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// © 2017 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html#License
package com.ibm.icu.text;
import java.nio.BufferOverflowException;
import java.util.Arrays;
/**
* Records lengths of string edits but not replacement text.
* Supports replacements, insertions, deletions in linear progression.
* Does not support moving/reordering of text.
*
* @stable ICU 59
*/
public final class Edits {
// 0000uuuuuuuuuuuu records u+1 unchanged text units.
private static final int MAX_UNCHANGED_LENGTH = 0x1000;
private static final int MAX_UNCHANGED = MAX_UNCHANGED_LENGTH - 1;
// 0mmmnnnccccccccc with m=1..6 records ccc+1 replacements of m:n text units.
private static final int MAX_SHORT_CHANGE_OLD_LENGTH = 6;
private static final int MAX_SHORT_CHANGE_NEW_LENGTH = 7;
private static final int SHORT_CHANGE_NUM_MASK = 0x1ff;
private static final int MAX_SHORT_CHANGE = 0x6fff;
// 0111mmmmmmnnnnnn records a replacement of m text units with n.
// m or n = 61: actual length follows in the next edits array unit.
// m or n = 62..63: actual length follows in the next two edits array units.
// Bit 30 of the actual length is in the head unit.
// Trailing units have bit 15 set.
private static final int LENGTH_IN_1TRAIL = 61;
private static final int LENGTH_IN_2TRAIL = 62;
private static final int STACK_CAPACITY = 100;
private char[] array;
private int length;
private int delta;
private int numChanges;
/**
* Constructs an empty object.
* @stable ICU 59
*/
public Edits() {
array = new char[STACK_CAPACITY];
}
/**
* Resets the data but may not release memory.
* @stable ICU 59
*/
public void reset() {
length = delta = numChanges = 0;
}
private void setLastUnit(int last) {
array[length - 1] = (char)last;
}
private int lastUnit() {
return length > 0 ? array[length - 1] : 0xffff;
}
/**
* Adds a record for an unchanged segment of text.
* Normally called from inside ICU string transformation functions, not user code.
* @stable ICU 59
*/
public void addUnchanged(int unchangedLength) {
if(unchangedLength < 0) {
throw new IllegalArgumentException(
"addUnchanged(" + unchangedLength + "): length must not be negative");
}
// Merge into previous unchanged-text record, if any.
int last = lastUnit();
if(last < MAX_UNCHANGED) {
int remaining = MAX_UNCHANGED - last;
if (remaining >= unchangedLength) {
setLastUnit(last + unchangedLength);
return;
}
setLastUnit(MAX_UNCHANGED);
unchangedLength -= remaining;
}
// Split large lengths into multiple units.
while(unchangedLength >= MAX_UNCHANGED_LENGTH) {
append(MAX_UNCHANGED);
unchangedLength -= MAX_UNCHANGED_LENGTH;
}
// Write a small (remaining) length.
if(unchangedLength > 0) {
append(unchangedLength - 1);
}
}
/**
* Adds a record for a text replacement/insertion/deletion.
* Normally called from inside ICU string transformation functions, not user code.
* @stable ICU 59
*/
public void addReplace(int oldLength, int newLength) {
if(oldLength < 0 || newLength < 0) {
throw new IllegalArgumentException(
"addReplace(" + oldLength + ", " + newLength +
"): both lengths must be non-negative");
}
if (oldLength == 0 && newLength == 0) {
return;
}
++numChanges;
int newDelta = newLength - oldLength;
if (newDelta != 0) {
if ((newDelta > 0 && delta >= 0 && newDelta > (Integer.MAX_VALUE - delta)) ||
(newDelta < 0 && delta < 0 && newDelta < (Integer.MIN_VALUE - delta))) {
// Integer overflow or underflow.
throw new IndexOutOfBoundsException();
}
delta += newDelta;
}
if(0 < oldLength && oldLength <= MAX_SHORT_CHANGE_OLD_LENGTH &&
newLength <= MAX_SHORT_CHANGE_NEW_LENGTH) {
// Merge into previous same-lengths short-replacement record, if any.
int u = (oldLength << 12) | (newLength << 9);
int last = lastUnit();
if(MAX_UNCHANGED < last && last < MAX_SHORT_CHANGE &&
(last & ~SHORT_CHANGE_NUM_MASK) == u &&
(last & SHORT_CHANGE_NUM_MASK) < SHORT_CHANGE_NUM_MASK) {
setLastUnit(last + 1);
return;
}
append(u);
return;
}
int head = 0x7000;
if (oldLength < LENGTH_IN_1TRAIL && newLength < LENGTH_IN_1TRAIL) {
head |= oldLength << 6;
head |= newLength;
append(head);
} else if ((array.length - length) >= 5 || growArray()) {
int limit = length + 1;
if(oldLength < LENGTH_IN_1TRAIL) {
head |= oldLength << 6;
} else if(oldLength <= 0x7fff) {
head |= LENGTH_IN_1TRAIL << 6;
array[limit++] = (char)(0x8000 | oldLength);
} else {
head |= (LENGTH_IN_2TRAIL + (oldLength >> 30)) << 6;
array[limit++] = (char)(0x8000 | (oldLength >> 15));
array[limit++] = (char)(0x8000 | oldLength);
}
if(newLength < LENGTH_IN_1TRAIL) {
head |= newLength;
} else if(newLength <= 0x7fff) {
head |= LENGTH_IN_1TRAIL;
array[limit++] = (char)(0x8000 | newLength);
} else {
head |= LENGTH_IN_2TRAIL + (newLength >> 30);
array[limit++] = (char)(0x8000 | (newLength >> 15));
array[limit++] = (char)(0x8000 | newLength);
}
array[length] = (char)head;
length = limit;
}
}
private void append(int r) {
if(length < array.length || growArray()) {
array[length++] = (char)r;
}
}
private boolean growArray() {
int newCapacity;
if (array.length == STACK_CAPACITY) {
newCapacity = 2000;
} else if (array.length == Integer.MAX_VALUE) {
throw new BufferOverflowException();
} else if (array.length >= (Integer.MAX_VALUE / 2)) {
newCapacity = Integer.MAX_VALUE;
} else {
newCapacity = 2 * array.length;
}
// Grow by at least 5 units so that a maximal change record will fit.
if ((newCapacity - array.length) < 5) {
throw new BufferOverflowException();
}
array = Arrays.copyOf(array, newCapacity);
return true;
}
/**
* How much longer is the new text compared with the old text?
* @return new length minus old length
* @stable ICU 59
*/
public int lengthDelta() { return delta; }
/**
* @return true if there are any change edits
* @stable ICU 59
*/
public boolean hasChanges() { return numChanges != 0; }
/**
* @return the number of change edits
* @draft ICU 60
* @provisional This API might change or be removed in a future release.
*/
public int numberOfChanges() { return numChanges; }
/**
* Access to the list of edits.
* @see #getCoarseIterator
* @see #getFineIterator
* @stable ICU 59
*/
public static final class Iterator {
private final char[] array;
private int index;
private final int length;
/**
* 0 if we are not within compressed equal-length changes.
* Otherwise the number of remaining changes, including the current one.
*/
private int remaining;
private final boolean onlyChanges_, coarse;
private int dir; // iteration direction: back(<0), initial(0), forward(>0)
private boolean changed;
private int oldLength_, newLength_;
private int srcIndex, replIndex, destIndex;
private Iterator(char[] a, int len, boolean oc, boolean crs) {
array = a;
length = len;
onlyChanges_ = oc;
coarse = crs;
}
private int readLength(int head) {
if (head < LENGTH_IN_1TRAIL) {
return head;
} else if (head < LENGTH_IN_2TRAIL) {
assert(index < length);
assert(array[index] >= 0x8000);
return array[index++] & 0x7fff;
} else {
assert((index + 2) <= length);
assert(array[index] >= 0x8000);
assert(array[index + 1] >= 0x8000);
int len = ((head & 1) << 30) |
((array[index] & 0x7fff) << 15) |
(array[index + 1] & 0x7fff);
index += 2;
return len;
}
}
private void updateNextIndexes() {
srcIndex += oldLength_;
if (changed) {
replIndex += newLength_;
}
destIndex += newLength_;
}
private void updatePreviousIndexes() {
srcIndex -= oldLength_;
if (changed) {
replIndex -= newLength_;
}
destIndex -= newLength_;
}
private boolean noNext() {
// No change before or beyond the string.
dir = 0;
changed = false;
oldLength_ = newLength_ = 0;
return false;
}
/**
* Advances to the next edit.
* @return true if there is another edit
* @stable ICU 59
*/
public boolean next() {
return next(onlyChanges_);
}
private boolean next(boolean onlyChanges) {
// Forward iteration: Update the string indexes to the limit of the current span,
// and post-increment-read array units to assemble a new span.
// Leaves the array index one after the last unit of that span.
if (dir > 0) {
updateNextIndexes();
} else {
if (dir < 0) {
// Turn around from previous() to next().
// Post-increment-read the same span again.
if (remaining > 0) {
// Fine-grained iterator:
// Stay on the current one of a sequence of compressed changes.
++index; // next() rests on the index after the sequence unit.
dir = 1;
return true;
}
}
dir = 1;
}
if (remaining >= 1) {
// Fine-grained iterator: Continue a sequence of compressed changes.
if (remaining > 1) {
--remaining;
return true;
}
remaining = 0;
}
if (index >= length) {
return noNext();
}
int u = array[index++];
if (u <= MAX_UNCHANGED) {
// Combine adjacent unchanged ranges.
changed = false;
oldLength_ = u + 1;
while (index < length && (u = array[index]) <= MAX_UNCHANGED) {
++index;
oldLength_ += u + 1;
}
newLength_ = oldLength_;
if (onlyChanges) {
updateNextIndexes();
if (index >= length) {
return noNext();
}
// already fetched u > MAX_UNCHANGED at index
++index;
} else {
return true;
}
}
changed = true;
if (u <= MAX_SHORT_CHANGE) {
int oldLen = u >> 12;
int newLen = (u >> 9) & MAX_SHORT_CHANGE_NEW_LENGTH;
int num = (u & SHORT_CHANGE_NUM_MASK) + 1;
if (coarse) {
oldLength_ = num * oldLen;
newLength_ = num * newLen;
} else {
// Split a sequence of changes that was compressed into one unit.
oldLength_ = oldLen;
newLength_ = newLen;
if (num > 1) {
remaining = num; // This is the first of two or more changes.
}
return true;
}
} else {
assert(u <= 0x7fff);
oldLength_ = readLength((u >> 6) & 0x3f);
newLength_ = readLength(u & 0x3f);
if (!coarse) {
return true;
}
}
// Combine adjacent changes.
while (index < length && (u = array[index]) > MAX_UNCHANGED) {
++index;
if (u <= MAX_SHORT_CHANGE) {
int num = (u & SHORT_CHANGE_NUM_MASK) + 1;
oldLength_ += (u >> 12) * num;
newLength_ += ((u >> 9) & MAX_SHORT_CHANGE_NEW_LENGTH) * num;
} else {
assert(u <= 0x7fff);
oldLength_ += readLength((u >> 6) & 0x3f);
newLength_ += readLength(u & 0x3f);
}
}
return true;
}
private boolean previous() {
// Backward iteration: Pre-decrement-read array units to assemble a new span,
// then update the string indexes to the start of that span.
// Leaves the array index on the head unit of that span.
if (dir >= 0) {
if (dir > 0) {
// Turn around from next() to previous().
// Set the string indexes to the span limit and
// pre-decrement-read the same span again.
if (remaining > 0) {
// Fine-grained iterator:
// Stay on the current one of a sequence of compressed changes.
--index; // previous() rests on the sequence unit.
dir = -1;
return true;
}
updateNextIndexes();
}
dir = -1;
}
if (remaining > 0) {
// Fine-grained iterator: Continue a sequence of compressed changes.
int u = array[index];
assert(MAX_UNCHANGED < u && u <= MAX_SHORT_CHANGE);
if (remaining <= (u & SHORT_CHANGE_NUM_MASK)) {
++remaining;
updatePreviousIndexes();
return true;
}
remaining = 0;
}
if (index <= 0) {
return noNext();
}
int u = array[--index];
if (u <= MAX_UNCHANGED) {
// Combine adjacent unchanged ranges.
changed = false;
oldLength_ = u + 1;
while (index > 0 && (u = array[index - 1]) <= MAX_UNCHANGED) {
--index;
oldLength_ += u + 1;
}
newLength_ = oldLength_;
// No need to handle onlyChanges as long as previous() is called only from findIndex().
updatePreviousIndexes();
return true;
}
changed = true;
if (u <= MAX_SHORT_CHANGE) {
int oldLen = u >> 12;
int newLen = (u >> 9) & MAX_SHORT_CHANGE_NEW_LENGTH;
int num = (u & SHORT_CHANGE_NUM_MASK) + 1;
if (coarse) {
oldLength_ = num * oldLen;
newLength_ = num * newLen;
} else {
// Split a sequence of changes that was compressed into one unit.
oldLength_ = oldLen;
newLength_ = newLen;
if (num > 1) {
remaining = 1; // This is the last of two or more changes.
}
updatePreviousIndexes();
return true;
}
} else {
if (u <= 0x7fff) {
// The change is encoded in u alone.
oldLength_ = readLength((u >> 6) & 0x3f);
newLength_ = readLength(u & 0x3f);
} else {
// Back up to the head of the change, read the lengths,
// and reset the index to the head again.
assert(index > 0);
while ((u = array[--index]) > 0x7fff) {}
assert(u > MAX_SHORT_CHANGE);
int headIndex = index++;
oldLength_ = readLength((u >> 6) & 0x3f);
newLength_ = readLength(u & 0x3f);
index = headIndex;
}
if (!coarse) {
updatePreviousIndexes();
return true;
}
}
// Combine adjacent changes.
while (index > 0 && (u = array[index - 1]) > MAX_UNCHANGED) {
--index;
if (u <= MAX_SHORT_CHANGE) {
int num = (u & SHORT_CHANGE_NUM_MASK) + 1;
oldLength_ += (u >> 12) * num;
newLength_ += ((u >> 9) & MAX_SHORT_CHANGE_NEW_LENGTH) * num;
} else if (u <= 0x7fff) {
// Read the lengths, and reset the index to the head again.
int headIndex = index++;
oldLength_ += readLength((u >> 6) & 0x3f);
newLength_ += readLength(u & 0x3f);
index = headIndex;
}
}
updatePreviousIndexes();
return true;
}
/**
* Finds the edit that contains the source index.
* The source index may be found in a non-change
* even if normal iteration would skip non-changes.
* Normal iteration can continue from a found edit.
*
* The iterator state before this search logically does not matter.
* (It may affect the performance of the search.)
*
*
The iterator state after this search is undefined
* if the source index is out of bounds for the source string.
*
* @param i source index
* @return true if the edit for the source index was found
* @stable ICU 59
*/
public boolean findSourceIndex(int i) {
return findIndex(i, true) == 0;
}
/**
* Finds the edit that contains the destination index.
* The destination index may be found in a non-change
* even if normal iteration would skip non-changes.
* Normal iteration can continue from a found edit.
*
*
The iterator state before this search logically does not matter.
* (It may affect the performance of the search.)
*
*
The iterator state after this search is undefined
* if the source index is out of bounds for the source string.
*
* @param i destination index
* @return true if the edit for the destination index was found
* @draft ICU 60
* @provisional This API might change or be removed in a future release.
*/
public boolean findDestinationIndex(int i) {
return findIndex(i, false) == 0;
}
/** @return -1: error or i<0; 0: found; 1: i>=string length */
private int findIndex(int i, boolean findSource) {
if (i < 0) { return -1; }
int spanStart, spanLength;
if (findSource) { // find source index
spanStart = srcIndex;
spanLength = oldLength_;
} else { // find destination index
spanStart = destIndex;
spanLength = newLength_;
}
if (i < spanStart) {
if (i >= (spanStart / 2)) {
// Search backwards.
for (;;) {
boolean hasPrevious = previous();
assert(hasPrevious); // because i>=0 and the first span starts at 0
spanStart = findSource ? srcIndex : destIndex;
if (i >= spanStart) {
// The index is in the current span.
return 0;
}
if (remaining > 0) {
// Is the index in one of the remaining compressed edits?
// spanStart is the start of the current span, first of the remaining ones.
spanLength = findSource ? oldLength_ : newLength_;
int u = array[index];
assert(MAX_UNCHANGED < u && u <= MAX_SHORT_CHANGE);
int num = (u & SHORT_CHANGE_NUM_MASK) + 1 - remaining;
int len = num * spanLength;
if (i >= (spanStart - len)) {
int n = ((spanStart - i - 1) / spanLength) + 1;
// 1 <= n <= num
srcIndex -= n * oldLength_;
replIndex -= n * newLength_;
destIndex -= n * newLength_;
remaining += n;
return 0;
}
// Skip all of these edits at once.
srcIndex -= num * oldLength_;
replIndex -= num * newLength_;
destIndex -= num * newLength_;
remaining = 0;
}
}
}
// Reset the iterator to the start.
dir = 0;
index = remaining = oldLength_ = newLength_ = srcIndex = replIndex = destIndex = 0;
} else if (i < (spanStart + spanLength)) {
// The index is in the current span.
return 0;
}
while (next(false)) {
if (findSource) {
spanStart = srcIndex;
spanLength = oldLength_;
} else {
spanStart = destIndex;
spanLength = newLength_;
}
if (i < (spanStart + spanLength)) {
// The index is in the current span.
return 0;
}
if (remaining > 1) {
// Is the index in one of the remaining compressed edits?
// spanStart is the start of the current span, first of the remaining ones.
int len = remaining * spanLength;
if (i < (spanStart + len)) {
int n = (i - spanStart) / spanLength; // 1 <= n <= remaining - 1
srcIndex += n * oldLength_;
replIndex += n * newLength_;
destIndex += n * newLength_;
remaining -= n;
return 0;
}
// Make next() skip all of these edits at once.
oldLength_ *= remaining;
newLength_ *= remaining;
remaining = 0;
}
}
return 1;
}
/**
* Returns the destination index corresponding to the given source index.
* If the source index is inside a change edit (not at its start),
* then the destination index at the end of that edit is returned,
* since there is no information about index mapping inside a change edit.
*
*
(This means that indexes to the start and middle of an edit,
* for example around a grapheme cluster, are mapped to indexes
* encompassing the entire edit.
* The alternative, mapping an interior index to the start,
* would map such an interval to an empty one.)
*
*
This operation will usually but not always modify this object.
* The iterator state after this search is undefined.
*
* @param i source index
* @return destination index; undefined if i is not 0..string length
* @draft ICU 60
* @provisional This API might change or be removed in a future release.
*/
public int destinationIndexFromSourceIndex(int i) {
int where = findIndex(i, true);
if (where < 0) {
// Error or before the string.
return 0;
}
if (where > 0 || i == srcIndex) {
// At or after string length, or at start of the found span.
return destIndex;
}
if (changed) {
// In a change span, map to its end.
return destIndex + newLength_;
} else {
// In an unchanged span, offset 1:1 within it.
return destIndex + (i - srcIndex);
}
}
/**
* Returns the source index corresponding to the given destination index.
* If the destination index is inside a change edit (not at its start),
* then the source index at the end of that edit is returned,
* since there is no information about index mapping inside a change edit.
*
*
(This means that indexes to the start and middle of an edit,
* for example around a grapheme cluster, are mapped to indexes
* encompassing the entire edit.
* The alternative, mapping an interior index to the start,
* would map such an interval to an empty one.)
*
*
This operation will usually but not always modify this object.
* The iterator state after this search is undefined.
*
* @param i destination index
* @return source index; undefined if i is not 0..string length
* @draft ICU 60
* @provisional This API might change or be removed in a future release.
*/
public int sourceIndexFromDestinationIndex(int i) {
int where = findIndex(i, false);
if (where < 0) {
// Error or before the string.
return 0;
}
if (where > 0 || i == destIndex) {
// At or after string length, or at start of the found span.
return srcIndex;
}
if (changed) {
// In a change span, map to its end.
return srcIndex + oldLength_;
} else {
// In an unchanged span, offset within it.
return srcIndex + (i - destIndex);
}
}
/**
* @return true if this edit replaces oldLength() units with newLength() different ones.
* false if oldLength units remain unchanged.
* @stable ICU 59
*/
public boolean hasChange() { return changed; }
/**
* @return the number of units in the original string which are replaced or remain unchanged.
* @stable ICU 59
*/
public int oldLength() { return oldLength_; }
/**
* @return the number of units in the modified string, if hasChange() is true.
* Same as oldLength if hasChange() is false.
* @stable ICU 59
*/
public int newLength() { return newLength_; }
/**
* @return the current index into the source string
* @stable ICU 59
*/
public int sourceIndex() { return srcIndex; }
/**
* @return the current index into the replacement-characters-only string,
* not counting unchanged spans
* @stable ICU 59
*/
public int replacementIndex() { return replIndex; }
/**
* @return the current index into the full destination string
* @stable ICU 59
*/
public int destinationIndex() { return destIndex; }
};
/**
* Returns an Iterator for coarse-grained changes for simple string updates.
* Skips non-changes.
* @return an Iterator that merges adjacent changes.
* @stable ICU 59
*/
public Iterator getCoarseChangesIterator() {
return new Iterator(array, length, true, true);
}
/**
* Returns an Iterator for coarse-grained changes and non-changes for simple string updates.
* @return an Iterator that merges adjacent changes.
* @stable ICU 59
*/
public Iterator getCoarseIterator() {
return new Iterator(array, length, false, true);
}
/**
* Returns an Iterator for fine-grained changes for modifying styled text.
* Skips non-changes.
* @return an Iterator that separates adjacent changes.
* @stable ICU 59
*/
public Iterator getFineChangesIterator() {
return new Iterator(array, length, true, false);
}
/**
* Returns an Iterator for fine-grained changes and non-changes for modifying styled text.
* @return an Iterator that separates adjacent changes.
* @stable ICU 59
*/
public Iterator getFineIterator() {
return new Iterator(array, length, false, false);
}
/**
* Merges the two input Edits and appends the result to this object.
*
*
Consider two string transformations (for example, normalization and case mapping)
* where each records Edits in addition to writing an output string.
* Edits ab reflect how substrings of input string a
* map to substrings of intermediate string b.
* Edits bc reflect how substrings of intermediate string b
* map to substrings of output string c.
* This function merges ab and bc such that the additional edits
* recorded in this object reflect how substrings of input string a
* map to substrings of output string c.
*
*
If unrelated Edits are passed in where the output string of the first
* has a different length than the input string of the second,
* then an IllegalArgumentException is thrown.
*
* @param ab reflects how substrings of input string a
* map to substrings of intermediate string b.
* @param bc reflects how substrings of intermediate string b
* map to substrings of output string c.
* @return this, with the merged edits appended
* @draft ICU 60
* @provisional This API might change or be removed in a future release.
*/
public Edits mergeAndAppend(Edits ab, Edits bc) {
// Picture string a --(Edits ab)--> string b --(Edits bc)--> string c.
// Parallel iteration over both Edits.
Iterator abIter = ab.getFineIterator();
Iterator bcIter = bc.getFineIterator();
boolean abHasNext = true, bcHasNext = true;
// Copy iterator state into local variables, so that we can modify and subdivide spans.
// ab old & new length, bc old & new length
int aLength = 0, ab_bLength = 0, bc_bLength = 0, cLength = 0;
// When we have different-intermediate-length changes, we accumulate a larger change.
int pending_aLength = 0, pending_cLength = 0;
for (;;) {
// At this point, for each of the two iterators:
// Either we are done with the locally cached current edit,
// and its intermediate-string length has been reset,
// or we will continue to work with a truncated remainder of this edit.
//
// If the current edit is done, and the iterator has not yet reached the end,
// then we fetch the next edit. This is true for at least one of the iterators.
//
// Normally it does not matter whether we fetch from ab and then bc or vice versa.
// However, the result is observably different when
// ab deletions meet bc insertions at the same intermediate-string index.
// Some users expect the bc insertions to come first, so we fetch from bc first.
if (bc_bLength == 0) {
if (bcHasNext && (bcHasNext = bcIter.next())) {
bc_bLength = bcIter.oldLength();
cLength = bcIter.newLength();
if (bc_bLength == 0) {
// insertion
if (ab_bLength == 0 || !abIter.hasChange()) {
addReplace(pending_aLength, pending_cLength + cLength);
pending_aLength = pending_cLength = 0;
} else {
pending_cLength += cLength;
}
continue;
}
}
// else see if the other iterator is done, too.
}
if (ab_bLength == 0) {
if (abHasNext && (abHasNext = abIter.next())) {
aLength = abIter.oldLength();
ab_bLength = abIter.newLength();
if (ab_bLength == 0) {
// deletion
if (bc_bLength == bcIter.oldLength() || !bcIter.hasChange()) {
addReplace(pending_aLength + aLength, pending_cLength);
pending_aLength = pending_cLength = 0;
} else {
pending_aLength += aLength;
}
continue;
}
} else if (bc_bLength == 0) {
// Both iterators are done at the same time:
// The intermediate-string lengths match.
break;
} else {
throw new IllegalArgumentException(
"The ab output string is shorter than the bc input string.");
}
}
if (bc_bLength == 0) {
throw new IllegalArgumentException(
"The bc input string is shorter than the ab output string.");
}
// Done fetching: ab_bLength > 0 && bc_bLength > 0
// The current state has two parts:
// - Past: We accumulate a longer ac edit in the "pending" variables.
// - Current: We have copies of the current ab/bc edits in local variables.
// At least one side is newly fetched.
// One side might be a truncated remainder of an edit we fetched earlier.
if (!abIter.hasChange() && !bcIter.hasChange()) {
// An unchanged span all the way from string a to string c.
if (pending_aLength != 0 || pending_cLength != 0) {
addReplace(pending_aLength, pending_cLength);
pending_aLength = pending_cLength = 0;
}
int unchangedLength = aLength <= cLength ? aLength : cLength;
addUnchanged(unchangedLength);
ab_bLength = aLength -= unchangedLength;
bc_bLength = cLength -= unchangedLength;
// At least one of the unchanged spans is now empty.
continue;
}
if (!abIter.hasChange() && bcIter.hasChange()) {
// Unchanged a->b but changed b->c.
if (ab_bLength >= bc_bLength) {
// Split the longer unchanged span into change + remainder.
addReplace(pending_aLength + bc_bLength, pending_cLength + cLength);
pending_aLength = pending_cLength = 0;
aLength = ab_bLength -= bc_bLength;
bc_bLength = 0;
continue;
}
// Handle the shorter unchanged span below like a change.
} else if (abIter.hasChange() && !bcIter.hasChange()) {
// Changed a->b and then unchanged b->c.
if (ab_bLength <= bc_bLength) {
// Split the longer unchanged span into change + remainder.
addReplace(pending_aLength + aLength, pending_cLength + ab_bLength);
pending_aLength = pending_cLength = 0;
cLength = bc_bLength -= ab_bLength;
ab_bLength = 0;
continue;
}
// Handle the shorter unchanged span below like a change.
} else { // both abIter.hasChange() && bcIter.hasChange()
if (ab_bLength == bc_bLength) {
// Changes on both sides up to the same position. Emit & reset.
addReplace(pending_aLength + aLength, pending_cLength + cLength);
pending_aLength = pending_cLength = 0;
ab_bLength = bc_bLength = 0;
continue;
}
}
// Accumulate the a->c change, reset the shorter side,
// keep a remainder of the longer one.
pending_aLength += aLength;
pending_cLength += cLength;
if (ab_bLength < bc_bLength) {
bc_bLength -= ab_bLength;
cLength = ab_bLength = 0;
} else { // ab_bLength > bc_bLength
ab_bLength -= bc_bLength;
aLength = bc_bLength = 0;
}
}
if (pending_aLength != 0 || pending_cLength != 0) {
addReplace(pending_aLength, pending_cLength);
}
return this;
}
}