[dart:io] Namespaces for file IO

runtime/bin/namespace_linux.cc

Index: runtime/bin/namespace_linux.cc
diff --git a/runtime/bin/namespace_linux.cc b/runtime/bin/namespace_linux.cc
new file mode 100644
index 0000000000000000000000000000000000000000..72bc3ac8b4241920aa4cb869b8fd2d4a2342117f
--- /dev/null
+++ b/runtime/bin/namespace_linux.cc
@@ -0,0 +1,103 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#include "platform/globals.h"
+#if defined(HOST_OS_LINUX)
+
+#include "bin/namespace.h"
+
+#include <errno.h>
+#include <fcntl.h>
+
+#include "bin/fdutils.h"
+#include "bin/file.h"
+#include "platform/signal_blocker.h"
+
+namespace dart {
+namespace bin {
+
+Namespace* Namespace::Create(const char* path) {
+  const intptr_t fd = TEMP_FAILURE_RETRY(open64(path, O_PATH));
+  if (fd < 0) {
+    return NULL;
+  }
+  return new Namespace(fd);
+}
+
+Namespace::~Namespace() {
+  if (namespc_ != kNone) {
+    VOID_TEMP_FAILURE_RETRY(close(namespc_));
+  }
+}
+
+intptr_t Namespace::Default() {
+  return kNone;
+}
+
+const char* Namespace::GetCurrent(Namespace* namespc) {
+  if ((namespc == NULL) || (namespc->namespc() == kNone)) {
+    // TODO(zra): When there are isolate-specific namespaces, extract it from
+    // the namespace instead of calling getcwd.
+    char buffer[PATH_MAX];
+    if (getcwd(buffer, PATH_MAX) == NULL) {
+      return NULL;
+    }
+    return DartUtils::ScopedCopyCString(buffer);
+  }
+
+  // TODO(zra): Allow changing the current working directory when there is
+  // a non-default namespace.
+  return DartUtils::ScopedCopyCString("/");
+}
+
+bool Namespace::SetCurrent(Namespace* namespc, const char* path) {
+  if ((namespc == NULL) || (namespc->namespc() == kNone)) {
+    return (NO_RETRY_EXPECTED(chdir(path)) == 0);
+  }
+
+  // TODO(zra): If a non-default namespace is set up, changing the current
+  // working directoy is disallowed. We should relax this restriction when
+  // isolate-specific cwds are implemented.
+  errno = ENOSYS;
+  return false;
+}
+
+bool Namespace::ResolvePath(Namespace* namespc,
+                            const char* path,
+                            intptr_t* dirfd,
+                            const char** resolved_path) {
+  ASSERT(dirfd != NULL);
+  ASSERT(resolved_path != NULL);
+  if ((namespc == NULL) || (namespc->namespc() == kNone)) {
+    *dirfd = AT_FDCWD;
+    *resolved_path = path;
+    return false;
+  }
+  *dirfd = namespc->namespc();
+  if (File::IsAbsolutePath(path)) {
+    if (strcmp(path, File::PathSeparator()) == 0) {
+      *resolved_path = ".";
+    } else {
+      *resolved_path = &path[1];
+    }
+  } else {
+    *resolved_path = path;
+  }
+  return false;
+}
+
+NamespaceScope::NamespaceScope(Namespace* namespc, const char* path) {
+  owns_fd_ = Namespace::ResolvePath(namespc, path, &fd_, &path_);
+}
+
+NamespaceScope::~NamespaceScope() {
+  if (owns_fd_) {
+    FDUtils::SaveErrorAndClose(fd_);
+  }
+}
+
+}  // namespace bin
+}  // namespace dart
+
+#endif  // defined(HOST_OS_LINUX)