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Unified Diff: chrome/common/descriptor_set_posix.h

Issue 21208: POSIX: Transfer network data using shared memory (Closed)
Patch Set: ... Created 11 years, 10 months ago
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Index: chrome/common/descriptor_set_posix.h
diff --git a/chrome/common/descriptor_set_posix.h b/chrome/common/descriptor_set_posix.h
new file mode 100644
index 0000000000000000000000000000000000000000..36a0433f195b268a967e159ff795ec882b03eabe
--- /dev/null
+++ b/chrome/common/descriptor_set_posix.h
@@ -0,0 +1,109 @@
+// Copyright (c) 2006-2009 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.
+
+#ifndef CHROME_COMMON_DESCRIPTOR_SET_POSIX_H_
+#define CHROME_COMMON_DESCRIPTOR_SET_POSIX_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/file_descriptor_posix.h"
+
+// -----------------------------------------------------------------------------
+// A DescriptorSet is an ordered set of POSIX file descriptors. These are
+// associated with IPC messages so that descriptors can be transmitted over a
+// UNIX domain socket.
+// -----------------------------------------------------------------------------
+class DescriptorSet {
+ public:
+ DescriptorSet();
+ ~DescriptorSet();
+
+ // This is the maximum number of descriptors per message. We need to know this
+ // because the control message kernel interface has to be given a buffer which
+ // is large enough to store all the descriptor numbers. Otherwise the kernel
+ // tells us that it truncated the control data and the extra descriptors are
+ // lost.
+ //
+ // In debugging mode, it's a fatal error to try and add more than this number
+ // of descriptors to a DescriptorSet.
+ enum {
+ MAX_DESCRIPTORS_PER_MESSAGE = 4,
+ };
+
+ // ---------------------------------------------------------------------------
+ // Interfaces for building during message serialisation...
+
+ // Add a descriptor to the end of the set. Returns false iff the set is full.
+ bool Add(int fd);
+ // Add a descriptor to the end of the set and automatically close it after
+ // transmission. Returns false iff the set is full.
+ bool AddAndAutoClose(int fd);
+
+ // ---------------------------------------------------------------------------
+
+
+ // ---------------------------------------------------------------------------
+ // Interfaces for accessing during message deserialisation...
+
+ // Return the number of descriptors remaining
+ unsigned size() const { return descriptors_.size() - next_descriptor_; }
+ // Return true if no unconsumed descriptors remain
+ bool empty() const { return descriptors_.size() == next_descriptor_; }
+ // Fetch the next descriptor from the beginning of the set. This interface is
+ // designed for the deserialising code as it doesn't support close flags.
+ // returns: file descriptor, or -1 on error
+ int NextDescriptor();
+
+ // ---------------------------------------------------------------------------
+
+
+ // ---------------------------------------------------------------------------
+ // Interfaces for transmission...
+
+ // Fill an array with file descriptors without 'consuming' them. CommitAll
+ // must be called after these descriptors have been transmitted.
+ // buffer: (output) a buffer of, at least, size() integers.
+ void GetDescriptors(int* buffer) const;
+ // This must be called after transmitting the descriptors returned by
+ // GetDescriptors. It marks all the descriptors as consumed and closes those
+ // which are auto-close.
+ void CommitAll();
+
+ // ---------------------------------------------------------------------------
+
+
+ // ---------------------------------------------------------------------------
+ // Interfaces for receiving...
+
+ // Set the contents of the set from the given buffer. This set must be empty
+ // before calling. The auto-close flag is set on all the descriptors so that
+ // unconsumed descriptors are closed on destruction.
+ void SetDescriptors(const int* buffer, unsigned count);
+
+ // ---------------------------------------------------------------------------
+
+ // ---------------------------------------------------------------------------
+ // Interfaces for IPC::Message...
+
+ // Take all the FileDescriptors from another set. Just like a copy
+ // constructor, except that the source is emptied.
+ void TakeFrom(DescriptorSet* other);
+
+ // ---------------------------------------------------------------------------
+
+ private:
+ // A vector of descriptors and close flags. If this message is sent, then
+ // these descriptors are sent as control data. After sending, any descriptors
+ // with a true flag are closed. If this message has been received, then these
+ // are the descriptors which were received and all close flags are true.
+ std::vector<base::FileDescriptor> descriptors_;
+ // When deserialising the message, the descriptors will be extracted
+ // one-by-one. This contains the index of the next unused descriptor.
+ unsigned next_descriptor_;
+
+ DISALLOW_COPY_AND_ASSIGN(DescriptorSet);
+};
+
+#endif // CHROME_COMMON_FILE_DESCRIPTOR_POSIX_H_
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