1 /* 2 * [The "BSD licence"] 3 * Copyright (c) 2005-2008 Terence Parr 4 * All rights reserved. 5 * 6 * Conversion to C#: 7 * Copyright (c) 2008-2009 Sam Harwell, Pixel Mine, Inc. 8 * All rights reserved. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. The name of the author may not be used to endorse or promote products 19 * derived from this software without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 24 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33 namespace Antlr.Runtime.Tree 34 { 35 using System.Collections.Generic; 36 using IList = System.Collections.IList; 37 38 /** <summary> 39 * A generic list of elements tracked in an alternative to be used in 40 * a -> rewrite rule. We need to subclass to fill in the next() method, 41 * which returns either an AST node wrapped around a token payload or 42 * an existing subtree. 43 * </summary> 44 * 45 * <remarks> 46 * Once you start next()ing, do not try to add more elements. It will 47 * break the cursor tracking I believe. 48 * 49 * TODO: add mechanism to detect/puke on modification after reading from stream 50 * </remarks> 51 * 52 * <see cref="RewriteRuleSubtreeStream"/> 53 * <see cref="RewriteRuleTokenStream"/> 54 */ 55 [System.Serializable] 56 public abstract class RewriteRuleElementStream 57 { 58 /** <summary> 59 * Cursor 0..n-1. If singleElement!=null, cursor is 0 until you next(), 60 * which bumps it to 1 meaning no more elements. 61 * </summary> 62 */ 63 protected int cursor = 0; 64 65 /** <summary>Track single elements w/o creating a list. Upon 2nd add, alloc list */ 66 protected object singleElement; 67 68 /** <summary>The list of tokens or subtrees we are tracking */ 69 protected IList elements; 70 71 /** <summary>Once a node / subtree has been used in a stream, it must be dup'd 72 * from then on. Streams are reset after subrules so that the streams 73 * can be reused in future subrules. So, reset must set a dirty bit. 74 * If dirty, then next() always returns a dup.</summary> 75 */ 76 protected bool dirty = false; 77 78 /** <summary>The element or stream description; usually has name of the token or 79 * rule reference that this list tracks. Can include rulename too, but 80 * the exception would track that info. 81 */ 82 protected string elementDescription; 83 protected ITreeAdaptor adaptor; 84 85 public RewriteRuleElementStream( ITreeAdaptor adaptor, string elementDescription ) 86 { 87 this.elementDescription = elementDescription; 88 this.adaptor = adaptor; 89 } 90 91 /** <summary>Create a stream with one element</summary> */ 92 public RewriteRuleElementStream( ITreeAdaptor adaptor, string elementDescription, object oneElement ) 93 : this( adaptor, elementDescription ) 94 { 95 Add( oneElement ); 96 } 97 98 /** <summary>Create a stream, but feed off an existing list</summary> */ 99 public RewriteRuleElementStream( ITreeAdaptor adaptor, string elementDescription, IList elements ) 100 : this( adaptor, elementDescription ) 101 { 102 this.singleElement = null; 103 this.elements = elements; 104 } 105 106 /** <summary> 107 * Reset the condition of this stream so that it appears we have 108 * not consumed any of its elements. Elements themselves are untouched. 109 * Once we reset the stream, any future use will need duplicates. Set 110 * the dirty bit. 111 * </summary> 112 */ 113 public virtual void Reset() 114 { 115 cursor = 0; 116 dirty = true; 117 } 118 119 public virtual void Add( object el ) 120 { 121 //System.out.println("add '"+elementDescription+"' is "+el); 122 if ( el == null ) 123 { 124 return; 125 } 126 if ( elements != null ) 127 { // if in list, just add 128 elements.Add( el ); 129 return; 130 } 131 if ( singleElement == null ) 132 { // no elements yet, track w/o list 133 singleElement = el; 134 return; 135 } 136 // adding 2nd element, move to list 137 elements = new List<object>( 5 ); 138 elements.Add( singleElement ); 139 singleElement = null; 140 elements.Add( el ); 141 } 142 143 /** <summary> 144 * Return the next element in the stream. If out of elements, throw 145 * an exception unless size()==1. If size is 1, then return elements[0]. 146 * Return a duplicate node/subtree if stream is out of elements and 147 * size==1. If we've already used the element, dup (dirty bit set). 148 * </summary> 149 */ 150 public virtual object NextTree() 151 { 152 int n = Count; 153 if ( dirty || ( cursor >= n && n == 1 ) ) 154 { 155 // if out of elements and size is 1, dup 156 object el = NextCore(); 157 return Dup( el ); 158 } 159 // test size above then fetch 160 object el2 = NextCore(); 161 return el2; 162 } 163 164 /** <summary> 165 * Do the work of getting the next element, making sure that it's 166 * a tree node or subtree. Deal with the optimization of single- 167 * element list versus list of size > 1. Throw an exception 168 * if the stream is empty or we're out of elements and size>1. 169 * protected so you can override in a subclass if necessary. 170 * </summary> 171 */ 172 protected virtual object NextCore() 173 { 174 int n = Count; 175 if ( n == 0 ) 176 { 177 throw new RewriteEmptyStreamException( elementDescription ); 178 } 179 if ( cursor >= n ) 180 { // out of elements? 181 if ( n == 1 ) 182 { // if size is 1, it's ok; return and we'll dup 183 return ToTree( singleElement ); 184 } 185 // out of elements and size was not 1, so we can't dup 186 throw new RewriteCardinalityException( elementDescription ); 187 } 188 // we have elements 189 if ( singleElement != null ) 190 { 191 cursor++; // move cursor even for single element list 192 return ToTree( singleElement ); 193 } 194 // must have more than one in list, pull from elements 195 object o = ToTree( elements[cursor] ); 196 cursor++; 197 return o; 198 } 199 200 /** <summary> 201 * When constructing trees, sometimes we need to dup a token or AST 202 * subtree. Dup'ing a token means just creating another AST node 203 * around it. For trees, you must call the adaptor.dupTree() unless 204 * the element is for a tree root; then it must be a node dup. 205 * </summary> 206 */ 207 protected abstract object Dup( object el ); 208 209 /** <summary> 210 * Ensure stream emits trees; tokens must be converted to AST nodes. 211 * AST nodes can be passed through unmolested. 212 * </summary> 213 */ 214 protected virtual object ToTree( object el ) 215 { 216 return el; 217 } 218 219 public virtual bool HasNext 220 { 221 get 222 { 223 return ( singleElement != null && cursor < 1 ) || 224 ( elements != null && cursor < elements.Count ); 225 } 226 } 227 228 public virtual int Count 229 { 230 get 231 { 232 int n = 0; 233 if ( singleElement != null ) 234 { 235 n = 1; 236 } 237 if ( elements != null ) 238 { 239 return elements.Count; 240 } 241 return n; 242 } 243 } 244 245 public virtual string Description 246 { 247 get 248 { 249 return elementDescription; 250 } 251 } 252 } 253 } 254
