sentenceextractor.cs

这是一个gps的数据读写器。大家可以借鉴学习一下。

using System;
using System.Text;
using System.Threading;

namespace BLT
{
	/// <summary>
	/// Used to Collect and break down gps-input in to single gps sentences
	/// </summary>
	public class GPSSentenceExtractor
	{
		/// <summary>
		/// received content
		/// </summary>
		string strReceivedContent;
		

		public GPSSentenceExtractor()
		{
			this.strReceivedContent= String.Empty;
		}

		/// <summary>
		/// Length of received content
		/// </summary>
		int Length
		{
			get
			{
				return this.strReceivedContent.Length;
			}
		}
		
		public bool Get(out string strGPSSentence)
		{  
			strGPSSentence=String.Empty;
			bool bValid=false;
			try
			{
				// lock the resource
				Monitor.Enter(strReceivedContent);
			    if(this.strReceivedContent!=String.Empty)
			    {
					
					// trim the uncomplete sentence
					// it is used to only at the begin of reading process
					if(this.strReceivedContent.StartsWith("$")!=true)
					{
						int nCStart=this.strReceivedContent.IndexOf('$',0);
						strReceivedContent=this.strReceivedContent.Remove(0,nCStart);

					}

					if(this.Length>0)
					{
						int nCEnd=this.strReceivedContent.IndexOf('$',1);
						if(nCEnd>0) // exists a full sentence
						{
							// extract the sentence
							strGPSSentence=this.strReceivedContent.Substring(0,nCEnd);
							strGPSSentence=strGPSSentence.Replace("\r\n",String.Empty);
							bValid=true;
							// remove the extracted  sentence from the content
							this.strReceivedContent=this.strReceivedContent.Remove(0,nCEnd);
						
						}

					}
					 	
			  }
				
			}
			catch(Exception oException)
			{
				throw oException;

			}
			finally
			{
				Monitor.Exit(strReceivedContent);

			}
			return bValid;
		}

		/// <summary>
		/// Collects received data  from GPS
		/// </summary>
		/// <param name="strInput"></param>
		public void Add(string strInput)
		{
			try
			{
			    // lock
				Monitor.Enter(strReceivedContent);
				// add
				this.strReceivedContent+=strInput;

			}
			catch(Exception oException)
			{
				throw oException;
			}
			finally
			{
				// unlock
				Monitor.Exit(strReceivedContent);

			}

		}

		
	}
}