From 2c9c848ae275705ce315b6061cd06640834c9d9d Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Mon, 13 Mar 2017 18:16:25 -0400
Subject: lazy-parse the version and startTime

---
 dslog/DseventsReader.java | 106 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 84 insertions(+), 22 deletions(-)

(limited to 'dslog/DseventsReader.java')

diff --git a/dslog/DseventsReader.java b/dslog/DseventsReader.java
index 1f7afa7..4ae0215 100644
--- a/dslog/DseventsReader.java
+++ b/dslog/DseventsReader.java
@@ -1,42 +1,78 @@
 package dslog;
 
+import java.io.BufferedInputStream;
 import java.io.Closeable;
 import java.io.IOException;
 import java.io.InputStream;
-import java.lang.UnsupportedOperationException;
 import java.time.Instant;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
 
-class DseventsReader implements Closeable {
-	private final InputStream reader;
+class DseventsReader implements Closeable, Iterator<DseventsReader.Event> {
+	public static class Event {
+		public Instant time;
+		public String message;
+	}
 
-	public final int version;
-	public final Instant startTime;
+	/*============================================================*\
+	|| Primitive IO                                               ||
+	\*============================================================*/
 
+	private final InputStream reader;
 	public DseventsReader(InputStream reader) throws IOException {
+		if (!reader.markSupported()) {
+			reader = new BufferedInputStream(reader);
+		}
 		this.reader = reader;
-		this.version = Read.i32(reader);
-		switch (this.version) {
-		case 0:
-			throw new UnsupportedOperationException("TODO: DSEVENTS v0 support");
-		case 1:
-		case 2:
-		case 3: // 2016-now
-			this.startTime = Read.LVTimestamp(reader);
-			break;
-		default:
-			throw new UnsupportedOperationException("DSEVENTS file version ("+this.version+") newer than log reader (3)");
+	}
+
+	private boolean atEOF() throws IOException {
+		reader.mark(2);
+		boolean eof = (reader.read() < 0);
+		reader.reset();
+		return eof;
+	}
+
+	/*============================================================*\
+	|| Parsing                                                    ||
+	\*============================================================*/
+
+	private int m_version;
+	private boolean m_haveVersion = false;
+	public int version() throws IOException {
+		if (!m_haveVersion) {
+			m_version = Read.i32(reader);
+			m_haveVersion = true;
 		}
+		return m_version;
 	}
 
-	public static class Event {
-		public Instant time;
-		public String message;
+	private Instant m_startTime;
+	public Instant startTime() throws IOException {
+		if (m_startTime == null) {
+			switch (version()) {
+			case 0:
+				throw new UnsupportedVersionException("DSEVENTS (TODO)", 0);
+			case 1:
+			case 2:
+			case 3: // 2016-now
+				m_startTime = Read.LVTimestamp(reader);
+				break;
+			default:
+				throw new UnsupportedVersionException("DSEVENTS", version(), 3);
+			}
+		}
+		return m_startTime;
 	}
 
 	public Event readEvent() throws IOException{
-		switch (version) {
+		startTime();
+		if (atEOF()) {
+			return null;
+		}
+		switch (version()) {
 		case 0:
-			throw new UnsupportedOperationException("TODO: DSEVENTS v0 support");
+			throw new UnsupportedVersionException("DSEVENTS (TODO)", 0);
 		case 1:
 		case 2:
 		case 3:
@@ -45,10 +81,36 @@ class DseventsReader implements Closeable {
 				message = Read.LVString(reader);
 			}};
 		default:
-			throw new UnsupportedOperationException("DSEVENTS file version newer than log reader");
+			throw new UnsupportedVersionException("DSEVENTS", version(), 3);
 		}
 	}
 
+	/*============================================================*\
+	|| Interfaces                                                 ||
+	\*============================================================*/
+
+	private IOException m_err;
+	private Event m_next;
+	public boolean hasNext() {
+		if (m_next == null) {
+			try {
+				m_next = readEvent();
+			} catch (IOException e) {
+				m_err = e;
+			}
+		}
+		return m_next != null;
+	}
+	public Event next() {
+		if (!hasNext()) {
+			throw new NoSuchElementException();
+		}
+		return m_next;
+	}
+	public IOException err() {
+		return m_err;
+	}
+
 	public void close() throws IOException {
 		reader.close();
 	}
-- 
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