Yonah
1354a2c9a3
For representing full identifiers of system and member. Signed-off-by: Yonah <contrib@gensokyo.uk>
99 lines
2.6 KiB
Go
99 lines
2.6 KiB
Go
package ident
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import (
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"encoding/base64"
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"encoding/binary"
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"unsafe"
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)
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const (
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// TrivialSite is conventionally reserved for the [S.Site] field on a
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// trivial, single-host server implementation.
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TrivialSite = 0xfeedcafe
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// TrivialHost is conventionally reserved for the [S.Host] field on a
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// trivial, single-host server implementation.
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TrivialHost = 0xcafebabe
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)
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// S represents a unique system identifier.
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type S struct {
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// Deployment site, typically denoting a datacenter servicing a region.
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Site uint32
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// Servicing host behind load balancer, unique within its Site.
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Host uint32
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// An instant in time, some time after the corresponding system metadata
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// first appeared to the backend, represented in nanoseconds since
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// 1970-01-01.
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Time uint64
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// Randomly generated value. The implementation must guarantee that the same
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// value cannot be emitted for a Time value on a servicing Host.
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ID uint64
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}
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func (*S) ident() {}
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const (
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// SizeSystem is the size of the binary representation of [S].
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SizeSystem = 24
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// EncodedSizeSystem is the size of the string representation of [S].
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EncodedSizeSystem = SizeSystem / 3 * 4
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)
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// EncodedSize returns the number of bytes appended by Encode.
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func (*S) EncodedSize() int { return EncodedSizeSystem }
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// Encode appends the canonical string representation of sid to dst and returns
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// the extended buffer.
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func (sid *S) Encode(dst []byte) []byte {
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var buf [SizeSystem]byte
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p := buf[:]
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binary.LittleEndian.PutUint32(p, sid.Site)
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p = p[4:]
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binary.LittleEndian.PutUint32(p, sid.Host)
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p = p[4:]
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binary.LittleEndian.PutUint64(p, sid.Time)
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p = p[8:]
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binary.LittleEndian.PutUint64(p, sid.ID)
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return base64.URLEncoding.AppendEncode(dst, buf[:])
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}
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// String returns the canonical string representation of sid.
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func (sid *S) String() string {
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s := sid.Encode(nil)
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return unsafe.String(unsafe.SliceData(s), len(s))
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}
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// MarshalText returns the result of Encode.
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func (sid *S) MarshalText() (data []byte, err error) {
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return sid.Encode(nil), nil
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}
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// UnmarshalText strictly decodes data into sid.
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func (sid *S) UnmarshalText(data []byte) error {
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if len(data) != EncodedSizeSystem {
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return &UnexpectedSizeError{data, EncodedSizeSystem}
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}
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var buf [SizeSystem]byte
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if n, err := base64.URLEncoding.Decode(
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buf[:],
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data,
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); err != nil {
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return err
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} else if n != SizeSystem {
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return ErrNewline
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}
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p := buf[:]
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sid.Site = binary.LittleEndian.Uint32(p)
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p = p[4:]
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sid.Host = binary.LittleEndian.Uint32(p)
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p = p[4:]
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sid.Time = binary.LittleEndian.Uint64(p)
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p = p[8:]
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sid.ID = binary.LittleEndian.Uint64(p)
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return nil
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}
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