dbmessage.h

// dbmessage.h

/*    Copyright 2014 MongoDB 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 "mongo/bson/bson_validate.h"
#include "mongo/client/constants.h"
#include "mongo/db/jsobj.h"
#include "mongo/util/net/message.h"
#include "mongo/util/net/message_port.h"

namespace mongo {

/* db response format

   Query or GetMore: // see struct QueryResult
      int resultFlags;
      int64 cursorID;
      int startingFrom;
      int nReturned;
      list of marshalled JSObjects;
*/

/* db request message format

   unsigned opid;         // arbitary; will be echoed back
   byte operation;
   int options;

   then for:

   dbInsert:
      string collection;
      a series of JSObjects
   dbDelete:
      string collection;
      int flags=0; // 1=DeleteSingle
      JSObject query;
   dbUpdate:
      string collection;
      int flags; // 1=upsert
      JSObject query;
      JSObject objectToUpdate;
        objectToUpdate may include { $inc: <field> } or { $set: ... }, see struct Mod.
   dbQuery:
      string collection;
      int nToSkip;
      int nToReturn; // how many you want back as the beginning of the cursor data (0=no limit)
                     // greater than zero is simply a hint on how many objects to send back per
                     // "cursor batch". a negative number indicates a hard limit.
      JSObject query;
      [JSObject fieldsToReturn]
   dbGetMore:
      string collection; // redundant, might use for security.
      int nToReturn;
      int64 cursorID;
   dbKillCursors=2007:
      int n;
      int64 cursorIDs[n];

   Note that on Update, there is only one object, which is different
   from insert where you can pass a list of objects to insert in the db.
   Note that the update field layout is very similar layout to Query.
*/

namespace QueryResult {
#pragma pack(1)
/* see http://dochub.mongodb.org/core/mongowireprotocol
*/
struct Layout {
    MsgData::Layout msgdata;
    int64_t cursorId;
    int32_t startingFrom;
    int32_t nReturned;
};
#pragma pack()

class ConstView {
public:
    ConstView(const char* storage) : _storage(storage) {}

    const char* view2ptr() const {
        return storage().view();
    }

    MsgData::ConstView msgdata() const {
        return storage().view(offsetof(Layout, msgdata));
    }

    int64_t getCursorId() const {
        return storage().readLE<int64_t>(offsetof(Layout, cursorId));
    }

    int32_t getStartingFrom() const {
        return storage().readLE<int32_t>(offsetof(Layout, startingFrom));
    }

    int32_t getNReturned() const {
        return storage().readLE<int32_t>(offsetof(Layout, nReturned));
    }

    const char* data() const {
        return storage().view(sizeof(Layout));
    }

protected:
    const ConstDataView& storage() const {
        return _storage;
    }

private:
    ConstDataView _storage;
};

class View : public ConstView {
public:
    View(char* data) : ConstView(data) {}

    using ConstView::view2ptr;
    char* view2ptr() {
        return storage().view();
    }

    using ConstView::msgdata;
    MsgData::View msgdata() {
        return storage().view(offsetof(Layout, msgdata));
    }

    void setCursorId(int64_t value) {
        storage().writeLE(value, offsetof(Layout, cursorId));
    }

    void setStartingFrom(int32_t value) {
        storage().writeLE(value, offsetof(Layout, startingFrom));
    }

    void setNReturned(int32_t value) {
        storage().writeLE(value, offsetof(Layout, nReturned));
    }

    int32_t getResultFlags() {
        return DataView(msgdata().data()).readLE<int32_t>();
    }

    void setResultFlags(int32_t value) {
        DataView(msgdata().data()).writeLE(value);
    }

    void setResultFlagsToOk() {
        setResultFlags(ResultFlag_AwaitCapable);
    }

    void initializeResultFlags() {
        setResultFlags(0);
    }

private:
    DataView storage() 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 QueryResult

/* For the database/server protocol, these objects and functions encapsulate
   the various messages transmitted over the connection.

   See http://dochub.mongodb.org/core/mongowireprotocol
*/
class DbMessage {
    // Assume sizeof(int) == 4 bytes
    BOOST_STATIC_ASSERT(sizeof(int) == 4);

public:
    // Note: DbMessage constructor reads the first 4 bytes and stores it in reserved
    DbMessage(const Message& msg);

    // Indicates whether this message is expected to have a ns
    // or in the case of dbMsg, a string in the same place as ns
    bool messageShouldHaveNs() const {
        return (_msg.operation() >= dbMsg) & (_msg.operation() <= dbDelete);
    }

    int reservedField() const {
        return _reserved;
    }

    const char* getns() const;
    int getQueryNToReturn() const;

    int pullInt();
    long long pullInt64();
    const char* getArray(size_t count) const;

    /* for insert and update msgs */
    bool moreJSObjs() const {
        return _nextjsobj != 0;
    }

    BSONObj nextJsObj();

    const Message& msg() const {
        return _msg;
    }

    const char* markGet() const {
        return _nextjsobj;
    }

    void markSet() {
        _mark = _nextjsobj;
    }

    void markReset(const char* toMark);

private:
    // Check if we have enough data to read
    template <typename T>
    void checkRead(const char* start, size_t count = 0) const;

    // Read some type without advancing our position
    template <typename T>
    T read() const;

    // Read some type, and advance our position
    template <typename T>
    T readAndAdvance();

    const Message& _msg;
    int _reserved;  // flags or zero depending on packet, starts the packet

    const char* _nsStart;    // start of namespace string, +4 from message start
    const char* _nextjsobj;  // current position reading packet
    const char* _theEnd;     // end of packet

    const char* _mark;

    unsigned int _nsLen;
};


/* a request to run a query, received from the database */
class QueryMessage {
public:
    const char* ns;
    int ntoskip;
    int ntoreturn;
    int queryOptions;
    BSONObj query;
    BSONObj fields;

    QueryMessage(DbMessage& d) {
        ns = d.getns();
        ntoskip = d.pullInt();
        ntoreturn = d.pullInt();
        query = d.nextJsObj();
        if (d.moreJSObjs()) {
            fields = d.nextJsObj();
        }
        queryOptions = DataView(d.msg().header().data()).readLE<int32_t>();
    }
};

struct DbResponse {
    Message* response;
    MSGID responseTo;
    std::string exhaustNS; /* points to ns if exhaust mode. 0=normal mode*/
    DbResponse(Message* r, MSGID rt) : response(r), responseTo(rt) {}
    DbResponse() {
        response = 0;
    }
    ~DbResponse() {
        delete response;
    }
};

void replyToQuery(int queryResultFlags,
                  AbstractMessagingPort* p,
                  Message& requestMsg,
                  void* data,
                  int size,
                  int nReturned,
                  int startingFrom = 0,
                  long long cursorId = 0);


/* object reply helper. */
void replyToQuery(int queryResultFlags,
                  AbstractMessagingPort* p,
                  Message& requestMsg,
                  const BSONObj& responseObj);

/* helper to do a reply using a DbResponse object */
void replyToQuery(int queryResultFlags, Message& m, DbResponse& dbresponse, BSONObj obj);

void replyToQuery(int queryResultFlags, Message& response, const BSONObj& resultObj);
}  // namespace mongo