Source Code Cross Referenced for Namespace.java in  » Scripting » Kawa » gnu » mapping » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Scripting » Kawa » gnu.mapping 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        // Copyright (c) 1996-2000, 2001, 2002, 2004  Per M.A. Bothner.
002:        // This is free software;  for terms and warranty disclaimer see ./COPYING.
003:
004:        package gnu.mapping;
005:
006:        import java.util.Hashtable;
007:        import java.io.*;
008:
009:        /** A mapping from strings ("print names") to <code>Symbol</code>s.
010:         * Namespaces are normally named and can be accessed from a global table.
011:         * They correspond to Common Lisp "packages" (which are implemented
012:         * using <code>gnu.kawa.lispexpr.LispPackage</code>,
013:         * which extends <code>Namespace</code>).
014:         * A <code>Namespace</code> is a "weak" mapping in the sense that a
015:         * <code>Symbol</code> can be garbage collected even though it is
016:         * referenced from a <code>Namespace</code>.
017:         * @author	Per Bothner
018:         */
019:
020:        public class Namespace implements  Externalizable, HasNamedParts {
021:            /** Map namepsace names (and nick-names) to Namespaces. */
022:            protected static final Hashtable nsTable = new Hashtable(50);
023:
024:            /** The Namespace with the empty name. */
025:            public static final Namespace EmptyNamespace = getInstance("");
026:
027:            /** Should be interned. */
028:            String name;
029:
030:            protected String prefix = "";
031:
032:            /** Get the name of this Namespace. */
033:            public final String getName() {
034:                return name;
035:            }
036:
037:            /** Set the name of this Namespace. */
038:            public final void setName(String name) {
039:                this .name = name;
040:            }
041:
042:            public Namespace() {
043:                this (64);
044:            }
045:
046:            public Namespace(int capacity) {
047:                log2Size = 4;
048:                while (capacity > (1 << log2Size))
049:                    log2Size++;
050:                capacity = 1 << log2Size;
051:                table = new SymbolRef[capacity];
052:                mask = capacity - 1;
053:            }
054:
055:            public static Namespace getDefault() {
056:                return EmptyNamespace;
057:            }
058:
059:            public static Symbol getDefaultSymbol(String name) {
060:                return EmptyNamespace.getSymbol(name);
061:            }
062:
063:            public static Namespace make(String name) // Needed for Literals.
064:            {
065:                return getInstance(name);
066:            }
067:
068:            public static Namespace getInstance(String name) {
069:                if (name == null)
070:                    name = "";
071:                synchronized (nsTable) {
072:                    Namespace ns = (Namespace) nsTable.get(name);
073:                    if (ns != null)
074:                        return ns;
075:                    ns = new Namespace();
076:                    ns.setName(name.intern());
077:                    nsTable.put(name, ns);
078:                    return ns;
079:                }
080:            }
081:
082:            public static Namespace make(String uri, String prefix) {
083:                if (prefix == null || prefix.length() == 0)
084:                    return getInstance(uri);
085:                String xname = prefix + " -> " + uri;
086:                synchronized (nsTable) {
087:                    Object old = nsTable.get(xname);
088:                    if (old instanceof  Namespace)
089:                        return (Namespace) old;
090:                    Namespace ns = new Namespace();
091:                    ns.setName(uri);
092:                    ns.prefix = prefix;
093:                    nsTable.put(xname, ns);
094:                    return ns;
095:                }
096:            }
097:
098:            /** Create a "placeholder" for a namespace with a known prefix
099:             * but unknown uri.
100:             * @see Symbol#makeWithUnknownNamespace
101:             */
102:            public static Namespace makeUnknownNamespace(String prefix) {
103:                String uri;
104:                if (prefix == null || prefix == "")
105:                    uri = "";
106:                else
107:                    uri = "http://kawa.gnu.org/unknown-namespace/" + prefix;
108:                return Namespace.make(uri, prefix);
109:            }
110:
111:            public Object get(String key) {
112:                return Environment.getCurrent().get(getSymbol(key));
113:            }
114:
115:            public boolean isConstant(String key) {
116:                return false;
117:            }
118:
119:            /** Get a Symbol matching the given name.
120:             * Creates a new Symbol if one is not found.
121:             * Equivalent to Common Lisp's "intern" function.
122:             */
123:            public Symbol getSymbol(String key) {
124:                return lookup(key, key.hashCode(), true);
125:            }
126:
127:            /** Get a Symbol matching the given name.
128:             * Returns null if one is not found.
129:             */
130:            public Symbol lookup(String key) {
131:                return lookup(key, key.hashCode(), false);
132:            }
133:
134:            protected final Symbol lookupInternal(String key, int hash) {
135:                int index = hash & mask;
136:                SymbolRef prev = null;
137:                for (SymbolRef ref = table[index]; ref != null;) {
138:                    SymbolRef next = ref.next;
139:                    Symbol sym = ref.getSymbol();
140:                    if (sym == null) {
141:                        // Weakly referenced object has been collected.
142:                        if (prev == null)
143:                            table[index] = next;
144:                        else
145:                            prev.next = next;
146:                        num_bindings--;
147:                    } else {
148:                        if (sym.getLocalPart().equals(key))
149:                            return sym;
150:                        prev = ref;
151:                    }
152:                    ref = next;
153:                }
154:                return null;
155:            }
156:
157:            public Symbol add(Symbol sym, int hash) {
158:                int index = hash & mask;
159:                SymbolRef ref = new SymbolRef(sym, this );
160:                sym.namespace = this ;
161:                ref.next = table[index];
162:                table[index] = ref;
163:                num_bindings++;
164:                if (num_bindings >= table.length)
165:                    rehash();
166:                return sym;
167:            }
168:
169:            public Symbol lookup(String key, int hash, boolean create) {
170:                synchronized (this ) {
171:                    Symbol sym = lookupInternal(key, hash);
172:                    if (sym != null)
173:                        return sym;
174:
175:                    /*
176:                    // Do we need to synchronize on nsTable as well?  FIXME
177:                    for (NamespaceUse used = imported;  used != null;
178:                         used = used.nextImported)
179:                      {
180:                        el = lookup(key, hash, false);
181:                        if (el != null)
182:                          return el;
183:                      }
184:                     */
185:                    if (create)
186:                        return add(new Symbol(this , key), hash);
187:                    else
188:                        return null;
189:                }
190:            }
191:
192:            public boolean remove(Symbol symbol) {
193:                synchronized (this ) {
194:                    String name = symbol.getLocalPart();
195:                    int hash = name.hashCode();
196:                    int index = hash & mask;
197:                    SymbolRef prev = null;
198:                    SymbolRef ref = table[index];
199:                    while (ref != null) {
200:                        SymbolRef next = ref.next;
201:                        Symbol refsym = ref.getSymbol();
202:                        if (refsym == null || refsym == symbol) {
203:                            if (prev == null)
204:                                table[index] = next;
205:                            else
206:                                prev.next = next;
207:                            num_bindings--;
208:                            if (refsym != null)
209:                                return true;
210:                        } else
211:                            prev = ref;
212:                        ref = next;
213:                    }
214:                    return false;
215:                }
216:            }
217:
218:            protected SymbolRef[] table;
219:            int log2Size;
220:            private int mask;
221:            int num_bindings;
222:
223:            protected void rehash() {
224:                int oldCapacity = table.length;
225:                int newCapacity = 2 * oldCapacity;
226:                int newMask = newCapacity - 1;
227:                int countInserted = 0;
228:                SymbolRef[] oldTable = table;
229:                SymbolRef[] newTable = new SymbolRef[newCapacity];
230:
231:                for (int i = oldCapacity; --i >= 0;) {
232:                    for (SymbolRef ref = oldTable[i]; ref != null;) {
233:                        SymbolRef next = ref.next;
234:                        Symbol sym = ref.getSymbol();
235:                        if (sym != null) {
236:                            String key = sym.getName();
237:                            int hash = key.hashCode();
238:                            int index = hash & newMask;
239:                            countInserted++;
240:                            ref.next = newTable[index];
241:                            newTable[index] = ref;
242:                        }
243:                        ref = next;
244:                    }
245:                }
246:
247:                table = newTable;
248:                log2Size++;
249:                mask = newMask;
250:                num_bindings = countInserted;
251:            }
252:
253:            public void writeExternal(ObjectOutput out) throws IOException {
254:                out.writeObject(getName());
255:                out.writeObject(prefix);
256:            }
257:
258:            public void readExternal(ObjectInput in) throws IOException,
259:                    ClassNotFoundException {
260:                name = ((String) in.readObject()).intern();
261:                prefix = (String) in.readObject();
262:            }
263:
264:            public Object readResolve() throws ObjectStreamException {
265:                String name = getName();
266:                if (name != null) {
267:                    String xname = (prefix == null || prefix.length() == 0 ? name
268:                            : (prefix + " -> " + name));
269:                    Namespace ns = (Namespace) nsTable.get(xname);
270:                    if (ns != null)
271:                        return ns;
272:                    nsTable.put(xname, this );
273:                }
274:                return this ;
275:
276:            }
277:
278:            public String toString() {
279:                return "#,(namespace \"" + name + "\")";
280:            }
281:        }
282:
283:        /** A week reference to a <code>Symbol</code>.
284:         * This is to allow <code>Symbol</code>s to be garbage collected,
285:         * even though they're referenced from a <code>Namespace</code>. */
286:
287:        class SymbolRef
288:        /* #ifdef JAVA2 */
289:        extends java.lang.ref.WeakReference
290:        /* #endif */
291:        {
292:            SymbolRef next;
293:
294:            /* #ifndef JAVA2 */
295:            // Symbol sym;
296:            /* #endif */
297:
298:            /*
299:            String getName ()
300:            {
301:              Symbol sym = getSymbol();
302:              return sym == null ? null : sym.getName();
303:            }
304:             */
305:
306:            SymbolRef(Symbol sym, Namespace ns) {
307:                /* #ifdef JAVA2 */
308:                super (sym);
309:                /* #else */
310:                // this.sym = sym;
311:                /* #endif */
312:            }
313:
314:            Symbol getSymbol() {
315:                /* #ifdef JAVA2 */
316:                return (Symbol) get();
317:                /* #endif */
318:                /* #ifndef JAVA2 */
319:                // return sym;
320:                /* #endif */
321:            }
322:
323:            public String toString() {
324:                return "SymbolRef[" + getSymbol() + "]";
325:            }
326:        }
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