Make fs.readFile support asar package

atom/common/lib/asar.coffee

@@ -25,6 +25,13 @@ asarStatsToFsStats = (stats) ->
     isSocket: -> false
   }
 
+# Create a ENOENT error.
+createNotFoundError = (asarPath, filePath) ->
+  error = new Error("ENOENT, #{filePath} not found in #{asarPath}")
+  error.code = "ENOENT"
+  error.errno = -2
+  error
+
 # Override fs APIs.
 statSync = fs.statSync
 fs.statSync = (p) ->
@@ -35,7 +42,7 @@ fs.statSync = (p) ->
   throw new Error("Invalid package #{asarPath}") unless archive
 
   stats = archive.stat filePath
-  throw new Error("#{filePath} not found in #{asarPath}") unless stats
+  throw createNotFoundError(asarPath, filePath) unless stats
 
   asarStatsToFsStats stats
 
@@ -48,7 +55,7 @@ fs.stat = (p, callback) ->
   return callback throw new Error("Invalid package #{asarPath}") unless archive
 
   stats = asar.createArchive(asarPath).stat filePath
-  return callback new Error("#{filePath} not found in #{asarPath}") unless stats
+  return callback createNotFoundError(asarPath, filePath) unless stats
 
   callback undefined, asarStatsToFsStats stats
 
@@ -62,3 +69,58 @@ fs.statSyncNoException = (p) ->
   stats = asar.createArchive(asarPath).stat filePath
   return false unless stats
   asarStatsToFsStats stats
+
+exists = fs.exists
+fs.exists = (p, callback) ->
+  [isAsar, asarPath, filePath] = splitPath p
+  return exists p, callback unless isAsar
+
+  archive = asar.createArchive asarPath
+  return callback throw new Error("Invalid package #{asarPath}") unless archive
+
+  callback archive.stat(filePath) isnt false
+
+existsSync = fs.existsSync
+fs.existsSync = (p) ->
+  [isAsar, asarPath, filePath] = splitPath p
+  return existsSync p unless isAsar
+
+  archive = asar.createArchive asarPath
+  return false unless archive
+
+  archive.stat(filePath) isnt false
+
+readFile = fs.readFile
+fs.readFile = (p, callback) ->
+  [isAsar, asarPath, filePath] = splitPath p
+  return readFile.apply this, arguments unless isAsar
+
+  archive = asar.createArchive asarPath
+  return callback throw new Error("Invalid package #{asarPath}") unless archive
+
+  info = archive.getFileInfo filePath
+  return callback createNotFoundError(asarPath, filePath) unless info
+
+  buffer = new Buffer(info.size)
+  fs.open archive.path, 'r', (error, fd) ->
+    return callback error if error
+    fs.read fd, buffer, 0, info.size, info.offset, (error) ->
+      fs.close fd, ->
+        callback error, buffer
+
+readFileSync = fs.readFileSync
+fs.readFileSync = (p) ->
+  [isAsar, asarPath, filePath] = splitPath p
+  return readFileSync.apply this, arguments unless isAsar
+
+  archive = asar.createArchive asarPath
+  throw new Error("Invalid package #{asarPath}") unless archive
+
+  info = archive.getFileInfo filePath
+  throw createNotFoundError(asarPath, filePath) unless info
+
+  buffer = new Buffer(info.size)
+  fd = fs.openSync archive.path, 'r'
+  fs.readSync fd, buffer, 0, info.size, info.offset
+  fs.closeSync fd
+  buffer