gecko-dev/toolkit/components/osfile/modules/osfile_async_worker.js

if (this.Components) {
  throw new Error("This worker can only be loaded from a worker thread");
}

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */


// Worker thread for osfile asynchronous front-end

(function(exports) {
  "use strict";

  importScripts("resource://gre/modules/osfile.jsm");

  let LOG = exports.OS.Shared.LOG.bind(exports.OS.Shared.LOG, "Agent");

 /**
  * Communications with the controller.
  *
  * Accepts messages:
  * {fun:function_name, args:array_of_arguments_or_null, id:id}
  *
  * Sends messages:
  * {ok: result, id:id} / {fail: serialized_form_of_OS.File.Error, id:id}
  */
  self.onmessage = function onmessage(msg) {
   let data = msg.data;
   LOG("Received message", data);
   let id = data.id;

   let start;
   let options;
   if (data.args) {
     options = data.args[data.args.length - 1];
   }
   // If |outExecutionDuration| option was supplied, start measuring the
   // duration of the operation.
   if (options && typeof options === "object" && "outExecutionDuration" in options) {
     start = Date.now();
   }

   let result;
   let exn;
   let durationMs;
   try {
     let method = data.fun;
     LOG("Calling method", method);
     result = Agent[method].apply(Agent, data.args);
     LOG("Method", method, "succeeded");
   } catch (ex) {
     exn = ex;
     LOG("Error while calling agent method", exn, exn.stack || "");
   }

   if (start) {
     // Record duration
     durationMs = Date.now() - start;
     LOG("Method took", durationMs, "ms");
   }

   // Now, post a reply, possibly as an uncaught error.
   // We post this message from outside the |try ... catch| block
   // to avoid capturing errors that take place during |postMessage| and
   // built-in serialization.
   if (!exn) {
     LOG("Sending positive reply", result, "id is", id);
     if (result instanceof Transfer) {
       // Take advantage of zero-copy transfers
       self.postMessage({ok: result.data, id: id, durationMs: durationMs},
         result.transfers);
     } else {
       self.postMessage({ok: result, id:id, durationMs: durationMs});
     }
   } else if (exn == StopIteration) {
     // StopIteration cannot be serialized automatically
     LOG("Sending back StopIteration");
     self.postMessage({StopIteration: true, id: id, durationMs: durationMs});
   } else if (exn instanceof exports.OS.File.Error) {
     LOG("Sending back OS.File error", exn, "id is", id);
     // Instances of OS.File.Error know how to serialize themselves
     // (deserialization ensures that we end up with OS-specific
     // instances of |OS.File.Error|)
     self.postMessage({fail: exports.OS.File.Error.toMsg(exn), id:id, durationMs: durationMs});
   } else {
     LOG("Sending back regular error", exn, exn.stack, "id is", id);
     // Other exceptions do not, and should be propagated through DOM's
     // built-in mechanism for uncaught errors, although this mechanism
     // may lose interesting information.
     throw exn;
   }
  };

 /**
  * A data structure used to track opened resources
  */
  let ResourceTracker = function ResourceTracker() {
   // A number used to generate ids
   this._idgen = 0;
   // A map from id to resource
   this._map = new Map();
  };
  ResourceTracker.prototype = {
   /**
    * Get a resource from its unique identifier.
    */
   get: function(id) {
     let result = this._map.get(id);
     if (result == null) {
       return result;
     }
     return result.resource;
   },
   /**
    * Remove a resource from its unique identifier.
    */
   remove: function(id) {
     if (!this._map.has(id)) {
       throw new Error("Cannot find resource id " + id);
     }
     this._map.delete(id);
   },
   /**
    * Add a resource, return a new unique identifier
    *
    * @param {*} resource A resource.
    * @param {*=} info Optional information. For debugging purposes.
    *
    * @return {*} A unique identifier. For the moment, this is a number,
    * but this might not remain the case forever.
    */
   add: function(resource, info) {
     let id = this._idgen++;
     this._map.set(id, {resource:resource, info:info});
     return id;
   },
   /**
    * Return a list of all open resources i.e. the ones still present in
    * ResourceTracker's _map.
    */
   listOpenedResources: function listOpenedResources() {
     return [resource.info.path for ([id, resource] of this._map)];
   }
  };

 /**
  * A map of unique identifiers to opened files.
  */
  let OpenedFiles = new ResourceTracker();

 /**
  * Execute a function in the context of a given file.
  *
  * @param {*} id A unique identifier, as used by |OpenFiles|.
  * @param {Function} f A function to call.
  * @param {boolean} ignoreAbsent If |true|, the error is ignored. Otherwise, the error causes an exception.
  * @return The return value of |f()|
  *
  * This function attempts to get the file matching |id|. If
  * the file exists, it executes |f| within the |this| set
  * to the corresponding file. Otherwise, it throws an error.
  */
  let withFile = function withFile(id, f, ignoreAbsent) {
   let file = OpenedFiles.get(id);
   if (file == null) {
     if (!ignoreAbsent) {
       throw OS.File.Error.closed("accessing file");
     }
     return undefined;
   }
   return f.call(file);
  };

  let OpenedDirectoryIterators = new ResourceTracker();
  let withDir = function withDir(fd, f, ignoreAbsent) {
   let file = OpenedDirectoryIterators.get(fd);
   if (file == null) {
     if (!ignoreAbsent) {
       throw OS.File.Error.closed("accessing directory");
     }
     return undefined;
   }
   if (!(file instanceof File.DirectoryIterator)) {
     throw new Error("file is not a directory iterator " + file.__proto__.toSource());
   }
   return f.call(file);
  };

  let Type = exports.OS.Shared.Type;

  let File = exports.OS.File;

 /**
  * A constructor used to transfer data to the caller
  * without copy.
  *
  * @param {*} data The data to return to the caller.
  * @param {Array} transfers An array of Transferable
  * values that should be moved instead of being copied.
  *
  * @constructor
  */
  let Transfer = function Transfer(data, transfers) {
   this.data = data;
   this.transfers = transfers;
  };

 /**
  * The agent.
  *
  * It is in charge of performing method-specific deserialization
  * of messages, calling the function/method of OS.File and serializing
  * back the results.
  */
  let Agent = {
   // Update worker's OS.Shared.DEBUG flag message from controller.
   SET_DEBUG: function SET_DEBUG (aDEBUG) {
     exports.OS.Shared.DEBUG = aDEBUG;
   },
   // Return worker's current OS.Shared.DEBUG value to controller.
   // Note: This is used for testing purposes.
   GET_DEBUG: function GET_DEBUG () {
     return exports.OS.Shared.DEBUG;
   },
   // Report file descriptors leaks.
   System_shutdown: function System_shutdown () {
     // Return information about both opened files and opened
     // directory iterators.
     return {
       openedFiles: OpenedFiles.listOpenedResources(),
       openedDirectoryIterators:
         OpenedDirectoryIterators.listOpenedResources()
     };
   },
   // Functions of OS.File
   stat: function stat(path) {
     return exports.OS.File.Info.toMsg(
       exports.OS.File.stat(Type.path.fromMsg(path)));
   },
   getCurrentDirectory: function getCurrentDirectory() {
     return exports.OS.Shared.Type.path.toMsg(File.getCurrentDirectory());
   },
   setCurrentDirectory: function setCurrentDirectory(path) {
     File.setCurrentDirectory(exports.OS.Shared.Type.path.fromMsg(path));
   },
   copy: function copy(sourcePath, destPath, options) {
     return File.copy(Type.path.fromMsg(sourcePath),
       Type.path.fromMsg(destPath), options);
   },
   move: function move(sourcePath, destPath, options) {
     return File.move(Type.path.fromMsg(sourcePath),
       Type.path.fromMsg(destPath), options);
   },
   makeDir: function makeDir(path, options) {
     return File.makeDir(Type.path.fromMsg(path), options);
   },
   removeEmptyDir: function removeEmptyDir(path, options) {
     return File.removeEmptyDir(Type.path.fromMsg(path), options);
   },
   remove: function remove(path) {
     return File.remove(Type.path.fromMsg(path));
   },
   open: function open(path, mode, options) {
     let filePath = Type.path.fromMsg(path);
     let file = File.open(filePath, mode, options);
     return OpenedFiles.add(file, {
       // Adding path information to keep track of opened files
       // to report leaks when debugging.
       path: filePath
     });
   },
   read: function read(path, bytes, options) {
     let data = File.read(Type.path.fromMsg(path), bytes);
     return new Transfer({buffer: data.buffer, byteOffset: data.byteOffset, byteLength: data.byteLength}, [data.buffer]);
   },
   exists: function exists(path) {
     return File.exists(Type.path.fromMsg(path));
   },
   writeAtomic: function writeAtomic(path, buffer, options) {
     if (options.tmpPath) {
       options.tmpPath = Type.path.fromMsg(options.tmpPath);
     }
     return File.writeAtomic(Type.path.fromMsg(path),
                             Type.voidptr_t.fromMsg(buffer),
                             options
                            );
   },
   removeDir: function(path, options) {
     return File.removeDir(Type.path.fromMsg(path), options);
   },
   new_DirectoryIterator: function new_DirectoryIterator(path, options) {
     let directoryPath = Type.path.fromMsg(path);
     let iterator = new File.DirectoryIterator(directoryPath, options);
     return OpenedDirectoryIterators.add(iterator, {
       // Adding path information to keep track of opened directory
       // iterators to report leaks when debugging.
       path: directoryPath
     });
   },
   // Methods of OS.File
   File_prototype_close: function close(fd) {
     return withFile(fd,
       function do_close() {
         try {
           return this.close();
         } finally {
           OpenedFiles.remove(fd);
         }
     });
   },
   File_prototype_stat: function stat(fd) {
     return withFile(fd,
       function do_stat() {
         return exports.OS.File.Info.toMsg(this.stat());
       });
   },
   File_prototype_read: function read(fd, nbytes, options) {
     return withFile(fd,
       function do_read() {
         let data = this.read(nbytes, options);
         return new Transfer({buffer: data.buffer, byteOffset: data.byteOffset, byteLength: data.byteLength}, [data.buffer]);
       }
     );
   },
   File_prototype_readTo: function readTo(fd, buffer, options) {
     return withFile(fd,
       function do_readTo() {
         return this.readTo(exports.OS.Shared.Type.voidptr_t.fromMsg(buffer),
         options);
       });
   },
   File_prototype_write: function write(fd, buffer, options) {
     return withFile(fd,
       function do_write() {
         return this.write(exports.OS.Shared.Type.voidptr_t.fromMsg(buffer),
         options);
       });
   },
   File_prototype_setPosition: function setPosition(fd, pos, whence) {
     return withFile(fd,
       function do_setPosition() {
         return this.setPosition(pos, whence);
       });
   },
   File_prototype_getPosition: function getPosition(fd) {
     return withFile(fd,
       function do_getPosition() {
         return this.getPosition();
       });
   },
   // Methods of OS.File.DirectoryIterator
   DirectoryIterator_prototype_next: function next(dir) {
     return withDir(dir,
       function do_next() {
         try {
           return File.DirectoryIterator.Entry.toMsg(this.next());
         } catch (x) {
           if (x == StopIteration) {
             OpenedDirectoryIterators.remove(dir);
           }
           throw x;
         }
       }, false);
   },
   DirectoryIterator_prototype_nextBatch: function nextBatch(dir, size) {
     return withDir(dir,
       function do_nextBatch() {
         let result;
         try {
           result = this.nextBatch(size);
         } catch (x) {
           OpenedDirectoryIterators.remove(dir);
           throw x;
         }
         return result.map(File.DirectoryIterator.Entry.toMsg);
       }, false);
   },
   DirectoryIterator_prototype_close: function close(dir) {
     return withDir(dir,
       function do_close() {
         this.close();
         OpenedDirectoryIterators.remove(dir);
       }, true);// ignore error to support double-closing |DirectoryIterator|
   },
   DirectoryIterator_prototype_exists: function exists(dir) {
     return withDir(dir,
       function do_exists() {
         return this.exists();
       });
   }
  };
})(this);