Profiler tick processor: exploit d8's readline to avoid reading

tools/logreader.js

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 58 matching lines @@
    * @type {Object}
    */
   this.backRefsCommands_ = {};
   this.initBackRefsCommands_();
 
   /**
    * Back references for decompression.
    * @type {Array.<string>}
    */
   this.backRefs_ = [];
+
+  /**
+   * Current line.
+   * @type {number}
+   */
+  this.lineNum_ = 0;
+
+  /**
+   * CSV lines parser.
+   * @type {devtools.profiler.CsvParser}
+   */
+  this.csvParser_ = new devtools.profiler.CsvParser();
 };
 
 
 /**
  * Creates a parser for an address entry.
  *
  * @param {string} addressTag Address tag to perform offset decoding.
  * @return {function(string):number} Address parser.
  */
 devtools.profiler.LogReader.prototype.createAddressParser = function(
@@ skipping 40 matching lines @@
  * Processes a portion of V8 profiler event log.
  *
  * @param {string} chunk A portion of log.
  */
 devtools.profiler.LogReader.prototype.processLogChunk = function(chunk) {
   this.processLog_(chunk.split('\n'));
 };
 
 
 /**
+ * Processes a line of V8 profiler event log.
+ *
+ * @param {string} line A line of log.
+ */
+devtools.profiler.LogReader.prototype.processLogLine = function(line) {
+  this.processLog_([line]);
+};
+
+
+/**
  * Processes stack record.
  *
  * @param {number} pc Program counter.
  * @param {number} func JS Function.
  * @param {Array.<string>} stack String representation of a stack.
  * @return {Array.<number>} Processed stack.
  */
 devtools.profiler.LogReader.prototype.processStack = function(pc, func, stack) {
   var fullStack = func ? [pc, func] : [pc];
   var prevFrame = pc;
@@ skipping 124 matching lines @@
 };
 
 
 /**
  * Processes log lines.
  *
  * @param {Array.<string>} lines Log lines.
  * @private
  */
 devtools.profiler.LogReader.prototype.processLog_ = function(lines) {
-  var csvParser = new devtools.profiler.CsvParser();
-  try {
-    for (var i = 0, n = lines.length; i < n; ++i) {
-      var line = lines[i];
-      if (!line) {
-        continue;
-      }
+  for (var i = 0, n = lines.length; i < n; ++i, ++this.lineNum_) {
+    var line = lines[i];
+    if (!line) {
+      continue;
+    }
+    try {
       if (line.charAt(0) == '#' ||
           line.substr(0, line.indexOf(',')) in this.backRefsCommands_) {
         line = this.expandBackRef_(line);
       }
-      var fields = csvParser.parseLine(line);
+      var fields = this.csvParser_.parseLine(line);
       this.dispatchLogRow_(fields);
-    }
-  } catch (e) {
-    // An error on the last line is acceptable since log file can be truncated.
-    if (i < n - 1) {
-      this.printError('line ' + (i + 1) + ': ' + (e.message || e));
-      throw e;
+    } catch (e) {
+      this.printError('line ' + (this.lineNum_ + 1) + ': ' + (e.message || e));
     }
   }
 };
 
 
 /**
  * Processes repeat log record. Expands it according to calls count and
  * invokes processing.
  *
  * @param {number} count Count.
  * @param {Array.<string>} cmd Parsed command.
  * @private
  */
 devtools.profiler.LogReader.prototype.processRepeat_ = function(count, cmd) {
   // Replace the repeat-prefixed command from backrefs list with a non-prefixed.
   this.backRefs_[0] = cmd.join(',');
   for (var i = 0; i < count; ++i) {
     this.dispatchLogRow_(cmd);
   }
 };