaction_t*)DynArr_at(blk->transactions, j);
+            if (fwrite(tx, sizeof(signed_transaction_t), 1, blockFile) != 1) {
+                fclose(blockFile);
+                fclose(metaFile);
+                return false;
+            }
+        }
+
+        fclose(blockFile);
+    }
+
+    // Update metadata with new size and last block hash
+    size_t newSize = DynArr_size(chain->blocks);
+    fseek(metaFile, 0, SEEK_SET);
+    fwrite(&newSize, sizeof(size_t), 1, metaFile);
+    if (newSize > 0) {
+        block_t* lastBlock = (block_t*)DynArr_at(chain->blocks, newSize - 1);
+        uint8_t lastHash[32];
+        Block_CalculateHash(lastBlock, lastHash);
+        fwrite(lastHash, sizeof(uint8_t), 32, metaFile);
+    }
+    fclose(metaFile);
+
+    return true;
+}
+
+bool Chain_LoadFromFile(blockchain_t* chain, const char* dirpath) {
+    if (!chain || !chain->blocks || !dirpath) {
+        return false;
+    }
+
+    struct stat st;
+    if (stat(dirpath, &st) != 0 || !S_ISDIR(st.st_mode)) {
+        return false;
+    }
+
+    char metaPath[512];
+    if (!BuildPath(metaPath, sizeof(metaPath), dirpath, "chain.meta")) {
+        return false;
+    }
+
+    // Read metadata file to get saved chain size (+ other things)
+    FILE* metaFile = fopen(metaPath, "rb");
+    if (!metaFile) {
+        return false;
+    }
+
+    size_t savedSize = 0;
+    fread(&savedSize, sizeof(size_t), 1, metaFile);
+    uint8_t lastSavedHash[32];
+    fread(lastSavedHash, sizeof(uint8_t), 32, metaFile);
+    fclose(metaFile);
+
+    // TODO: Might add a flag to allow reading from a point onward, but just rewrite for now
+    DynArr_erase(chain->blocks); // Clear current chain blocks, but keep allocated memory for efficiency, since we will likely be loading a similar number of blocks as currently in memory.
+
+    // Load blocks
+    for (size_t i = 0; i < savedSize; i++) {
+        // Construct file path
+        char filePath[256];
+        snprintf(filePath, sizeof(filePath), "%s/block_%zu.dat", dirpath, i);
+
+        block_t* blk = Block_Create();
+        if (!blk) {
+            return false;
+        }
+
+        FILE* blockFile = fopen(filePath, "rb");
+        if (!blockFile) {
+            Block_Destroy(blk);
+            return false;
+        }
+
+        // Read block header and transactions
+        if (fread(&blk->header, sizeof(block_header_t), 1, blockFile) != 1) {
+            fclose(blockFile);
+            Block_Destroy(blk);
+            return false;
+        }
+
+        size_t txSize = 0;
+        if (fread(&txSize, sizeof(size_t), 1, blockFile) != 1) {
+            fclose(blockFile);
+            Block_Destroy(blk);
+            return false;
+        }
+
+        for (size_t j = 0; j < txSize; j++) {
+            signed_transaction_t tx;
+            if (fread(&tx, sizeof(signed_transaction_t), 1, blockFile) != 1) {
+                fclose(blockFile);
+                Block_Destroy(blk);
+                return false;
+            }
+            Block_AddTransaction(blk, &tx);
+        }
+        fclose(blockFile);
+
+        Chain_AddBlock(chain, blk);
+    }
+
+    chain->size = savedSize;
+
+    // After read, you SHOULD verify chain validity. We're not doing it here since returning false is a bit unclear if the read failed or if the chain is invalid.
     return true;
 }

src/main.c

@@ -11,6 +11,10 @@
 #include <randomx/librx_wrapper.h>
 #include <signal.h>
 
+#ifndef CHAIN_DATA_DIR
+#define CHAIN_DATA_DIR "chain_data"
+#endif
+
 void handle_sigint(int sig) {
     printf("Caught signal %d, exiting...\n", sig);
     RandomX_Destroy();
@@ -121,8 +125,10 @@ static bool MineBlock(block_t* block) {
 int main(void) {
     signal(SIGINT, handle_sigint);
 
+    const char* chainDataDir = CHAIN_DATA_DIR;
+
     // Init RandomX
-    if (!RandomX_Init("minicoin")) { // TODO: Use a key that is not hardcoded; E.g. hash of the last block, every thousand blocks, etc.
+    if (!RandomX_Init("minicoin", false)) { // TODO: Use a key that is not hardcoded; E.g. hash of the last block, every thousand blocks, difficulty recalibration, etc.
         fprintf(stderr, "failed to initialize RandomX\n");
         return 1;
     }
@@ -133,6 +139,33 @@ int main(void) {
         return 1;
     }
 
+    // Attempt read
+    if (!Chain_LoadFromFile(chain, chainDataDir)) {
+        printf("No existing chain loaded from %s\n", chainDataDir);
+    }
+
+    if (Chain_Size(chain) > 0) {
+        if (Chain_IsValid(chain)) {
+            printf("Loaded chain with %zu blocks from disk\n", Chain_Size(chain));
+        } else {
+            fprintf(stderr, "loaded chain is invalid, scrapping, resyncing.\n"); // TODO: Actually implement resyncing from peers instead of just scrapping the chain
+            const size_t badSize = Chain_Size(chain);
+
+            // Delete files (wipe dir)
+            for (size_t i = 0; i < badSize; i++) {
+                char filePath[256];
+                snprintf(filePath, sizeof(filePath), "%s/block_%zu.dat", chainDataDir, i);
+                remove(filePath);
+            }
+
+            char metaPath[256];
+            snprintf(metaPath, sizeof(metaPath), "%s/chain.meta", chainDataDir);
+            remove(metaPath);
+
+            Chain_Wipe(chain);
+        }
+    }
+
     secp256k1_context* secpCtx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
     if (!secpCtx) {
         fprintf(stderr, "failed to create secp256k1 context\n");
@@ -153,6 +186,17 @@ int main(void) {
         return 1;
     }
 
+    // Coinbase TX - no signature needed, one per block
+    signed_transaction_t coinbaseTx;
+    memset(&coinbaseTx, 0, sizeof(coinbaseTx));
+    coinbaseTx.transaction.version = 1;
+    coinbaseTx.transaction.amount = 50; // Block reward
+    coinbaseTx.transaction.fee = 0;
+    SHA256(receiverCompressedPublicKey, 33, coinbaseTx.transaction.recipientAddress);
+    memset(coinbaseTx.transaction.compressedPublicKey, 0x00, 33); // No public key for coinbase
+    memset(coinbaseTx.transaction.senderAddress, 0xFF, 32); // Coinbase marker
+
+    // Test TX
     signed_transaction_t tx;
     memset(&tx, 0, sizeof(tx));
     tx.transaction.version = 1;
@@ -182,22 +226,36 @@ int main(void) {
     }
 
     block->header.version = 1;
-    block->header.blockNumber = (uint32_t)Chain_Size(chain);
+    block->header.blockNumber = (uint64_t)Chain_Size(chain);
-    memset(block->header.prevHash, 0, sizeof(block->header.prevHash));
+    // Get prevHash from last block if exists
+    if (Chain_Size(chain) > 0) {
+        block_t* lastBlock = Chain_GetBlock(chain, Chain_Size(chain) - 1);
+        if (lastBlock) {
+            Block_CalculateHash(lastBlock, block->header.prevHash);
+        } else {
+            memset(block->header.prevHash, 0, sizeof(block->header.prevHash));
+        }
+    } else {
+        memset(block->header.prevHash, 0, sizeof(block->header.prevHash));
+    }
     memset(block->header.merkleRoot, 0, sizeof(block->header.merkleRoot));
     block->header.timestamp = (uint64_t)time(NULL);
 
-        const double hps = MeasureRandomXHashrate();
+    const double hps = MeasureRandomXHashrate();
-        const double targetSeconds = 60.0;
+    const double targetSeconds = 10.0;
-        const double expectedHashes = (hps > 0.0) ? (hps * targetSeconds) : 65536.0;
+    const double expectedHashes = (hps > 0.0) ? (hps * targetSeconds) : 65536.0;
-        block->header.difficultyTarget = CompactTargetForExpectedHashes(expectedHashes);
+    block->header.difficultyTarget = CompactTargetForExpectedHashes(expectedHashes);
     block->header.nonce = 0;
 
-        printf("RandomX benchmark: %.2f H/s, target %.0fs, nBits=0x%08x\n",
+    printf("RandomX benchmark: %.2f H/s, target %.0fs, nBits=0x%08x\n",
-            hps,
+        hps,
-            targetSeconds,
+        targetSeconds,
-            block->header.difficultyTarget);
+        block->header.difficultyTarget);
 
+    Block_AddTransaction(block, &coinbaseTx);
+    printf("Added coinbase transaction to block: recipient %02x... -> amount %lu\n",
+           coinbaseTx.transaction.recipientAddress[0], coinbaseTx.transaction.recipientAddress[31],
+           coinbaseTx.transaction.amount);
     Block_AddTransaction(block, &tx);
     printf("Added transaction to block: sender %02x... -> recipient %02x..., amount %lu, fee %lu\n",
            tx.transaction.senderAddress[0], tx.transaction.senderAddress[31],
@@ -222,10 +280,10 @@ int main(void) {
         return 1;
     }
 
-        printf("Mined block %u with nonce %llu and chain size %zu\n",
+    printf("Mined block %llu with nonce %llu and chain size %zu\n",
-           block->header.blockNumber,
+        (unsigned long long)block->header.blockNumber,
-            (unsigned long long)block->header.nonce,
+        (unsigned long long)block->header.nonce,
-           Chain_Size(chain));
+        Chain_Size(chain));
 
     printf("Block hash (SHA256): ");
     uint8_t blockHash[32];
@@ -241,6 +299,12 @@ int main(void) {
     }
     printf("\n");
 
+    if (!Chain_SaveToFile(chain, chainDataDir)) {
+        fprintf(stderr, "failed to save chain to %s\n", chainDataDir);
+    } else {
+        printf("Saved chain with %zu blocks to %s\n", Chain_Size(chain), chainDataDir);
+    }
+
     // Chain currently stores a copy of block_t that references the same tx array pointer,
     // so we do not destroy `block` here to avoid invalidating chain data.
     secp256k1_context_destroy(secpCtx);

src/randomx/librx_wrapper.c

@@ -8,7 +8,7 @@ static randomx_cache* rxCache = NULL;
 static randomx_dataset* rxDataset = NULL;
 static randomx_vm* rxVm = NULL;
 
-bool RandomX_Init(const char* key) {
+bool RandomX_Init(const char* key, bool preferFullMemory) {
     if (!key || rxCache || rxVm) {
         return false;
     }
@@ -24,18 +24,20 @@ bool RandomX_Init(const char* key) {
     randomx_init_cache(rxCache, key, strlen(key));
 
     // Prefer full-memory mode. If dataset allocation fails, fall back to light mode.
-    rxDataset = randomx_alloc_dataset(vmFlags);
+    if (preferFullMemory) {
-    if (rxDataset) {
+        rxDataset = randomx_alloc_dataset(vmFlags);
-        const unsigned long datasetItems = randomx_dataset_item_count();
+        if (rxDataset) {
-        randomx_init_dataset(rxDataset, rxCache, 0, datasetItems);
+            const unsigned long datasetItems = randomx_dataset_item_count();
-        rxVm = randomx_create_vm(vmFlags, NULL, rxDataset);
+            randomx_init_dataset(rxDataset, rxCache, 0, datasetItems);
-        if (rxVm) {
+            rxVm = randomx_create_vm(vmFlags, NULL, rxDataset);
-            printf("RandomX initialized in full-memory mode\n");
+            if (rxVm) {
-            return true;
+                printf("RandomX initialized in full-memory mode\n");
-        }
+                return true;
+            }
 
-        randomx_release_dataset(rxDataset);
+            randomx_release_dataset(rxDataset);
-        rxDataset = NULL;
+            rxDataset = NULL;
+        }
     }
 
     vmFlags = baseFlags;