Java example source code file (StackMachine.java)

This example Java source code file (StackMachine.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

call_frame, invalid_index, mask_pop_used, mem_end, mem_start, null_check_end, null_check_start, repeat_inc, return, stackentry, stackmachine, threadlocal, void, weakreference

The StackMachine.java Java example source code

/*
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is furnished to do
 * so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package jdk.nashorn.internal.runtime.regexp.joni;

import static jdk.nashorn.internal.runtime.regexp.joni.BitStatus.bsAt;

import java.lang.ref.WeakReference;

import jdk.nashorn.internal.runtime.regexp.joni.constants.StackPopLevel;
import jdk.nashorn.internal.runtime.regexp.joni.constants.StackType;

abstract class StackMachine extends Matcher implements StackType {
    protected static final int INVALID_INDEX = -1;

    protected StackEntry[]stack;
    protected int stk;  // stkEnd

    protected final int[]repeatStk;
    protected final int memStartStk, memEndStk;

    protected StackMachine(Regex regex, char[] chars, int p , int end) {
        super(regex, chars, p, end);

        this.stack = regex.stackNeeded ? fetchStack() : null;
        int n = regex.numRepeat + (regex.numMem << 1);
        this.repeatStk = n > 0 ? new int[n] : null;

        memStartStk = regex.numRepeat - 1;
        memEndStk   = memStartStk + regex.numMem;
        /* for index start from 1, mem_start_stk[1]..mem_start_stk[num_mem] */
        /* for index start from 1, mem_end_stk[1]..mem_end_stk[num_mem] */
    }

    private static StackEntry[] allocateStack() {
        StackEntry[]stack = new StackEntry[Config.INIT_MATCH_STACK_SIZE];
        stack[0] = new StackEntry();
        return stack;
    }

    private void doubleStack() {
        StackEntry[] newStack = new StackEntry[stack.length << 1];
        System.arraycopy(stack, 0, newStack, 0, stack.length);
        stack = newStack;
    }

    static final ThreadLocal<WeakReference stacks
            = new ThreadLocal<WeakReference() {
        @Override
        protected WeakReference<StackEntry[]> initialValue() {
            return new WeakReference<StackEntry[]>(allocateStack());
        }
    };

    private static StackEntry[] fetchStack() {
        WeakReference<StackEntry[]> ref = stacks.get();
        StackEntry[] stack = ref.get();
        if (stack == null) {
            ref = new WeakReference<StackEntry[]>(stack = allocateStack());
            stacks.set(ref);
        }
        return stack;
    }

    protected final void init() {
        if (stack != null) pushEnsured(ALT, regex.codeLength - 1); /* bottom stack */
        if (repeatStk != null) {
            for (int i=1; i<=regex.numMem; i++) {
                repeatStk[i + memStartStk] = repeatStk[i + memEndStk] = INVALID_INDEX;
            }
        }
    }

    protected final StackEntry ensure1() {
        if (stk >= stack.length) doubleStack();
        StackEntry e = stack[stk];
        if (e == null) stack[stk] = e = new StackEntry();
        return e;
    }

    protected final void pushType(int type) {
        ensure1().type = type;
        stk++;
    }

    private void push(int type, int pat, int s, int prev) {
        StackEntry e = ensure1();
        e.type = type;
        e.setStatePCode(pat);
        e.setStatePStr(s);
        e.setStatePStrPrev(prev);
        stk++;
    }

    protected final void pushEnsured(int type, int pat) {
        StackEntry e = stack[stk];
        e.type = type;
        e.setStatePCode(pat);
        stk++;
    }

    protected final void pushAlt(int pat, int s, int prev) {
        push(ALT, pat, s, prev);
    }

    protected final void pushPos(int s, int prev) {
        push(POS, -1 /*NULL_UCHARP*/, s, prev);
    }

    protected final void pushPosNot(int pat, int s, int prev) {
        push(POS_NOT, pat, s, prev);
    }

    protected final void pushStopBT() {
        pushType(STOP_BT);
    }

    protected final void pushLookBehindNot(int pat, int s, int sprev) {
        push(LOOK_BEHIND_NOT, pat, s, sprev);
    }

    protected final void pushRepeat(int id, int pat) {
        StackEntry e = ensure1();
        e.type = REPEAT;
        e.setRepeatNum(id);
        e.setRepeatPCode(pat);
        e.setRepeatCount(0);
        stk++;
    }

    protected final void pushRepeatInc(int sindex) {
        StackEntry e = ensure1();
        e.type = REPEAT_INC;
        e.setSi(sindex);
        stk++;
    }

    protected final void pushMemStart(int mnum, int s) {
        StackEntry e = ensure1();
        e.type = MEM_START;
        e.setMemNum(mnum);
        e.setMemPstr(s);
        e.setMemStart(repeatStk[memStartStk + mnum]);
        e.setMemEnd(repeatStk[memEndStk + mnum]);
        repeatStk[memStartStk + mnum] = stk;
        repeatStk[memEndStk + mnum] = INVALID_INDEX;
        stk++;
    }

    protected final void pushMemEnd(int mnum, int s) {
        StackEntry e = ensure1();
        e.type = MEM_END;
        e.setMemNum(mnum);
        e.setMemPstr(s);
        e.setMemStart(repeatStk[memStartStk + mnum]);
        e.setMemEnd(repeatStk[memEndStk + mnum]);
        repeatStk[memEndStk + mnum] = stk;
        stk++;
    }

    protected final void pushMemEndMark(int mnum) {
        StackEntry e = ensure1();
        e.type = MEM_END_MARK;
        e.setMemNum(mnum);
        stk++;
    }

    protected final int getMemStart(int mnum) {
        int level = 0;
        int stkp = stk;

        while (stkp > 0) {
            stkp--;
            StackEntry e = stack[stkp];
            if ((e.type & MASK_MEM_END_OR_MARK) != 0 && e.getMemNum() == mnum) {
                level++;
            } else if (e.type == MEM_START && e.getMemNum() == mnum) {
                if (level == 0) break;
                level--;
            }
        }
        return stkp;
    }

    protected final void pushNullCheckStart(int cnum, int s) {
        StackEntry e = ensure1();
        e.type = NULL_CHECK_START;
        e.setNullCheckNum(cnum);
        e.setNullCheckPStr(s);
        stk++;
    }

    protected final void pushNullCheckEnd(int cnum) {
        StackEntry e = ensure1();
        e.type = NULL_CHECK_END;
        e.setNullCheckNum(cnum);
        stk++;
    }

    // stack debug routines here
    // ...

    protected final void popOne() {
        stk--;
    }

    protected final StackEntry pop() {
        switch (regex.stackPopLevel) {
        case StackPopLevel.FREE:
            return popFree();
        case StackPopLevel.MEM_START:
            return popMemStart();
        default:
            return popDefault();
        }
    }

    private StackEntry popFree() {
        while (true) {
            StackEntry e = stack[--stk];

            if ((e.type & MASK_POP_USED) != 0) {
                return e;
            }
        }
    }

    private StackEntry popMemStart() {
        while (true) {
            StackEntry e = stack[--stk];

            if ((e.type & MASK_POP_USED) != 0) {
                return e;
            } else if (e.type == MEM_START) {
                repeatStk[memStartStk + e.getMemNum()] = e.getMemStart();
                repeatStk[memEndStk + e.getMemNum()] = e.getMemEnd();
            }
        }
    }

    private StackEntry popDefault() {
        while (true) {
            StackEntry e = stack[--stk];

            if ((e.type & MASK_POP_USED) != 0) {
                return e;
            } else if (e.type == MEM_START) {
                repeatStk[memStartStk + e.getMemNum()] = e.getMemStart();
                repeatStk[memEndStk + e.getMemNum()] = e.getMemEnd();
            } else if (e.type == REPEAT_INC) {
                //int si = stack[stk + IREPEAT_INC_SI];
                //stack[si + IREPEAT_COUNT]--;
                stack[e.getSi()].decreaseRepeatCount();
            } else if (e.type == MEM_END) {
                repeatStk[memStartStk + e.getMemNum()] = e.getMemStart();
                repeatStk[memEndStk + e.getMemNum()] = e.getMemEnd();
            }
        }
    }

    protected final void popTilPosNot() {
        while (true) {
            stk--;
            StackEntry e = stack[stk];

            if (e.type == POS_NOT) {
                break;
            } else if (e.type == MEM_START) {
                repeatStk[memStartStk + e.getMemNum()] = e.getMemStart();
                repeatStk[memEndStk + e.getMemNum()] = e.getMemStart();
            } else if (e.type == REPEAT_INC) {
                //int si = stack[stk + IREPEAT_INC_SI];
                //stack[si + IREPEAT_COUNT]--;
                stack[e.getSi()].decreaseRepeatCount();
            } else if (e.type == MEM_END){
                repeatStk[memStartStk + e.getMemNum()] = e.getMemStart();
                repeatStk[memEndStk + e.getMemNum()] = e.getMemStart();
            }
        }
    }

    protected final void popTilLookBehindNot() {
        while (true) {
            stk--;
            StackEntry e = stack[stk];

            if (e.type == LOOK_BEHIND_NOT) {
                break;
            } else if (e.type == MEM_START) {
                repeatStk[memStartStk + e.getMemNum()] = e.getMemStart();
                repeatStk[memEndStk + e.getMemNum()] = e.getMemEnd();
            } else if (e.type == REPEAT_INC) {
                //int si = stack[stk + IREPEAT_INC_SI];
                //stack[si + IREPEAT_COUNT]--;
                stack[e.getSi()].decreaseRepeatCount();
            } else if (e.type == MEM_END) {
                repeatStk[memStartStk + e.getMemNum()] = e.getMemStart();
                repeatStk[memEndStk + e.getMemNum()] = e.getMemEnd();
            }
        }
    }

    protected final int posEnd() {
        int k = stk;
        while (true) {
            k--;
            StackEntry e = stack[k];
            if ((e.type & MASK_TO_VOID_TARGET) != 0) {
                e.type = VOID;
            } else if (e.type == POS) {
                e.type = VOID;
                break;
            }
        }
        return k;
    }

    protected final void stopBtEnd() {
        int k = stk;
        while (true) {
            k--;
            StackEntry e = stack[k];

            if ((e.type & MASK_TO_VOID_TARGET) != 0) {
                e.type = VOID;
            } else if (e.type == STOP_BT) {
                e.type = VOID;
                break;
            }
        }
    }

    // int for consistency with other null check routines
    protected final int nullCheck(int id, int s) {
        int k = stk;
        while (true) {
            k--;
            StackEntry e = stack[k];

            if (e.type == NULL_CHECK_START) {
                if (e.getNullCheckNum() == id) {
                    return e.getNullCheckPStr() == s ? 1 : 0;
                }
            }
        }
    }

    protected final int nullCheckRec(int id, int s) {
        int level = 0;
        int k = stk;
        while (true) {
            k--;
            StackEntry e = stack[k];

            if (e.type == NULL_CHECK_START) {
                if (e.getNullCheckNum() == id) {
                    if (level == 0) {
                        return e.getNullCheckPStr() == s ? 1 : 0;
                    } else {
                        level--;
                    }
                }
            } else if (e.type == NULL_CHECK_END) {
                level++;
            }
        }
    }

    protected final int nullCheckMemSt(int id, int s) {
        int k = stk;
        int isNull;
        while (true) {
            k--;
            StackEntry e = stack[k];

            if (e.type == NULL_CHECK_START) {
                if (e.getNullCheckNum() == id) {
                    if (e.getNullCheckPStr() != s) {
                        isNull = 0;
                        break;
                    } else {
                        int endp;
                        isNull = 1;
                        while (k < stk) {
                            if (e.type == MEM_START) {
                                if (e.getMemEnd() == INVALID_INDEX) {
                                    isNull = 0;
                                    break;
                                }
                                if (bsAt(regex.btMemEnd, e.getMemNum())) {
                                    endp = stack[e.getMemEnd()].getMemPStr();
                                } else {
                                    endp = e.getMemEnd();
                                }
                                if (stack[e.getMemStart()].getMemPStr() != endp) {
                                    isNull = 0;
                                    break;
                                } else if (endp != s) {
                                    isNull = -1; /* empty, but position changed */
                                }
                            }
                            k++;
                            e = stack[k]; // !!
                        }
                        break;
                    }
                }
            }
        }
        return isNull;
    }

    protected final int nullCheckMemStRec(int id, int s) {
        int level = 0;
        int k = stk;
        int isNull;
        while (true) {
            k--;
            StackEntry e = stack[k];

            if (e.type == NULL_CHECK_START) {
                if (e.getNullCheckNum() == id) {
                    if (level == 0) {
                        if (e.getNullCheckPStr() != s) {
                            isNull = 0;
                            break;
                        } else {
                            int endp;
                            isNull = 1;
                            while (k < stk) {
                                if (e.type == MEM_START) {
                                    if (e.getMemEnd() == INVALID_INDEX) {
                                        isNull = 0;
                                        break;
                                    }
                                    if (bsAt(regex.btMemEnd, e.getMemNum())) {
                                        endp = stack[e.getMemEnd()].getMemPStr();
                                    } else {
                                        endp = e.getMemEnd();
                                    }
                                    if (stack[e.getMemStart()].getMemPStr() != endp) {
                                        isNull = 0;
                                        break;
                                    } else if (endp != s) {
                                        isNull = -1; /* empty, but position changed */
                                    }
                                }
                                k++;
                                e = stack[k];
                            }
                            break;
                        }
                    } else {
                        level--;
                    }
                }
            } else if (e.type == NULL_CHECK_END) {
                if (e.getNullCheckNum() == id) level++;
            }
        }
        return isNull;
    }

    protected final int getRepeat(int id) {
        int level = 0;
        int k = stk;
        while (true) {
            k--;
            StackEntry e = stack[k];

            if (e.type == REPEAT) {
                if (level == 0) {
                    if (e.getRepeatNum() == id) return k;
                }
            } else if (e.type == CALL_FRAME) {
                level--;
            } else if (e.type == RETURN) {
                level++;
            }
        }
    }

    protected final int sreturn() {
        int level = 0;
        int k = stk;
        while (true) {
            k--;
            StackEntry e = stack[k];

            if (e.type == CALL_FRAME) {
                if (level == 0) {
                    return e.getCallFrameRetAddr();
                } else {
                    level--;
                }
            } else if (e.type == RETURN) {
                level++;
            }
        }
    }
}