130 lines
2.5 KiB
C++
130 lines
2.5 KiB
C++
/*
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* \brief Linux-specific layout of IPC message buffer
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* \author Norman Feske
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* \date 2006-06-14
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*/
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/*
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* Copyright (C) 2006-2013 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__BASE__IPC_MSGBUF_H_
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#define _INCLUDE__BASE__IPC_MSGBUF_H_
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#include <base/stdint.h>
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namespace Genode {
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class Ipc_marshaller;
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/**
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* IPC message buffer layout
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*/
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class Msgbuf_base
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{
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public:
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enum { MAX_CAPS_PER_MSG = 8 };
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protected:
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friend class Ipc_marshaller;
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/*
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* Capabilities (file descriptors) to be transferred
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*/
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int _caps[MAX_CAPS_PER_MSG];
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Genode::size_t _used_caps = 0;
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Genode::size_t _read_cap_index = 0;
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/**
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* Maximum size of plain-data message payload
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*/
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Genode::size_t const _capacity;
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/**
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* Actual size of plain-data message payload
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*/
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Genode::size_t _data_size = 0;
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Msgbuf_base(size_t capacity) : _capacity(capacity) { }
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struct Headroom { long space[4]; } _headroom;
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char _msg_start[]; /* symbol marks start of message buffer data */
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/*
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* No member variables are allowed beyond this point!
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*/
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public:
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template <typename T>
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T &header()
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{
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static_assert(sizeof(T) <= sizeof(Headroom),
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"Header size exceeds message headroom");
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return *reinterpret_cast<T *>(_msg_start - sizeof(T));
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}
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/**
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* Return size of message buffer
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*/
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Genode::size_t capacity() const { return _capacity; };
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/**
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* Return pointer of message data payload
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*/
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void *data() { return &_msg_start[0]; };
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void const *data() const { return &_msg_start[0]; };
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size_t data_size() const { return _data_size; }
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void reset_caps() { _used_caps = 0; _read_cap_index = 0; }
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bool append_cap(int cap)
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{
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if (_used_caps == MAX_CAPS_PER_MSG)
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return false;
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_caps[_used_caps++] = cap;
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return true;
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}
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int read_cap()
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{
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if (_read_cap_index == _used_caps)
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return -1;
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return _caps[_read_cap_index++];
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}
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size_t used_caps() const { return _used_caps; }
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int cap(unsigned index) const
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{
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return index < _used_caps ? _caps[index] : -1;
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}
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};
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/**
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* Pump up IPC message buffer to specified buffer size
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*/
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template <unsigned BUF_SIZE>
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class Msgbuf : public Msgbuf_base
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{
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public:
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char buf[BUF_SIZE];
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Msgbuf() : Msgbuf_base(BUF_SIZE) { }
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};
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}
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#endif /* _INCLUDE__BASE__IPC_MSGBUF_H_ */
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