82 lines
2.6 KiB
Go
82 lines
2.6 KiB
Go
package catalogue
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import (
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"bytes"
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"encoding/json"
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"fmt"
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)
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// The mesh's caps on a log, in MiB: what a module may ask, and what it gets when it asks nothing.
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const (
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LogLeastMiB = 1
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LogMostMiB = 8192
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LogDefaultMiB = 1024
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)
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// LogDeclaration is one log a module owns: its local name, and how large it may grow.
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type LogDeclaration struct {
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Name string `json:"name"`
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// MaxMiB is the log's cap in MiB; zero is LogDefaultMiB. When full, the log refuses new entries
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// and never drops old ones.
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MaxMiB int `json:"max-mib,omitempty"`
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// MaxAgeDays is how long an entry is kept, in days; zero is as long as the log (novox/hq ADR 0297). The one way an
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// entry leaves a log: the server ages it out, never a delete or a purge (novox/hq ADR 0565 §10: the hand-act log
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// keeps every act 400 days; issue 1953 S-age).
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MaxAgeDays int `json:"max-age-days,omitempty"`
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}
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// LogMostAgeDays is the longest a log may keep an entry by age: past it, a log keeps its entries as long as it is.
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const LogMostAgeDays = 3650
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// Cap is the log's cap in MiB, the default where none is said.
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func (l LogDeclaration) Cap() int {
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if l.MaxMiB == 0 {
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return LogDefaultMiB
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}
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return l.MaxMiB
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}
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// UnmarshalJSON reads a log as its bare name, or as {name, max-mib, max-age-days}.
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func (l *LogDeclaration) UnmarshalJSON(raw []byte) error {
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trimmed := bytes.TrimSpace(raw)
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if len(trimmed) > 0 && trimmed[0] == '"' {
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return json.Unmarshal(trimmed, &l.Name)
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}
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var full struct {
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Name string `json:"name"`
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MaxMiB *int `json:"max-mib"`
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MaxAgeDays *int `json:"max-age-days"`
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}
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dec := json.NewDecoder(bytes.NewReader(trimmed))
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dec.DisallowUnknownFields()
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if err := dec.Decode(&full); err != nil {
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return fmt.Errorf("a log is either a name or {name, max-mib, max-age-days}: %w", typedUnknown(err))
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}
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l.Name = full.Name
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l.MaxMiB = 0
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if full.MaxMiB != nil {
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// Said, and said as nothing: refused rather than read as the default, which it did not say.
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if *full.MaxMiB == 0 {
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return fmt.Errorf("log %q: max-mib is between %d and %d, not 0", full.Name, LogLeastMiB, LogMostMiB)
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}
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l.MaxMiB = *full.MaxMiB
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}
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l.MaxAgeDays = 0
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if full.MaxAgeDays != nil {
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if *full.MaxAgeDays < 1 || *full.MaxAgeDays > LogMostAgeDays {
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return fmt.Errorf("log %q: max-age-days is between 1 and %d, not %d", full.Name, LogMostAgeDays, *full.MaxAgeDays)
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}
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l.MaxAgeDays = *full.MaxAgeDays
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}
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return nil
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}
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// MarshalJSON writes back the short form when there is nothing else to say.
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func (l LogDeclaration) MarshalJSON() ([]byte, error) {
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if l.MaxMiB == 0 && l.MaxAgeDays == 0 {
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return json.Marshal(l.Name)
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}
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type plain LogDeclaration
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return json.Marshal(plain(l))
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}
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