Add RedisCommandEncoder

We want to be able to efficiently encode Redis commands that are sent to a server. This patch adds a new `RedisCommandEncoder` that allows us to efficiently create Redis commands without needing to go through RESP representations, that may require us to create Arrays. Further it introduces a `RESP3BlobStringEncodable` that must be implement to send blob strings using `RedisCommandEncoder`. This patch also adds implementations for `String` and `ByteBuffer` for the new `RESP3BlobStringEncodable` protocol.
swift-server · Jun 21, 2023 · 89bf654 · 89bf654
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diff --git a/Sources/RediStack/RedisCommandEncoder-multi-encode.swift b/Sources/RediStack/RedisCommandEncoder-multi-encode.swift
@@ -0,0 +1,82 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the RediStack open source project
+//
+// Copyright (c) 2023 RediStack project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of RediStack project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+//
+// NOTE: THIS FILE IS AUTO-GENERATED BY scripts/generate_rediscommandencoder_multi_encode.sh
+
+#if swift(<5.9)
+extension RedisCommandEncoder {
+    @inlinable
+    mutating func encodeRESPArray<T0: RESP3BlobStringEncodable>(_ t0: T0) {
+        self.buffer.writeBytes("*1\r\n".utf8)
+        t0.encodeRedisBlobString(into: &self.buffer)
+    }
+
+    @inlinable
+    mutating func encodeRESPArray<T0: RESP3BlobStringEncodable, T1: RESP3BlobStringEncodable>(_ t0: T0, _ t1: T1) {
+        self.buffer.writeBytes("*2\r\n".utf8)
+        t0.encodeRedisBlobString(into: &self.buffer)
+        t1.encodeRedisBlobString(into: &self.buffer)
+    }
+
+    @inlinable
+    mutating func encodeRESPArray<T0: RESP3BlobStringEncodable, T1: RESP3BlobStringEncodable, T2: RESP3BlobStringEncodable>(_ t0: T0, _ t1: T1, _ t2: T2) {
+        self.buffer.writeBytes("*3\r\n".utf8)
+        t0.encodeRedisBlobString(into: &self.buffer)
+        t1.encodeRedisBlobString(into: &self.buffer)
+        t2.encodeRedisBlobString(into: &self.buffer)
+    }
+
+    @inlinable
+    mutating func encodeRESPArray<T0: RESP3BlobStringEncodable, T1: RESP3BlobStringEncodable, T2: RESP3BlobStringEncodable, T3: RESP3BlobStringEncodable>(_ t0: T0, _ t1: T1, _ t2: T2, _ t3: T3) {
+        self.buffer.writeBytes("*4\r\n".utf8)
+        t0.encodeRedisBlobString(into: &self.buffer)
+        t1.encodeRedisBlobString(into: &self.buffer)
+        t2.encodeRedisBlobString(into: &self.buffer)
+        t3.encodeRedisBlobString(into: &self.buffer)
+    }
+
+    @inlinable
+    mutating func encodeRESPArray<T0: RESP3BlobStringEncodable, T1: RESP3BlobStringEncodable, T2: RESP3BlobStringEncodable, T3: RESP3BlobStringEncodable, T4: RESP3BlobStringEncodable>(_ t0: T0, _ t1: T1, _ t2: T2, _ t3: T3, _ t4: T4) {
+        self.buffer.writeBytes("*5\r\n".utf8)
+        t0.encodeRedisBlobString(into: &self.buffer)
+        t1.encodeRedisBlobString(into: &self.buffer)
+        t2.encodeRedisBlobString(into: &self.buffer)
+        t3.encodeRedisBlobString(into: &self.buffer)
+        t4.encodeRedisBlobString(into: &self.buffer)
+    }
+
+    @inlinable
+    mutating func encodeRESPArray<T0: RESP3BlobStringEncodable, T1: RESP3BlobStringEncodable, T2: RESP3BlobStringEncodable, T3: RESP3BlobStringEncodable, T4: RESP3BlobStringEncodable, T5: RESP3BlobStringEncodable>(_ t0: T0, _ t1: T1, _ t2: T2, _ t3: T3, _ t4: T4, _ t5: T5) {
+        self.buffer.writeBytes("*6\r\n".utf8)
+        t0.encodeRedisBlobString(into: &self.buffer)
+        t1.encodeRedisBlobString(into: &self.buffer)
+        t2.encodeRedisBlobString(into: &self.buffer)
+        t3.encodeRedisBlobString(into: &self.buffer)
+        t4.encodeRedisBlobString(into: &self.buffer)
+        t5.encodeRedisBlobString(into: &self.buffer)
+    }
+
+    @inlinable
+    mutating func encodeRESPArray<T0: RESP3BlobStringEncodable, T1: RESP3BlobStringEncodable, T2: RESP3BlobStringEncodable, T3: RESP3BlobStringEncodable, T4: RESP3BlobStringEncodable, T5: RESP3BlobStringEncodable, T6: RESP3BlobStringEncodable>(_ t0: T0, _ t1: T1, _ t2: T2, _ t3: T3, _ t4: T4, _ t5: T5, _ t6: T6) {
+        self.buffer.writeBytes("*7\r\n".utf8)
+        t0.encodeRedisBlobString(into: &self.buffer)
+        t1.encodeRedisBlobString(into: &self.buffer)
+        t2.encodeRedisBlobString(into: &self.buffer)
+        t3.encodeRedisBlobString(into: &self.buffer)
+        t4.encodeRedisBlobString(into: &self.buffer)
+        t5.encodeRedisBlobString(into: &self.buffer)
+        t6.encodeRedisBlobString(into: &self.buffer)
+    }
+}
+#endif
diff --git a/Sources/RediStack/RedisCommandEncoder.swift b/Sources/RediStack/RedisCommandEncoder.swift
@@ -0,0 +1,82 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the RediStack open source project
+//
+// Copyright (c) 2023 RediStack project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of RediStack project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import NIOCore
+
+protocol RESP3BlobStringEncodable {
+    func encodeRedisBlobString(into buffer: inout ByteBuffer)
+}
+
+/// A Redis client sends commands to a Redis server using RESP. However clients are expected to only
+/// sent [RESP Array of Bulk Strings](https://redis.io/docs/reference/protocol-spec/).
+/// This allows us to make some heavy optimizations.
+///
+/// ``RedisCommandEncoder`` supports writing ``RESP3BlobStringEncodable`` into an outgoing buffer.
+struct RedisCommandEncoder {
+    var buffer: ByteBuffer
+
+#if swift(>=5.9)
+    mutating func encodeRESPArray<each S: RESP3BlobStringEncodable>(_ first: some RESP3BlobStringEncodable, _ args: repeat each S) {
+        let count = ComputeParameterPackLength.count(ofPack: repeat each args)
+
+        self.buffer.writeBytes("*".utf8)
+        self.buffer.writeBytes("\(count + 1)".utf8)
+        self.buffer.writeRESPNewLine()
+        first.encodeRedisBlobString(into: &self.buffer)
+        repeat (
+            (each args).encodeRedisBlobString(into: &self.buffer)
+        )
+    }
+#endif
+}
+
+extension String: RESP3BlobStringEncodable {
+    func encodeRedisBlobString(into buffer: inout ByteBuffer) {
+        buffer.writeBytes("$".utf8)
+        buffer.writeBytes("\(self.utf8.count)".utf8)
+        buffer.writeRESPNewLine()
+        buffer.writeBytes(self.utf8)
+        buffer.writeRESPNewLine()
+    }
+}
+
+extension ByteBuffer: RESP3BlobStringEncodable {
+    func encodeRedisBlobString(into buffer: inout ByteBuffer) {
+        var mutable = self
+        buffer.writeBytes("$".utf8)
+        buffer.writeBytes("\(self.readableBytes)".utf8)
+        buffer.writeRESPNewLine()
+        buffer.writeBuffer(&mutable)
+        buffer.writeRESPNewLine()
+    }
+}
+
+
+#if swift(>=5.9)
+private enum ComputeParameterPackLength {
+    enum BoolConverter<T> {
+        typealias Bool = Swift.Bool
+    }
+
+    static func count<each T>(ofPack t: repeat each T) -> Int {
+        MemoryLayout<(repeat BoolConverter<each T>.Bool)>.size / MemoryLayout<Bool>.stride
+    }
+}
+#endif
+
+extension ByteBuffer {
+    mutating func writeRESPNewLine() {
+        self.writeBytes("\r\n".utf8)
+    }
+}
diff --git a/Tests/RediStackTests/RedisCommandEncoderTests.swift b/Tests/RediStackTests/RedisCommandEncoderTests.swift
@@ -0,0 +1,79 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the RediStack open source project
+//
+// Copyright (c) 2023 RediStack project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of RediStack project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+import NIOCore
+@testable import RediStack
+import XCTest
+
+final class RedisCommandEncoderTests: XCTestCase {
+
+    var encoder: RedisCommandEncoder!
+
+    override func setUp() {
+        self.encoder = RedisCommandEncoder(buffer: ByteBuffer())
+        super.setUp()
+    }
+
+    func testSimple() {
+        self.encoder.encodeRESPArray("GET", "foo")
+        var buffer = self.encoder.buffer
+
+        var resp: RESPValue?
+        XCTAssertNoThrow(resp = try RESPTranslator().parseBytes(from: &buffer))
+        XCTAssertEqual(resp, .array([.bulkString(.init(string: "GET")), .bulkString(.init(string: "foo"))]))
+    }
+
+    func testStringAndByteBuffer() {
+        let twelves = ByteBuffer(repeating: UInt8(ascii: "a"), count: 8)
+        self.encoder.encodeRESPArray("SET", twelves)
+        var buffer = self.encoder.buffer
+
+        XCTAssert(buffer.readableBytesView.elementsEqual("*2\r\n$3\r\nSET\r\n$8\r\naaaaaaaa\r\n".utf8))
+
+        var resp: RESPValue?
+        XCTAssertNoThrow(resp = try RESPTranslator().parseBytes(from: &buffer))
+        XCTAssertEqual(resp, .array([.bulkString(.init(string: "SET")), .bulkString(twelves)]))
+    }
+
+    func testSingleElement() {
+        self.encoder.encodeRESPArray("FOO")
+        var buffer = self.encoder.buffer
+
+        XCTAssert(buffer.readableBytesView.elementsEqual("*1\r\n$3\r\nFOO\r\n".utf8))
+
+        var resp: RESPValue?
+        XCTAssertNoThrow(resp = try RESPTranslator().parseBytes(from: &buffer))
+        XCTAssertEqual(resp, .array([.bulkString(.init(string: "FOO"))]))
+    }
+
+    func testSevenElements() {
+        self.encoder.encodeRESPArray("SET", "key", "value", "NX", "GET", "EX", "60")
+        var buffer = self.encoder.buffer
+
+
+        var resp: RESPValue?
+        XCTAssertNoThrow(resp = try RESPTranslator().parseBytes(from: &buffer))
+        let expected = RESPValue.array([
+            .bulkString(.init(string: "SET")),
+            .bulkString(.init(string: "key")),
+            .bulkString(.init(string: "value")),
+            .bulkString(.init(string: "NX")),
+            .bulkString(.init(string: "GET")),
+            .bulkString(.init(string: "EX")),
+            .bulkString(.init(string: "60"))
+        ])
+        XCTAssertEqual(resp, expected)
+    }
+
+}
diff --git a/scripts/generate_rediscommandencoder_multi_encode.sh b/scripts/generate_rediscommandencoder_multi_encode.sh
@@ -0,0 +1,83 @@
+#!/bin/bash
+##===----------------------------------------------------------------------===##
+##
+## This source file is part of the RediStack open source project
+##
+## Copyright (c) 2023 RediStack project authors
+## Licensed under Apache License v2.0
+##
+## See LICENSE.txt for license information
+## See CONTRIBUTORS.txt for the list of RediStack project authors
+##
+## SPDX-License-Identifier: Apache-2.0
+##
+##===----------------------------------------------------------------------===##
+
+set -eu
+
+here="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
+
+function genWithContextParameter() {
+    how_many=$1
+
+    if [[ $how_many -ne 1 ]] ; then
+        echo ""
+    fi
+
+    echo "    @inlinable"
+    echo -n "    mutating func encodeRESPArray<T0: RESP3BlobStringEncodable"
+    for ((n = 1; n<$how_many; n +=1)); do
+        echo -n ", T$(($n)): RESP3BlobStringEncodable"
+    done
+
+    echo -n ">(_ t0: T0"
+    for ((n = 1; n<$how_many; n +=1)); do
+        echo -n ", _ t$(($n)): T$(($n))"
+    done
+    echo ") {"
+
+    echo "        self.buffer.writeBytes(\"*"$how_many"\\r\\n\".utf8)"
+
+    for ((n = 0; n<$how_many; n +=1)); do
+        echo "        t$(($n)).encodeRedisBlobString(into: &self.buffer)"
+    done
+    echo "    }"
+}
+
+grep -q "ByteBuffer" "${BASH_SOURCE[0]}" || {
+    echo >&2 "ERROR: ${BASH_SOURCE[0]}: file or directory not found (this should be this script)"
+    exit 1
+}
+
+{
+cat <<"EOF"
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the RediStack open source project
+//
+// Copyright (c) 2023 RediStack project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of RediStack project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+//
+// NOTE: THIS FILE IS AUTO-GENERATED BY scripts/generate_rediscommandencoder_multi_encode.sh
+EOF
+echo
+
+echo "#if swift(<5.9)"
+echo "extension RedisCommandEncoder {"
+
+# note:
+# - widening the inverval below (eg. going from {1..15} to {1..25}) is Semver minor
+# - narrowing the interval below is SemVer _MAJOR_!
+for n in {1..7}; do
+    genWithContextParameter "$n"
+done
+echo "}"
+echo "#endif"
+} > "$here/../Sources/RediStack/RedisCommandEncoder-multi-encode.swift"