history_styleset.go RawHistoryFolder

1package vt
2
3import (
4	"iter"
5	"slices"
6
7	renderer "github.com/bnema/vev-vt/core"
8)
9
10// styleSetInline is the number of distinct styles kept in a linear slice
11// before the set switches to a map. Typical rows use a handful of styles, where
12// a short compare loop beats hashing the 56-byte Style key.
13const styleSetInline = 16
14
15// styleSet is a reusable set of canonical styles for one history row. It keeps
16// small sets in a slice and only builds a map for high-cardinality rows. The
17// zero value is empty and ready to use.
18type styleSet struct {
19	small []renderer.Style
20	large map[renderer.Style]struct{}
21}
22
23func (s *styleSet) reset() {
24	s.small = s.small[:0]
25	if len(s.large) > maxRetainedStyleScratch {
26		s.large = nil
27	} else {
28		clear(s.large)
29	}
30}
31
32func (s *styleSet) add(style renderer.Style) {
33	if len(s.large) > 0 {
34		s.large[style] = struct{}{}
35		return
36	}
37	if slices.Contains(s.small, style) {
38		return
39	}
40	if len(s.small) < styleSetInline {
41		s.small = append(s.small, style)
42		return
43	}
44	if s.large == nil {
45		s.large = make(map[renderer.Style]struct{}, 2*styleSetInline)
46	}
47	for _, existing := range s.small {
48		s.large[existing] = struct{}{}
49	}
50	s.large[style] = struct{}{}
51	s.small = s.small[:0]
52}
53
54func (s *styleSet) len() int {
55	if len(s.large) > 0 {
56		return len(s.large)
57	}
58	return len(s.small)
59}
60
61// all yields each style once, in unspecified order.
62func (s *styleSet) all() iter.Seq[renderer.Style] {
63	return func(yield func(renderer.Style) bool) {
64		if len(s.large) > 0 {
65			for style := range s.large {
66				if !yield(style) {
67					return
68				}
69			}
70			return
71		}
72		for _, style := range s.small {
73			if !yield(style) {
74				return
75			}
76		}
77	}
78}