history_config.go RawHistoryFolder

1package vt
2
3import (
4	"errors"
5	"math"
6)
7
8var ErrInvalidHistoryConfig = errors.New("invalid history configuration")
9
10// HistoryConfig enforces limits selected by the application. The library
11// supplies no byte or line defaults. Each positive limit is an independent
12// ceiling; zero omits that ceiling. Both zero disable history. Live grids are
13// excluded. ChunkRows is an internal grouping hint in [1,256]; zero selects
14// 256 and does not grant space beyond the application's retention limits.
15type HistoryConfig struct {
16	MaxRows   int
17	MaxBytes  uint64
18	ChunkRows int
19}
20
21func (c HistoryConfig) Validate() error {
22	if c.MaxRows < 0 || c.ChunkRows < 0 || c.ChunkRows > maxHistoryChunkRows {
23		return ErrInvalidHistoryConfig
24	}
25	return nil
26}
27
28// NewHistory constructs owned bounded history. Invalid programmer-supplied
29// configuration panics; user-input boundaries should call Validate first.
30func NewHistory(config HistoryConfig) *History {
31	h := &History{nextRowID: 1}
32	if err := h.SetLimits(config); err != nil {
33		panic(err)
34	}
35	return h
36}
37
38// SetLimits validates first, then updates limits and evicts oldest rows before
39// returning. Existing borrowed views remain valid. Disabling history releases
40// its owned backing but preserves the next row identity. The owner must serialize
41// this operation with all other History mutations.
42func (h *History) SetLimits(config HistoryConfig) error {
43	if h == nil {
44		return ErrInvalidHistoryConfig
45	}
46	if err := config.Validate(); err != nil {
47		return err
48	}
49	if config.MaxRows == 0 && config.MaxBytes == 0 {
50		*h = History{nextRowID: h.NextRowID()}
51		return nil
52	}
53	rows := config.MaxRows
54	if rows == 0 {
55		rows = math.MaxInt
56	}
57	chunkRows := config.ChunkRows
58	if chunkRows == 0 {
59		chunkRows = maxHistoryChunkRows
60	}
61	chunkRows = min(chunkRows, rows)
62	bytes := config.MaxBytes
63	if bytes == 0 {
64		bytes = math.MaxUint64
65	}
66	if len(h.tail) >= chunkRows {
67		h.sealTail()
68	}
69	h.maxRows, h.rowCeiling, h.maxBytes, h.chunkRows = rows, config.MaxRows, bytes, chunkRows
70	h.byteCeiling = config.MaxBytes
71	for h.rows > rows || h.logicalBytes > bytes {
72		h.evictOldest()
73	}
74	clear(h.payloadScratch)
75	return nil
76}
77
78// Limits reports the application's policy. A zero limit is omitted; both
79// zero mean history is disabled. ChunkRows reports the resolved grouping size.
80func (h *History) Limits() HistoryConfig {
81	if h == nil {
82		return HistoryConfig{}
83	}
84	return HistoryConfig{MaxRows: h.rowCeiling, MaxBytes: h.byteCeiling, ChunkRows: h.chunkRows}
85}