Bitmap transport

chrome/common/transport_dib_linux.cc

+// Copyright (c) 2009 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 <errno.h>
+#include <stdlib.h>
+#include <sys/ipc.h>
+#include <sys/shm.h>
+
+#include "base/logging.h"
+#include "chrome/common/transport_dib.h"
+
+// The shmat system call uses this as it's invalid return address
+static void *const kInvalidAddress = (void*) -1;
+
+TransportDIB::TransportDIB()
+    : key_(-1),
+      address_(kInvalidAddress),
+      size_(0) {
+}
+
+TransportDIB::~TransportDIB() {
+  if (address_ != kInvalidAddress) {
+    shmdt(address_);
+    address_ = kInvalidAddress;
+  }
+}
+
+// static
+TransportDIB* TransportDIB::Create(size_t size, uint32 sequence_num) {
+  // We use a mode of 0666 since the X server won't attach to memory which is
+  // 0600 since it can't know if it (as a root process) is being asked to map
+  // someone else's private shared memory region.
+  const int shmkey = shmget(IPC_PRIVATE, size, 0666);
+  if (shmkey == -1) {
+    DLOG(ERROR) << "Failed to create SysV shared memory region"
+                << " errno:" << errno;
+    return false;
+  }
+
+  void* address = shmat(shmkey, NULL /* desired address */, 0 /* flags */);
+  // Here we mark the shared memory for deletion. Since we attached it in the
+  // line above, it doesn't actually get deleted but, if we crash, this means
+  // that the kernel will automatically clean it up for us.
+  shmctl(shmkey, IPC_RMID, 0);
+  if (address == kInvalidAddress)
+    return false;
+
+  TransportDIB* dib = new TransportDIB;
+
+  dib->key_ = shmkey;
+  dib->address_ = address;
+  dib->size_ = size;
+  return dib;
+}
+
+TransportDIB* TransportDIB::Map(Handle shmkey) {
+  struct shmid_ds shmst;
+  if (shmctl(shmkey, IPC_STAT, &shmst) == -1)
+    return NULL;
+
+  void* address = shmat(shmkey, NULL /* desired address */, 0 /* flags */);
+  if (address == kInvalidAddress)
+    return NULL;
+
+  TransportDIB* dib = new TransportDIB;
+
+  dib->address_ = address;
+  dib->size_ = shmst.shm_segsz;
+  dib->key_ = shmkey;
+  return dib;
+}
+
+void* TransportDIB::memory() const {
+  DCHECK_NE(address_, kInvalidAddress);
+  return address_;
+}
+
+TransportDIB::Id TransportDIB::id() const {
+  return key_;
+}
+
+TransportDIB::Handle TransportDIB::handle() const {
+  return key_;
+}