From ea88542aec97f570a01303a7e73336701e266259 Mon Sep 17 00:00:00 2001
From: "Benjamin J. Culkin" <bjculkin@mix.wvu.edu>
Date: Sun, 10 Sep 2017 21:07:22 -0300
Subject: More BlockReader work

This includes some minor fixes to the BlockReaderCLI, and two new
BlockReader types
* MappedBlockReader - Apply a function to each block, transforming it.
* FlatMappedBlockReader - Apply a function to each block, expanding it
into one or more blocks.
---
 .../ioutils/blocks/FlatMappedBlockReader.java      | 86 ++++++++++++++++++++++
 .../utils/ioutils/blocks/MappedBlockReader.java    |  7 +-
 2 files changed, 92 insertions(+), 1 deletion(-)
 create mode 100644 BJC-Utils2/src/main/java/bjc/utils/ioutils/blocks/FlatMappedBlockReader.java

(limited to 'BJC-Utils2/src/main/java/bjc/utils/ioutils/blocks')

diff --git a/BJC-Utils2/src/main/java/bjc/utils/ioutils/blocks/FlatMappedBlockReader.java b/BJC-Utils2/src/main/java/bjc/utils/ioutils/blocks/FlatMappedBlockReader.java
new file mode 100644
index 0000000..f4d8439
--- /dev/null
+++ b/BJC-Utils2/src/main/java/bjc/utils/ioutils/blocks/FlatMappedBlockReader.java
@@ -0,0 +1,86 @@
+package bjc.utils.ioutils.blocks;
+
+import java.io.IOException;
+
+import java.util.Iterator;
+import java.util.List;
+import java.util.function.Function;
+import java.util.function.UnaryOperator;
+
+/**
+ * A block reader that supports applying a flatmap operation to blocks.
+ *
+ * The use-case in mind for this was tokenizing blocks.
+ *
+ * @author Benjamin Culkin
+ */
+public class FlatMappedBlockReader implements BlockReader {
+	/*
+	 * The source reader.
+	 */
+	private BlockReader reader;
+
+	/*
+	 * The current block, and any blocks pending from the last source block.
+	 */
+	private Iterator<Block> pending;
+	private Block           current;
+
+	/*
+	 * The operator to open blocks with.
+	 */
+	private Function<Block, List<Block>> transform;
+
+	/*
+	 * The current block number.
+	 */
+	private int blockNo;
+
+	public FlatMappedBlockReader(BlockReader source, Function<Block, List<Block>> trans) {
+		reader    = source;
+		transform = trans;
+
+		blockNo = 0;
+	}
+
+	@Override
+	public boolean hasNextBlock() {
+		return pending.hasNext() || reader.hasNextBlock();
+	}
+
+	@Override
+	public Block getBlock() {
+		return current;
+	}
+
+	@Override	
+	public boolean nextBlock() {
+		/*
+		 * Attempt to get a new pending list if the one we have isn't
+		 * valid.
+		 */
+		while(pending == null || !pending.hasNext()) {
+			if(!reader.hasNext()) return false;
+
+			pending = transform.apply(reader.next()).iterator();
+		}
+
+		/*
+		 * Advance the iterator.
+		 */
+		current  = pending.next();
+		blockNo += 1;
+
+		return true;
+	}
+
+	@Override
+	public int getBlockCount() {
+		return blockNo;
+	}
+
+	@Override
+	public void close() throws IOException {
+		reader.close();
+	}
+}
diff --git a/BJC-Utils2/src/main/java/bjc/utils/ioutils/blocks/MappedBlockReader.java b/BJC-Utils2/src/main/java/bjc/utils/ioutils/blocks/MappedBlockReader.java
index 1996421..a9cfa57 100644
--- a/BJC-Utils2/src/main/java/bjc/utils/ioutils/blocks/MappedBlockReader.java
+++ b/BJC-Utils2/src/main/java/bjc/utils/ioutils/blocks/MappedBlockReader.java
@@ -29,7 +29,7 @@ public class MappedBlockReader implements BlockReader {
 	@Override	
 	public boolean nextBlock() {
 		if(hasNextBlock()) {
-			current = trans.apply(reader.next());
+			current = transform.apply(reader.next());
 
 			return true;
 		}
@@ -41,4 +41,9 @@ public class MappedBlockReader implements BlockReader {
 	public int getBlockCount() {
 		return reader.getBlockCount();
 	}
+
+	@Override
+	public void close() throws IOException {
+		reader.close();
+	}
 }
-- 
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