blvm_primitives/

types.rs

//! Essential Bitcoin types for consensus validation

use serde::{Deserialize, Serialize};
use std::sync::atomic::{AtomicI64, AtomicU64, Ordering};

#[cfg(feature = "production")]
use rustc_hash::FxHashMap;
#[cfg(feature = "production")]
use smallvec::SmallVec;
#[cfg(not(feature = "production"))]
use std::collections::HashMap;

// Re-export smallvec for macro use in other crates
#[cfg(feature = "production")]
pub use smallvec;

/// Helper macro to create Transaction inputs/outputs that works with both Vec and SmallVec
#[cfg(feature = "production")]
#[macro_export]
macro_rules! tx_inputs {
    ($($item:expr),* $(,)?) => {
        {
            $crate::smallvec::SmallVec::from_vec(vec![$($item),*])
        }
    };
}

#[cfg(not(feature = "production"))]
#[macro_export]
macro_rules! tx_inputs {
    ($($item:expr),* $(,)?) => {
        vec![$($item),*]
    };
}

#[cfg(feature = "production")]
#[macro_export]
macro_rules! tx_outputs {
    ($($item:expr),* $(,)?) => {
        {
            $crate::smallvec::SmallVec::from_vec(vec![$($item),*])
        }
    };
}

#[cfg(not(feature = "production"))]
#[macro_export]
macro_rules! tx_outputs {
    ($($item:expr),* $(,)?) => {
        vec![$($item),*]
    };
}

/// Hash type: 256-bit hash
pub type Hash = [u8; 32];

/// Byte string type
pub type ByteString = Vec<u8>;

/// Witness data: stack of witness elements (SegWit/Taproot)
///
/// For SegWit: Vector of byte strings representing witness stack elements.
/// For Taproot: Vector containing control block and script path data.
pub type Witness = Vec<ByteString>;

/// Maximum script_pubkey stored inline (no `Arc` heap allocation). On-disk format is unaffected
/// (custom Serde serializes only the live bytes). 25 bytes covers P2PKH (25 bytes exactly),
/// P2SH (23), and P2WPKH (22) — ~97% of all UTXOs on mainnet at heights ≤ 600k.
/// P2WSH (34) and P2TR (34) fall through to the `Arc<[u8]>` path transparently; they are
/// negligible pre-SegWit and still a small minority post-SegWit at these heights.
/// Saves ~40 bytes per UTXO vs the old 64-byte cap (~2.2 GB at 55M entries).
/// Reducing below 25 would push P2PKH to Arc, adding back ~1.6 GB for 70% of UTXOs.
const SHARED_BYTE_INLINE_CAP: usize = 25;

/// Live count of SharedByteString instances using heap Arc<[u8]> (script > 25 bytes).
/// Each live Shared variant holds one Arc heap allocation of (16 + script_len) bytes.
/// If this grows unboundedly it means Arc<[u8]> script refs are being retained somewhere.
pub static SBS_SHARED_LIVE: std::sync::atomic::AtomicI64 = std::sync::atomic::AtomicI64::new(0);
/// Total Shared variants ever created (never decremented).
pub static SBS_SHARED_TOTAL: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(0);

enum SharedRepr {
    Inline {
        len: u8,
        data: [u8; SHARED_BYTE_INLINE_CAP],
    },
    Shared(std::sync::Arc<[u8]>),
}

/// Shareable script_pubkey for UTXO: small scripts use inline storage; longer use `Arc<[u8]>`.
/// Clone is cheap (inline copies up to `SHARED_BYTE_INLINE_CAP` bytes, shared is `Arc::clone`). Serde matches `ByteString`.
#[derive(Clone)]
pub struct SharedByteString(SharedRepr);

impl std::fmt::Debug for SharedByteString {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_tuple("SharedByteString")
            .field(&self.as_slice())
            .finish()
    }
}

impl PartialEq for SharedByteString {
    #[inline]
    fn eq(&self, other: &Self) -> bool {
        self.as_slice() == other.as_slice()
    }
}

impl Eq for SharedByteString {}

impl std::hash::Hash for SharedByteString {
    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
        self.as_slice().hash(state);
    }
}

impl SharedByteString {
    #[inline]
    fn as_slice(&self) -> &[u8] {
        match &self.0 {
            SharedRepr::Inline { len, data } => &data[..*len as usize],
            SharedRepr::Shared(a) => a,
        }
    }

    #[inline]
    fn from_bytes(v: &[u8]) -> Self {
        if v.len() <= SHARED_BYTE_INLINE_CAP {
            let mut data = [0u8; SHARED_BYTE_INLINE_CAP];
            data[..v.len()].copy_from_slice(v);
            Self(SharedRepr::Inline {
                len: v.len() as u8,
                data,
            })
        } else {
            SBS_SHARED_LIVE.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
            SBS_SHARED_TOTAL.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
            Self(SharedRepr::Shared(std::sync::Arc::from(v)))
        }
    }
}

// Manual Clone (not `#[derive]`): SharedRepr::Shared must bump SBS_SHARED_LIVE on clone.
// Arc<[u8]> refcount increments but no new heap allocation. SBS_SHARED_TOTAL counts
// distinct heap allocations (from_bytes only). SBS_SHARED_LIVE counts live Shared
// *instances* across clones.
impl Clone for SharedRepr {
    fn clone(&self) -> Self {
        match self {
            SharedRepr::Inline { len, data } => SharedRepr::Inline {
                len: *len,
                data: *data,
            },
            SharedRepr::Shared(a) => {
                SBS_SHARED_LIVE.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
                SharedRepr::Shared(std::sync::Arc::clone(a))
            }
        }
    }
}

impl Drop for SharedRepr {
    fn drop(&mut self) {
        if matches!(self, SharedRepr::Shared(_)) {
            SBS_SHARED_LIVE.fetch_sub(1, std::sync::atomic::Ordering::Relaxed);
        }
    }
}

impl std::ops::Deref for SharedByteString {
    type Target = [u8];
    #[inline]
    fn deref(&self) -> &[u8] {
        self.as_slice()
    }
}

impl Serialize for SharedByteString {
    fn serialize<S: serde::Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
        self.as_slice().serialize(s)
    }
}

impl<'de> Deserialize<'de> for SharedByteString {
    fn deserialize<D: serde::Deserializer<'de>>(d: D) -> Result<Self, D::Error> {
        let v: Vec<u8> = Deserialize::deserialize(d)?;
        Ok(Self::from_bytes(&v))
    }
}

impl From<ByteString> for SharedByteString {
    #[inline]
    fn from(v: ByteString) -> Self {
        Self::from_bytes(v.as_slice())
    }
}

impl From<&[u8]> for SharedByteString {
    #[inline]
    fn from(v: &[u8]) -> Self {
        Self::from_bytes(v)
    }
}

impl Default for SharedByteString {
    #[inline]
    fn default() -> Self {
        Self(SharedRepr::Inline {
            len: 0,
            data: [0u8; SHARED_BYTE_INLINE_CAP],
        })
    }
}

impl AsRef<[u8]> for SharedByteString {
    #[inline]
    fn as_ref(&self) -> &[u8] {
        self.as_slice()
    }
}

impl SharedByteString {
    /// Owning clone of bytes as `Arc<[u8]>`. May allocate once when storing an inline script.
    #[inline]
    pub fn as_arc(&self) -> std::sync::Arc<[u8]> {
        match &self.0 {
            SharedRepr::Shared(a) => std::sync::Arc::clone(a),
            SharedRepr::Inline { len, data } => {
                std::sync::Arc::from(data[..*len as usize].to_vec().into_boxed_slice())
            }
        }
    }
}

/// Natural number type
pub type Natural = u64;

/// Integer type
pub type Integer = i64;

/// Network type for consensus validation
///
/// Used to determine activation heights for various BIPs and consensus rules.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub enum Network {
    /// Bitcoin mainnet
    Mainnet,
    /// Bitcoin testnet (testnet3)
    Testnet,
    /// Bitcoin testnet4 (BIP94)
    Testnet4,
    /// Bitcoin regtest (local testing)
    Regtest,
    /// Bitcoin signet (BIP325 test network with block-solution challenge)
    Signet,
}

/// Time context for consensus validation
///
/// Provides network time and median time-past for timestamp validation.
/// Required for proper block header timestamp validation (BIP113).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct TimeContext {
    /// Current network time (Unix timestamp)
    /// Used to reject blocks with timestamps too far in the future
    pub network_time: u64,
    /// Median time-past of previous 11 blocks (BIP113)
    /// Used to reject a block whose timestamp is not strictly later than this median
    pub median_time_past: u64,
}

/// BIP54 timewarp: timestamps of boundary blocks for period-boundary checks.
///
/// When BIP54 is active, at height N with N % 2016 == 2015 we require
/// header.timestamp >= timestamp_n_minus_2015; at N % 2016 == 0 we require
/// header.timestamp >= timestamp_n_minus_1 - 7200. Callers (e.g. node) pass
/// these when connecting a block at a period boundary.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Bip54BoundaryTimestamps {
    /// Timestamp of block at height N-1 (for first block of period check)
    pub timestamp_n_minus_1: u64,
    /// Timestamp of block at height N-2015 (for last block of period check)
    pub timestamp_n_minus_2015: u64,
}

/// Stable identifier for each consensus-affecting fork (BIP or soft-fork bundle).
///
/// Used to query "is fork X active at height H?" via a unified activation table
/// without hardcoding names in every validation function.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum ForkId {
    /// BIP30: duplicate coinbase prevention (deactivation fork: active when height <= deactivation_height).
    Bip30,
    /// BIP16: P2SH.
    Bip16,
    /// BIP34: block height in coinbase.
    Bip34,
    /// BIP66: strict DER signatures.
    Bip66,
    /// BIP65: OP_CHECKLOCKTIMEVERIFY.
    Bip65,
    /// BIP112/BIP113: OP_CHECKSEQUENCEVERIFY (CSV). Activates at 419328 mainnet — **before** BIP147.
    Bip112,
    /// BIP147: SCRIPT_VERIFY_NULLDUMMY (SegWit deployment; mainnet 481824).
    Bip147,
    /// BIP141: SegWit.
    SegWit,
    /// BIP341: Taproot.
    Taproot,
    /// BIP119: OP_CTV (feature-gated).
    Ctv,
    /// BIP348: OP_CSFS (feature-gated).
    Csfs,
    /// BIP54: consensus cleanup (version-bits or override).
    Bip54,
}

impl Network {
    /// Get network from environment variable or default to mainnet
    ///
    /// Checks `BITCOIN_NETWORK` environment variable:
    /// - "testnet" -> Network::Testnet
    /// - "regtest" -> Network::Regtest
    /// - "signet" -> Network::Signet
    /// - otherwise -> Network::Mainnet
    pub fn from_env() -> Self {
        match std::env::var("BITCOIN_NETWORK").as_deref() {
            Ok("testnet") => Network::Testnet,
            Ok("testnet4") => Network::Testnet4,
            Ok("regtest") => Network::Regtest,
            Ok("signet") => Network::Signet,
            _ => Network::Mainnet,
        }
    }

    /// Get human-readable part (HRP) for Bech32 encoding
    ///
    /// Used by blvm-protocol for address encoding (BIP173/350/351)
    pub fn hrp(&self) -> &'static str {
        match self {
            Network::Mainnet => "bc",
            Network::Testnet | Network::Testnet4 | Network::Signet => "tb",
            Network::Regtest => "bcrt",
        }
    }
}

/// Block height: newtype wrapper for type safety
///
/// Prevents mixing up block heights with other u64 values (e.g., timestamps, counts).
/// Uses `#[repr(transparent)]` for zero-cost abstraction - same memory layout as u64.
#[repr(transparent)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
pub struct BlockHeight(pub u64);

impl BlockHeight {
    /// Create a new BlockHeight from a u64
    #[inline(always)]
    pub fn new(height: u64) -> Self {
        BlockHeight(height)
    }

    /// Get the inner u64 value
    #[inline(always)]
    pub fn as_u64(self) -> u64 {
        self.0
    }
}

impl From<u64> for BlockHeight {
    #[inline(always)]
    fn from(height: u64) -> Self {
        BlockHeight(height)
    }
}

impl From<BlockHeight> for u64 {
    #[inline(always)]
    fn from(height: BlockHeight) -> Self {
        height.0
    }
}

impl std::ops::Deref for BlockHeight {
    type Target = u64;

    #[inline(always)]
    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

/// Block hash: newtype wrapper for type safety
///
/// Prevents mixing up block hashes with other Hash values (e.g., transaction hashes, merkle roots).
/// Uses `#[repr(transparent)]` for zero-cost abstraction - same memory layout as Hash.
#[repr(transparent)]
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub struct BlockHash(pub Hash);

impl BlockHash {
    /// Create a new BlockHash from a Hash
    #[inline(always)]
    pub fn new(hash: Hash) -> Self {
        BlockHash(hash)
    }

    /// Get the inner Hash value
    #[inline(always)]
    pub fn as_hash(self) -> Hash {
        self.0
    }

    /// Get a reference to the inner Hash
    #[inline(always)]
    pub fn as_hash_ref(&self) -> &Hash {
        &self.0
    }
}

impl From<Hash> for BlockHash {
    #[inline(always)]
    fn from(hash: Hash) -> Self {
        BlockHash(hash)
    }
}

impl From<BlockHash> for Hash {
    #[inline(always)]
    fn from(hash: BlockHash) -> Self {
        hash.0
    }
}

impl std::ops::Deref for BlockHash {
    type Target = Hash;

    #[inline(always)]
    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

/// OutPoint: 𝒪 = ℍ × ℕ
///
/// Uses u32 for index (Bitcoin wire format); saves 24 bytes vs repr(align(64)) padding.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
pub struct OutPoint {
    pub hash: Hash,
    pub index: u32,
}

/// Transaction Input: ℐ = 𝒪 × 𝕊 × ℕ
///
/// Performance optimization: Hot fields (prevout, sequence) grouped together
/// for better cache locality. script_sig is accessed less frequently.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct TransactionInput {
    pub prevout: OutPoint,      // Hot: 40 bytes (frequently accessed)
    pub sequence: Natural,      // Hot: 8 bytes (frequently accessed)
    pub script_sig: ByteString, // Cold: Vec (pointer, less frequently accessed)
}

/// Transaction Output: 𝒯 = ℤ × 𝕊
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct TransactionOutput {
    pub value: Integer,
    pub script_pubkey: ByteString,
}

/// Transaction: 𝒯𝒳 = ℕ × ℐ* × 𝒯* × ℕ
///
/// Performance optimization: Uses SmallVec for inputs/outputs to eliminate
/// heap allocations for the common case of 1-2 inputs/outputs (80%+ of transactions).
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct Transaction {
    pub version: Natural,
    #[cfg(feature = "production")]
    pub inputs: SmallVec<[TransactionInput; 2]>,
    #[cfg(not(feature = "production"))]
    pub inputs: Vec<TransactionInput>,
    #[cfg(feature = "production")]
    pub outputs: SmallVec<[TransactionOutput; 2]>,
    #[cfg(not(feature = "production"))]
    pub outputs: Vec<TransactionOutput>,
    pub lock_time: Natural,
}

/// Block Header: ℋ = ℤ × ℍ × ℍ × ℕ × ℕ × ℕ
///
/// `Default` is only used as a placeholder when extracting the header for BIP113
/// tracking; the default value is never used for consensus.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Default)]
pub struct BlockHeader {
    pub version: Integer,
    pub prev_block_hash: Hash,
    pub merkle_root: Hash,
    pub timestamp: Natural,
    pub bits: Natural,
    pub nonce: Natural,
}

impl std::convert::AsRef<BlockHeader> for BlockHeader {
    #[inline]
    fn as_ref(&self) -> &BlockHeader {
        self
    }
}

/// Total Arc<Block> heap allocations created on IBD production paths.
/// Incremented at: download `received_put` (live + CHUNK_OBSOLETE drain),
/// `local_block` gap inject. Test dummies do not increment (not in MEM_REPORT).
pub static ARC_BLOCK_CREATED: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(0);

/// Total Arc<BlockHeader> heap allocations created (each Arc::new(header) call).
/// Compare to jemalloc bin112 curregs to see how many have been freed.
pub static ARC_BLOCKHEADER_CREATED: std::sync::atomic::AtomicU64 =
    std::sync::atomic::AtomicU64::new(0);

/// Live `Block` values created via `from_parts` / serde / `Clone` (IBD wire decode
/// + store + deep copies). Struct-literal test/miner blocks are not incremented.
///
/// `Drop` floors at 0 (i64 saturating_sub does not).
pub static BLOCK_LIVE: AtomicI64 = AtomicI64::new(0);

/// Live `Box<[Transaction]>` whose heap size falls in jemalloc 768KiB–1.5MiB
/// large classes (`n_tx * size_of::<Transaction>()`). dest-ba 650k bins of
/// 1.00 / 1.25 MiB are this size class (256 B × 4096 / 5120 txs).
pub static LARGE_TX_SLICE_LIVE: AtomicI64 = AtomicI64::new(0);

/// Sum of those large slice heaps (bytes).
pub static LARGE_TX_SLICE_BYTES: AtomicU64 = AtomicU64::new(0);

/// Inclusive jemalloc-large window that covers the 768KiB / 1.00 / 1.25 / 1.50 MiB classes.
pub const TX_SLICE_LARGE_MIN: usize = 786_432;
pub const TX_SLICE_LARGE_MAX: usize = 1_572_864;

#[inline]
pub fn tx_slice_heap_bytes(n_tx: usize) -> usize {
    n_tx.saturating_mul(std::mem::size_of::<Transaction>())
}

#[inline]
fn note_block_new(n_tx: usize) {
    BLOCK_LIVE.fetch_add(1, Ordering::Relaxed);
    let b = tx_slice_heap_bytes(n_tx);
    if (TX_SLICE_LARGE_MIN..=TX_SLICE_LARGE_MAX).contains(&b) {
        LARGE_TX_SLICE_LIVE.fetch_add(1, Ordering::Relaxed);
        LARGE_TX_SLICE_BYTES.fetch_add(b as u64, Ordering::Relaxed);
    }
}

#[inline]
fn note_block_drop(n_tx: usize) {
    // i64 saturating_sub floors at i64::MIN, not 0. M-1 claimed this could
    // not go negative; dest S-15 printed Block_live=-455775 because wire
    // decode used a struct literal (no increment) and Drop still decremented.
    BLOCK_LIVE
        .fetch_update(Ordering::Relaxed, Ordering::Relaxed, |v| {
            Some(if v > 0 { v - 1 } else { 0 })
        })
        .ok();
    let b = tx_slice_heap_bytes(n_tx);
    if (TX_SLICE_LARGE_MIN..=TX_SLICE_LARGE_MAX).contains(&b) {
        LARGE_TX_SLICE_LIVE
            .fetch_update(Ordering::Relaxed, Ordering::Relaxed, |v| {
                Some(if v > 0 { v - 1 } else { 0 })
            })
            .ok();
        LARGE_TX_SLICE_BYTES
            .fetch_update(Ordering::Relaxed, Ordering::Relaxed, |v| {
                Some(v.saturating_sub(b as u64))
            })
            .ok();
    }
}

/// Block: ℬ = ℋ × 𝒯𝒳*
///
/// Performance optimization: Uses Box<[Transaction]> instead of Vec<Transaction>
/// since transactions are never modified after block creation. This saves 8 bytes
/// (no capacity field) and provides better cache usage.
#[derive(Debug, PartialEq, Eq, Serialize)]
pub struct Block {
    pub header: BlockHeader,
    pub transactions: Box<[Transaction]>,
}

impl Block {
    /// Wire-decode / explicit construction. Counts as live (M-2: serde-only
    /// hooks missed `deserialize_block_with_witnesses`, which uses this path).
    pub fn from_parts(header: BlockHeader, transactions: Box<[Transaction]>) -> Self {
        note_block_new(transactions.len());
        Self {
            header,
            transactions,
        }
    }
}

impl Clone for Block {
    fn clone(&self) -> Self {
        Self::from_parts(self.header.clone(), self.transactions.clone())
    }
}

impl<'de> Deserialize<'de> for Block {
    fn deserialize<D: serde::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
        #[derive(Deserialize)]
        struct BlockDe {
            header: BlockHeader,
            transactions: Box<[Transaction]>,
        }
        let raw = BlockDe::deserialize(deserializer)?;
        note_block_new(raw.transactions.len());
        Ok(Self {
            header: raw.header,
            transactions: raw.transactions,
        })
    }
}

impl Drop for Block {
    fn drop(&mut self) {
        note_block_drop(self.transactions.len());
    }
}

/// UTXO: 𝒰 = ℤ × 𝕊 × ℕ
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Default)]
pub struct UTXO {
    pub value: Integer,
    pub script_pubkey: SharedByteString,
    pub height: Natural,
    /// Whether this UTXO is from a coinbase transaction
    /// Coinbase outputs require maturity (COINBASE_MATURITY blocks) before they can be spent
    pub is_coinbase: bool,
}

/// UTXO Set: 𝒰𝒮 = 𝒪 → 𝒰
///
/// Arc<UTXO> avoids ~1500+ clones/block during IBD supplement_utxo_map and apply_sync_batch.
/// In production builds, uses FxHashMap for 2-3x faster lookups in large UTXO sets.
#[cfg(feature = "production")]
pub type UtxoSet = FxHashMap<OutPoint, std::sync::Arc<UTXO>>;

#[cfg(not(feature = "production"))]
pub type UtxoSet = HashMap<OutPoint, std::sync::Arc<UTXO>>;

/// Pre-allocate a UtxoSet for `n` entries. Avoids costly reallocation spikes when loading large
/// checkpoints (at 50M entries the HashMap table alone is ~2.5 GB; a growth-triggered realloc
/// temporarily doubles that).
#[inline]
pub fn utxo_set_with_capacity(n: usize) -> UtxoSet {
    #[cfg(feature = "production")]
    {
        FxHashMap::with_capacity_and_hasher(n, Default::default())
    }
    #[cfg(not(feature = "production"))]
    {
        HashMap::with_capacity(n)
    }
}

/// Insert owned UTXO into UtxoSet (wraps in Arc). Convenience for tests and one-off inserts.
#[inline]
pub fn utxo_set_insert(set: &mut UtxoSet, op: OutPoint, u: UTXO) {
    use std::sync::Arc;
    set.insert(op, Arc::new(u));
}

/// Validation result
///
/// Important: This result must be checked - ignoring validation results
/// may cause consensus violations or security issues.
#[must_use = "Validation result must be checked - ignoring may cause consensus violations"]
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ValidationResult {
    Valid,
    Invalid(String),
}

/// Script execution context
#[derive(Debug, Clone)]
pub struct ScriptContext {
    pub script_sig: ByteString,
    pub script_pubkey: ByteString,
    pub witness: Option<ByteString>,
    pub flags: u32,
}

/// Block validation context
#[derive(Debug, Clone)]
pub struct BlockContext {
    pub height: Natural,
    pub prev_headers: Vec<BlockHeader>,
    pub utxo_set: UtxoSet,
}

#[cfg(test)]
mod m1_block_live_tests {
    use super::*;

    #[test]
    fn dest_ba_1mib_classes_are_tx_slice_widths() {
        let tsz = std::mem::size_of::<Transaction>();
        assert_eq!(tx_slice_heap_bytes(4096), 4096 * tsz);
        assert_eq!(tx_slice_heap_bytes(5120), 5120 * tsz);
        // production IBD: Transaction=256 → jemalloc 768KiB / 1.00 / 1.25 / 1.50 MiB.
        if tsz == 256 {
            assert_eq!(tx_slice_heap_bytes(3072), 786_432);
            assert_eq!(tx_slice_heap_bytes(4096), 1_048_576);
            assert_eq!(tx_slice_heap_bytes(5120), 1_310_720);
            assert_eq!(tx_slice_heap_bytes(6144), 1_572_864);
            assert!((TX_SLICE_LARGE_MIN..=TX_SLICE_LARGE_MAX).contains(&tx_slice_heap_bytes(4096)));
            assert!((TX_SLICE_LARGE_MIN..=TX_SLICE_LARGE_MAX).contains(&tx_slice_heap_bytes(5120)));
        }
    }

    #[test]
    fn serde_notes_block_live() {
        let literal = Block {
            header: BlockHeader::default(),
            transactions: Vec::new().into_boxed_slice(),
        };
        let json = serde_json::to_string(&literal).expect("ser");
        drop(literal);
        let before = BLOCK_LIVE.load(Ordering::Relaxed);
        let decoded: Block = serde_json::from_str(&json).expect("de");
        assert_eq!(BLOCK_LIVE.load(Ordering::Relaxed), before + 1);
        drop(decoded);
        assert_eq!(BLOCK_LIVE.load(Ordering::Relaxed), before);
    }

    #[test]
    fn wire_decode_notes_block_live() {
        use crate::serialization::block::{deserialize_block_with_witnesses, serialize_block};
        let tx = Transaction {
            version: 1,
            inputs: crate::tx_inputs![TransactionInput {
                prevout: OutPoint {
                    hash: [1; 32],
                    index: 0
                },
                script_sig: vec![0x51],
                sequence: 0xffffffff,
            }],
            outputs: crate::tx_outputs![TransactionOutput {
                value: 50_0000_0000,
                script_pubkey: vec![0x51],
            }],
            lock_time: 0,
        };
        let built = Block::from_parts(BlockHeader::default(), vec![tx].into_boxed_slice());
        let wire = serialize_block(&built);
        drop(built);
        let before = BLOCK_LIVE.load(Ordering::Relaxed);
        let (decoded, _) = deserialize_block_with_witnesses(&wire).expect("wire decode");
        assert_eq!(BLOCK_LIVE.load(Ordering::Relaxed), before + 1);
        drop(decoded);
        assert_eq!(BLOCK_LIVE.load(Ordering::Relaxed), before);
    }

    #[test]
    fn drop_floors_live_at_zero() {
        let before = BLOCK_LIVE.load(Ordering::Relaxed);
        {
            let _literal = Block {
                header: BlockHeader::default(),
                transactions: Vec::new().into_boxed_slice(),
            };
        }
        assert_eq!(BLOCK_LIVE.load(Ordering::Relaxed), before);
    }
}