JAL-1807 Bob's first commit -- Applet loaded; needs image

[jalview.git] / src / javajs / util / LimitedLineReader.java

diff --git a/src/javajs/util/LimitedLineReader.java b/src/javajs/util/LimitedLineReader.java
new file mode 100644 (file)
index 0000000..e1d973f
--- /dev/null
+++ b/src/javajs/util/LimitedLineReader.java
@@ -0,0 +1,48 @@
+package javajs.util;
+
+import java.io.BufferedReader;
+
+/**
+ *  A simple class to read a designated number of bytes from a 
+ *  file and then return them line by line, skipping lines that
+ *  start with #, and including the \n or \r characters at line ends.
+ *  
+ *  Generally useful for determining what sort of data a file contains.
+ *   
+ */
+public class LimitedLineReader {
+  private char[] buf;
+  private int cchBuf;
+  private int ichCurrent;
+
+  public LimitedLineReader(BufferedReader bufferedReader, int readLimit)
+    throws Exception {  
+    bufferedReader.mark(readLimit + 1);
+    buf = new char[readLimit];
+    cchBuf = Math.max(bufferedReader.read(buf, 0, readLimit), 0);
+    ichCurrent = 0;
+    bufferedReader.reset();
+  }
+
+  public String getHeader(int n) {
+    return (n == 0 ? new String(buf) : new String(buf, 0, Math.min(cchBuf, n)));
+  }
+  
+  public String readLineWithNewline() {
+    while (ichCurrent < cchBuf) {
+      int ichBeginningOfLine = ichCurrent;
+      char ch = 0;
+      while (ichCurrent < cchBuf &&
+             (ch = buf[ichCurrent++]) != '\r' && ch != '\n') {
+      }
+      if (ch == '\r' && ichCurrent < cchBuf && buf[ichCurrent] == '\n')
+        ++ichCurrent;
+      int cchLine = ichCurrent - ichBeginningOfLine;
+      if (buf[ichBeginningOfLine] == '#')
+        continue; // flush comment lines;
+      return new String(buf, ichBeginningOfLine, cchLine);
+    }
+    return "";
+  }
+}
+