[JGIT PATCH 11/14] Expose beginning of iterator indication from AbstractTreeIterator

["Shawn O. Pearce" <spearce@xxxxxxxxxxx>]

Callers like TreeWalk need to know if back(1) is going to be a valid
operation for a given AbstractTreeIterator before they try to make a
call to move the iterator backwards.  The new method first() returns
true only if the iterator is already positioned on its first entry,
in which case a call to back(n) (for any n) is invalid.

Signed-off-by: Shawn O. Pearce <spearce@xxxxxxxxxxx>
---
 .../spearce/jgit/dircache/DirCacheIterator.java    |   12 +++++++++++-
 .../jgit/treewalk/AbstractTreeIterator.java        |   13 +++++++++++++
 .../spearce/jgit/treewalk/CanonicalTreeParser.java |    5 +++++
 .../spearce/jgit/treewalk/EmptyTreeIterator.java   |    5 +++++
 .../spearce/jgit/treewalk/WorkingTreeIterator.java |    5 +++++
 5 files changed, 39 insertions(+), 1 deletions(-)

diff --git a/org.spearce.jgit/src/org/spearce/jgit/dircache/DirCacheIterator.java b/org.spearce.jgit/src/org/spearce/jgit/dircache/DirCacheIterator.java
index 84cefa5..8384723 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/dircache/DirCacheIterator.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/dircache/DirCacheIterator.java
@@ -64,6 +64,9 @@
 	/** The tree this iterator is walking. */
 	private final DirCacheTree tree;
 
+	/** First position in this tree. */
+	private final int treeStart;
+
 	/** Last position in this tree. */
 	private final int treeEnd;
 
@@ -95,6 +98,7 @@
 	public DirCacheIterator(final DirCache dc) {
 		cache = dc;
 		tree = dc.getCacheTree(true);
+		treeStart = 0;
 		treeEnd = tree.getEntrySpan();
 		subtreeId = new byte[Constants.OBJECT_ID_LENGTH];
 		if (!eof())
@@ -105,7 +109,8 @@ protected DirCacheIterator(final DirCacheIterator p, final DirCacheTree dct) {
 		super(p, p.path, p.pathLen + 1);
 		cache = p.cache;
 		tree = dct;
-		treeEnd = p.ptr + tree.getEntrySpan();
+		treeStart = p.ptr;
+		treeEnd = treeStart + tree.getEntrySpan();
 		subtreeId = p.subtreeId;
 		ptr = p.ptr;
 		parseEntry();
@@ -139,6 +144,11 @@ public int idOffset() {
 	}
 
 	@Override
+	public boolean first() {
+		return ptr == treeStart;
+	}
+
+	@Override
 	public boolean eof() {
 		return ptr == treeEnd;
 	}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/treewalk/AbstractTreeIterator.java b/org.spearce.jgit/src/org/spearce/jgit/treewalk/AbstractTreeIterator.java
index 8ec506c..c1b7ad8 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/treewalk/AbstractTreeIterator.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/treewalk/AbstractTreeIterator.java
@@ -340,6 +340,19 @@ public abstract AbstractTreeIterator createSubtreeIterator(Repository repo)
 			throws IncorrectObjectTypeException, IOException;
 
 	/**
+	 * Is this tree iterator positioned on its first entry?
+	 * <p>
+	 * An iterator is positioned on the first entry if <code>back(1)</code>
+	 * would be an invalid request as there is no entry before the current one.
+	 * <p>
+	 * An empty iterator (one with no entries) will be
+	 * <code>first() &amp;&amp; eof()</code>.
+	 * 
+	 * @return true if the iterator is positioned on the first entry.
+	 */
+	public abstract boolean first();
+
+	/**
 	 * Is this tree iterator at its EOF point (no more entries)?
 	 * <p>
 	 * An iterator is at EOF if there is no current entry.
diff --git a/org.spearce.jgit/src/org/spearce/jgit/treewalk/CanonicalTreeParser.java b/org.spearce.jgit/src/org/spearce/jgit/treewalk/CanonicalTreeParser.java
index 111d03b..dcc53cd 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/treewalk/CanonicalTreeParser.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/treewalk/CanonicalTreeParser.java
@@ -126,6 +126,11 @@ public int idOffset() {
 		return nextPtr - Constants.OBJECT_ID_LENGTH;
 	}
 
+	@Override
+	public boolean first() {
+		return currPtr == 0;
+	}
+
 	public boolean eof() {
 		return currPtr == raw.length;
 	}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/treewalk/EmptyTreeIterator.java b/org.spearce.jgit/src/org/spearce/jgit/treewalk/EmptyTreeIterator.java
index 232e3b1..eaca04e 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/treewalk/EmptyTreeIterator.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/treewalk/EmptyTreeIterator.java
@@ -79,6 +79,11 @@ public int idOffset() {
 	}
 
 	@Override
+	public boolean first() {
+		return true;
+	}
+
+	@Override
 	public boolean eof() {
 		return true;
 	}
diff --git a/org.spearce.jgit/src/org/spearce/jgit/treewalk/WorkingTreeIterator.java b/org.spearce.jgit/src/org/spearce/jgit/treewalk/WorkingTreeIterator.java
index 41fd47b..9c53224 100644
--- a/org.spearce.jgit/src/org/spearce/jgit/treewalk/WorkingTreeIterator.java
+++ b/org.spearce.jgit/src/org/spearce/jgit/treewalk/WorkingTreeIterator.java
@@ -231,6 +231,11 @@ public int idOffset() {
 	}
 
 	@Override
+	public boolean first() {
+		return ptr == 0;
+	}
+
+	@Override
 	public boolean eof() {
 		return ptr == entryCnt;
 	}
-- 
1.6.0.87.g2858d

--
To unsubscribe from this list: send the line "unsubscribe git" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html