2014-07-30 18:30:38 +02:00
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// Copyright (c) 2014 Couchbase, Inc.
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
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// except in compliance with the License. You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software distributed under the
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// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
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// either express or implied. See the License for the specific language governing permissions
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// and limitations under the License.
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2014-06-26 17:43:13 +02:00
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package search
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import ()
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const DEFAULT_FRAGMENT_SIZE = 100
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type SimpleFragmenter struct {
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fragmentSize int
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}
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func NewSimpleFragmenter() *SimpleFragmenter {
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return &SimpleFragmenter{
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fragmentSize: DEFAULT_FRAGMENT_SIZE,
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}
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}
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func NewSimpleFragmenterWithSize(fragmentSize int) *SimpleFragmenter {
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return &SimpleFragmenter{
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fragmentSize: fragmentSize,
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}
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}
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func (s *SimpleFragmenter) Fragment(orig []byte, ot termLocations) []*Fragment {
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rv := make([]*Fragment, 0)
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maxbegin := 0
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for currTermIndex, termLocation := range ot {
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// start with with this
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// it should be the highest scoring fragment with this term first
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start := termLocation.Start
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end := start + s.fragmentSize
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if end > len(orig) {
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end = len(orig)
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// we hit end, so push back as far as we can without crossing maxbegin
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extra := s.fragmentSize - (end - start)
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if start-extra >= maxbegin {
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start -= extra
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} else {
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start = maxbegin
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}
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}
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// however, we'd rather have the tokens centered more in the frag
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// lets try to do that as best we can, without affecting the score
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// find the end of the last term in this fragment
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minend := end
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for _, innerTermLocation := range ot[currTermIndex:] {
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if innerTermLocation.End > end {
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break
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}
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minend = innerTermLocation.End
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}
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// find the smaller of the two rooms to move
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roomToMove := end - minend
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if start-maxbegin < roomToMove {
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roomToMove = start - maxbegin
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}
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offset := roomToMove / 2
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rv = append(rv, &Fragment{orig: orig, start: start - offset, end: end - offset})
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// set maxbegin to the end of the current term location
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// so that next one won't back up to include it
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maxbegin = termLocation.End
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}
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return rv
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}
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