/*****************************************************************************
* *
* This file is part of the BeanShell Java Scripting distribution. *
* Documentation and updates may be found at http://www.beanshell.org/ *
* *
* Sun Public License Notice: *
* *
* The contents of this file are subject to the Sun Public License Version *
* 1.0 (the "License"); you may not use this file except in compliance with *
* the License. A copy of the License is available at http://www.sun.com *
* *
* The Original Code is BeanShell. The Initial Developer of the Original *
* Code is Pat Niemeyer. Portions created by Pat Niemeyer are Copyright *
* (C) 2000. All Rights Reserved. *
* *
* GNU Public License Notice: *
* *
* Alternatively, the contents of this file may be used under the terms of *
* the GNU Lesser General Public License (the "LGPL"), in which case the *
* provisions of LGPL are applicable instead of those above. If you wish to *
* allow use of your version of this file only under the terms of the LGPL *
* and not to allow others to use your version of this file under the SPL, *
* indicate your decision by deleting the provisions above and replace *
* them with the notice and other provisions required by the LGPL. If you *
* do not delete the provisions above, a recipient may use your version of *
* this file under either the SPL or the LGPL. *
* *
* Patrick Niemeyer ([email protected]) *
* Author of Learning Java, O'Reilly & Associates *
* http://www.pat.net/~pat/ *
* *
*****************************************************************************/
package bsh;
/**
Static routines supporing type comparison and conversion in BeanShell.
The following are notes on type comparison and conversion in BeanShell.
*/
class Types
{
/*
Type conversion identifiers. An ASSIGNMENT allows conversions that would
normally happen on assignment. A CAST performs numeric conversions to smaller
types (as in an explicit Java cast) and things allowed only in variable and array
declarations (e.g. byte b = 42;)
*/
static final int CAST=0, ASSIGNMENT=1;
static final int
JAVA_BASE_ASSIGNABLE = 1,
JAVA_BOX_TYPES_ASSIGABLE = 2,
JAVA_VARARGS_ASSIGNABLE = 3,
BSH_ASSIGNABLE = 4;
static final int
FIRST_ROUND_ASSIGNABLE = JAVA_BASE_ASSIGNABLE,
LAST_ROUND_ASSIGNABLE = BSH_ASSIGNABLE;
/**
Special value that indicates by identity that the result of a cast
operation was a valid cast. This is used by castObject() and
castPrimitive() in the checkOnly mode of operation. This value is a
Primitive type so that it can be returned by castPrimitive.
*/
static Primitive VALID_CAST = new Primitive(1);
static Primitive INVALID_CAST = new Primitive(-1);
/**
Get the Java types of the arguments.
*/
public static Class[] getTypes( Object[] args )
{
if ( args == null )
return new Class[0];
Class[] types = new Class[ args.length ];
for( int i=0; i<args.length; i++ )
{
if ( args[i] == null )
types[i] = null;
else
if ( args[i] instanceof Primitive )
types[i] = ((Primitive)args[i]).getType();
else
types[i] = args[i].getClass();
}
return types;
}
/**
Is the 'from' signature (argument types) assignable to the 'to'
signature (candidate method types)
This method handles the special case of null values in 'to' types
indicating a loose type and matching anything.
*/
/* Should check for strict java here and limit to isJavaAssignable() */
static boolean isSignatureAssignable( Class[] from, Class[] to, int round )
{
if ( round != JAVA_VARARGS_ASSIGNABLE && from.length != to.length )
return false;
switch ( round )
{
case JAVA_BASE_ASSIGNABLE:
for( int i=0; i<from.length; i++ )
if ( !isJavaBaseAssignable( to[i], from[i] ) )
return false;
return true;
case JAVA_BOX_TYPES_ASSIGABLE:
for( int i=0; i<from.length; i++ )
if ( !isJavaBoxTypesAssignable( to[i], from[i] ) )
return false;
return true;
case JAVA_VARARGS_ASSIGNABLE:
return isSignatureVarargsAssignable( from, to );
case BSH_ASSIGNABLE:
for( int i=0; i<from.length; i++ )
if ( !isBshAssignable( to[i], from[i] ) )
return false;
return true;
default:
throw new InterpreterError("bad case");
}
}
/**
* Are the two signatures exactly equal? This is checked for a special
* case in overload resolution.
*/
static boolean areSignaturesEqual(Class[] from, Class[] to)
{
if (from.length != to.length)
return false;
for (int i = 0; i < from.length; i++)
if (from[i] != to[i])
return false;
return true;
}
private static boolean isSignatureVarargsAssignable(
Class[] from, Class[] to )
{
return false;
}
/**
Test if a conversion of the rhsType type to the lhsType type is legal via
standard Java assignment conversion rules (i.e. without a cast).
The rules include Java 5 autoboxing/unboxing.
<p/>
For Java primitive TYPE classes this method takes primitive promotion
into account. The ordinary Class.isAssignableFrom() does not take
primitive promotion conversions into account. Note that Java allows
additional assignments without a cast in combination with variable
declarations and array allocations. Those are handled elsewhere
(maybe should be here with a flag?)
<p/>
This class accepts a null rhsType type indicating that the rhsType was the
value Primitive.NULL and allows it to be assigned to any reference lhsType
type (non primitive).
<p/>
Note that the getAssignableForm() method is the primary bsh method for
checking assignability. It adds additional bsh conversions, etc.
@see #isBshAssignable( Class, Class )
@param lhsType assigning from rhsType to lhsType
@param rhsType assigning from rhsType to lhsType
*/
static boolean isJavaAssignable( Class lhsType, Class rhsType ) {
return isJavaBaseAssignable( lhsType, rhsType )
|| isJavaBoxTypesAssignable( lhsType, rhsType );
}
/**
Is the assignment legal via original Java (up to version 1.4)
assignment rules, not including auto-boxing/unboxing.
@param rhsType may be null to indicate primitive null value
*/
static boolean isJavaBaseAssignable( Class lhsType, Class rhsType )
{
/*
Assignment to loose type, defer to bsh extensions
Note: we could shortcut this here:
if ( lhsType == null ) return true;
rather than forcing another round. It's not strictly a Java issue,
so does it belong here?
*/
if ( lhsType == null )
return false;
// null rhs type corresponds to type of Primitive.NULL
// assignable to any object type
if ( rhsType == null )
return !lhsType.isPrimitive();
if ( lhsType.isPrimitive() && rhsType.isPrimitive() )
{
if ( lhsType == rhsType )
return true;
// handle primitive widening conversions - JLS 5.1.2
if ( (rhsType == Byte.TYPE) &&
(lhsType == Short.TYPE || lhsType == Integer.TYPE
|| lhsType == Long.TYPE || lhsType == Float.TYPE
|| lhsType == Double.TYPE))
return true;
if ( (rhsType == Short.TYPE) &&
(lhsType == Integer.TYPE || lhsType == Long.TYPE ||
lhsType == Float.TYPE || lhsType == Double.TYPE))
return true;
if ((rhsType == Character.TYPE) &&
(lhsType == Integer.TYPE || lhsType == Long.TYPE ||
lhsType == Float.TYPE || lhsType == Double.TYPE))
return true;
if ((rhsType == Integer.TYPE) &&
(lhsType == Long.TYPE || lhsType == Float.TYPE ||
lhsType == Double.TYPE))
return true;
if ((rhsType == Long.TYPE) &&
(lhsType == Float.TYPE || lhsType == Double.TYPE))
return true;
if ((rhsType == Float.TYPE) && (lhsType == Double.TYPE))
return true;
}
else
if ( lhsType.isAssignableFrom(rhsType) )
return true;
return false;
}
/**
Determine if the type is assignable via Java boxing/unboxing rules.
*/
static boolean isJavaBoxTypesAssignable(
Class lhsType, Class rhsType )
{
// Assignment to loose type... defer to bsh extensions
if ( lhsType == null )
return false;
// prim can be boxed and assigned to Object
if ( lhsType == Object.class )
return true;
// prim numeric type can be boxed and assigned to number
if ( lhsType == Number.class
&& rhsType != Character.TYPE
&& rhsType != Boolean.TYPE
)
return true;
// General case prim type to wrapper or vice versa.
// I don't know if this is faster than a flat list of 'if's like above.
// wrapperMap maps both prim to wrapper and wrapper to prim types,
// so this test is symmetric
if ( Primitive.wrapperMap.get( lhsType ) == rhsType )
return true;
return false;
}
/**
Test if a type can be converted to another type via BeanShell
extended syntax rules (a superset of Java conversion rules).
*/
static boolean isBshAssignable( Class toType, Class fromType )
{
try {
return castObject(
toType, fromType, null/*fromValue*/,
ASSIGNMENT, true/*checkOnly*/
) == VALID_CAST;
} catch ( UtilEvalError e ) {
// This should not happen with checkOnly true
throw new InterpreterError("err in cast check: "+e);
}
}
/**
Attempt to cast an object instance to a new type if possible via
BeanShell extended syntax rules. These rules are always a superset of
Java conversion rules. If you wish to impose context sensitive
conversion rules then you must test before calling this method.
<p/>
This method can handle fromValue Primitive types (representing
primitive casts) as well as fromValue object casts requiring interface
generation, etc.
@param toType the class type of the cast result, which may include
primitive types, e.g. Byte.TYPE
@param fromValue an Object or bsh.Primitive primitive value (including
Primitive.NULL or Primitive.VOID )
@see #isBshAssignable( Class, Class )
*/
public static Object castObject(
Object fromValue, Class toType, int operation )
throws UtilEvalError
{
if ( fromValue == null )
throw new InterpreterError("null fromValue");
Class fromType =
fromValue instanceof Primitive ?
((Primitive)fromValue).getType()
: fromValue.getClass();
return castObject(
toType, fromType, fromValue, operation, false/*checkonly*/ );
}
/**
Perform a type conversion or test if a type conversion is possible with
respect to BeanShell extended rules. These rules are always a superset of
the Java language rules, so this method can also perform (but not test)
any Java language assignment or cast conversion.
<p/>
This method can perform the functionality of testing if an assignment
or cast is ultimately possible (with respect to BeanShell) as well as the
functionality of performing the necessary conversion of a value based
on the specified target type. This combined functionality is done for
expediency and could be separated later.
<p/>
Other methods such as isJavaAssignable() should be used to determine the
suitability of an assignment in a fine grained or restrictive way based
on context before calling this method
<p/>
A CAST is stronger than an ASSIGNMENT operation in that it will attempt to
perform primtive operations that cast to a smaller type. e.g. (byte)myLong;
These are used in explicit primitive casts, primitive delclarations and
array declarations. I don't believe there are any object conversions which are
different between ASSIGNMENT and CAST (e.g. scripted object to interface proxy
in bsh is done on assignment as well as cast).
<p/>
This method does not obey strictJava(), you must test first before
using this method if you care. (See #isJavaAssignable()).
<p/>
@param toType the class type of the cast result, which may include
primitive types, e.g. Byte.TYPE. toType may be null to indicate a
loose type assignment (which matches any fromType).
@param fromType is the class type of the value to be cast including
java primitive TYPE classes for primitives.
If fromValue is (or would be) Primitive.NULL then fromType should be null.
@param fromValue an Object or bsh.Primitive primitive value (including
Primitive.NULL or Primitive.VOID )
@param checkOnly If checkOnly is true then fromValue must be null.
FromType is checked for the cast to toType...
If checkOnly is false then fromValue must be non-null
(Primitive.NULL is ok) and the actual cast is performed.
@throws UtilEvalError on invalid assignment (when operation is
assignment ).
@throws UtilTargetError wrapping ClassCastException on cast error
(when operation is cast)
@param operation is Types.CAST or Types.ASSIGNMENT
@see bsh.Primitive.getType()
*/
/*
Notes: This method is currently responsible for auto-boxing/unboxing
conversions... Where does that need to go?
*/
private static Object castObject(
Class toType, Class fromType, Object fromValue,
int operation, boolean checkOnly )
throws UtilEvalError
{
/*
Lots of preconditions checked here...
Once things are running smoothly we might comment these out
(That's what assertions are for).
*/
if ( checkOnly && fromValue != null )
throw new InterpreterError("bad cast params 1");
if ( !checkOnly && fromValue == null )
throw new InterpreterError("bad cast params 2");
if ( fromType == Primitive.class )
throw new InterpreterError("bad from Type, need to unwrap");
if ( fromValue == Primitive.NULL && fromType != null )
throw new InterpreterError("inconsistent args 1");
if ( fromValue == Primitive.VOID && fromType != Void.TYPE )
throw new InterpreterError("inconsistent args 2");
if ( toType == Void.TYPE )
throw new InterpreterError("loose toType should be null");
// assignment to loose type, void type, or exactly same type
if ( toType == null || toType == fromType )
return checkOnly ? VALID_CAST :
fromValue;
// Casting to primitive type
if ( toType.isPrimitive() )
{
if ( fromType == Void.TYPE || fromType == null
|| fromType.isPrimitive() )
{
// Both primitives, do primitive cast
return Primitive.castPrimitive(
toType, fromType, (Primitive)fromValue,
checkOnly, operation );
} else
{
if ( Primitive.isWrapperType( fromType ) )
{
// wrapper to primitive
// Convert value to Primitive and check/cast it.
//Object r = checkOnly ? VALID_CAST :
Class unboxedFromType = Primitive.unboxType( fromType );
Primitive primFromValue;
if ( checkOnly )
primFromValue = null; // must be null in checkOnly
else
primFromValue = (Primitive)Primitive.wrap(
fromValue, unboxedFromType );
return Primitive.castPrimitive(
toType, unboxedFromType, primFromValue,
checkOnly, operation );
} else
{
// Cannot cast from arbitrary object to primitive
if ( checkOnly )
return INVALID_CAST;
else
throw castError( toType, fromType, operation );
}
}
}
// Else, casting to reference type
// Casting from primitive or void (to reference type)
if ( fromType == Void.TYPE || fromType == null
|| fromType.isPrimitive() )
{
// cast from primitive to wrapper type
if ( Primitive.isWrapperType( toType )
&& fromType != Void.TYPE && fromType != null )
{
// primitive to wrapper type
return checkOnly ? VALID_CAST :
Primitive.castWrapper(
Primitive.unboxType(toType),
((Primitive)fromValue).getValue() );
}
// Primitive (not null or void) to Object.class type
if ( toType == Object.class
&& fromType != Void.TYPE && fromType != null )
{
// box it
return checkOnly ? VALID_CAST :
((Primitive)fromValue).getValue();
}
// Primitive to arbitrary object type.
// Allow Primitive.castToType() to handle it as well as cases of
// Primitive.NULL and Primitive.VOID
return Primitive.castPrimitive(
toType, fromType, (Primitive)fromValue, checkOnly, operation );
}
// If type already assignable no cast necessary
// We do this last to allow various errors above to be caught.
// e.g cast Primitive.Void to Object would pass this
if ( toType.isAssignableFrom( fromType ) )
return checkOnly ? VALID_CAST :
fromValue;
// Can we use the proxy mechanism to cast a bsh.This to
// the correct interface?
if ( toType.isInterface()
&& bsh.This.class.isAssignableFrom( fromType )
&& Capabilities.canGenerateInterfaces()
)
return checkOnly ? VALID_CAST :
((bsh.This)fromValue).getInterface( toType );
// Both numeric wrapper types?
// Try numeric style promotion wrapper cast
if ( Primitive.isWrapperType( toType )
&& Primitive.isWrapperType( fromType )
)
return checkOnly ? VALID_CAST :
Primitive.castWrapper( toType, fromValue );
if ( checkOnly )
return INVALID_CAST;
else
throw castError( toType, fromType , operation );
}
/**
Return a UtilEvalError or UtilTargetError wrapping a ClassCastException
describing an illegal assignment or illegal cast, respectively.
*/
static UtilEvalError castError(
Class lhsType, Class rhsType, int operation )
{
return castError(
Reflect.normalizeClassName(lhsType),
Reflect.normalizeClassName(rhsType), operation );
}
static UtilEvalError castError(
String lhs, String rhs, int operation )
{
if ( operation == ASSIGNMENT )
return new UtilEvalError (
"Can't assign " + rhs + " to "+ lhs );
Exception cce = new ClassCastException(
"Cannot cast " + rhs + " to " + lhs );
return new UtilTargetError( cce );
}
}
|