Paginator: Eagerly walk to the first matching commit
This allows getPreviousStart() to be called before the entire walk is
done, which will be necessary for streaming log results. It does mean
the Paginator constructor may block for a while, but we never
construct a Paginator without more or less immediately iterating
through it, so this difference is not noticeable.
Change-Id: Ie40c77678df4e2c3192c1c1fcc16463be57d5efc
diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/Paginator.java b/gitiles-servlet/src/main/java/com/google/gitiles/Paginator.java
index 62dfb55..f1969a0 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/Paginator.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/Paginator.java
@@ -46,30 +46,46 @@
*/
class Paginator implements Iterable<RevCommit> {
private final RevWalk walk;
- private final ObjectId start;
private final int limit;
- private final Deque<ObjectId> prevBuffer;
+ private final ObjectId prevStart;
+ private RevCommit first;
private boolean done;
- private int i;
private int n;
- private int foundIndex;
private ObjectId nextStart;
/**
+ * Construct a paginator and walk eagerly to the first returned commit.
+ *
* @param walk revision walk.
* @param limit page size.
* @param start commit at which to start the walk, or null to start at the
* beginning.
*/
- Paginator(RevWalk walk, int limit, @Nullable ObjectId start) {
+ Paginator(RevWalk walk, int limit, @Nullable ObjectId start) throws MissingObjectException,
+ IncorrectObjectTypeException, IOException {
this.walk = checkNotNull(walk, "walk");
- this.start = start;
checkArgument(limit > 0, "limit must be positive: %s", limit);
this.limit = limit;
- prevBuffer = new ArrayDeque<ObjectId>(start != null ? limit : 0);
- i = -1;
- foundIndex = -1;
+
+
+ Deque<ObjectId> prevBuffer = new ArrayDeque<ObjectId>(start != null ? limit : 0);
+ while (true) {
+ RevCommit commit = walk.next();
+ if (commit == null) {
+ done = true;
+ break;
+ }
+ if (start == null || start.equals(commit)) {
+ first = commit;
+ break;
+ }
+ if (prevBuffer.size() == limit) {
+ prevBuffer.remove();
+ }
+ prevBuffer.add(commit);
+ }
+ prevStart = prevBuffer.pollFirst();
}
/**
@@ -83,34 +99,21 @@
*/
public RevCommit next() throws MissingObjectException, IncorrectObjectTypeException,
IOException {
+ if (done) {
+ return null;
+ }
RevCommit commit;
- if (foundIndex < 0) {
- while (true) {
- commit = walk.next();
- if (commit == null) {
- done = true;
- return null;
- }
- i++;
- if (start == null || start.equals(commit)) {
- foundIndex = i;
- break;
- }
- if (prevBuffer.size() == limit) {
- prevBuffer.remove();
- }
- prevBuffer.add(commit);
- }
+ if (first != null) {
+ commit = first;
+ first = null;
} else {
commit = walk.next();
}
-
if (++n == limit) {
+ nextStart = walk.next();
done = true;
- } else if (n == limit + 1 || commit == null) {
- nextStart = commit;
+ } else if (commit == null) {
done = true;
- return null;
}
return commit;
}
@@ -120,8 +123,7 @@
* null if this is the first page.
*/
public ObjectId getPreviousStart() {
- checkState(done, "getPreviousStart() invalid before walk done");
- return prevBuffer.pollFirst();
+ return prevStart;
}
/**
