Class MagicNumberFileFilter
- All Implemented Interfaces:
FileFilter,FilenameFilter,Serializable,FileVisitor<Path>,PathMatcher,PathFilter,PathVisitor,IOFileFilter
File filter for matching files containing a "magic number". A magic number
is a unique series of bytes common to all files of a specific file format.
For instance, all Java class files begin with the bytes
0xCAFEBABE.
Using Classic IO
File dir = FileUtils.current();
MagicNumberFileFilter javaClassFileFilter =
MagicNumberFileFilter(new byte[] {(byte) 0xCA, (byte) 0xFE,
(byte) 0xBA, (byte) 0xBE});
String[] javaClassFiles = dir.list(javaClassFileFilter);
for (String javaClassFile : javaClassFiles) {
System.out.println(javaClassFile);
}
Sometimes, such as in the case of TAR files, the magic number will be offset by a certain number of bytes in the file. In the case of TAR archive files, this offset is 257 bytes.
File dir = FileUtils.current();
MagicNumberFileFilter tarFileFilter =
MagicNumberFileFilter("ustar", 257);
String[] tarFiles = dir.list(tarFileFilter);
for (String tarFile : tarFiles) {
System.out.println(tarFile);
}
Using NIO
final Path dir = PathUtils.current();
final AccumulatorPathVisitor visitor = AccumulatorPathVisitor.withLongCounters(MagicNumberFileFilter("ustar", 257));
//
// Walk one dir
Files.walkFileTree(dir, Collections.emptySet(), 1, visitor);
System.out.println(visitor.getPathCounters());
System.out.println(visitor.getFileList());
//
visitor.getPathCounters().reset();
//
// Walk dir tree
Files.walkFileTree(dir, visitor);
System.out.println(visitor.getPathCounters());
System.out.println(visitor.getDirList());
System.out.println(visitor.getFileList());
Deprecating Serialization
Serialization is deprecated and will be removed in 3.0.
Deprecating Serialization
Serialization is deprecated and will be removed in 3.0.
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Field Summary
Fields inherited from interface org.apache.commons.io.filefilter.IOFileFilter
EMPTY_STRING_ARRAY -
Constructor Summary
ConstructorsConstructorDescriptionMagicNumberFileFilter(byte[] magicNumber) Constructs a new MagicNumberFileFilter and associates it with the magic number to test for in files.MagicNumberFileFilter(byte[] magicNumbers, long offset) Constructs a new MagicNumberFileFilter and associates it with the magic number to test for in files and the byte offset location in the file to to look for that magic number.MagicNumberFileFilter(String magicNumber) Constructs a new MagicNumberFileFilter and associates it with the magic number to test for in files.MagicNumberFileFilter(String magicNumber, long offset) Constructs a new MagicNumberFileFilter and associates it with the magic number to test for in files and the byte offset location in the file to to look for that magic number. -
Method Summary
Modifier and TypeMethodDescriptionbooleanAccepts the provided file if the file contains the file filter's magic number at the specified offset.accept(Path file, BasicFileAttributes attributes) Accepts the provided file if the file contains the file filter's magic number at the specified offset.toString()Returns a String representation of the file filter, which includes the magic number bytes and byte offset.Methods inherited from class org.apache.commons.io.filefilter.AbstractFileFilter
accept, handle, postVisitDirectory, preVisitDirectory, visitFile, visitFileFailedMethods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, waitMethods inherited from interface org.apache.commons.io.filefilter.IOFileFilter
and, matches, negate, or
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Constructor Details
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MagicNumberFileFilter
Constructs a new MagicNumberFileFilter and associates it with the magic number to test for in files. This constructor assumes a starting offset of
0.It is important to note that the array is not cloned and that any changes to the magic number array after construction will affect the behavior of this file filter.
MagicNumberFileFilter javaClassFileFilter = MagicNumberFileFilter(new byte[] {(byte) 0xCA, (byte) 0xFE, (byte) 0xBA, (byte) 0xBE});- Parameters:
magicNumber- the magic number to look for in the file.- Throws:
IllegalArgumentException- ifmagicNumberisnull, or contains no bytes.
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MagicNumberFileFilter
Constructs a new MagicNumberFileFilter and associates it with the magic number to test for in files and the byte offset location in the file to to look for that magic number.
MagicNumberFileFilter tarFileFilter = MagicNumberFileFilter(new byte[] {0x75, 0x73, 0x74, 0x61, 0x72}, 257);MagicNumberFileFilter javaClassFileFilter = MagicNumberFileFilter(new byte[] {0xCA, 0xFE, 0xBA, 0xBE}, 0);- Parameters:
magicNumbers- the magic number to look for in the file.offset- the byte offset in the file to start comparing bytes.- Throws:
IllegalArgumentException- ifmagicNumbercontains no bytes, oroffsetis a negative number.
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MagicNumberFileFilter
Constructs a new MagicNumberFileFilter and associates it with the magic number to test for in files. This constructor assumes a starting offset of
Example usage:0.MagicNumberFileFilter xmlFileFilter = MagicNumberFileFilter("<?xml");- Parameters:
magicNumber- the magic number to look for in the file. The string is converted to bytes using the platform default charset.- Throws:
IllegalArgumentException- ifmagicNumberisnullor the empty String.
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MagicNumberFileFilter
Constructs a new MagicNumberFileFilter and associates it with the magic number to test for in files and the byte offset location in the file to to look for that magic number.
MagicNumberFileFilter tarFileFilter = MagicNumberFileFilter("ustar", 257);- Parameters:
magicNumber- the magic number to look for in the file. The string is converted to bytes using the platform default charset.offset- the byte offset in the file to start comparing bytes.- Throws:
IllegalArgumentException- ifmagicNumberis the empty String, oroffsetis a negative number.
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Method Details
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accept
Accepts the provided file if the file contains the file filter's magic number at the specified offset.
If any
IOExceptions occur while reading the file, the file will be rejected.- Specified by:
acceptin interfaceFileFilter- Specified by:
acceptin interfaceIOFileFilter- Overrides:
acceptin classAbstractFileFilter- Parameters:
file- the file to accept or reject.- Returns:
trueif the file contains the filter's magic number at the specified offset,falseotherwise.
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accept
Accepts the provided file if the file contains the file filter's magic number at the specified offset.
If any
IOExceptions occur while reading the file, the file will be rejected.- Specified by:
acceptin interfaceIOFileFilter- Specified by:
acceptin interfacePathFilter- Parameters:
file- the file to accept or reject.attributes- the file's basic attributes (TODO may be null).- Returns:
trueif the file contains the filter's magic number at the specified offset,falseotherwise.- Since:
- 2.9.0
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toString
Returns a String representation of the file filter, which includes the magic number bytes and byte offset.- Overrides:
toStringin classAbstractFileFilter- Returns:
- a String representation of the file filter.
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