/*
* @(#)Format.java 1.40 02/08/21
*
* Copyright (c) 1996-2002 Sun Microsystems, Inc. All rights reserved.
*/
package javax.media;
import java.lang.Class;
/**
* A <code>Format</code> abstracts an exact media format.
* It carries no encoding-specific parameters
* or timing information global to the presentation.
* <p>
* <h3> Comparing different formats </h3>
* Not all of the attributes in a <code>Format</code> object have to be specified.
* This enables selected attributes to be specified, making it possible to
* locate a supported <CODE>Format</CODE> that meets certain requirements without needing to
* find an exact match.
* <p>
* Two methods are provided for comparing <code>Formats</code>.
* The <code>equals</code> method returns <CODE>true</CODE> if two <CODE>Format</CODE>
* objects are exactly the same--they're the same type and all of their attributes are the
* same. The <code>matches</code> method relaxes the comparison, comparing
* only the attributes that are explicitly specified in the <CODE>Format</CODE> you are comparing.
* @since JMF 2.0
*/
public class Format implements java.lang.Cloneable, java.io.Serializable {
public static final int NOT_SPECIFIED = -1;
public static final int TRUE = 1;
public static final int FALSE = 0;
protected String encoding;
/**
* The data object required by the <CODE>Format</CODE> is an integer array.
*/
public static final Class intArray = (new int[0]).getClass();
/**
* The data object required by the <CODE>Format</CODE> is a short array.
*/
public static final Class shortArray = (new short[0]).getClass();
/**
* The data object required by the <CODE>Format</CODE> is a byte array.
*/
public static final Class byteArray = (new byte[0]).getClass();
/**
* The data object required by the <CODE>Format</CODE> is an array of <CODE>Format</CODE> objects.
*/
public static final Class formatArray = (new Format[0]).getClass();
protected Class dataType = byteArray;
protected Class clz = getClass(); // Cache the to optimize on
// equals, matches & intersect.
private long encodingCode = 0;
/**
* Constructs a <CODE>Format</CODE> that has the specified encoding type.
* @param encoding A <CODE>String</CODE> that contains the encoding
* type of the <CODE>Format</CODE> to be constructed.
*/
public Format(String encoding) {
this.encoding = encoding;
}
/**
* Constructs a <CODE>Format</CODE> that has the specified encoding and data types.
* @param encoding A <CODE>String</CODE> that contains the encoding
* type of the <CODE>Format</CODE> to be constructed.
* @param dataType The type of data object required by the <CODE>Format</CODE> to be constructed,
* such as:
* <CODE>byteArray</CODE>, <CODE>intArray</CODE>, or <CODE>shortArray</CODE>.
* For example, for a byte array the data type would be "<CODE>Format.byteArray</CODE>".
*/
public Format(String encoding, Class dataType) {
this(encoding);
this.dataType = dataType;
}
/**
* Gets the uniquely-qualified encoding name for this <CODE>Format</CODE>.
* <p>
* In the reference implementation of JMF, these strings follow the QuickTime
* codec strings.
*
* @return The encoding of the <CODE>Format</CODE>.
*/
public String getEncoding() {
return encoding;
}
/**
* Gets the type of the data that this <CODE>Format</CODE> requires.
* For example, for byte array it returns "<CODE>byte[].class</CODE>".
* @return The data type of this <CODE>Format</CODE>.
*/
public Class getDataType() {
return dataType;
}
/**
* Checks whether or not the specified <CODE>Format</CODE> is the same as this <CODE>Format</CODE>.
* To be equal, the two <CODE>Formats</CODE> must be of the same type and all of their attributes must be the same.
* @param format The <CODE>Format</CODE> to compare with this one.
* @return <CODE>true</CODE> if the specified <CODE>Format</CODE> is the same as this one, <CODE>false</CODE> if it is not.
*/
public boolean equals(Object format) {
if (format == null || clz != ((Format)format).clz)
return false;
String otherEncoding = ((Format)format).encoding;
Class otherType = ((Format)format).dataType;
return (dataType == otherType) &&
(encoding == otherEncoding ||
((encoding != null && otherEncoding != null) &&
isSameEncoding((Format)format)));
}
/**
* Checks whether or not the specified <CODE>Format</CODE> <EM>matches</EM> this <CODE>Format</CODE>.
* Matches only compares the attributes that are defined in the specified <CODE>Format</CODE>,
* unspecified attributes are ignored.
* <p>
* The two <CODE>Format</CODE> objects do not have to be of the same class to
* match. For example, if "A" are "B" are being compared, a
* match is possible if "A" is derived from "B"
* or "B" is derived from "A". (The compared attributes must still match, or <CODE>matches</CODE> fails.)
* @param format The <CODE>Format</CODE> to compare with this one.
* @return <CODE>true</CODE> if the specified <CODE>Format</CODE> matches this one, <CODE>false</CODE> if it does not.
*/
public boolean matches(Format format) {
if( format == null) return false;
return (format.encoding == null || encoding == null ||
isSameEncoding(format)) &&
(format.dataType == null || dataType == null ||
format.dataType == dataType) &&
(clz.isAssignableFrom(format.clz) ||
format.clz.isAssignableFrom(clz));
}
/**
* Intersects the attributes of this format and the specified format to create
* a new <CODE>Format</code> object. The two objects being intersected should either be of the
* same type or one should be a subclass of the other. The resulting object will be
* the same type as the subclass. <P>
* Common attributes are intersected as follows: If both objects have NOT_SPECIFIED
* values for an attribute, the result will also have a NOT_SPECIFIED value. If one
* of them has a NOT_SPECIFIED value then the result will have the value that is
* specified in the other object. If both objects have specified values then the value
* in this object will be used. <P>
* Attributes that are specific to the subclass will be carried forward to the result.
* @param other The <CODE>Format</CODE> object to intersect with this
* <CODE>Format</CODE>.
* @return A <CODE>Format</CODE> object
* with its attributes set to those attributes common to both <CODE>Format</CODE> objects.
* @see #matches
*/
public Format intersects(Format other) {
Format res;
if (clz.isAssignableFrom(other.clz))
res = (Format)other.clone();
else if (other.clz.isAssignableFrom(clz))
res = (Format)clone();
else
return null;
if (res.encoding == null)
res.encoding = (encoding != null ? encoding : other.encoding);
if (res.dataType == null)
res.dataType = (dataType != null ? dataType : other.dataType);
return res;
}
/**
* Checks if the encodings of both format objects are the same. Its
* faster than calling String.equalsIgnoreCase to compare the two
* encodings.
* @return true if the encodings are the same, false otherwise.
*/
public boolean isSameEncoding(Format other) {
if (encoding == null || other == null || other.encoding == null)
return false;
// Quick checks
if (encoding == other.encoding)
return true;
if (encodingCode > 0 && other.encodingCode > 0)
return encodingCode == other.encodingCode;
// Works faster only for shorter strings of 10 chars or less.
if (encoding.length() > 10)
return encoding.equalsIgnoreCase(other.encoding);
if (encodingCode == 0) {
encodingCode = getEncodingCode(encoding);
}
// If the encoding code cannot be computed (out of bounds chars)
// or in the off chance that its all spaces.
if (encodingCode <= 0)
return encoding.equalsIgnoreCase(other.encoding);
if (other.encodingCode == 0)
return other.isSameEncoding(this);
else
return encodingCode == other.encodingCode;
}
/**
* Checks if the encoding of this format is same as the parameter. Its
* faster than calling String.equalsIgnoreCase to compare the two
* encodings.
* @return true if the encodings are the same, false otherwise.
*/
public boolean isSameEncoding(String encoding) {
if (this.encoding == null || encoding == null)
return false;
// Quick check
if (this.encoding == encoding)
return true;
// Works faster only for shorter strings of 10 chars or less.
if (this.encoding.length() > 10)
return this.encoding.equalsIgnoreCase(encoding);
// Compute encoding code only once
if (encodingCode == 0) {
encodingCode = getEncodingCode(this.encoding);
}
// If the encoding code cannot be computed (out of bounds chars)
if (encodingCode < 0)
return this.encoding.equalsIgnoreCase(encoding);
long otherEncodingCode = getEncodingCode(encoding);
return encodingCode == otherEncodingCode;
}
private long getEncodingCode(String enc) {
byte chars[] = enc.getBytes();
byte b;
long code = 0;
for (int i = 0; i < enc.length(); i++) {
b = chars[i];
if (b > 96 && b < 123)
b -= 32; // lower to upper
b -= 32;
if (b > 63)
return -1;
code = (code << 6) | (long) b;
}
return code;
}
/**
* Generate a format that's less restrictive than this format but
* contains the basic attributes that will make this resulting format
* useful for format matching.
* @return A <CODE>Format</CODE> that's less restrictive than the
* this format.
*/
public Format relax() {
return (Format)clone();
}
/**
* Creates a clone of this <CODE>Format</CODE>.
* @return A clone of this format.
*/
public Object clone() {
Format f = new Format(encoding);
f.copy(this);
return f;
}
/**
* Copies the attributes from the specified <CODE>Format</CODE> into this <CODE>Format</CODE>.
* @param f The <CODE>Format</CODE> to copy the attributes from.
*/
protected void copy(Format f) {
dataType = f.dataType;
}
/**
* Gets a <CODE>String</CODE> representation of the <CODE>Format</CODE> attributes.
* For example: "PCM, 44.1 KHz, Stereo, Signed".
* @return A <CODE>String</CODE> that describes the <CODE>Format</CODE> attributes.
*/
public String toString() {
return getEncoding();
}
}
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