kdelibs/kjs/lookup.h

// -*- c-basic-offset: 2 -*-
/*
 *  This file is part of the KDE libraries
 *  Copyright (C) 1999-2000 Harri Porten (porten@kde.org)
 *  Copyright (C) 2003 Apple Computer, Inc.
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

#ifndef _KJSLOOKUP_H_
#define _KJSLOOKUP_H_

#include "JSVariableObject.h"
#include "interpreter.h"
#include "identifier.h"
#include "object.h"
#include <stdio.h>

namespace KJS {
  class FunctionPrototype;

  /**
   * An entry in a hash table.
   */
  struct KJS_EXPORT HashEntry {
    /**
     * s is the key (e.g. a property name)
     */
    const char *s;

    /**
     * value is the result value (usually an enum value)
     */
    int value;
    /**
     * attr is a set for flags (e.g. the property flags, see object.h)
     */
    short int attr;
    /**
     * params is another number. For property hashtables, it is used to
     * denote the number of argument of the function
     */
    short int params;
    /**
     * next is the pointer to the next entry for the same hash value
     */
    const HashEntry *next;
  };

  /**
   * A hash table
   * Usually the hashtable is generated by the create_hash_table script, from a .table file.
   *
   * The implementation uses an array of entries, "size" is the total size of that array.
   * The entries between 0 and hashSize-1 are the entry points
   * for each hash value, and the entries between hashSize and size-1
   * are the overflow entries for the hash values that need one.
   * The "next" pointer of the entry links entry points to overflow entries,
   * and links overflow entries between them.
   */
  struct HashTable {
    /**
     * type is a version number. Currently always 2
     */
    int type;
    /**
     * size is the total number of entries in the hashtable, including the null entries,
     * i.e. the size of the "entries" array.
     * Used to iterate over all entries in the table
     */
    int size;
    /**
     * pointer to the array of entries
     * Mind that some entries in the array are null (0,0,0,0).
     */
    const HashEntry *entries;
    /**
     * the maximum value for the hash. Always smaller than size.
     */
    int hashSize;
  };

  /**
   * @short Fast keyword lookup.
   */
  class KJS_EXPORT Lookup {
  public:
    /**
     * Find an entry in the table, and return its value (i.e. the value field of HashEntry)
     */
    static int find(const struct HashTable *table, const Identifier &s);
    static int find(const struct HashTable *table,
                    const UChar *c, unsigned int len);


    /**
     * Find an entry in the table, and return the entry
     * This variant gives access to the other attributes of the entry,
     * especially the attr field.
     */
    static const HashEntry* findEntry(const struct HashTable *table,
                                      const Identifier &s);

  };

  class ExecState;
    /**
   * @internal
   * Helper for getStaticFunctionSlot and getStaticPropertySlot
   */
  template <class FuncImp>
  inline JSValue *staticFunctionGetter(ExecState *exec, JSObject * /*originalObject*/, const Identifier& propertyName, const PropertySlot& slot)
  {
      // Look for cached value in dynamic map of properties (in JSObject)
      JSObject *thisObj = slot.slotBase();
      JSValue *cachedVal = thisObj->getDirect(propertyName);
      if (cachedVal)
        return cachedVal;

      const HashEntry *entry = slot.staticEntry();
      JSValue *val = new FuncImp(exec, entry->value, entry->params, propertyName);
      thisObj->putDirect(propertyName, val, entry->attr);
      return val;
  }

  /**
   * @internal
   * Helper for getStaticValueSlot and getStaticPropertySlot
   */
  template <class ThisImp>
  inline JSValue *staticValueGetter(ExecState *exec, JSObject*, const Identifier&, const PropertySlot& slot)
  {
      ThisImp* thisObj = static_cast<ThisImp*>(slot.slotBase());
      const HashEntry* entry = slot.staticEntry();
      return thisObj->getValueProperty(exec, entry->value);
  }

  /**
   * Helper method for property lookups
   *
   * This method does it all (looking in the hashtable, checking for function
   * overrides, creating the function or retrieving from cache, calling
   * getValueProperty in case of a non-function property, forwarding to parent if
   * unknown property).
   *
   * Template arguments:
   * @param FuncImp the class which implements this object's functions
   * @param ThisImp the class of "this". It must implement the getValueProperty(exec,token) method,
   * for non-function properties.
   * @param ParentImp the class of the parent, to propagate the lookup.
   *
   * Method arguments:
   * @param exec execution state, as usual
   * @param propertyName the property we're looking for
   * @param table the static hashtable for this class
   * @param thisObj "this"
   */
  template <class FuncImp, class ThisImp, class ParentImp>
  inline bool getStaticPropertySlot(ExecState *exec, const HashTable* table,
                                    ThisImp* thisObj, const Identifier& propertyName, PropertySlot& slot)
  {
    const HashEntry* entry = Lookup::findEntry(table, propertyName);

    if (!entry) // not found, forward to parent
      return thisObj->ParentImp::getOwnPropertySlot(exec, propertyName, slot);

    if (entry->attr & Function)
      slot.setStaticEntry(thisObj, entry, staticFunctionGetter<FuncImp>);
    else
      slot.setStaticEntry(thisObj, entry, staticValueGetter<ThisImp>);

    return true;
  }

  /**
   * Simplified version of getStaticPropertySlot in case there are only functions.
   * Using this instead of getStaticPropertySlot allows 'this' to avoid implementing
   * a dummy getValueProperty.
   */
  template <class FuncImp, class ParentImp>
  inline bool getStaticFunctionSlot(ExecState *exec, const HashTable *table,
                                    JSObject* thisObj, const Identifier& propertyName, PropertySlot& slot)
  {
    const HashEntry* entry = Lookup::findEntry(table, propertyName);

    if (!entry) // not found, forward to parent
      return static_cast<ParentImp *>(thisObj)->ParentImp::getOwnPropertySlot(exec, propertyName, slot);

    assert(entry->attr & Function);

    slot.setStaticEntry(thisObj, entry, staticFunctionGetter<FuncImp>);
    return true;
  }

  /**
   * Simplified version of getStaticPropertySlot in case there are no functions, only "values".
   * Using this instead of getStaticPropertySlot removes the need for a FuncImp class.
   */
  template <class ThisImp, class ParentImp>
  inline bool getStaticValueSlot(ExecState *exec, const HashTable* table,
                                 ThisImp* thisObj, const Identifier &propertyName, PropertySlot& slot)
  {
    const HashEntry* entry = Lookup::findEntry(table, propertyName);

    if (!entry) // not found, forward to parent
      return thisObj->ParentImp::getOwnPropertySlot(exec, propertyName, slot);

    assert(!(entry->attr & Function));

    slot.setStaticEntry(thisObj, entry, staticValueGetter<ThisImp>);
    return true;
  }

  /**
   * This one is for "put".
   * It looks up a hash entry for the property to be set.  If an entry
   * is found it sets the value and returns true, else it returns false.
   */
  template <class ThisImp>
  inline bool lookupPut(ExecState* exec, const Identifier &propertyName,
                        JSValue* value, int attr,
                        const HashTable* table, ThisImp* thisObj)
  {
    const HashEntry* entry = Lookup::findEntry(table, propertyName);
    if (!entry)
      return false;

    if (entry->attr & Function) // function: put as override property
      thisObj->JSObject::put(exec, propertyName, value, attr);
    else if (entry->attr & ReadOnly) // readonly! Can't put!
#ifdef KJS_VERBOSE
      fprintf(stderr,"WARNING: Attempt to change value of readonly property '%s'\n",propertyName.ascii());
#else
      ; // do nothing
#endif
    else
      thisObj->putValueProperty(exec, entry->value, value, attr);

    return true;
  }

  /**
   * This one is for "put".
   * It calls lookupPut<ThisImp>() to set the value.  If that call
   * returns false (meaning no entry in the hash table was found),
   * then it calls put() on the ParentImp class.
   */
  template <class ThisImp, class ParentImp>
  inline void lookupPut(ExecState* exec, const Identifier &propertyName,
                        JSValue* value, int attr,
                        const HashTable* table, ThisImp* thisObj)
  {
    if (!lookupPut<ThisImp>(exec, propertyName, value, attr, table, thisObj))
      thisObj->ParentImp::put(exec, propertyName, value, attr); // not found: forward to parent
  }
} // namespace

#if COMPILER(GCC)
// Work around a bug in GCC 4.1. The original code was
//	#if !COMPILER(GCC)
//	#define KJS_GCC_ROOT_NS_HACK ::
//	#else
//	#define KJS_GCC_ROOT_NS_HACK
//	#endif
// We separate use and declaration here; the define KJS_OBJECTCAHE_IN_KJS
// distinguishes if the cache is in KJS (value 1) or not (value 0).
#define KJS_OBJECTCACHE_IN_KJS (0)
#define KJS_CACHEGLOBALOBJECT_NS
#define KJS_CACHEGLOBALOBJECT_NS_USE ::
#else
#if COMPILER(SUNPRO)
// SunPro puts the whole thing in namespace KJS::, no linking problems.
#define KJS_OBJECTCACHE_IN_KJS (1)
#define KJS_CACHEGLOBALOBJECT_NS KJS::
#define KJS_CACHEGLOBALOBJECT_NS_USE KJS::
#else
// All other non-Studio, non-GCC compilers are forced to put the
// object cache outside the KJS namespace, and don't use the GCC
// hack to do so.
#define KJS_OBJECTCACHE_IN_KJS (0)
#define KJS_CACHEGLOBALOBJECT_NS ::
#define KJS_CACHEGLOBALOBJECT_NS_USE ::
#endif
#endif

#if KJS_OBJECTCACHE_IN_KJS
namespace KJS {
#endif
/*
 * The template method below can't be in the KJS namespace because it's used in
 * KJS_DEFINE_PROPERTY which can be used outside of the KJS namespace. It can 
 * be moved back when a gcc with a fix for
 *     http://gcc.gnu.org/bugzilla/show_bug.cgi?id=8355 
 * is mainstream enough.
 *
 * This note applies only to GCC and other non-Studio12 compilers. Studio12
 * does support having this template in namespace KJS. The macro
 * KJS_OBJECTCACHE_IN_KJS expands to 1 when it is safe to put the template
 * in the KJS namespace.
 */

/**
 * This template method retrieves or create an object that is unique
 * (for a given interpreter) The first time this is called (for a given
 * property name), the Object will be constructed, and set as a property
 * of the interpreter's global object. Later calls will simply retrieve
 * that cached object. Note that the object constructor must take 1 argument, exec.
 */
template <class ClassCtor>
inline KJS::JSObject *cacheGlobalObject(KJS::ExecState *exec, const KJS::Identifier &propertyName)
{
  KJS::JSObject *globalObject = static_cast<KJS::JSObject *>(exec->lexicalInterpreter()->globalObject());
  KJS::JSValue *obj = globalObject->getDirect(propertyName);
  if (obj) {
    assert(obj->isObject());
    return static_cast<KJS::JSObject *>(obj);
  }
  KJS::JSObject *newObject = new ClassCtor(exec);
  globalObject->put(exec, propertyName, newObject, KJS::Internal | KJS::DontEnum);
  return newObject;
}
#if KJS_OBJECTCACHE_IN_KJS
}
#endif

/**
 * Helpers to define prototype objects (each of which simply implements
 * the functions for a type of objects).
 * Sorry for this not being very readable, but it actually saves much copy-n-paste.
 * ParentProto is not our base class, it's the object we use as fallback.
 * The reason for this is that there should only be ONE DOMNode.hasAttributes (e.g.),
 * not one in each derived class. So we link the (unique) prototypes between them.
 *
 * Using those macros is very simple: define the hashtable (e.g. "DOMNodeProtoTable"), then
 * KJS_DEFINE_PROTOTYPE(DOMNodeProto)
 * KJS_IMPLEMENT_PROTOFUNC(DOMNodeProtoFunc)
 * KJS_IMPLEMENT_PROTOTYPE("DOMNode", DOMNodeProto,DOMNodeProtoFunc)
 * and use DOMNodeProto::self(exec) as prototype in the DOMNode constructor.
 * If the prototype has a "parent prototype", e.g. DOMElementProto falls back on DOMNodeProto,
 * then the first line will use KJS_DEFINE_PROTOTYPE_WITH_PROTOTYPE, with DOMNodeProto as the second argument.
 */

// These macros assume that a prototype's only properties are functions
#define KJS_DEFINE_PROTOTYPE(ClassProto) \
  class ClassProto : public KJS::JSObject { \
    friend KJS::JSObject* KJS_CACHEGLOBALOBJECT_NS cacheGlobalObject<ClassProto>(KJS::ExecState *exec, const KJS::Identifier &propertyName); \
  public: \
    static KJS::JSObject *self(KJS::ExecState *exec); \
    virtual const KJS::ClassInfo *classInfo() const { return &info; } \
    static const KJS::ClassInfo info; \
    bool getOwnPropertySlot(KJS::ExecState *, const KJS::Identifier&, KJS::PropertySlot&); \
    using JSObject::getOwnPropertySlot; \
  protected: \
    ClassProto(KJS::ExecState *exec);\
    static KJS::Identifier* s_name;           \
    static KJS::Identifier* name(); \
  };

#define KJS_IMPLEMENT_PROTOTYPE_IMP(ClassName,ClassProto,ClassFunc,ClassProtoProto) \
    const KJS::ClassInfo ClassProto::info = { ClassName, 0, &ClassProto##Table, 0 }; \
    KJS::Identifier* ClassProto::s_name = 0; \
    KJS::JSObject *ClassProto::self(KJS::ExecState *exec) \
    { \
      return KJS_CACHEGLOBALOBJECT_NS cacheGlobalObject<ClassProto>(exec, *name()); \
    } \
    bool ClassProto::getOwnPropertySlot(KJS::ExecState *exec, const KJS::Identifier& propertyName, KJS::PropertySlot& slot) \
    { \
      return KJS::getStaticFunctionSlot<ClassFunc, KJS::JSObject>(exec, &ClassProto##Table, this, propertyName, slot); \
    } \
    KJS::Identifier* ClassProto::name() \
    { \
      if (!s_name) s_name = new KJS::Identifier("[[" ClassName ".prototype]]"); \
      return s_name; \
    }\
    ClassProto::ClassProto(KJS::ExecState *exec): KJS::JSObject(ClassProtoProto::self(exec))

#define KJS_IMPLEMENT_PROTOTYPE(ClassName,ClassProto,ClassFunc,ClassProtoProto) \
    KJS_IMPLEMENT_PROTOTYPE_IMP(ClassName,ClassProto,ClassFunc,ClassProtoProto) {}
    
#define KJS_IMPLEMENT_PROTOFUNC(ClassFunc) \
  class ClassFunc : public KJS::InternalFunctionImp {   \
  public: \
    ClassFunc(KJS::ExecState* exec, int i, int len, const KJS::Identifier& name) \
      : InternalFunctionImp(static_cast<KJS::FunctionPrototype*>(exec->lexicalInterpreter()->builtinFunctionPrototype()), name) \
      , id(i) \
    { \
       put(exec, exec->propertyNames().length, KJS::jsNumber(len), KJS::DontDelete|KJS::ReadOnly|KJS::DontEnum); \
    } \
    /* Macro user needs to implement the callAsFunction function. */ \
      virtual KJS::JSValue *callAsFunction(KJS::ExecState *exec, KJS::JSObject *thisObj, const KJS::List &args); \
  private: \
    int id; \
  };

/*
 * List of things to do when porting an objectimp to the 'static hashtable' mechanism:
 * - write the hashtable source, between @begin and @end
 * - add a rule to build the .lut.h
 * - include the .lut.h
 * - mention the table in the classinfo (add a classinfo if necessary)
 * - write/update the class enum (for the tokens)
 * - turn get() into getValueProperty(), put() into putValueProperty(), using a switch and removing funcs
 * - write get() and/or put() using a template method
 * - cleanup old stuff (e.g. hasProperty)
 * - compile, test, commit ;)
 */


#endif