Implement basic source maps. Closes #1252.

1 files changed, 118 insertions, 0 deletions

diff --git a/tools/sourcemapper.js b/tools/sourcemapper.js
new file mode 100755
index 00000000..1f28b371
--- /dev/null
+++ b/tools/sourcemapper.js
@@ -0,0 +1,118 @@
+#! /usr/bin/env node
+
+"use strict";
+
+function countLines(s) {
+  var count = 0;
+  for (var i = 0, l = s.length; i < l; i ++) {
+    var c = s[i];
+    if (c === '\n') count++;
+  }
+  return count;
+}
+
+/*
+ * Extracts the line (not block) comments from the generated function code and
+ * invokes commentHandler with (comment content, line number of comment). This
+ * function implements a simplistic lexer with the following assumptions:
+ *     1. "// EMSCRIPTEN_START_FUNCS" and "// EMSCRIPTEN_END_FUNCS" are unique
+ *     markers for separating library code from generated function code. Things
+ *     will break if they appear as part of a string in library code (but OK if
+ *     they occur in generated code).
+ *     2. Between these two markers, no regexes are used.
+ */
+function extractComments(source, commentHandler) {
+  var state = 'code';
+  var commentContent = '';
+  var functionStartIdx = source.indexOf('// EMSCRIPTEN_START_FUNCS');
+  var functionEndIdx = source.lastIndexOf('// EMSCRIPTEN_END_FUNCS');
+  var lineCount = countLines(source.slice(0, functionStartIdx));
+
+  for (var i = functionStartIdx; i < functionEndIdx; i++) {
+    var c = source[i];
+    var nextC = source[i+1];
+    if (c === '\n') lineCount++;
+    switch (state) {
+      case 'code':
+          if (c === '/') {
+            if (nextC === '/') { state = 'lineComment'; i++; }
+            else if (nextC === '*') { state = 'blockComment'; i++; }
+          }
+          else if (c === '"') state = 'doubleQuotedString';
+          else if (c === '\'') state = 'singleQuotedString';
+          break;
+      case 'lineComment':
+          if (c === '\n') {
+            state = 'code';
+            commentHandler(commentContent, lineCount);
+            commentContent = "";
+          } else {
+            commentContent += c;
+          }
+          break;
+      case 'blockComment':
+          if (c === '*' && nextC === '/') state = 'code';
+      case 'singleQuotedString':
+          if (c === '\\') i++;
+          else if (c === '\'') state = 'code';
+          break;
+      case 'doubleQuotedString':
+          if (c === '\\') i++;
+          else if (c === '"') state = 'code';
+          break;
+      }
+  }
+}
+
+function generateMap(fileName, sourceRoot, mapFileBaseName) {
+  var fs = require('fs');
+  var path = require('path');
+  var SourceMapGenerator = require('source-map').SourceMapGenerator;
+
+  var generator = new SourceMapGenerator({ file: fileName });
+  var generatedSource = fs.readFileSync(fileName, 'utf-8');
+  var seenFiles = Object.create(null);
+
+  extractComments(generatedSource, function(content, generatedLineNumber) {
+      console.log(content, generatedLineNumber)
+    var matches = /@line (\d+) "([^"]*)"/.exec(content);
+    if (matches === null) return;
+    var originalLineNumber = parseInt(matches[1], 10);
+    var originalFileName = matches[2];
+
+    if (!(originalFileName in seenFiles)) {
+      seenFiles[originalFileName] = true;
+      try {
+        generator.setSourceContent(originalFileName,
+                                   fs.readFileSync(sourceRoot + "/" + originalFileName));
+      } catch (e) {
+        console.warn("Unable to find original file for " + originalFileName);
+      }
+    }
+
+    generator.addMapping({
+      generated: { line: generatedLineNumber, column: 0 },
+      original: { line: originalLineNumber, column: 0 },
+      source: originalFileName
+    });
+  });
+
+  var mapFileName = mapFileBaseName + '.map';
+  fs.writeFileSync(mapFileName, generator.toString());
+
+  var lastLine = generatedSource.slice(generatedSource.lastIndexOf('\n'));
+  if (!/sourceMappingURL/.test(lastLine))
+    fs.appendFileSync(fileName, '//@ sourceMappingURL=' + path.basename(mapFileName));
+}
+
+if (require.main === module) {
+  if (process.argv.length < 3) {
+    console.log('Usage: ./sourcemapper.js <filename> <source root (default: .)> ' +
+                '<map file basename (default: filename)>');
+    process.exit(1);
+  } else {
+    var sourceRoot = process.argv.length > 3 ? process.argv[3] : ".";
+    var mapFileBaseName = process.argv.length > 4 ? process.argv[4] : process.argv[2];
+    generateMap(process.argv[2], sourceRoot, mapFileBaseName);
+  }
+}