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Added generations to LeafMap.
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@nbronson
nbronson committed Dec 29, 2009
1 parent 5a91eff commit a9ba55d
Showing 1 changed file with 48 additions and 18 deletions.
66 changes: 48 additions & 18 deletions src/main/java/edu/stanford/ppl/concurrent/SnapHashMap.java
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Original file line number Diff line number Diff line change
Expand Up @@ -9,24 +9,29 @@ public class SnapHashMap<K,V> {
private static final int BF = 1 << LOG_BF;
private static final int BF_MASK = BF - 1;

static class Generation {
}

static class Node<K,V> {
final Generation gen;
final K key;
final int hash;
V value;
final Node<K,V> next;

Node(final K key, final int hash, final V value, final Node<K,V> next) {
Node(final Generation gen, final K key, final int hash, final V value, final Node<K,V> next) {
this.gen = gen;
this.key = key;
this.hash = hash;
this.value = value;
this.next = next;
}

Node<K,V> withRemoved(final Node<K,V> target) {
Node<K,V> withRemoved(final Generation gen, final Node<K,V> target) {
if (this == target) {
return next;
} else {
return new Node<K,V>(key, hash, value, next.withRemoved(target));
return new Node<K,V>(gen, key, hash, value, next.withRemoved(gen, target));
}
}
}
Expand All @@ -38,6 +43,8 @@ static class LeafMap<K,V> {
static final int MIN_CAPACITY = 8;
static final int MAX_CAPACITY = MIN_CAPACITY * BF;

final Generation gen;

/** The number of unique hash codes recorded in this LeafMap. This is also
* used to establish synchronization order, by reading in containsKey and
* get and writing in any updating function. We track unique hash codes
Expand All @@ -52,7 +59,8 @@ static class LeafMap<K,V> {
final float loadFactor;

@SuppressWarnings("unchecked")
LeafMap(final float loadFactor) {
LeafMap(final Generation gen, final float loadFactor) {
this.gen = gen;
this.table = (Node<K,V>[]) new Node[MIN_CAPACITY];
this.threshold = (int) (MIN_CAPACITY * loadFactor);
this.loadFactor = loadFactor;
Expand Down Expand Up @@ -148,21 +156,28 @@ private void reputL(final Node<K,V> e) {
// no new entry needed
table[i] = e;
} else {
table[i] = new Node<K,V>(e.key, e.hash, e.value, next);
table[i] = new Node<K,V>(gen, e.key, e.hash, e.value, next);
}
}

V putL(final K key, final int hash, final V value) {
growIfNecessaryL();
final int i = hash & (table.length - 1);
Node<K,V> e = table[i];
final Node<K,V> head = table[i];
Node<K,V> e = head;
int insDelta = 1;
while (e != null) {
if (e.hash == hash) {
if (key.equals(e.key)) {
// match
final V prev = e.value;
e.value = value;
if (e.gen == gen) {
// we have permission to mutate the node
e.value = value;
} else {
// we must replace the node
table[i] = new Node<K,V>(gen, key, hash, value, head.withRemoved(gen, e));
}
uniq = uniq; // volatile store
return prev;
}
Expand All @@ -173,7 +188,7 @@ V putL(final K key, final int hash, final V value) {
e = e.next;
}
// no match
table[i] = new Node<K,V>(key, hash, value, null);
table[i] = new Node<K,V>(gen, key, hash, value, head);
uniq += insDelta; // volatile store
return null;
}
Expand Down Expand Up @@ -204,7 +219,7 @@ V removeL(final K key, final int hash) {

// match
uniq += delDelta; // volatile store
table[i] = head.withRemoved(target);
table[i] = head.withRemoved(gen, target);
return target.value;
}
// hash match, but not key match
Expand All @@ -221,7 +236,8 @@ V removeL(final K key, final int hash) {
V putIfAbsentL(final K key, final int hash, final V value) {
growIfNecessaryL();
final int i = hash & (table.length - 1);
Node<K,V> e = table[i];
final Node<K,V> head = table[i];
Node<K,V> e = head;
int insDelta = 1;
while (e != null) {
if (e.hash == hash) {
Expand All @@ -236,20 +252,27 @@ V putIfAbsentL(final K key, final int hash, final V value) {
e = e.next;
}
// no match
table[i] = new Node<K,V>(key, hash, value, null);
table[i] = new Node<K,V>(gen, key, hash, value, head);
uniq += insDelta; // volatile store
return null;
}

boolean replaceL(final K key, final int hash, final V oldValue, final V newValue) {
final int i = hash & (table.length - 1);
Node<K,V> e = table[i];
final Node<K,V> head = table[i];
Node<K,V> e = head;
while (e != null) {
if (e.hash == hash && key.equals(e.key)) {
// key match
if (oldValue.equals(e.value)) {
// CAS success
e.value = newValue;
if (e.gen == gen) {
// we have permission to mutate the node
e.value = newValue;
} else {
// we must replace the node
table[i] = new Node<K,V>(gen, key, hash, newValue, head.withRemoved(gen, e));
}
uniq = uniq; // volatile store
return true;
} else {
Expand All @@ -265,12 +288,19 @@ boolean replaceL(final K key, final int hash, final V oldValue, final V newValue

V replaceL(final K key, final int hash, final V value) {
final int i = hash & (table.length - 1);
Node<K,V> e = table[i];
final Node<K,V> head = table[i];
Node<K,V> e = head;
while (e != null) {
if (e.hash == hash && key.equals(e.key)) {
// match
final V prev = e.value;
e.value = value;
if (e.gen == gen) {
// we have permission to mutate the node
e.value = value;
} else {
// we must replace the node
table[i] = new Node<K,V>(gen, key, hash, value, head.withRemoved(gen, e));
}
uniq = uniq; // volatile store
return prev;
}
Expand Down Expand Up @@ -311,7 +341,7 @@ boolean removeL(final K key, final int hash, final V value) {

// match
uniq += delDelta; // volatile store
table[i] = head.withRemoved(target);
table[i] = head.withRemoved(gen, target);
return true;
}
// hash match, but not key match
Expand All @@ -333,7 +363,7 @@ boolean shouldSplitL() {
LeafMap<K,V>[] splitL(final int shift, final int bf) {
final LeafMap<K,V>[] pieces = (LeafMap<K,V>[]) new LeafMap[bf];
for (int i = 0; i < pieces.length; ++i) {
pieces[i] = new LeafMap<K,V>(loadFactor);
pieces[i] = new LeafMap<K,V>(gen, loadFactor);
}
for (Node<K,V> head : table) {
scatterAllL(pieces, shift, head);
Expand Down Expand Up @@ -366,7 +396,7 @@ private void putL(final Node<K,V> entry) {
// no new entry needed
table[i] = e;
} else {
table[i] = new Node<K,V>(e.key, e.hash, e.value, head);
table[i] = new Node<K,V>(gen, e.key, e.hash, e.value, head);
}
}
}
Expand Down

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