mirror of https://github.com/mum4k/termdash.git
104 lines
2.7 KiB
Go
104 lines
2.7 KiB
Go
// Copyright 2019 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package attrrange simplifies tracking of attributes that apply to a range of
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// items.
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// Refer to the examples in the test file for details on usage.
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package attrrange
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import (
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"fmt"
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"sort"
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)
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// AttrRange is a range of items that share the same attributes.
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type AttrRange struct {
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// Low is the first position where these attributes apply.
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Low int
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// High is the end of the range. The attributes apply to all items in range
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// Low <= b < high.
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High int
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// AttrIdx is the index of the attributes that apply to this range.
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AttrIdx int
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}
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// newAttrRange returns a new AttrRange instance.
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func newAttrRange(low, high, attrIdx int) *AttrRange {
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return &AttrRange{
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Low: low,
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High: high,
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AttrIdx: attrIdx,
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}
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}
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// Tracker tracks attributes that apply to a range of items.
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// This object is not thread safe.
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type Tracker struct {
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// ranges maps low indices of ranges to the attribute ranges.
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ranges map[int]*AttrRange
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}
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// NewTracker returns a new tracker of ranges that share the same attributes.
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func NewTracker() *Tracker {
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return &Tracker{
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ranges: map[int]*AttrRange{},
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}
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}
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// Add adds a new range of items that share attributes with the specified
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// index.
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// The low position of the range must not overlap with low position of any
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// existing range.
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func (t *Tracker) Add(low, high, attrIdx int) error {
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ar := newAttrRange(low, high, attrIdx)
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if ar, ok := t.ranges[low]; ok {
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return fmt.Errorf("already have range starting on low:%d, existing:%+v", low, ar)
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}
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t.ranges[low] = ar
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return nil
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}
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// ForPosition returns attribute index that apply to the specified position.
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// Returns ErrNotFound when the requested position wasn't found in any of the
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// known ranges.
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func (t *Tracker) ForPosition(pos int) (*AttrRange, error) {
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if ar, ok := t.ranges[pos]; ok {
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return ar, nil
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}
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var keys []int
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for k := range t.ranges {
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keys = append(keys, k)
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}
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sort.Ints(keys)
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var res *AttrRange
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for _, k := range keys {
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ar := t.ranges[k]
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if ar.Low > pos {
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break
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}
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if ar.High > pos {
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res = ar
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}
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}
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if res == nil {
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return nil, fmt.Errorf("did not find attribute range for position %d", pos)
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}
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return res, nil
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}
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