Cursor.cs

using System;
using System.Collections.Generic;
using System.IO;

using MongoDB.Driver.Bson;
using MongoDB.Driver.IO;

namespace MongoDB.Driver
{
    
	public class Cursor : ICursor {
        private Connection connection;
        
        private long id = -1;
        public long Id{
            get {return id;}
        }       
        
        private String fullCollectionName;
        public string FullCollectionName {
            get {return fullCollectionName;}
            set {fullCollectionName = value;}
        }
        
        private String collName;
        public string CollName {
            get {return collName;}
            set {collName = value;}
        }
        
        private Document spec;
        public Document Spec{
            get {return spec;}
            set {spec = value;}
        }
        
        private int limit;
        public int Limit{
            get {return limit;}
            set {limit = value;}
        }
        
        private int skip;
        public int Skip{
            get {return skip;}
            set {skip = value;}
        }

        private Document fields;
        public Document Fields{
            get {return fields;}
            set {fields = value;}
        }
        
        private bool modifiable = true;
        public bool Modifiable{
            get {return modifiable;}
        }
        
        private ReplyMessage reply;
        
        public Cursor(Connection conn, String fullCollectionName, Document spec, int limit, int skip, Document fields){
            this.connection = conn;
            this.FullCollectionName = fullCollectionName;
            if(spec == null)spec = new Document();
            this.Spec = spec;
            this.Limit = limit;
            this.Skip = skip;
            this.Fields = fields;
        }
        
        public IEnumerable<Document> Documents{
            get{
                if(this.reply == null){
                    RetrieveData();
                }
                int docsReturned = 0;
                BsonDocument[] bdocs = this.reply.Documents;
                Boolean shouldBreak = false;
                while(!shouldBreak){
                    foreach(BsonDocument bdoc in bdocs){
                        if((this.Limit == 0) || (this.Limit != 0 && docsReturned < this.Limit)){
                            docsReturned++;
                            yield return (Document)bdoc.ToNative();
                        }else{
                            shouldBreak = true;
                            yield break;
                        }
                    }
                    if(this.Id != 0 && shouldBreak == false){
                        RetrieveMoreData();                 
                        bdocs = this.reply.Documents;
                        if(bdocs == null){
                            shouldBreak = true; 
                        }
                    }else{
                        shouldBreak = true;
                    }
                }
            }           
        }
        
        private void RetrieveData(){
            QueryMessage query = new QueryMessage();
            query.FullCollectionName = this.FullCollectionName;
            query.Query = BsonConvert.From(this.Spec);
            query.NumberToReturn = this.Limit;
            query.NumberToSkip = this.Skip;
            if(this.Fields != null){
                query.ReturnFieldSelector = BsonConvert.From(this.Fields);
            }
            try{
                this.reply = connection.SendTwoWayMessage(query);
                this.id = this.reply.CursorID;
                if(this.Limit < 0)this.Limit = this.Limit * -1;
            }catch(IOException ioe){
                throw new MongoCommException("Could not read data, communication failure", this.connection,ioe);
            }

        }
        
        private void RetrieveMoreData(){
            GetMoreMessage gmm = new GetMoreMessage(this.FullCollectionName, this.Id, this.Limit);
            try{
                this.reply = connection.SendTwoWayMessage(gmm);
                this.id = this.reply.CursorID;
            }catch(IOException ioe){
                this.id = 0;
                throw new MongoCommException("Could not read data, communication failure", this.connection,ioe);
            }
        }
        
        
        public void Dispose(){
            if(this.Id == 0) return; //All server side resources disposed of.
            KillCursorsMessage kcm = new KillCursorsMessage(this.Id);
            try{
                this.id = 0;
                connection.SendMessage(kcm);
            }catch(IOException ioe){
                throw new MongoCommException("Could not read data, communication failure", this.connection,ioe);
            }
        }
    }
}