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com.lutris.util
Class BMByteSearch
java.lang.Objectcom.lutris.util.BMByteSearch
- public class BMByteSearch
- extends java.lang.Object
Implements the Boyer-Moore pattern matching algorithm for a given byte pattern. This object implements searches on signed byte arrays. The algorithm was obtained from "Computer Algorithms - Introduction to Design and Analysis, Second Edition" by Sara Baase.
| Field Summary | |
private int[] |
charJump
Table of jump distances for each mismatched character in the alphabet for a given search pattern. |
private int |
m
The length of the search pattern. |
private int[] |
matchJump
Table of partial suffix match jump distances for a given pattern. |
private byte[] |
P
Byte array, beginning at index 1 (for algorithmic convenience), that contains the intended search pattern data. |
| Constructor Summary | |
BMByteSearch(byte[] pattern)
Creates a precomputed Boyer-Moore byte string search object from the given pattern. |
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BMByteSearch(byte[] pattern,
int offset,
int length)
Creates a precomputed Boyer-Moore byte string search object from a portion of the given pattern array. |
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BMByteSearch(java.lang.String pattern)
Creates a precomputed Boyer-Moore byte string search object from the given pattern. |
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| Method Summary | |
private void |
computeJumps()
Initializes the per-character jump table charJump
as specified by the Boyer-Moore algorithm. |
private void |
computeMatchJumps()
Computes a partial-match jump table that skips over partially matching suffixes. |
private void |
genPatternFromByteArray(byte[] bytes,
int off,
int length)
Generates the pattern byte string P from a portion
of another byte string. |
private void |
genPatternFromCharArray(char[] chars)
Generates the pattern byte string P from a character
array. |
int |
getPatternLength()
Returns the length of the pattern for this searcher. |
private static int |
max(int i1,
int i2)
Compares two integers and returns the greater value. |
private static int |
min(int i1,
int i2)
Compares two integers and returns the lesser value. |
int |
search(byte[] byteString)
Search for the previously pre-compiled pattern string in an array of bytes. |
int |
search(byte[] byteString,
int offset,
int length)
Search for the previously pre-compiled pattern string in an array of bytes. |
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Field Detail |
P
private byte[] P
- Byte array, beginning at index 1 (for algorithmic convenience),
that contains the intended search pattern data.
m
private int m
- The length of the search pattern.
charJump
private int[] charJump
- Table of jump distances for each mismatched character in the
alphabet for a given search pattern. Must be recomputed for
each new pattern.
matchJump
private int[] matchJump
- Table of partial suffix match jump distances for a given pattern.
Must be recomputed for each new pattern.
| Constructor Detail |
BMByteSearch
public BMByteSearch(java.lang.String pattern)
- Creates a precomputed Boyer-Moore byte string search object
from the given pattern. The unicode characters in
patternare truncated if greater than 255, and converted in twos-complement fashion, to appropriate negative byte values, if necessary. This method is provided as a convenience for searching for patterns within 8 bit byte strings composed of character data.
BMByteSearch
public BMByteSearch(byte[] pattern)
- Creates a precomputed Boyer-Moore byte string search object
from the given pattern.
BMByteSearch
public BMByteSearch(byte[] pattern,
int offset,
int length)
- Creates a precomputed Boyer-Moore byte string search object
from a portion of the given pattern array.
| Method Detail |
min
private static final int min(int i1,
int i2)
- Compares two integers and returns the lesser value.
max
private static final int max(int i1,
int i2)
- Compares two integers and returns the greater value.
genPatternFromByteArray
private final void genPatternFromByteArray(byte[] bytes,
int off,
int length)
- Generates the pattern byte string
Pfrom a portion of another byte string.
genPatternFromCharArray
private final void genPatternFromCharArray(char[] chars)
- Generates the pattern byte string
Pfrom a character array. The signed unicode characters are truncated to 8 bits, and converted into signed byte values. Characters between 128 and 255 are converted to their signed negative counterpart in twos-complement fashion by subtracting 256.
computeJumps
private final void computeJumps()
- Initializes the per-character jump table
charJumpas specified by the Boyer-Moore algorithm.
computeMatchJumps
private void computeMatchJumps()
- Computes a partial-match jump table that skips over
partially matching suffixes.
getPatternLength
public int getPatternLength()
- Returns the length of the pattern for this searcher.
search
public int search(byte[] byteString)
- Search for the previously pre-compiled pattern string in an
array of bytes. This method uses the Boyer-Moore pattern
search algorithm.
search
public int search(byte[] byteString,
int offset,
int length)
- Search for the previously pre-compiled pattern string in an
array of bytes. This method uses the Boyer-Moore pattern
search algorithm.
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DETAIL: FIELD | CONSTR | METHOD | ||||||||