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blockchain: replace Rc mess with internal raw pointers

This commit is contained in:
Andrew Poelstra 2014-07-19 15:23:04 -07:00
parent 93dadd6a6e
commit a3846965e3
1 changed files with 205 additions and 205 deletions
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410
src/blockdata/blockchain.rs
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@ -22,8 +22,6 @@
//! to make sure we are holding the only references.
//!
use alloc::rc::Rc;
use std::cell::{Ref, RefCell};
use std::io::{IoResult, IoError, OtherIoError};
use std::num::Zero;
use std::kinds::marker;
@ -41,8 +39,8 @@ use util::hash::Sha256dHash;
use util::misc::prepend_err;
use util::patricia_tree::PatriciaTree;
type BlockTree = PatriciaTree<Rc<BlockchainNode>, Uint256>;
type NodePtr = Option<Rc<BlockchainNode>>;
type BlockTree = PatriciaTree<Box<BlockchainNode>, Uint256>;
type NodePtr = *const BlockchainNode;
/// A link in the blockchain
pub struct BlockchainNode {
@ -58,52 +56,31 @@ pub struct BlockchainNode {
/// Whether the transaction data is stored
pub has_txdata: bool,
/// Pointer to block's parent
prev: RefCell<NodePtr>,
prev: NodePtr,
/// Pointer to block's child
next: RefCell<NodePtr>
next: NodePtr
}
impl BlockchainNode {
/// Look up the previous link, caching the result
fn prev(&self, tree: &BlockTree) -> NodePtr {
let mut cache = self.prev.borrow_mut();
if cache.is_some() {
return Some(cache.get_ref().clone())
}
match tree.lookup(&self.block.header.prev_blockhash.as_uint256(), 256) {
Some(prev) => { *cache = Some(prev.clone()); return Some(prev.clone()); }
None => { return None; }
}
}
/// Look up the next link
fn next<'a>(&'a self) -> Ref<'a, NodePtr> {
self.next.borrow()
}
/// Set the next link
fn set_next(&self, next: Rc<BlockchainNode>) {
let mut cache = self.next.borrow_mut();
*cache = Some(next);
}
/// Is the node on the main chain?
fn is_on_main_chain(&self, chain: &Blockchain) -> bool {
if self.block.header == chain.best_tip.block.header {
if self.block.header == unsafe { (*chain.best_tip).block.header } {
return true;
}
let mut scan = self.next().clone();
while scan.is_some() {
if scan.get_ref().block.header == chain.best_tip.block.header {
return true;
unsafe {
let mut scan = self.next;
while scan.is_not_null() {
if (*scan).block.header == (*chain.best_tip).block.header {
return true;
}
scan = (*scan).next;
}
scan = scan.get_ref().next().clone();
}
return false;
}
}
impl Serializable for Rc<BlockchainNode> {
impl Serializable for BlockchainNode {
fn serialize(&self) -> Vec<u8> {
let mut ret = vec![];
ret.extend(self.block.serialize().move_iter());
@ -111,20 +88,20 @@ impl Serializable for Rc<BlockchainNode> {
ret.extend(self.required_difficulty.serialize().move_iter());
ret.extend(self.height.serialize().move_iter());
ret.extend(self.has_txdata.serialize().move_iter());
// Don't serialize the prev pointer
// Don't serialize the prev or next pointers
ret
}
fn deserialize<I: Iterator<u8>>(mut iter: I) -> IoResult<Rc<BlockchainNode>> {
Ok(Rc::new(BlockchainNode {
fn deserialize<I: Iterator<u8>>(mut iter: I) -> IoResult<BlockchainNode> {
Ok(BlockchainNode {
block: try!(prepend_err("block", Serializable::deserialize(iter.by_ref()))),
total_work: try!(prepend_err("total_work", Serializable::deserialize(iter.by_ref()))),
required_difficulty: try!(prepend_err("req_difficulty", Serializable::deserialize(iter.by_ref()))),
height: try!(prepend_err("height", Serializable::deserialize(iter.by_ref()))),
has_txdata: try!(prepend_err("has_txdata", Serializable::deserialize(iter.by_ref()))),
prev: RefCell::new(None),
next: RefCell::new(None)
}))
prev: RawPtr::null(),
next: RawPtr::null()
})
}
// Override Serialize::hash to return the blockheader hash, since the
@ -138,7 +115,7 @@ impl Serializable for Rc<BlockchainNode> {
pub struct Blockchain {
network: Network,
tree: BlockTree,
best_tip: Rc<BlockchainNode>,
best_tip: NodePtr,
best_hash: Sha256dHash,
genesis_hash: Sha256dHash
}
@ -167,12 +144,12 @@ impl Serializable for Blockchain {
fn deserialize<I: Iterator<u8>>(mut iter: I) -> IoResult<Blockchain> {
let network: Network = try!(prepend_err("network", Serializable::deserialize(iter.by_ref())));
let tree: BlockTree = try!(prepend_err("tree", Serializable::deserialize(iter.by_ref())));
let mut tree: BlockTree = try!(prepend_err("tree", Serializable::deserialize(iter.by_ref())));
let best_hash: Sha256dHash = try!(prepend_err("best_hash", Serializable::deserialize(iter.by_ref())));
let genesis_hash: Sha256dHash = try!(prepend_err("genesis_hash", Serializable::deserialize(iter.by_ref())));
// Lookup best tip
let best = match tree.lookup(&best_hash.as_uint256(), 256) {
Some(rc) => rc.clone(),
Some(node) => &**node as NodePtr,
None => { return Err(IoError {
kind: OtherIoError,
desc: "best tip reference not found in tree",
@ -188,63 +165,78 @@ impl Serializable for Blockchain {
detail: Some(format!("genesis {:x} not found", genesis_hash))
});
}
// Reconnect next and prev pointers back to "genesis", the first node
// with no prev pointer.
let mut scan = best.clone();
let mut prev = best.prev(&tree);
while prev.is_some() {
prev.get_mut_ref().set_next(scan);
scan = prev.get_ref().clone();
prev = prev.get_ref().prev(&tree);
// Reconnect all prev pointers
let raw_tree = &tree as *const _;
for node in tree.mut_iter() {
let hash = node.block.header.prev_blockhash.as_uint256();
let prevptr =
match unsafe { (*raw_tree).lookup(&hash, 256) } {
Some(node) => &**node as NodePtr,
None => RawPtr::null()
};
node.prev = prevptr;
}
// Check that "genesis" is the genesis
if scan.block.header.hash() != genesis_hash {
Err(IoError {
kind: OtherIoError,
desc: "best tip did not link back to genesis",
detail: Some(format!("no path from tip {:x} to genesis {:x}", best_hash, genesis_hash))
})
} else {
// Return the chain
Ok(Blockchain {
network: network,
tree: tree,
best_tip: best.clone(),
best_hash: best_hash,
genesis_hash: genesis_hash
})
// Reconnect next pointers on the main chain
unsafe {
let mut scan = best;
while (*scan).prev.is_not_null() {
let prev = (*scan).prev as *mut BlockchainNode;
(*prev).next = scan;
scan = prev as NodePtr;
}
// Check that "genesis" is the genesis
if (*scan).block.header.hash() != genesis_hash {
return Err(IoError {
kind: OtherIoError,
desc: "best tip did not link back to genesis",
detail: Some(format!("no path from tip {:x} to genesis {:x}", best_hash, genesis_hash))
});
}
}
// Return the chain
Ok(Blockchain {
network: network,
tree: tree,
best_tip: best,
best_hash: best_hash,
genesis_hash: genesis_hash
})
}
}
struct LocatorHashIter<'tree> {
// TODO: this should maybe be public, in which case it needs to be tagged
// with a ContravariantLifetime marker tying it to the tree's lifetime.
struct LocatorHashIter {
index: NodePtr,
tree: &'tree BlockTree,
count: uint,
skip: uint
}
impl<'tree> LocatorHashIter<'tree> {
fn new<'tree>(init: Rc<BlockchainNode>, tree: &'tree BlockTree) -> LocatorHashIter<'tree> {
LocatorHashIter { index: Some(init), tree: tree, count: 0, skip: 1 }
impl LocatorHashIter {
fn new(init: NodePtr) -> LocatorHashIter {
LocatorHashIter { index: init, count: 0, skip: 1 }
}
}
impl<'tree> Iterator<Sha256dHash> for LocatorHashIter<'tree> {
impl Iterator<Sha256dHash> for LocatorHashIter {
fn next(&mut self) -> Option<Sha256dHash> {
let ret = match self.index {
Some(ref node) => Some(node.hash()),
None => { return None; }
};
if self.index.is_null() {
return None;
}
let ret = Some(unsafe { (*self.index).hash() });
// Rewind once (if we are at the genesis, this will set self.index to None)
self.index = self.index.get_ref().prev(self.tree);
self.index = unsafe { (*self.index).prev };
// If we are not at the genesis, rewind `self.skip` times, or until we are.
if self.index.is_some() {
if self.index.is_not_null() {
for _ in range(1, self.skip) {
self.index = match self.index.get_ref().prev(self.tree) {
Some(rc) => Some(rc),
None => { break; }
unsafe {
if (*self.index).prev.is_null() {
break;
}
self.index = (*self.index).prev;
}
}
}
@ -276,7 +268,8 @@ pub struct BlockIter<'tree> {
/// this suprising behaviour we simply use separate iterators.
pub struct RevBlockIter<'tree> {
index: NodePtr,
tree: &'tree BlockTree
// See comment in BlockIter for why we need this
marker: marker::ContravariantLifetime<'tree>
}
/// An iterator over blocks in reverse blockheight order, which yielding only
@ -299,60 +292,48 @@ pub struct RevStaleBlockIter<'tree> {
impl<'tree> Iterator<&'tree BlockchainNode> for BlockIter<'tree> {
fn next(&mut self) -> Option<&'tree BlockchainNode> {
match self.index.clone() {
Some(rc) => {
use core::mem::transmute;
self.index = rc.next().clone();
// This transmute is just to extend the lifetime of rc.block
// There is unsafety here because we need to be assured that
// another copy of the rc (presumably the one in the tree)
// exists and will live as long as 'tree.
Some(unsafe { transmute(&*rc) } )
},
None => None
if self.index.is_null() {
return None;
}
unsafe {
let ret = Some(&*self.index);
self.index = (*self.index).next;
ret
}
}
}
impl<'tree> Iterator<&'tree BlockchainNode> for RevBlockIter<'tree> {
fn next(&mut self) -> Option<&'tree BlockchainNode> {
match self.index.clone() {
Some(rc) => {
use core::mem::transmute;
self.index = rc.prev(self.tree).clone();
// This transmute is just to extend the lifetime of rc.block
// There is unsafety here because we need to be assured that
// another copy of the rc (presumably the one in the tree)
// exists and will live as long as 'tree.
Some(unsafe { transmute(&*rc) } )
},
None => None
if self.index.is_null() {
return None;
}
unsafe {
let ret = Some(&*self.index);
self.index = (*self.index).prev;
ret
}
}
}
impl<'tree> Iterator<&'tree Block> for RevStaleBlockIter<'tree> {
fn next(&mut self) -> Option<&'tree Block> {
match self.index.clone() {
Some(rc) => {
use core::mem::transmute;
let next_index = rc.prev(&self.chain.tree);
if self.index.is_null() {
return None;
}
// Check if the next block is going to be on the main chain
if next_index.is_some() &&
next_index.get_ref().next().get_ref().block.header != rc.block.header &&
next_index.get_ref().is_on_main_chain(self.chain) {
self.index = None;
} else {
self.index = next_index.clone();
}
// This transmute is just to extend the lifetime of rc.block
// There is unsafety here because we need to be assured that
// another copy of the rc (presumably the one in the tree)
// exists and will live as long as 'tree.
Some(unsafe { transmute(&rc.block) } )
},
None => None
unsafe {
let ret = Some(&(*self.index).block);
let next_index = (*self.index).prev;
// Check if the next block is going to be on the main chain
if next_index.is_not_null() &&
(*next_index).next != self.index &&
(&*next_index).is_on_main_chain(self.chain) {
self.index = RawPtr::null();
} else {
self.index = next_index;
}
ret
}
}
}
@ -377,25 +358,26 @@ impl Blockchain {
pub fn new(network: Network) -> Blockchain {
let genesis = genesis_block(network);
let genhash = genesis.header.hash();
let rc_gen = Rc::new(BlockchainNode {
let new_node = box BlockchainNode {
total_work: Zero::zero(),
required_difficulty: genesis.header.target(),
block: genesis,
height: 0,
has_txdata: true,
prev: RefCell::new(None),
next: RefCell::new(None)
});
prev: RawPtr::null(),
next: RawPtr::null()
};
let raw_ptr = &*new_node as NodePtr;
Blockchain {
network: network,
tree: {
let mut pat = PatriciaTree::new();
pat.insert(&genhash.as_uint256(), 256, rc_gen.clone());
pat.insert(&genhash.as_uint256(), 256, new_node);
pat
},
best_hash: genhash,
genesis_hash: genhash,
best_tip: rc_gen,
best_tip: raw_ptr
}
}
@ -433,6 +415,11 @@ impl Blockchain {
}
}
/// Looks up a block in the chain and returns a reference to it
pub fn get_block<'a>(&'a self, hash: Sha256dHash) -> Option<&'a Block> {
self.tree.lookup(&hash.as_uint256(), 256).as_ref().map(|node| &node.block)
}
/// Locates a block in the chain and overwrites its txdata
pub fn add_txdata(&mut self, block: Block) -> BitcoinResult<()> {
self.replace_txdata(&block.header.hash().as_uint256(), block.txdata, true)
@ -455,36 +442,41 @@ impl Blockchain {
fn real_add_block(&mut self, block: Block, has_txdata: bool) -> BitcoinResult<()> {
// get_prev optimizes the common case where we are extending the best tip
fn get_prev<'a>(chain: &'a Blockchain, hash: Sha256dHash) -> Option<&'a Rc<BlockchainNode>> {
if hash == chain.best_hash { return Some(&chain.best_tip); }
chain.tree.lookup(&hash.as_uint256(), 256)
#[inline]
fn get_prev<'a>(chain: &'a Blockchain, hash: Sha256dHash) -> Option<NodePtr> {
if hash == chain.best_hash {
Some(chain.best_tip)
} else {
chain.tree.lookup(&hash.as_uint256(), 256).map(|boxptr| &**boxptr as NodePtr)
}
}
// Check for multiple inserts (bitcoind from c9a09183 to 3c85d2ec doesn't
// handle locator hashes properly and may return blocks multiple times,
// and this may also happen in case of a reorg.
if self.tree.lookup(&block.header.hash().as_uint256(), 256).is_some() {
println!("Warning: tried to add block {} twice!", block.header.hash());
return Err(DuplicateHash);
}
// Construct node, if possible
let rc_block = match get_prev(self, block.header.prev_blockhash) {
let new_block = match get_prev(self, block.header.prev_blockhash) {
Some(prev) => {
let difficulty =
// Compute required difficulty if this is a diffchange block
if (prev.height + 1) % DIFFCHANGE_INTERVAL == 0 {
// Scan back DIFFCHANGE_INTERVAL blocks
let mut scan = prev.clone();
for _ in range(0, DIFFCHANGE_INTERVAL - 1) {
scan = scan.prev(&self.tree).unwrap();
}
// Get clamped timespan between first and last blocks
let timespan = match prev.block.header.time - scan.block.header.time {
n if n < DIFFCHANGE_TIMESPAN / 4 => DIFFCHANGE_TIMESPAN / 4,
n if n > DIFFCHANGE_TIMESPAN * 4 => DIFFCHANGE_TIMESPAN * 4,
n => n
if (unsafe { (*prev).height } + 1) % DIFFCHANGE_INTERVAL == 0 {
let timespan = unsafe {
// Scan back DIFFCHANGE_INTERVAL blocks
let mut scan = prev;
for _ in range(0, DIFFCHANGE_INTERVAL - 1) {
scan = (*scan).prev;
}
// Get clamped timespan between first and last blocks
match (*prev).block.header.time - (*scan).block.header.time {
n if n < DIFFCHANGE_TIMESPAN / 4 => DIFFCHANGE_TIMESPAN / 4,
n if n > DIFFCHANGE_TIMESPAN * 4 => DIFFCHANGE_TIMESPAN * 4,
n => n
}
};
// Compute new target
let mut target = prev.block.header.target();
let mut target = unsafe { (*prev).block.header.target() };
target = target.mul_u32(timespan);
target = target / FromPrimitive::from_u64(DIFFCHANGE_TIMESPAN as u64).unwrap();
// Clamp below MAX_TARGET (difficulty 1)
@ -495,34 +487,39 @@ impl Blockchain {
// On non-diffchange blocks, Testnet has a rule that any 20-minute-long
// block intervals result the difficulty
} else if self.network == BitcoinTestnet &&
block.header.time > prev.block.header.time + 2*TARGET_BLOCK_SPACING {
block.header.time > unsafe { (*prev).block.header.time } + 2*TARGET_BLOCK_SPACING {
max_target(self.network)
// On the other hand, if we are in Testnet and the block interval is less
// than 20 minutes, we need to scan backward to find a block for which the
// previous rule did not apply, to find the "real" difficulty.
} else if self.network == BitcoinTestnet {
// Scan back DIFFCHANGE_INTERVAL blocks
let mut scan = prev.clone();
while scan.height % DIFFCHANGE_INTERVAL != 0 &&
scan.required_difficulty == max_target(self.network) {
scan = scan.prev(&self.tree).unwrap();
unsafe {
let mut scan = prev;
while (*scan).height % DIFFCHANGE_INTERVAL != 0 &&
(*scan).required_difficulty == max_target(self.network) {
scan = (*scan).prev;
}
(*scan).required_difficulty
}
scan.required_difficulty
// Otherwise just use the last block's difficulty
} else {
prev.required_difficulty
unsafe { (*prev).required_difficulty }
};
// Create node
let ret = Rc::new(BlockchainNode {
total_work: block.header.work().add(&prev.total_work),
let ret = box BlockchainNode {
total_work: block.header.work().add(unsafe { &(*prev).total_work }),
block: block,
required_difficulty: difficulty,
height: prev.height + 1,
height: unsafe { (*prev).height + 1 },
has_txdata: has_txdata,
prev: RefCell::new(Some(prev.clone())),
next: RefCell::new(None)
});
prev.set_next(ret.clone());
prev: prev,
next: RawPtr::null()
};
unsafe {
let prev = prev as *mut BlockchainNode;
(*prev).next = &*ret as NodePtr;
}
ret
},
None => {
@ -531,51 +528,41 @@ impl Blockchain {
};
// spv validate the block
try!(rc_block.block.header.spv_validate(&rc_block.required_difficulty));
try!(new_block.block.header.spv_validate(&new_block.required_difficulty));
// Insert the new block
self.tree.insert(&rc_block.block.header.hash().as_uint256(), 256, rc_block.clone());
let raw_ptr = &*new_block as NodePtr;
self.tree.insert(&new_block.block.header.hash().as_uint256(), 256, new_block);
// Replace the best tip if necessary
if rc_block.total_work > self.best_tip.total_work {
self.set_best_tip(rc_block);
if unsafe { (*raw_ptr).total_work > (*self.best_tip).total_work } {
self.set_best_tip(raw_ptr);
}
Ok(())
}
/// Sets the best tip (not public)
fn set_best_tip(&mut self, tip: Rc<BlockchainNode>) {
let old_best = self.best_tip.clone();
// Set best
self.best_hash = tip.hash();
self.best_tip = tip;
fn set_best_tip(&mut self, tip: NodePtr) {
// Fix next links
let mut scan = self.best_tip.clone();
let mut prev = self.best_tip.prev(&self.tree);
// Scan backward
loop {
// If we hit the old best, there is no need to reorg
if scan.block.header == old_best.block.header {
break;
unsafe {
let mut scan = self.best_tip;
// Scan backward
while (*scan).prev.is_not_null() {
// If we hit the old best, there is no need to reorg.
if scan == self.best_tip { break; }
// Otherwise set the next-ptr and carry on
let prev = (*scan).prev as *mut BlockchainNode;
(*prev).next = scan;
scan = (*scan).prev;
}
// If we hit the genesis, stop
if prev.is_none() {
println!("Warning: reorg past the genesis. This is a bug.");
break;
}
// If we hit something pointing along the wrong chain, this is
// a branch point at which we are reorg'ing
if prev.get_ref().next().is_none() ||
prev.get_ref().next().get_ref().block.header != scan.block.header {
prev.get_mut_ref().set_next(scan);
}
scan = prev.clone().unwrap();
prev = prev.unwrap().prev(&self.tree);
}
// Set best
self.best_hash = unsafe { (*tip).hash() };
self.best_tip = tip;
}
/// Returns the best tip
pub fn best_tip<'a>(&'a self) -> &'a Block {
&self.best_tip.block
unsafe { &(*self.best_tip).block }
}
/// Returns the best tip's blockhash
@ -585,33 +572,46 @@ impl Blockchain {
/// Returns an array of locator hashes used in `getheaders` messages
pub fn locator_hashes(&self) -> Vec<Sha256dHash> {
LocatorHashIter::new(self.best_tip.clone(), &self.tree).collect()
LocatorHashIter::new(self.best_tip).collect()
}
/// An iterator over all blocks in the chain starting from `start_hash`
pub fn iter<'a>(&'a self, start_hash: Sha256dHash) -> BlockIter<'a> {
let start = match self.tree.lookup(&start_hash.as_uint256(), 256) {
Some(boxptr) => &**boxptr as NodePtr,
None => RawPtr::null()
};
BlockIter {
index: self.tree.lookup(&start_hash.as_uint256(), 256).map(|rc| rc.clone()),
index: start,
marker: marker::ContravariantLifetime::<'a>
}
}
/// An iterator over all blocks in reverse order to the genesis, starting with `start_hash`
pub fn rev_iter<'a>(&'a self, start_hash: Sha256dHash) -> RevBlockIter<'a> {
let start = match self.tree.lookup(&start_hash.as_uint256(), 256) {
Some(boxptr) => &**boxptr as NodePtr,
None => RawPtr::null()
};
RevBlockIter {
index: self.tree.lookup(&start_hash.as_uint256(), 256).map(|rc| rc.clone()),
tree: &self.tree
index: start,
marker: marker::ContravariantLifetime::<'a>
}
}
/// An iterator over all blocks -not- in the best chain, in reverse order, starting from `start_hash`
pub fn rev_stale_iter<'a>(&'a self, start_hash: Sha256dHash) -> RevStaleBlockIter<'a> {
let mut start = self.tree.lookup(&start_hash.as_uint256(), 256).map(|rc| rc.clone());
// If we are already on the main chain, we have a dead iterator
if start.is_some() && start.get_ref().is_on_main_chain(self) {
start = None;
}
// Return iterator
let start = match self.tree.lookup(&start_hash.as_uint256(), 256) {
Some(boxptr) => {
// If we are already on the main chain, we have a dead iterator
if boxptr.is_on_main_chain(self) {
RawPtr::null()
} else {
&**boxptr as NodePtr
}
}
None => RawPtr::null()
};
RevStaleBlockIter {
index: start,
chain: self
@ -632,7 +632,7 @@ mod tests {
#[test]
fn blockchain_serialize_test() {
let empty_chain = Blockchain::new(Bitcoin);
assert_eq!(empty_chain.best_tip.hash().serialize(),
assert_eq!(empty_chain.best_tip().header.hash().serialize(),
genesis_block(Bitcoin).header.hash().serialize());
let serial = empty_chain.serialize();
@ -641,7 +641,7 @@ mod tests {
let deserial: IoResult<Blockchain> = Serializable::deserialize(serial.iter().map(|n| *n));
assert!(deserial.is_ok());
let read_chain = deserial.unwrap();
assert_eq!(read_chain.best_tip.hash().serialize(),
assert_eq!(read_chain.best_tip().header.hash().serialize(),
genesis_block(Bitcoin).header.hash().serialize());
}
}