[NaCl SDK] nacl_io: Add flow control the JavaScript pipes.

native_client_sdk/src/libraries/nacl_io/devfs/jspipe_event_emitter.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "nacl_io/devfs/jspipe_event_emitter.h"
+
+#include <assert.h>
+#include <errno.h>
+#include <string.h>
+
+#include <algorithm>
+
+#define TRACE(format, ...) \
+    LOG_TRACE("jspipe[%s]: " format, name_.c_str(), ##__VA_ARGS__)
+#define ERROR(format, ...) \
+    LOG_ERROR("jspipe[%s]: " format, name_.c_str(), ##__VA_ARGS__)
+
+#include "nacl_io/log.h"
+#include "nacl_io/osinttypes.h"
+#include "nacl_io/pepper_interface.h"
+
+namespace {
+const size_t kMaxPostMessageSize = 64*1024;
+const char* kDictKeyPipe = "pipe";
+const char* kDictKeyOperation = "operation";
+const char* kDictKeyPayload = "payload";
+const char* kOperationNameAck = "ack";
+const char* kOperationNameWrite = "write";
+}
+
+namespace nacl_io {
+
+JSPipeEventEmitter::JSPipeEventEmitter(PepperInterface* ppapi, size_t size)
+  : input_fifo_(size),
+    post_message_buffer_size_(size),
+    bytes_sent_(0),
+    bytes_acked_(0),
+    bytes_read_(0),
+    ppapi_(ppapi),
+    messaging_iface_(NULL),
+    var_iface_(NULL),
+    array_iface_(NULL),
+    buffer_iface_(NULL),
+    dict_iface_(NULL),
+    pipe_name_var_(PP_MakeUndefined()),
+    pipe_key_(PP_MakeUndefined()),
+    operation_key_(PP_MakeUndefined()),
+    payload_key_(PP_MakeUndefined()),
+    write_var_(PP_MakeUndefined()),
+    ack_var_(PP_MakeUndefined()) {
+  UpdateStatus_Locked();
+  if (ppapi == NULL) {
+    TRACE("missing PPAPI provider");
+    return;
+  }
+  messaging_iface_ = ppapi->GetMessagingInterface();
+  var_iface_ = ppapi->GetVarInterface();
+  array_iface_ = ppapi->GetVarArrayInterface();
+  buffer_iface_ = ppapi->GetVarArrayBufferInterface();
+  dict_iface_ = ppapi->GetVarDictionaryInterface();
+
+  if (var_iface_ == NULL)
+    return;
+
+  pipe_key_ = VarFromCStr(kDictKeyPipe);
+  operation_key_ = VarFromCStr(kDictKeyOperation);
+  payload_key_ = VarFromCStr(kDictKeyPayload);
+  write_var_ = VarFromCStr(kOperationNameWrite);
+  ack_var_ = VarFromCStr(kOperationNameAck);
+}
+
+void JSPipeEventEmitter::Destroy() {
+  if (var_iface_ == NULL)
+    return;
+  var_iface_->Release(pipe_name_var_);
+  var_iface_->Release(pipe_key_);
+  var_iface_->Release(operation_key_);
+  var_iface_->Release(payload_key_);
+  var_iface_->Release(write_var_);
+  var_iface_->Release(ack_var_);
+}
+
+PP_Var JSPipeEventEmitter::VarFromCStr(const char* string) {
+  assert(var_iface_);
+  return var_iface_->VarFromUtf8(string, strlen(string));
+}
+
+void JSPipeEventEmitter::UpdateStatus_Locked() {
+  uint32_t status = 0;
+  if (!input_fifo_.IsEmpty())
+    status |= POLLIN;
+
+  if (GetOSpace() > 0)
+    status |= POLLOUT;
+
+  ClearEvents_Locked(~status);
+  RaiseEvents_Locked(status);
+}
+
+Error JSPipeEventEmitter::Read_Locked(char* data, size_t len, int* out_bytes) {
+  *out_bytes = input_fifo_.Read(data, len);
+  if (*out_bytes > 0) {
+    bytes_read_ += *out_bytes;
+    Error err = SendAckMessage(bytes_read_);
+    if (err != 0)
+      ERROR("Sending ACK failed: %d\n", err.error);
+  }
+
+  UpdateStatus_Locked();
+  return 0;
+}
+
+Error JSPipeEventEmitter::SendWriteMessage(const void* buf, size_t count) {
+  TRACE("SendWriteMessage [%"PRIuS"] total=%"PRIuS, count, bytes_sent_);
+  if (!var_iface_ || !buffer_iface_)
+    return EIO;
+
+  // Copy payload data in a new ArrayBuffer
+  PP_Var buffer = buffer_iface_->Create(count);
+  memcpy(buffer_iface_->Map(buffer), buf, count);
+  buffer_iface_->Unmap(buffer);
+
+  Error rtn = SendMessageToJS(write_var_, buffer);
+  var_iface_->Release(buffer);
+  return rtn;
+}
+
+Error JSPipeEventEmitter::SetName(const char* name) {
+  if (var_iface_ == NULL)
+    return EIO;
+
+  // name can only be set once
+  if (!name_.empty())
+    return EIO;
+
+  // new name must not be empty
+  if (!name || strlen(name) == 0)
+    return EIO;
+
+  TRACE("set name: %s", name);
+  name_ = name;
+  pipe_name_var_ = VarFromCStr(name);
+  return 0;
+}
+
+Error JSPipeEventEmitter::SendMessageToJS(PP_Var operation,
+                                          PP_Var payload) {
+  if (!ppapi_ || !messaging_iface_ || !var_iface_ || !dict_iface_)
+    return EIO;
+
+  // Create dict object which will be sent to JavaScript.
+  PP_Var dict = dict_iface_->Create();
+
+  // Set try keys in the dictionaty: 'pipe', 'operation', and 'payload'
+  dict_iface_->Set(dict, pipe_key_, pipe_name_var_);

[binji, 2014/05/08 18:18:33]

nice

+  dict_iface_->Set(dict, operation_key_, operation);
+  dict_iface_->Set(dict, payload_key_, payload);
+
+  // Send the dict via PostMessage
+  messaging_iface_->PostMessage(ppapi_->GetInstance(), dict);
+
+  // Release the dict
+  var_iface_->Release(dict);
+  return 0;
+}
+
+Error JSPipeEventEmitter::SendAckMessage(size_t byte_count) {
+  TRACE("SendAckMessage %"PRIuS, byte_count);
+  PP_Var payload;
+  payload.type = PP_VARTYPE_INT32;
+  payload.value.as_int = (int32_t)byte_count;
+
+  return SendMessageToJS(ack_var_, payload);
+}
+
+size_t JSPipeEventEmitter::HandleJSWrite(const char* data, size_t len) {
+  size_t out_len = input_fifo_.Write(data, len);
+  UpdateStatus_Locked();
+  return out_len;
+}
+
+void JSPipeEventEmitter::HandleJSAck(size_t byte_count) {
+  if (byte_count > bytes_sent_) {
+    ERROR("HandleAck unexpected byte count: %"PRIuS, byte_count);
+    return;
+  }
+
+  bytes_acked_ = byte_count;
+  TRACE("HandleAck: %" SCNuS "/%" PRIuS, bytes_acked_, bytes_sent_);

[binji, 2014/05/08 18:18:33]

PRIuS, SCNuS is for scanf

+  UpdateStatus_Locked();
+}
+
+Error JSPipeEventEmitter::HandleJSWrite(struct PP_Var message) {
+  TRACE("HandleJSWrite");
+  if (message.type != PP_VARTYPE_ARRAY_BUFFER) {
+    TRACE("HandleJSWrite expected ArrayBuffer but got %d.", message.type);
+    return EINVAL;
+  }
+  uint32_t length;
+  if (buffer_iface_->ByteLength(message, &length) != PP_TRUE)
+    return EINVAL;
+
+  char* buffer = (char*)buffer_iface_->Map(message);
+
+  // Write data to the input fifo
+  size_t wrote = HandleJSWrite(buffer, length);
+  buffer_iface_->Unmap(message);
+  if (wrote != length) {
+    LOG_ERROR("Only wrote %d of %d bytes to pipe", (int)wrote, (int)length);

[binji, 2014/05/08 18:18:33]

why cast?

+    return EIO;
+  }
+  TRACE("done HandleWrite: %d", length);
+  return 0;
+}
+
+Error JSPipeEventEmitter::HandleJSAck(PP_Var message) {
+  if (message.type != PP_VARTYPE_INT32) {
+    TRACE("HandleAck integer object expected but got %d.", message.type);
+    return EINVAL;
+  }
+  HandleJSAck(message.value.as_int);
+  return 0;
+}
+
+int JSPipeEventEmitter::VarStrcmp(PP_Var a, PP_Var b) {
+  uint32_t length_a = 0;
+  uint32_t length_b = 0;
+  const char* cstring_a = var_iface_->VarToUtf8(a, &length_a);
+  const char* cstring_b = var_iface_->VarToUtf8(a, &length_b);
+  std::string string_a(cstring_a, length_a);

[binji, 2014/05/08 18:18:33]

seems a bit cheesy to create a std::string just to compare. Why not memcmp
(since there could be embedded nulls)?

+  std::string string_b(cstring_b, length_a);
+  return strcmp(string_a.c_str(), string_b.c_str());
+}
+
+Error JSPipeEventEmitter::HandleJSMessage(struct PP_Var message) {
+  Error err = 0;
+  if (!messaging_iface_ || !var_iface_ || !dict_iface_ || !buffer_iface_) {
+    TRACE("HandleJSMessage: missing PPAPI interfaces");
+    return ENOSYS;
+  }
+
+  // Verify that we have an array with size two.
+  if (message.type != PP_VARTYPE_DICTIONARY) {
+    TRACE("HandleJSMessage passed non-dictionary var");
+    return EINVAL;
+  }
+
+#ifndef NDEBUG
+  PP_Var pipe_name_var = dict_iface_->Get(message, pipe_key_);
+  if (VarStrcmp(pipe_name_var, pipe_name_var_)) {
+    TRACE("HandleJSMessage wrong pipe name");
+    return EINVAL;
+  }
+  var_iface_->Release(pipe_name_var);
+#endif
+
+  PP_Var operation_var = dict_iface_->Get(message, operation_key_);
+  if (operation_var.type != PP_VARTYPE_STRING) {
+    TRACE("HandleJSMessage invalid operation");
+    err = EINVAL;
+  } else {
+    uint32_t length;
+    const char* operation_string;
+    operation_string = var_iface_->VarToUtf8(operation_var, &length);
+    std::string message_type(operation_string, length);
+
+    TRACE("HandleJSMessage %s", message_type.c_str());
+    PP_Var payload = dict_iface_->Get(message, payload_key_);
+    if (message_type == kOperationNameWrite) {
+      err = HandleJSWrite(payload);
+    } else if (message_type == kOperationNameAck) {
+      err = HandleJSAck(payload);
+    } else {
+      TRACE("Unknown message type: %s", message_type.c_str());
+      err = EINVAL;
+    }
+    var_iface_->Release(payload);
+  }
+
+  var_iface_->Release(operation_var);
+  return err;
+}
+
+Error JSPipeEventEmitter::Write_Locked(const char* data, size_t len,
+                                       int* out_bytes) {
+  if (GetOSpace() == 0) {
+    *out_bytes = 0;
+    return 0;
+  }
+
+  if (len > GetOSpace())
+    len = GetOSpace();
+
+  // Limit the size of the data we send with PostMessage to kMaxPostMessageSize
+  if (len > kMaxPostMessageSize)
+    len = kMaxPostMessageSize;
+
+  Error err = SendWriteMessage(data, len);
+  if (err != 0)
+    return err;
+  *out_bytes = len;
+  bytes_sent_ += len;
+
+  UpdateStatus_Locked();
+  return 0;
+}
+
+}  // namespace nacl_io