Merge branch 'releases/Release_2_10_0_Branch'

[jalview.git] / utils / BufferedLineReader.java

diff --git a/utils/BufferedLineReader.java b/utils/BufferedLineReader.java
new file mode 100644 (file)
index 0000000..b813fb2
--- /dev/null
+++ b/utils/BufferedLineReader.java
@@ -0,0 +1,182 @@
+import java.io.BufferedReader;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.StringReader;
+
+/**
+ * A file reader that concatenates lines
+ * 
+ * @author gmcarstairs
+ *
+ */
+public class BufferedLineReader
+{
+  interface LineCleaner
+  {
+    String cleanLine(String l);
+  }
+
+  /*
+   * a reader for the file being read
+   */
+  private BufferedReader br;
+  
+  /*
+   * optional handler to post-process each line as it is read
+   */
+  private LineCleaner cleaner;
+
+  /*
+   * current buffer of <bufferSize> post-processed input lines
+   */
+  private String[] buffer;
+
+  private boolean atEof;
+
+  /**
+   * Constructor
+   * 
+   * @param reader
+   * @param bufferSize
+   *          the number of lines to concatenate at a time while reading
+   * @param tidier
+   *          an optional callback handler to post-process each line after
+   *          reading
+   * @throws FileNotFoundException
+   */
+  public BufferedLineReader(BufferedReader reader, int bufferSize,
+          LineCleaner tidier)
+          throws IOException
+  {
+    br = reader;
+    buffer = new String[bufferSize];
+    cleaner = tidier;
+
+    /*
+     * load up the buffer with N-1 lines, ready for the first read
+     */
+    for (int i = 1; i < bufferSize; i++)
+    {
+      readLine();
+    }
+
+  }
+
+  /**
+   * Reads the next line from file, invokes the post-processor if one was
+   * provided, and returns the 'cleaned' line, or null at end of file.
+   * 
+   * @return
+   */
+  private String readLine() // throws IOException
+  {
+    if (atEof)
+    {
+      return null;
+    }
+
+    String line = null;
+    try
+    {
+      line = br.readLine();
+    } catch (IOException e)
+    {
+      e.printStackTrace();
+    }
+    if (line == null)
+    {
+      atEof = true;
+      return null;
+    }
+    if (cleaner != null)
+    {
+      line = cleaner.cleanLine(line);
+    }
+
+    /*
+     * shuffle down the lines buffer and add the new line
+     * in the last position
+     */
+    for (int i = 1; i < buffer.length; i++)
+    {
+      buffer[i - 1] = buffer[i];
+    }
+    buffer[buffer.length - 1] = line;
+    return line;
+  }
+
+  /**
+   * Returns a number of concatenated lines from the file, or null at end of
+   * file.
+   * 
+   * @return
+   */
+  public String read()
+  {
+    if (readLine() == null)
+    {
+      return null;
+    }
+    StringBuilder result = new StringBuilder(100 * buffer.length);
+    for (String line : buffer)
+    {
+      if (line != null)
+      {
+        result.append(line);
+      }
+    }
+    return result.toString();
+  }
+
+  /**
+   * A main 'test' method!
+   * 
+   * @throws IOException
+   */
+  public static void main(String[] args) throws IOException
+  {
+    String data = "Now is the winter\n" + "Of our discontent\n"
+            + "Made glorious summer\n" + "By this sun of York\n";
+    BufferedReader br = new BufferedReader(new StringReader(data));
+    BufferedLineReader reader = new BufferedLineReader(br, 3,
+            new LineCleaner()
+            {
+              @Override
+              public String cleanLine(String l)
+              {
+                return l.toUpperCase();
+              }
+            });
+    String line = reader.read();
+    String expect = "NOW IS THE WINTEROF OUR DISCONTENTMADE GLORIOUS SUMMER";
+    if (!line.equals(expect))
+    {
+      System.err.println("Fail: expected '" + expect + "', found '" + line
+              + ";");
+    }
+    else
+    {
+      System.out.println("Line one ok!");
+    }
+    line = reader.read();
+    expect = "OF OUR DISCONTENTMADE GLORIOUS SUMMERBY THIS SUN OF YORK";
+    if (!line.equals(expect))
+    {
+      System.err.println("Fail: expected '" + expect + "', found '" + line
+              + "'");
+    }
+    else
+    {
+      System.out.println("Line two ok!!");
+    }
+    line = reader.read();
+    if (line != null)
+    {
+      System.err.println("Fail: expected null at eof, got '" + line + "'");
+    }
+    else
+    {
+      System.out.println("EOF ok!!!");
+    }
+  }
+}