/interpreter/tags/at2dist170907/src/edu/vub/at/objects/natives/NATNamespace.java
Java | 220 lines | 112 code | 20 blank | 88 comment | 6 complexity | 8bd492881242be28e458f4127a85b632 MD5 | raw file
1/** 2 * AmbientTalk/2 Project 3 * NATNamespace.java created on 6-sep-2006 at 14:33:41 4 * (c) Programming Technology Lab, 2006 - 2007 5 * Authors: Tom Van Cutsem & Stijn Mostinckx 6 * 7 * Permission is hereby granted, free of charge, to any person 8 * obtaining a copy of this software and associated documentation 9 * files (the "Software"), to deal in the Software without 10 * restriction, including without limitation the rights to use, 11 * copy, modify, merge, publish, distribute, sublicense, and/or 12 * sell copies of the Software, and to permit persons to whom the 13 * Software is furnished to do so, subject to the following 14 * conditions: 15 * 16 * The above copyright notice and this permission notice shall be 17 * included in all copies or substantial portions of the Software. 18 * 19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 20 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES 21 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 22 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT 23 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 24 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 25 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 26 * OTHER DEALINGS IN THE SOFTWARE. 27 */ 28package edu.vub.at.objects.natives; 29 30import edu.vub.at.eval.Evaluator; 31import edu.vub.at.exceptions.InterpreterException; 32import edu.vub.at.exceptions.XDuplicateSlot; 33import edu.vub.at.exceptions.XIOProblem; 34import edu.vub.at.exceptions.XTypeMismatch; 35import edu.vub.at.objects.ATAbstractGrammar; 36import edu.vub.at.objects.ATClosure; 37import edu.vub.at.objects.ATObject; 38import edu.vub.at.objects.ATTable; 39import edu.vub.at.objects.ATTypeTag; 40import edu.vub.at.objects.grammar.ATSymbol; 41import edu.vub.at.objects.mirrors.NativeClosure; 42import edu.vub.at.objects.mirrors.Reflection; 43import edu.vub.at.parser.NATParser; 44 45import java.io.File; 46import java.io.IOException; 47import java.util.LinkedList; 48import java.util.Vector; 49 50/** 51 * Instances of the class NATNamespace represent namespace objects. 52 * 53 * Namespace objects act as regular AmbientTalk objects with the following differences and conventions: 54 * - Behaviourally, a namespace object is mirrored by a mirror whose doesNotUnderstand 55 * method reacts differently from the standard semantics of raising a 'selector not found' exception. 56 * - Structurally, a namespace has the lexical root as its lexical parent and the dynamic root as its dynamic parent. 57 * Furthermore, a namespace object encapsulates an absolute file system path and a relative 'path name'. 58 * The name should correspond to a portion of the tail of the absolute path. 59 * These variables are not visible to AmbientTalk code. 60 * 61 * When a slot is looked up in a namespace NS for a path P (via meta_select) and not found, the namespace object 62 * queries the local file system to see whether the selector corresponds to a directory or file in the 63 * directory P. Either the selector: 64 * - corresponds to a directory, in which case the missing slot is bound to a new namespace object corresponding to the path P/selector 65 * - corresponds to a file named selector.at, in which case: 66 * 1) the slot is temporarily bound to nil 67 * (this is to prevent loops when the code to be evaluated would refer to itself; 68 * it also means there can be no circular dependencies, because referring to a slot still under construction yields nil) 69 * 2) a new object FS (the 'file scope') is created. 70 * This object acts as the local scope for the file and has access to its 'enclosing' namespace via the '~' slot. 71 * Hence, it can refer to other files in the 'current directory' using ~.filename 72 * 3) the code in the file is loaded and evaluated in the context (current=FS, self=FS, super=FS.parent=dynroot) 73 * 4) the result of the evaluated code is bound to the missing slot. 74 * The next time the slot is queried for in the namespace, the value is immediately returned. This prevents 75 * files from being loaded twice. 76 * - does not correspond to any file or directory, resulting in a selector not found exception as usual. 77 * 78 * @author tvcutsem 79 * @author smostinc 80 */ 81public final class NATNamespace extends NATObject { 82 83 private static final String _AT_EXT_ = ".at"; 84 private final File path_; 85 private final String name_; 86 87 /** 88 * A namespace object encapsulates a given absolute path and represents the given relative path. 89 * 90 * @param name the name of this namespace (corresponding to a certain depth to the tail of the absolute path) 91 * @param path an absolute path referring to a local file system directory. 92 */ 93 public NATNamespace(String name, File path) { 94 super(); 95 name_ = name; 96 path_ = path; 97 } 98 99 /** 100 * Private constructor used only for cloning 101 */ 102 private NATNamespace(FieldMap map, 103 Vector state, 104 LinkedList customFields, 105 MethodDictionary methodDict, 106 ATObject dynamicParent, 107 ATObject lexicalParent, 108 byte flags, 109 ATTypeTag[] types, 110 File path, 111 String name) throws InterpreterException { 112 super(map, state, customFields, methodDict, dynamicParent, lexicalParent, flags, types); 113 path_ = path; 114 name_ = name; 115 } 116 117 /** 118 * For a namespace object, doesNotUnderstand triggers the querying of the local file system 119 * to load files corresponding to the missing selector. 120 */ 121 public ATClosure meta_doesNotUnderstand(ATSymbol selector) throws InterpreterException { 122 // first, convert the AmbientTalk name to a Java selector. Java selectors are always valid filenames because 123 // they do not contain special operator characters 124 String javaSelector = Reflection.upSelector(selector); 125 126 // first, try to see if the file exists and corresponds to a directory 127 File dir = new File(path_, javaSelector); 128 if (dir.exists() && dir.isDirectory()) { 129 // create a new namespace object for this directory 130 final NATNamespace childNS = new NATNamespace(name_ + "/" + javaSelector, dir); 131 132 // bind the new child namespace to the selector 133 this.meta_defineField(selector, childNS); 134 return new NativeClosure(this) { 135 public ATObject base_apply(ATTable args) { 136 return childNS; 137 } 138 }; 139 } else { 140 // try to see if a file with extension .at exists corresponding to the selector 141 File src = new File(path_, javaSelector + _AT_EXT_); 142 if (src.exists() && src.isFile()) { 143 144 // bind the missing slot to nil to prevent calling this dNU recursively when evaluating the code in the file 145 this.meta_defineField(selector, OBJNil._INSTANCE_); 146 147 // create a new file scope object for this file 148 NATObject fileScope = createFileScopeFor(this); 149 150 try { 151 // load the code from the file 152 String code = Evaluator.loadContentOfFile(src); 153 154 // construct the proper evaluation context for the code 155 NATContext ctx = new NATContext(fileScope, fileScope); 156 157 // parse and evaluate the code in the proper context and bind its result to the missing slot 158 ATAbstractGrammar source = NATParser.parse(src.getName(), code); 159 final ATObject result = source.meta_eval(ctx); 160 this.impl_invokeMutator(this, selector.asAssignmentSymbol(), NATTable.of(result)); 161 //this.meta_assignField(this, selector, result); 162 163 return new NativeClosure(this) { 164 public ATObject base_apply(ATTable args) { 165 return result; 166 } 167 }; 168 } catch (IOException e) { 169 throw new XIOProblem(e); 170 } 171 172 } else { // neither a matching directory nor a matching file.at were found 173 // perform the default dNU behaviour, which means raising a 'selector not found' exception 174 return super.meta_doesNotUnderstand(selector); 175 } 176 } 177 } 178 179 public NATText meta_print() throws InterpreterException { 180 return NATText.atValue("<ns:"+name_+">"); 181 } 182 183 public static NATObject createFileScopeFor(NATNamespace ns) { 184 NATObject fileScope = new NATObject(); 185 // a fileScope object is empty, save for a reference to its creating namespace 186 try { 187 fileScope.meta_defineField(Evaluator._CURNS_SYM_, ns); 188 } catch (XDuplicateSlot e) { 189 // impossible: the object is empty 190 e.printStackTrace(); 191 } catch (XTypeMismatch e) { 192 // impossible: the given selector is native 193 e.printStackTrace(); 194 } catch (InterpreterException e) { 195 // impossible : call cannot be intercepted : namespaces are not mirages 196 e.printStackTrace(); 197 } 198 return fileScope; 199 } 200 201 protected NATObject createClone(FieldMap map, 202 Vector state, 203 LinkedList customFields, 204 MethodDictionary methodDict, 205 ATObject dynamicParent, 206 ATObject lexicalParent, 207 byte flags, ATTypeTag[] types) throws InterpreterException { 208 return new NATNamespace(map, 209 state, 210 customFields, 211 methodDict, 212 dynamicParent, 213 lexicalParent, 214 flags, 215 types, 216 path_, 217 name_); 218 } 219 220}