org.python.core

Class BaseBytes.ReverseFinder

java.lang.Object

org.python.core.BaseBytes.Finder

org.python.core.BaseBytes.ReverseFinder

Enclosing class:

BaseBytes

protected static class BaseBytes.ReverseFinder
extends BaseBytes.Finder

This class is the complement of BaseBytes.Finder and implements the Boyer-Moore-Horspool Algorithm adapted for right-to-left search for a pattern in byte arrays.

Field Summary

Fields inherited from class org.python.core.BaseBytes.Finder

left, pattern, right, skipTable, text

Constructor Summary

Constructors

Constructor and Description
ReverseFinder(PyBuffer pattern) Construct a ReverseFinder object that may be used (repeatedly) to find matches with the pattern in text (arrays of bytes).

Method Summary

Modifier and Type	Method and Description
protected int[]	calculateSkipTable() This method creates a compressed table of bad-character skips from the pattern for reverse-searching.
int	currIndex() Return the index in the text array where the preceding pattern match ends (one beyond the last character matched), which may also be one beyond the effective end ofthe text.
int	nextIndex() Find the next index in the text array where the pattern starts, but working backwards.

Methods inherited from class org.python.core.BaseBytes.Finder

count, count, count, setText, setText, setText

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ReverseFinder

public ReverseFinder(PyBuffer pattern)

Construct a ReverseFinder object that may be used (repeatedly) to find matches with the pattern in text (arrays of bytes).

Parameters:

pattern - A vew that presents the pattern as an array of bytes

Method Detail

calculateSkipTable

protected int[] calculateSkipTable()

This method creates a compressed table of bad-character skips from the pattern for reverse-searching. The entry for a given byte value tells us how far it is from the start of the pattern, being 0 for the actual first byte, or is equal to the length of the pattern if the byte does not occur in the pattern. The table is compressed in that only the least-significant bits of the byte index are used. In the case where 5 bits are used, the table is only 32 elements long, rather than (as it might be) 256 bytes, the number of distinct byte values.

Overrides:

calculateSkipTable in class BaseBytes.Finder

currIndex

public int currIndex()

Description copied from class: BaseBytes.Finder

Return the index in the text array where the preceding pattern match ends (one beyond the last character matched), which may also be one beyond the effective end ofthe text. Between a call to setText() and the first call to nextIndex() return the start position.

The following idiom may be used:

 f.setText(text);
 int p = f.nextIndex();
 int q = f.currIndex();
 // The range text[p:q] is the matched segment.
 

Overrides:

currIndex in class BaseBytes.Finder

Returns:

the new effective end of the text

nextIndex

public int nextIndex()

Find the next index in the text array where the pattern starts, but working backwards. Successive calls to nextIndex() return the successive (non-overlapping) occurrences of the pattern in the text.

Overrides:

nextIndex in class BaseBytes.Finder

Returns:

matching index or -1 if no (further) occurrences found