Yonah
1354a2c9a3
For representing full identifiers of system and member. Signed-off-by: Yonah <contrib@gensokyo.uk>
90 lines
2.3 KiB
Go
90 lines
2.3 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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// M represents a unique member identifier.
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type M struct {
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// A per-system value incremented by some unspecified amount every time the
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// metadata of a member first appears to the backend.
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Serial uint64
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// An instant in time, some time after the corresponding member 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.
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ID uint64
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// Underlying system.
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System S
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}
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func (*M) ident() {}
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const (
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// SizeMember is the size of the binary representation of [M].
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SizeMember = SizeSystem * 2
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// EncodedSizeMember is the size of the string representation of [M].
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EncodedSizeMember = SizeMember / 3 * 4
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)
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// EncodedSize returns the number of bytes appended by Encode.
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func (*M) EncodedSize() int { return EncodedSizeMember }
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// Encode appends the canonical string representation of mid to dst and returns
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// the extended buffer.
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func (mid *M) Encode(dst []byte) []byte {
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var buf [SizeMember - SizeSystem]byte
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p := buf[:]
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binary.LittleEndian.PutUint64(p, mid.Serial)
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p = p[8:]
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binary.LittleEndian.PutUint64(p, mid.Time)
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p = p[8:]
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binary.LittleEndian.PutUint64(p, mid.ID)
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dst = base64.URLEncoding.AppendEncode(dst, buf[:])
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return mid.System.Encode(dst)
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}
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// String returns the canonical string representation of mid.
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func (mid *M) String() string {
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s := mid.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 (mid *M) MarshalText() (data []byte, err error) {
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return mid.Encode(nil), nil
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}
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// UnmarshalText strictly decodes data into mid.
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func (mid *M) UnmarshalText(data []byte) error {
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if len(data) != EncodedSizeMember {
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return &UnexpectedSizeError{data, EncodedSizeMember}
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}
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var buf [SizeMember - SizeSystem]byte
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if n, err := base64.URLEncoding.Decode(
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buf[:],
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data[:EncodedSizeMember-EncodedSizeSystem],
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); err != nil {
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return err
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} else if n != SizeMember-SizeSystem {
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return ErrNewline
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}
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p := buf[:]
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mid.Serial = binary.LittleEndian.Uint64(p)
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p = p[8:]
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mid.Time = binary.LittleEndian.Uint64(p)
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p = p[8:]
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mid.ID = binary.LittleEndian.Uint64(p)
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return mid.System.UnmarshalText(data[EncodedSizeMember-EncodedSizeSystem:])
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}
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