message.h

// message.h
 
/*    Copyright 2009 10gen Inc.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
 
#pragma once
 
#include <vector>
 
#include "mongo/platform/atomic_word.h"
#include "mongo/platform/cstdint.h"
#include "mongo/base/data_view.h"
#include "mongo/base/encoded_value_storage.h"
#include "mongo/util/mongoutils/str.h"
#include "mongo/util/net/hostandport.h"
#include "mongo/util/net/operation.h"
#include "mongo/util/net/sock.h"
 
namespace mongo {
 
    const size_t MaxMessageSizeBytes = 48 * 1000 * 1000;
 
    class Message;
    class MessagingPort;
    class PiggyBackData;
 
    typedef uint32_t MSGID;
 
    bool doesOpGetAResponse( int op );
 
    inline const char * opToString( int op ) {
        switch ( op ) {
        case 0: return "none";
        case opReply: return "reply";
        case dbMsg: return "msg";
        case dbUpdate: return "update";
        case dbInsert: return "insert";
        case dbQuery: return "query";
        case dbGetMore: return "getmore";
        case dbDelete: return "remove";
        case dbKillCursors: return "killcursors";
        default:
            massert( 16141, str::stream() << "cannot translate opcode " << op, !op );
            return "";
        }
    }
 
    inline bool opIsWrite( int op ) {
        switch ( op ) {
 
        case 0:
        case opReply:
        case dbMsg:
        case dbQuery:
        case dbGetMore:
        case dbKillCursors:
            return false;
 
        case dbUpdate:
        case dbInsert:
        case dbDelete:
            return true;
 
        default:
            verify(0);
            return "";
        }
 
    }
 
    namespace MSGHEADER {
#pragma pack(1)
        /* see http://dochub.mongodb.org/core/mongowireprotocol
        */
        struct Layout {
            int32_t messageLength; // total message size, including this
            int32_t requestID;     // identifier for this message
            int32_t responseTo;    // requestID from the original request
            //   (used in responses from db)
            int32_t opCode;
        };
#pragma pack()
 
        class ConstView {
        public:
            typedef ConstDataView view_type;
 
            ConstView(const char* data) : _data(data) { }
 
            const char* view2ptr() const {
                return data().view();
            }
 
            int32_t getMessageLength() const {
                return data().readLE<int32_t>(offsetof(Layout, messageLength));
            }
 
            int32_t getRequestID() const {
                return data().readLE<int32_t>(offsetof(Layout, requestID));
            }
 
            int32_t getResponseTo() const {
                return data().readLE<int32_t>(offsetof(Layout, responseTo));
            }
 
            int32_t getOpCode() const {
                return data().readLE<int32_t>(offsetof(Layout, opCode));
            }
 
        protected:
            const view_type& data() const {
                return _data;
            }
 
        private:
            view_type _data;
        };
 
        class View : public ConstView {
        public:
            typedef DataView view_type;
 
            View(char* data) : ConstView(data) {}
 
            using ConstView::view2ptr;
            char* view2ptr() {
                return data().view();
            }
 
            void setMessageLength(int32_t value) {
                data().writeLE(value, offsetof(Layout, messageLength));
            }
 
            void setRequestID(int32_t value) {
                data().writeLE(value, offsetof(Layout, requestID));
            }
 
            void setResponseTo(int32_t value) {
                data().writeLE(value, offsetof(Layout, responseTo));
            }
 
            void setOpCode(int32_t value) {
                data().writeLE(value, offsetof(Layout, opCode));
            }
 
        private:
            view_type data() const {
                return const_cast<char *>(ConstView::view2ptr());
            }
        };
 
        class Value : public EncodedValueStorage<Layout, ConstView, View> {
        public:
            Value() {
                BOOST_STATIC_ASSERT(sizeof(Value) == sizeof(Layout));
            }
 
            Value(ZeroInitTag_t zit) : EncodedValueStorage<Layout, ConstView, View>(zit) {}
        };
 
    } // namespace MSGHEADER
 
    namespace MsgData {
#pragma pack(1)
        struct Layout {
            MSGHEADER::Layout header;
            char data[4];
        };
#pragma pack()
 
        class ConstView {
        public:
            ConstView(const char* storage) : _storage(storage) { }
 
            const char* view2ptr() const {
                return storage().view();
            }
 
            int32_t getLen() const {
                return header().getMessageLength();
            }
 
            MSGID getId() const {
                return header().getRequestID();
            }
 
            MSGID getResponseTo() const {
                return header().getResponseTo();
            }
 
            int32_t getOperation() const {
                return header().getOpCode();
            }
 
            const char* data() const {
                return storage().view(offsetof(Layout, data));
            }
 
            bool valid() const {
                if ( getLen() <= 0 || getLen() > ( 4 * BSONObjMaxInternalSize ) )
                    return false;
                if ( getOperation() < 0 || getOperation() > 30000 )
                    return false;
                return true;
            }
 
            int64_t getCursor() const {
                verify( getResponseTo() > 0 );
                verify( getOperation() == opReply );
                return ConstDataView(data() + sizeof(int32_t)).readLE<int64_t>();
            }
 
            int dataLen() const; // len without header
 
        protected:
            const ConstDataView& storage() const {
                return _storage;
            }
 
            MSGHEADER::ConstView header() const {
                return storage().view(offsetof(Layout, header));
            }
 
        private:
            ConstDataView _storage;
        };
 
        class View : public ConstView {
        public:
            View(char* storage) : ConstView(storage) {}
 
            using ConstView::view2ptr;
            char* view2ptr() {
                return storage().view();
            }
 
            void setLen(int value) {
                return header().setMessageLength(value);
            }
 
            void setId(MSGID value) {
                return header().setRequestID(value);
            }
 
            void setResponseTo(MSGID value) {
                return header().setResponseTo(value);
            }
 
            void setOperation(int value) {
                return header().setOpCode(value);
            }
 
            using ConstView::data;
            char* data() {
                return storage().view(offsetof(Layout, data));
            }
 
        private:
            DataView storage() const {
                return const_cast<char *>(ConstView::view2ptr());
            }
 
            MSGHEADER::View header() const {
                return storage().view(offsetof(Layout, header));
            }
        };
 
        class Value : public EncodedValueStorage<Layout, ConstView, View> {
        public:
            Value() {
                BOOST_STATIC_ASSERT(sizeof(Value) == sizeof(Layout));
            }
 
            Value(ZeroInitTag_t zit) : EncodedValueStorage<Layout, ConstView, View>(zit) {}
        };
 
        const int MsgDataHeaderSize = sizeof(Value) - 4;
        inline int ConstView::dataLen() const {
            return getLen() - MsgDataHeaderSize;
        }
    } // namespace MsgData
 
    class Message {
    public:
        // we assume here that a vector with initial size 0 does no allocation (0 is the default, but wanted to make it explicit).
        Message() : _buf( 0 ), _data( 0 ), _freeIt( false ) {}
        Message( void * data , bool freeIt ) :
            _buf( 0 ), _data( 0 ), _freeIt( false ) {
            _setData( reinterpret_cast< char* >( data ), freeIt );
        };
        Message(Message& r) : _buf( 0 ), _data( 0 ), _freeIt( false ) {
            *this = r;
        }
        ~Message() {
            reset();
        }
 
        SockAddr _from;
 
        MsgData::View header() const {
            verify( !empty() );
            return _buf ? _buf : _data[ 0 ].first;
        }
 
        int operation() const { return header().getOperation(); }
 
        MsgData::View singleData() const {
            massert( 13273, "single data buffer expected", _buf );
            return header();
        }
 
        bool empty() const { return !_buf && _data.empty(); }
 
        int size() const {
            int res = 0;
            if ( _buf ) {
                res =  MsgData::ConstView(_buf).getLen();
            }
            else {
                for (MsgVec::const_iterator it = _data.begin(); it != _data.end(); ++it) {
                    res += it->second;
                }
            }
            return res;
        }
 
        int dataSize() const { return size() - sizeof(MSGHEADER::Value); }
 
        // concat multiple buffers - noop if <2 buffers already, otherwise can be expensive copy
        // can get rid of this if we make response handling smarter
        void concat() {
            if ( _buf || empty() ) {
                return;
            }
 
            verify( _freeIt );
            int totalSize = 0;
            for (std::vector< std::pair< char *, int > >::const_iterator i = _data.begin();
                 i != _data.end(); ++i) {
                totalSize += i->second;
            }
            char *buf = (char*)malloc( totalSize );
            char *p = buf;
            for (std::vector< std::pair< char *, int > >::const_iterator i = _data.begin();
                 i != _data.end(); ++i) {
                memcpy( p, i->first, i->second );
                p += i->second;
            }
            reset();
            _setData( buf, true );
        }
 
        // vector swap() so this is fast
        Message& operator=(Message& r) {
            verify( empty() );
            verify( r._freeIt );
            _buf = r._buf;
            r._buf = 0;
            if ( r._data.size() > 0 ) {
                _data.swap( r._data );
            }
            r._freeIt = false;
            _freeIt = true;
            return *this;
        }
 
        void reset() {
            if ( _freeIt ) {
                if ( _buf ) {
                    free( _buf );
                }
                for (std::vector< std::pair< char *, int > >::const_iterator i = _data.begin();
                     i != _data.end(); ++i) {
                    free(i->first);
                }
            }
            _buf = 0;
            _data.clear();
            _freeIt = false;
        }
 
        // use to add a buffer
        // assumes message will free everything
        void appendData(char *d, int size) {
            if ( size <= 0 ) {
                return;
            }
            if ( empty() ) {
                MsgData::View md = d;
                md.setLen(size); // can be updated later if more buffers added
                _setData( md.view2ptr(), true );
                return;
            }
            verify( _freeIt );
            if ( _buf ) {
                _data.push_back(std::make_pair(_buf, MsgData::ConstView(_buf).getLen()));
                _buf = 0;
            }
            _data.push_back(std::make_pair(d, size));
            header().setLen(header().getLen() + size);
        }
 
        // use to set first buffer if empty
        void setData(char* d, bool freeIt) {
            verify( empty() );
            _setData( d, freeIt );
        }
        void setData(int operation, const char *msgtxt) {
            setData(operation, msgtxt, strlen(msgtxt)+1);
        }
        void setData(int operation, const char *msgdata, size_t len) {
            verify( empty() );
            size_t dataLen = len + sizeof(MsgData::Value) - 4;
            MsgData::View d = reinterpret_cast<char *>(malloc(dataLen));
            memcpy(d.data(), msgdata, len);
            d.setLen(dataLen);
            d.setOperation(operation);
            _setData( d.view2ptr(), true );
        }
 
        bool doIFreeIt() {
            return _freeIt;
        }
 
        void send( MessagingPort &p, const char *context );
        
        std::string toString() const;
 
    private:
        void _setData( char* d, bool freeIt ) {
            _freeIt = freeIt;
            _buf = d;
        }
        // if just one buffer, keep it in _buf, otherwise keep a sequence of buffers in _data
        char* _buf;
        // byte buffer(s) - the first must contain at least a full MsgData unless using _buf for storage instead
        typedef std::vector< std::pair< char*, int > > MsgVec;
        MsgVec _data;
        bool _freeIt;
    };
 
 
    MSGID nextMessageId();
 
 
} // namespace mongo