/**
* Returns the comparison result of the next row from each cursor. If one cursor has no more rows
* but the other does then subsequent calls to this will indicate that the remaining rows are
* unique.
*
* <p>The caller must check that hasNext() returns true before calling this.
*
* <p>Once next() has been called the cursors specified in the result of the call to next() are
* guaranteed to point to the row that was indicated. Reading values from the cursor that was not
* indicated in the call to next() will result in undefined behavior.
*
* @return LEFT, if the row pointed to by the left cursor is unique, RIGHT if the row pointed to
* by the right cursor is unique, BOTH if the rows in both cursors are the same.
*/
public Result next() {
if (!hasNext()) {
throw new IllegalStateException("you must only call next() when hasNext() is true");
}
incrementCursors();
assert hasNext();
boolean hasLeft = !mCursorLeft.isAfterLast();
boolean hasRight = !mCursorRight.isAfterLast();
if (hasLeft && hasRight) {
populateValues(mValues, mCursorLeft, mColumnsLeft, 0 /* start filling at index 0 */);
populateValues(mValues, mCursorRight, mColumnsRight, 1 /* start filling at index 1 */);
switch (compareStrings(mValues)) {
case -1:
mCompareResult = Result.LEFT;
break;
case 0:
mCompareResult = Result.BOTH;
break;
case 1:
mCompareResult = Result.RIGHT;
break;
}
} else if (hasLeft) {
mCompareResult = Result.LEFT;
} else {
assert hasRight;
mCompareResult = Result.RIGHT;
}
mCompareResultIsValid = true;
return mCompareResult;
}
/**
* Returns whether or not there are more rows to compare using next().
*
* @return true if there are more rows to compare
*/
public boolean hasNext() {
if (mCompareResultIsValid) {
switch (mCompareResult) {
case BOTH:
return !mCursorLeft.isLast() || !mCursorRight.isLast();
case LEFT:
return !mCursorLeft.isLast() || !mCursorRight.isAfterLast();
case RIGHT:
return !mCursorLeft.isAfterLast() || !mCursorRight.isLast();
default:
throw new IllegalStateException("bad value for mCompareResult, " + mCompareResult);
}
} else {
return !mCursorLeft.isAfterLast() || !mCursorRight.isAfterLast();
}
}
