1 using System;
2 using System.Runtime.InteropServices;
3 using TextReader		= System.IO.TextReader;
4 using IOException		= System.IO.IOException;
5 
6 
7 namespace antlr
8 {
9 	/*ANTLR Translator Generator
10 	* Project led by Terence Parr at http://www.jGuru.com
11 	* Software rights: http://www.antlr.org/license.html
12 	*
13 	* $Id:$
14 	*/
15 
16 	//
17 	// ANTLR C# Code Generator by Micheal Jordan
18 	//                            Kunle Odutola       : kunle UNDERSCORE odutola AT hotmail DOT com
19 	//                            Anthony Oguntimehin
20 	//
21 	// With many thanks to Eric V. Smith from the ANTLR list.
22 	//
23 
24 	/*A Stream of characters fed to the lexer from a InputStream that can
25 	* be rewound via mark()/rewind() methods.
26 	* <p>
27 	* A dynamic array is used to buffer up all the input characters.  Normally,
28 	* "k" characters are stored in the buffer.  More characters may be stored during
29 	* guess mode (testing syntactic predicate), or when LT(i>k) is referenced.
30 	* Consumption of characters is deferred.  In other words, reading the next
31 	* character is not done by conume(), but deferred until needed by LA or LT.
32 	* <p>
33 	*/
34 
35 	// SAS: Move most functionality into InputBuffer -- just the file-specific
36 	//      stuff is in here
37 	public class CharBuffer : InputBuffer
38 	{
39 		// char source
40 		[NonSerialized()]
41 		internal TextReader input;
42 
43 		private const int BUF_SIZE = 16;
44 		/// <summary>
45 		/// Small buffer used to avoid reading individual chars
46 		/// </summary>
47 		private char[] buf = new char[BUF_SIZE];
48 
49 
50 		/*Create a character buffer */
CharBuffer(TextReader input_)51 		public CharBuffer(TextReader input_) : base()
52 		{
53 			input = input_;
54 		}
55 
56 		/*Ensure that the character buffer is sufficiently full */
fill(int amount)57 		override public void  fill(int amount)
58 		{
59 			try
60 			{
61 				syncConsume();
62 				// Fill the buffer sufficiently to hold needed characters
63 				int charsToRead = (amount + markerOffset) - queue.Count;
64 				int c;
65 
66 				while (charsToRead > 0)
67 				{
68 					// Read a few characters
69 					c = input.Read(buf, 0, BUF_SIZE);
70 					for (int i = 0; i < c; i++)
71 					{
72 						// Append the next character
73 						queue.Add(buf[i]);
74 					}
75 					if (c < BUF_SIZE)
76 					{
77 						while ((charsToRead-- > 0) && (queue.Count < BUF_SIZE))
78 						{
79 							queue.Add(CharScanner.EOF_CHAR);
80 						}
81 						break;
82 					}
83 					charsToRead -= c;
84 				}
85 			}
86 			catch (IOException io)
87 			{
88 				throw new CharStreamIOException(io);
89 			}
90 		}
91 	}
92 }