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evgeny-simplexevgeny-simplex
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encoding/decoding of LGET/LNK
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‎smp-web/src/protocol.ts‎

Lines changed: 96 additions & 0 deletions
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@@ -0,0 +1,96 @@
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// SMP protocol commands and transmission format.
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// Mirrors: Simplex.Messaging.Protocol
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import {
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Decoder, concatBytes,
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encodeBytes, decodeBytes,
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decodeLarge
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} from "@simplex-chat/xftp-web/dist/protocol/encoding.js"
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import {readTag, readSpace} from "@simplex-chat/xftp-web/dist/protocol/commands.js"
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// -- Transmission encoding (Protocol.hs:2201-2203)
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// encodeTransmission_ v (CorrId corrId, queueId, command) =
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// smpEncode (corrId, queueId) <> encodeProtocol v command
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export function encodeTransmission(corrId: Uint8Array, entityId: Uint8Array, command: Uint8Array): Uint8Array {
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return concatBytes(
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encodeBytes(new Uint8Array(0)), // empty auth
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encodeBytes(corrId),
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encodeBytes(entityId),
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command
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)
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}
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// -- Transmission parsing (Protocol.hs:1629-1642)
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// For implySessId = True (v7+): no sessId on wire
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export interface RawTransmission {
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corrId: Uint8Array
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entityId: Uint8Array
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command: Uint8Array
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}
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export function decodeTransmission(d: Decoder): RawTransmission {
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const _auth = decodeBytes(d) // authenticator (empty for unsigned)
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const corrId = decodeBytes(d)
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const entityId = decodeBytes(d)
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const command = d.takeAll()
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return {corrId, entityId, command}
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}
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// -- SMP command tags
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const SPACE = 0x20
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function ascii(s: string): Uint8Array {
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const buf = new Uint8Array(s.length)
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for (let i = 0; i < s.length; i++) buf[i] = s.charCodeAt(i)
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return buf
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}
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// -- LGET command (Protocol.hs:1709)
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// No parameters. EntityId carries LinkId in transmission.
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export function encodeLGET(): Uint8Array {
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return ascii("LGET")
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}
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// -- LNK response (Protocol.hs:1834)
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// LNK sId d -> e (LNK_, ' ', sId, d)
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// where d = (EncFixedDataBytes, EncUserDataBytes), both Large-encoded
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export interface LNKResponse {
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senderId: Uint8Array
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encFixedData: Uint8Array
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encUserData: Uint8Array
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}
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export function decodeLNK(d: Decoder): LNKResponse {
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const senderId = decodeBytes(d)
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const encFixedData = decodeLarge(d)
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const encUserData = decodeLarge(d)
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return {senderId, encFixedData, encUserData}
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}
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// -- Response dispatch (same pattern as xftp-web decodeResponse)
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export type SMPResponse =
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| {type: "LNK", response: LNKResponse}
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| {type: "OK"}
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| {type: "ERR", message: string}
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export function decodeResponse(d: Decoder): SMPResponse {
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const tag = readTag(d)
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switch (tag) {
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case "LNK": {
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readSpace(d)
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return {type: "LNK", response: decodeLNK(d)}
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}
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case "OK": return {type: "OK"}
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case "ERR": {
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readSpace(d)
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return {type: "ERR", message: readTag(d)}
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}
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default: throw new Error("unknown SMP response: " + tag)
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}
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}

‎tests/SMPWebTests.hs‎

Lines changed: 67 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,6 @@
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module SMPWebTests (smpWebTests) where
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import qualified Data.ByteString as B
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import Data.Word (Word16)
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import Simplex.Messaging.Encoding
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import Test.Hspec hiding (it)
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import Util
@@ -21,17 +20,73 @@ smpWebDir = "smp-web"
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callNode :: String -> IO B.ByteString
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callNode = callNode_ smpWebDir
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impEnc :: String
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impEnc = "import { encodeBytes, encodeWord16 } from '@simplex-chat/xftp-web/dist/protocol/encoding.js';"
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impProto :: String
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impProto = "import { encodeTransmission, decodeTransmission, encodeLGET, decodeLNK, decodeResponse } from './dist/protocol.js';"
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<> "import { Decoder } from '@simplex-chat/xftp-web/dist/protocol/encoding.js';"
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smpWebTests :: SpecWith ()
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smpWebTests = describe "SMP Web Client" $ do
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describe "xftp-web imports" $ do
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it "encodeBytes via xftp-web" $ do
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let val = "hello" :: B.ByteString
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actual <- callNode $ impEnc <> jsOut ("encodeBytes(" <> jsUint8 val <> ")")
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actual `shouldBe` smpEncode val
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it "encodeWord16 via xftp-web" $ do
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let val = 12345 :: Word16
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actual <- callNode $ impEnc <> jsOut ("encodeWord16(" <> show val <> ")")
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actual `shouldBe` smpEncode val
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describe "protocol" $ do
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describe "transmission" $ do
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it "encodeTransmission matches Haskell" $ do
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let corrId = "1"
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entityId = B.pack [1..24]
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command = "LGET"
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hsEncoded = smpEncode (corrId :: B.ByteString, entityId :: B.ByteString) <> command
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tsEncoded <- callNode $ impProto
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<> jsOut ("encodeTransmission("
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<> jsUint8 corrId <> ","
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<> jsUint8 entityId <> ","
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<> "new Uint8Array([0x4C,0x47,0x45,0x54])" -- "LGET"
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<> ")")
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-- TS encodes with empty auth prefix, HS encodeTransmission_ doesn't include auth
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-- So TS output = [0x00] ++ hsEncoded
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tsEncoded `shouldBe` (B.singleton 0 <> hsEncoded)
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it "decodeTransmission parses Haskell-encoded" $ do
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let corrId = "abc"
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entityId = B.pack [10..33]
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command = "TEST"
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encoded = smpEncode (B.empty :: B.ByteString) -- empty auth
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<> smpEncode corrId
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<> smpEncode entityId
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<> command
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-- TS decodes and returns corrId ++ entityId ++ command concatenated with length prefixes
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tsResult <- callNode $ impProto
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<> "const t = decodeTransmission(new Decoder(" <> jsUint8 encoded <> "));"
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<> jsOut ("new Uint8Array([...t.corrId, ...t.entityId, ...t.command])")
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tsResult `shouldBe` (corrId <> entityId <> command)
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describe "LGET" $ do
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it "encodeLGET produces correct bytes" $ do
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tsResult <- callNode $ impProto <> jsOut "encodeLGET()"
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tsResult `shouldBe` "LGET"
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describe "LNK" $ do
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it "decodeLNK parses correctly" $ do
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let senderId = B.pack [1..24]
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fixedData = B.pack [100..110]
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userData = B.pack [200..220]
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encoded = smpEncode senderId <> smpEncode (Large fixedData) <> smpEncode (Large userData)
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tsResult <- callNode $ impProto
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<> "const r = decodeLNK(new Decoder(" <> jsUint8 encoded <> "));"
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<> jsOut ("new Uint8Array([...r.senderId, ...r.encFixedData, ...r.encUserData])")
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tsResult `shouldBe` (senderId <> fixedData <> userData)
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describe "decodeResponse" $ do
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it "decodes LNK response" $ do
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let senderId = B.pack [1..24]
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fixedData = B.pack [100..110]
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userData = B.pack [200..220]
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commandBytes = "LNK " <> smpEncode senderId <> smpEncode (Large fixedData) <> smpEncode (Large userData)
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tsResult <- callNode $ impProto
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<> "const r = decodeResponse(new Decoder(" <> jsUint8 commandBytes <> "));"
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<> "if (r.type !== 'LNK') throw new Error('expected LNK, got ' + r.type);"
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<> jsOut ("new Uint8Array([...r.response.senderId])")
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tsResult `shouldBe` senderId
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it "decodes OK response" $ do
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tsResult <- callNode $ impProto
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<> "const r = decodeResponse(new Decoder(new Uint8Array([0x4F, 0x4B])));" -- "OK"
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<> jsOut ("new Uint8Array([r.type === 'OK' ? 1 : 0])")
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tsResult `shouldBe` B.singleton 1

‎xftp-web/src/protocol/commands.ts‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -81,7 +81,7 @@ export function encodePING(): Uint8Array { return ascii("PING") }
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// -- Response decoding
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84-
function readTag(d: Decoder): string {
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export function readTag(d: Decoder): string {
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const start = d.offset()
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while (d.remaining() > 0) {
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if (d.buf[d.offset()] === 0x20 || d.buf[d.offset()] === 0x0a) break
@@ -92,7 +92,7 @@ function readTag(d: Decoder): string {
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return s
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}
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95-
function readSpace(d: Decoder): void {
95+
export function readSpace(d: Decoder): void {
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if (d.anyByte() !== 0x20) throw new Error("expected space")
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}
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