63 lines
2.6 KiB
Go
63 lines
2.6 KiB
Go
package storage
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import (
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"github.com/google/uuid"
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)
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// NewUUID returns a new UUIDv7 encoded as 26-char Crockford Base32 (ULID
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// layout). Used as the root key for file metadata entries.
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//
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// Why this format over canonical 8-4-4-4-12 hex:
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// - 26 chars vs 36 — shorter keys, less prefix space waste
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// - Time-sortable prefix — KEYS file:01JKR* returns entries minted in a
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// given time window, restoring some of the debug-ability lost vs the
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// previous midhash256:abc rooting
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// - Case-insensitive — no ambiguity when copying from logs
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// - Crockford alphabet skips I/L/O/U, so eyeballed inspection of a key
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// can't be confused for an ambient digit/letter typo
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func NewUUID() (string, error) {
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u, err := uuid.NewV7()
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if err != nil {
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return "", err
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}
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return encodeCrockford(u[:]), nil
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}
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const crockfordAlphabet = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"
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// encodeCrockford encodes a 16-byte value as 26 Crockford Base32 chars.
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// 128 bits packs into 130 bits (26 × 5); the top 2 bits of the first char
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// carry the high bits of byte 0, the remaining 3 are implicit zero. This
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// matches the ULID encoding so the output is interchangeable with ULIDs in
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// any tool that accepts them.
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func encodeCrockford(b []byte) string {
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out := make([]byte, 26)
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out[0] = crockfordAlphabet[(b[0]&0xE0)>>5]
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out[1] = crockfordAlphabet[b[0]&0x1F]
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out[2] = crockfordAlphabet[(b[1]&0xF8)>>3]
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out[3] = crockfordAlphabet[((b[1]&0x07)<<2)|((b[2]&0xC0)>>6)]
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out[4] = crockfordAlphabet[(b[2]&0x3E)>>1]
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out[5] = crockfordAlphabet[((b[2]&0x01)<<4)|((b[3]&0xF0)>>4)]
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out[6] = crockfordAlphabet[((b[3]&0x0F)<<1)|((b[4]&0x80)>>7)]
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out[7] = crockfordAlphabet[(b[4]&0x7C)>>2]
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out[8] = crockfordAlphabet[((b[4]&0x03)<<3)|((b[5]&0xE0)>>5)]
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out[9] = crockfordAlphabet[b[5]&0x1F]
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out[10] = crockfordAlphabet[(b[6]&0xF8)>>3]
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out[11] = crockfordAlphabet[((b[6]&0x07)<<2)|((b[7]&0xC0)>>6)]
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out[12] = crockfordAlphabet[(b[7]&0x3E)>>1]
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out[13] = crockfordAlphabet[((b[7]&0x01)<<4)|((b[8]&0xF0)>>4)]
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out[14] = crockfordAlphabet[((b[8]&0x0F)<<1)|((b[9]&0x80)>>7)]
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out[15] = crockfordAlphabet[(b[9]&0x7C)>>2]
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out[16] = crockfordAlphabet[((b[9]&0x03)<<3)|((b[10]&0xE0)>>5)]
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out[17] = crockfordAlphabet[b[10]&0x1F]
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out[18] = crockfordAlphabet[(b[11]&0xF8)>>3]
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out[19] = crockfordAlphabet[((b[11]&0x07)<<2)|((b[12]&0xC0)>>6)]
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out[20] = crockfordAlphabet[(b[12]&0x3E)>>1]
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out[21] = crockfordAlphabet[((b[12]&0x01)<<4)|((b[13]&0xF0)>>4)]
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out[22] = crockfordAlphabet[((b[13]&0x0F)<<1)|((b[14]&0x80)>>7)]
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out[23] = crockfordAlphabet[(b[14]&0x7C)>>2]
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out[24] = crockfordAlphabet[((b[14]&0x03)<<3)|((b[15]&0xE0)>>5)]
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out[25] = crockfordAlphabet[b[15]&0x1F]
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return string(out)
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}
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