test send

include/uint256.h

@@ -55,6 +55,53 @@ static inline bool uint256_add(uint256_t* a, const uint256_t* b) {
     return carry > 0;
 }
 
+static inline bool uint256_subtract_u64(uint256_t* balance, uint64_t amount) {
+    if (!balance) {
+        return false;
+    }
+
+    if (balance->limbs[0] >= amount) {
+        balance->limbs[0] -= amount;
+        return false;
+    }
+
+    uint64_t borrow = amount - balance->limbs[0];
+    balance->limbs[0] = UINT64_MAX - borrow + 1ULL;
+
+    for (int i = 1; i < 4; ++i) {
+        if (balance->limbs[i] > 0) {
+            balance->limbs[i]--;
+            return false;
+        }
+
+        balance->limbs[i] = UINT64_MAX;
+    }
+
+    return true; // underflow past 256 bits
+}
+
+static inline bool uint256_subtract(uint256_t* a, const uint256_t* b) {
+    // Check if a < b to prevent underflow
+    for (int i = 3; i >= 0; i--) {
+        if (a->limbs[i] > b->limbs[i]) break;
+        if (a->limbs[i] < b->limbs[i]) return false; // Underflow
+    }
+
+    uint64_t borrow = 0;
+    for (int i = 0; i < 4; i++) {
+        uint64_t old_a = a->limbs[i];
+        a->limbs[i] -= b->limbs[i] + borrow;
+
+        // Detect borrow: if we subtracted more than we had, or we were at zero and had a borrow
+        if (borrow) {
+            borrow = (a->limbs[i] >= old_a);
+        } else {
+            borrow = (a->limbs[i] > old_a);
+        }
+    }
+    return true;
+}
+
 /**
  * Compares two uint256_t values in a greater-than manner.
  * Returns [-1, 0, 1] if a > b, a < b, or a == b respectively.
@@ -67,4 +114,35 @@ static inline int uint256_cmp(const uint256_t* a, const uint256_t* b) {
     return 0;
 }
 
+static inline void uint256_serialize(const uint256_t* value, char* out) {
+    if (!value || !out) {
+        return;
+    }
+
+    // Convert into string of decimal digits for easier readability; max 78 digits for 256 bits
+    char digits[80];
+    size_t digitCount = 0;
+    uint256_t tmp = *value;
+    while (tmp.limbs[0] != 0 || tmp.limbs[1] != 0 || tmp.limbs[2] != 0 || tmp.limbs[3] != 0) {
+        uint64_t remainder = 0;
+        for (int i = 3; i >= 0; --i) {
+            __uint128_t cur = ((__uint128_t)remainder << 64) | tmp.limbs[i];
+            tmp.limbs[i] = (uint64_t)(cur / 10u);
+            remainder = (uint64_t)(cur % 10u);
+        }
+
+        if (digitCount < sizeof(digits) - 1) {
+            digits[digitCount++] = (char)('0' + remainder);
+        } else {
+            break;
+        }
+    }
+    digits[digitCount] = '\0';
+
+    for (size_t i = 0; i < digitCount; ++i) {
+        out[i] = digits[digitCount - 1 - i];
+    }
+    out[digitCount] = '\0';
+}
+
 #endif