[wpiutil] DataLog: Add last value and change detection

wpiutil/src/main/java/edu/wpi/first/util/datalog/BooleanArrayLogEntry.java

@@ -4,6 +4,8 @@
 
 package edu.wpi.first.util.datalog;
 
+import java.util.Arrays;
+
 /** Log array of boolean values. */
 public class BooleanArrayLogEntry extends DataLogEntry {
   /** The data type for boolean array values. */
@@ -71,4 +73,79 @@ public void append(boolean[] value, long timestamp) {
   public void append(boolean[] value) {
     m_log.appendBooleanArray(m_entry, value, 0);
   }
+
+  /**
+   * Updates the last value and appends a record to the log if it has changed.
+   *
+   * <p>Note: the last value is local to this class instance; using update() with two instances
+   * pointing to the same underlying log entry name will likely result in unexpected results.
+   *
+   * @param value Value to record
+   * @param timestamp Time stamp (0 to indicate now)
+   */
+  public synchronized void update(boolean[] value, long timestamp) {
+    if (!equalsLast(value)) {
+      copyToLast(value);
+      append(value, timestamp);
+    }
+  }
+
+  /**
+   * Updates the last value and appends a record to the log if it has changed.
+   *
+   * <p>Note: the last value is local to this class instance; using update() with two instances
+   * pointing to the same underlying log entry name will likely result in unexpected results.
+   *
+   * @param value Value to record
+   */
+  public void update(boolean[] value) {
+    update(value, 0);
+  }
+
+  /**
+   * Gets whether there is a last value.
+   *
+   * <p>Note: the last value is local to this class instance and updated only with update(), not
+   * append().
+   *
+   * @return True if last value exists, false otherwise.
+   */
+  public synchronized boolean hasLastValue() {
+    return m_lastValue != null;
+  }
+
+  /**
+   * Gets the last value.
+   *
+   * <p>Note: the last value is local to this class instance and updated only with update(), not
+   * append().
+   *
+   * @return Last value, or null if none.
+   */
+  @SuppressWarnings("PMD.ReturnEmptyCollectionRatherThanNull")
+  public synchronized boolean[] getLastValue() {
+    if (m_lastValue == null) {
+      return null;
+    }
+    return Arrays.copyOf(m_lastValue, m_lastValueLen);
+  }
+
+  private boolean equalsLast(boolean[] value) {
+    if (m_lastValue == null || m_lastValueLen != value.length) {
+      return false;
+    }
+    return Arrays.equals(m_lastValue, 0, value.length, value, 0, value.length);
+  }
+
+  private void copyToLast(boolean[] value) {
+    if (m_lastValue == null || m_lastValue.length < value.length) {
+      m_lastValue = Arrays.copyOf(value, value.length);
+    } else {
+      System.arraycopy(value, 0, m_lastValue, 0, value.length);
+    }
+    m_lastValueLen = value.length;
+  }
+
+  private boolean[] m_lastValue;
+  private int m_lastValueLen;
 }

wpiutil/src/main/java/edu/wpi/first/util/datalog/BooleanLogEntry.java

@@ -71,4 +71,60 @@ public void append(boolean value, long timestamp) {
   public void append(boolean value) {
     m_log.appendBoolean(m_entry, value, 0);
   }
+
+  /**
+   * Updates the last value and appends a record to the log if it has changed.
+   *
+   * <p>Note: the last value is local to this class instance; using update() with two instances
+   * pointing to the same underlying log entry name will likely result in unexpected results.
+   *
+   * @param value Value to record
+   * @param timestamp Time stamp (0 to indicate now)
+   */
+  public synchronized void update(boolean value, long timestamp) {
+    if (!m_hasLastValue || m_lastValue != value) {
+      m_lastValue = value;
+      m_hasLastValue = true;
+      append(value, timestamp);
+    }
+  }
+
+  /**
+   * Updates the last value and appends a record to the log if it has changed.
+   *
+   * <p>Note: the last value is local to this class instance; using update() with two instances
+   * pointing to the same underlying log entry name will likely result in unexpected results.
+   *
+   * @param value Value to record
+   */
+  public void update(boolean value) {
+    update(value, 0);
+  }
+
+  /**
+   * Gets whether there is a last value.
+   *
+   * <p>Note: the last value is local to this class instance and updated only with update(), not
+   * append().
+   *
+   * @return True if last value exists, false otherwise.
+   */
+  public synchronized boolean hasLastValue() {
+    return m_hasLastValue;
+  }
+
+  /**
+   * Gets the last value.
+   *
+   * <p>Note: the last value is local to this class instance and updated only with update(), not
+   * append().
+   *
+   * @return Last value, or false if none.
+   */
+  public synchronized boolean getLastValue() {
+    return m_lastValue;
+  }
+
+  private boolean m_hasLastValue;
+  private boolean m_lastValue;
 }

wpiutil/src/main/java/edu/wpi/first/util/datalog/DataLog.java

@@ -269,6 +269,12 @@ public void setMetadata(int entry, String metadata) {
     setMetadata(entry, metadata, 0);
   }
 
+  @Override
+  public void close() {
+    DataLogJNI.close(m_impl);
+    m_impl = 0;
+  }
+
   /**
    * Appends a raw record to the log.
    *
@@ -318,12 +324,6 @@ public void appendRaw(int entry, ByteBuffer data, int start, int len, long times
     DataLogJNI.appendRaw(m_impl, entry, data, start, len, timestamp);
   }
 
-  @Override
-  public void close() {
-    DataLogJNI.close(m_impl);
-    m_impl = 0;
-  }
-
   /**
    * Appends a boolean record to the log.
    *

wpiutil/src/main/java/edu/wpi/first/util/datalog/DataLogJNI.java

@@ -46,13 +46,31 @@ public class DataLogJNI extends WPIUtilJNI {
    */
   static native long fgCreate(String filename, String extraHeader) throws IOException;
 
+  /**
+   * Create a new Data Log foreground writer to a memory buffer.
+   *
+   * @param extraHeader extra header data
+   * @return data log writer implementation handle
+   */
+  static native long fgCreateMemory(String extraHeader);
+
   /**
    * Explicitly flushes the log data to disk.
    *
    * @param impl data log background writer implementation handle
    */
   static native void flush(long impl);
 
+  /**
+   * Flushes the log data to a memory buffer (only valid with fgCreateMemory data logs).
+   *
+   * @param impl data log background writer implementation handle
+   * @param buf output data buffer
+   * @param pos position in write buffer to start copying from
+   * @return Number of bytes written to buffer; 0 if no more to copy
+   */
+  static native int copyWriteBuffer(long impl, byte[] buf, int pos);
+
   /**
    * Pauses appending of data records to the log. While paused, no data records are saved (e.g.
    * AppendX is a no-op). Has no effect on entry starts / finishes / metadata changes.

wpiutil/src/main/java/edu/wpi/first/util/datalog/DataLogWriter.java

@@ -5,6 +5,7 @@
 package edu.wpi.first.util.datalog;
 
 import java.io.IOException;
+import java.io.OutputStream;
 
 /** A data log writer that flushes the data log to a file when flush() is called. */
 public class DataLogWriter extends DataLog {
@@ -17,6 +18,8 @@ public class DataLogWriter extends DataLog {
    */
   public DataLogWriter(String filename, String extraHeader) throws IOException {
     super(DataLogJNI.fgCreate(filename, extraHeader));
+    m_os = null;
+    m_buf = null;
   }
 
   /**
@@ -28,4 +31,54 @@ public DataLogWriter(String filename, String extraHeader) throws IOException {
   public DataLogWriter(String filename) throws IOException {
     this(filename, "");
   }
+
+  /**
+   * Construct a new Data Log with an output stream. Prefer the filename version if possible; this
+   * is much slower!
+   *
+   * @param os output stream
+   * @param extraHeader extra header data
+   */
+  public DataLogWriter(OutputStream os, String extraHeader) {
+    super(DataLogJNI.fgCreateMemory(extraHeader));
+    m_os = os;
+    m_buf = new byte[kBufferSize];
+  }
+
+  /**
+   * Construct a new Data Log with an output stream.
+   *
+   * @param os output stream
+   */
+  public DataLogWriter(OutputStream os) {
+    this(os, "");
+  }
+
+  /** Explicitly flushes the log data to disk. */
+  @Override
+  public void flush() {
+    DataLogJNI.flush(m_impl);
+    if (m_os == null) {
+      return;
+    }
+    try {
+      int pos = 0;
+      for (; ; ) {
+        int qty = DataLogJNI.copyWriteBuffer(m_impl, m_buf, pos);
+        if (qty == 0) {
+          break;
+        }
+        pos += qty;
+        m_os.write(m_buf, 0, qty);
+      }
+      m_os.flush();
+    } catch (IOException e) {
+      // ignore
+    }
+  }
+
+  private static final int kBufferSize = 16 * 1024;
+
+  private final OutputStream m_os;
+  private final byte[] m_buf;
 }

wpiutil/src/main/java/edu/wpi/first/util/datalog/DoubleArrayLogEntry.java

@@ -4,6 +4,8 @@
 
 package edu.wpi.first.util.datalog;
 
+import java.util.Arrays;
+
 /** Log array of double values. */
 public class DoubleArrayLogEntry extends DataLogEntry {
   /** The data type for double array values. */
@@ -71,4 +73,79 @@ public void append(double[] value, long timestamp) {
   public void append(double[] value) {
     m_log.appendDoubleArray(m_entry, value, 0);
   }
+
+  /**
+   * Updates the last value and appends a record to the log if it has changed.
+   *
+   * <p>Note: the last value is local to this class instance; using update() with two instances
+   * pointing to the same underlying log entry name will likely result in unexpected results.
+   *
+   * @param value Value to record
+   * @param timestamp Time stamp (0 to indicate now)
+   */
+  public synchronized void update(double[] value, long timestamp) {
+    if (!equalsLast(value)) {
+      copyToLast(value);
+      append(value, timestamp);
+    }
+  }
+
+  /**
+   * Updates the last value and appends a record to the log if it has changed.
+   *
+   * <p>Note: the last value is local to this class instance; using update() with two instances
+   * pointing to the same underlying log entry name will likely result in unexpected results.
+   *
+   * @param value Value to record
+   */
+  public void update(double[] value) {
+    update(value, 0);
+  }
+
+  /**
+   * Gets whether there is a last value.
+   *
+   * <p>Note: the last value is local to this class instance and updated only with update(), not
+   * append().
+   *
+   * @return True if last value exists, false otherwise.
+   */
+  public synchronized boolean hasLastValue() {
+    return m_lastValue != null;
+  }
+
+  /**
+   * Gets the last value.
+   *
+   * <p>Note: the last value is local to this class instance and updated only with update(), not
+   * append().
+   *
+   * @return Last value, or false if none.
+   */
+  @SuppressWarnings("PMD.ReturnEmptyCollectionRatherThanNull")
+  public synchronized double[] getLastValue() {
+    if (m_lastValue == null) {
+      return null;
+    }
+    return Arrays.copyOf(m_lastValue, m_lastValueLen);
+  }
+
+  private boolean equalsLast(double[] value) {
+    if (m_lastValue == null || m_lastValueLen != value.length) {
+      return false;
+    }
+    return Arrays.equals(m_lastValue, 0, value.length, value, 0, value.length);
+  }
+
+  private void copyToLast(double[] value) {
+    if (m_lastValue == null || m_lastValue.length < value.length) {
+      m_lastValue = Arrays.copyOf(value, value.length);
+    } else {
+      System.arraycopy(value, 0, m_lastValue, 0, value.length);
+    }
+    m_lastValueLen = value.length;
+  }
+
+  private double[] m_lastValue;
+  private int m_lastValueLen;
 }