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make rehashing more efficient by not re-allocating entries

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This commit is contained in:
Niko Matsakis 2011-12-06 20:22:12 -08:00
parent 729345cb97
commit ddfe82a466
1 changed files with 17 additions and 18 deletions
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35
src/libstd/map.rs
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@ -125,7 +125,7 @@ mod chained {
};
tag search_result<copy K, copy V> {
not_found(uint);
not_found;
found_first(uint, @entry<K,V>);
found_after(@entry<K,V>, @entry<K,V>);
}
@ -133,13 +133,12 @@ mod chained {
fn search_rem<copy K, copy V>(tbl: t<K,V>,
k: K,
h: uint,
idx: uint,
e_root: @entry<K,V>) -> search_result<K,V> {
let e0 = e_root;
while true {
alt e0.next {
absent. {
ret not_found(idx);
ret not_found;
}
present(e1) {
let e1_key = e1.key; // Satisfy alias checker.
@ -161,23 +160,25 @@ mod chained {
alt tbl.chains[idx] {
absent. {
ret not_found(idx);
ret not_found;
}
present(e) {
let e_key = e.key; // Satisfy alias checker.
if e.hash == h && tbl.eqer(e_key, k) {
ret found_first(idx, e);
} else {
ret search_rem(tbl, k, h, idx, e);
ret search_rem(tbl, k, h, e);
}
}
}
}
fn insert_h<copy K, copy V>(tbl: t<K,V>, k: K, v: V, hash: uint) -> bool {
// internal routine: does not update size
fn insert<copy K, copy V>(tbl: t<K,V>, k: K, v: V) -> bool {
let hash = tbl.hasher(k);
alt search_tbl(tbl, k, hash) {
not_found(idx) {
not_found. {
tbl.size += 1u;
let idx = hash % vec::len(tbl.chains);
let old_chain = tbl.chains[idx];
tbl.chains[idx] = present(@{
hash: hash,
@ -197,14 +198,9 @@ mod chained {
}
}
fn insert<copy K, copy V>(tbl: t<K,V>, k: K, v: V) -> bool {
tbl.size += 1u;
ret insert_h(tbl, k, v, tbl.hasher(k));
}
fn get<copy K, copy V>(tbl: t<K,V>, k: K) -> option::t<V> {
alt search_tbl(tbl, k, tbl.hasher(k)) {
not_found(_) {
not_found. {
ret option::none;
}
@ -220,7 +216,7 @@ mod chained {
fn remove<copy K, copy V>(tbl: t<K,V>, k: K) -> option::t<V> {
alt search_tbl(tbl, k, tbl.hasher(k)) {
not_found(_) {
not_found. {
ret option::none;
}
@ -247,8 +243,9 @@ mod chained {
alt chain {
absent. { ret; }
present(entry) {
blk(entry);
chain = entry.next;
let next = entry.next;
blk(entry); // may modify entry.next!
chain = next;
}
}
}
@ -269,7 +266,9 @@ mod chained {
let n_new_chains: uint = uint::next_power_of_two(n_old_chains + 1u);
tbl.chains = chains(n_new_chains);
foreach_chain(old_chains) { |entry|
insert_h(tbl, entry.key, entry.value, entry.hash);
let idx = entry.hash % n_new_chains;
entry.next = tbl.chains[idx];
tbl.chains[idx] = present(entry);
}
}