com.codename1.util.regex.REProgram Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.codename1.util.regex;
/**
* A class that holds compiled regular expressions. You should not need to
* work directly with this class.
*
* @see RE
* @see RECompiler
*
* @author Jonathan Locke
* @version $Id: REProgram.java 518156 2007-03-14 14:31:26Z vgritsenko $
*/
public class REProgram
{
static final int OPT_HASBACKREFS = 1;
static final int OPT_HASBOL = 2;
char[] instruction; // The compiled regular expression 'program'
int lenInstruction; // The amount of the instruction buffer in use
char[] prefix; // Prefix string optimization
int flags; // Optimization flags (REProgram.OPT_*)
int maxParens = -1;
/**
* Constructs a program object from a character array
* @param instruction Character array with RE opcode instructions in it
*/
public REProgram(char[] instruction)
{
this(instruction, instruction.length);
}
/**
* Constructs a program object from a character array
* @param parens Count of parens in the program
* @param instruction Character array with RE opcode instructions in it
*/
public REProgram(int parens, char[] instruction)
{
this(instruction, instruction.length);
this.maxParens = parens;
}
/**
* Constructs a program object from a character array
* @param instruction Character array with RE opcode instructions in it
* @param lenInstruction Amount of instruction array in use
*/
public REProgram(char[] instruction, int lenInstruction)
{
setInstructions(instruction, lenInstruction);
}
/**
* Returns a copy of the current regular expression program in a character
* array that is exactly the right length to hold the program. If there is
* no program compiled yet, getInstructions() will return null.
* @return A copy of the current compiled RE program
*/
public char[] getInstructions()
{
// Ensure program has been compiled!
if (lenInstruction != 0)
{
// Return copy of program
char[] ret = new char[lenInstruction];
System.arraycopy(instruction, 0, ret, 0, lenInstruction);
return ret;
}
return null;
}
/**
* Sets a new regular expression program to run. It is this method which
* performs any special compile-time search optimizations. Currently only
* two optimizations are in place - one which checks for backreferences
* (so that they can be lazily allocated) and another which attempts to
* find a prefix anchor string so that substantial amounts of input can
* potentially be skipped without running the actual program.
* @param instruction Program instruction buffer
* @param lenInstruction Length of instruction buffer in use
*/
public void setInstructions(char[] instruction, int lenInstruction)
{
// Save reference to instruction array
this.instruction = instruction;
this.lenInstruction = lenInstruction;
// Initialize other program-related variables
this.flags = 0;
this.prefix = null;
// Try various compile-time optimizations if there's a program
if (instruction != null && lenInstruction != 0)
{
// If the first node is a branch
if (lenInstruction >= RE.nodeSize && instruction[0 + RE.offsetOpcode] == RE.OP_BRANCH)
{
// to the end node
int next = (short) instruction[0 + RE.offsetNext];
if (instruction[next + RE.offsetOpcode] == RE.OP_END && lenInstruction >= (RE.nodeSize * 2))
{
final char nextOp = instruction[RE.nodeSize + RE.offsetOpcode];
// the branch starts with an atom
if (nextOp == RE.OP_ATOM)
{
// then get that atom as a prefix because there's no other choice
int lenAtom = instruction[RE.nodeSize + RE.offsetOpdata];
this.prefix = new char[lenAtom];
System.arraycopy(instruction, RE.nodeSize * 2, prefix, 0, lenAtom);
}
// the branch starts with a BOL
else if (nextOp == RE.OP_BOL)
{
// then set the flag indicating that BOL is present
this.flags |= OPT_HASBOL;
}
}
}
BackrefScanLoop:
// Check for backreferences
for (int i = 0; i < lenInstruction; i += RE.nodeSize)
{
switch (instruction[i + RE.offsetOpcode])
{
case RE.OP_ANYOF:
i += (instruction[i + RE.offsetOpdata] * 2);
break;
case RE.OP_ATOM:
i += instruction[i + RE.offsetOpdata];
break;
case RE.OP_BACKREF:
flags |= OPT_HASBACKREFS;
break BackrefScanLoop;
}
}
}
}
/**
* Returns a copy of the prefix of current regular expression program
* in a character array. If there is no prefix, or there is no program
* compiled yet, getPrefix will return null.
* @return A copy of the prefix of current compiled RE program
*/
public char[] getPrefix()
{
if (prefix != null)
{
// Return copy of prefix
char[] ret = new char[prefix.length];
System.arraycopy(prefix, 0, ret, 0, prefix.length);
return ret;
}
return null;
}
}