Repository: apple/swift-nio
File: Tests/NIOCoreTests/ByteBufferTest.swift (Swift)

Code before:
        XCTAssertFalse(buffer.shrinkBufferCapacity(to: desiredCapacity))
        XCTAssertEqual(buffer.capacity, 2048)

        // If desired capacity is greater than the readable bytes and less than buffer capacity, should shrink to desiredCapacity.nextPowerOf2Clamp
        // Where desiredCapacity.nextPowerOf2Clamp == desiredCapacity as desiredCapacity should already be a power of 2 value
        buffer.clear()
        buffer.writeString(String(repeating: "x", count: desiredCapacity - 1))
        XCTAssertEqual(buffer.capacity, 2048)
        XCTAssertTrue(buffer.shrinkBufferCapacity(to: desiredCapacity))
        XCTAssertEqual(buffer.capacity, 1024)
    }

    func testShrinkBufferCapacityWithLeadingUnwrittenBytes() {
        var buffer = self.allocator.buffer(capacity: 16384)
        buffer.moveWriterIndex(to: 16000)
        buffer.moveReaderIndex(to: 16000)
        buffer.writeString("WW")
        buffer.shrinkBufferCapacity(to: 4)
        XCTAssertEqual("WW", String(buffer: buffer))

        // If readable bytes is exactly the same as buffer capacity shrunken to
        buffer = self.allocator.buffer(capacity: 16)
        buffer.moveWriterIndex(to: 8)
        buffer.moveReaderIndex(to: 8)
        buffer.writeString("WWWWWWWW")  // 8 bytes written
        buffer.shrinkBufferCapacity(to: 4)  // Invisible padding makes this 8 bytes
        XCTAssertEqual("WWWWWWWW", String(buffer: buffer))  // All 8 bytes are returned!
    }

    func testExpansionOfCapacityWithPadding() throws {
        XCTAssertEqual(ByteBuffer.addPaddingTo(12), 16)
        XCTAssertEqual(ByteBuffer.addPaddingTo(0), 0)
    }

    func testDumpBytesFormat() throws {
        self.buf.clear()
        for f in UInt8.min...UInt8.max {
            self.buf.writeInteger(f)
        }
        let actual = self.buf._storage.dumpBytes(slice: self.buf._slice, offset: 0, length: self.buf.readableBytes)
        let expected = """
            [ 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f \
            20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f \
            40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f 50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f \
            60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f 70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f \
            80 81 82 83 84 85 86 87 88 89 8a 8b 8c 8d 8e 8f 90 91 92 93 94 95 96 97 98 99 9a 9b 9c 9d 9e 9f \
            a0 a1 a2 a3 a4 a5 a6 a7 a8 a9 aa ab ac ad ae af b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 ba bb bc bd be bf \
            c0 c1 c2 c3 c4 c5 c6 c7 c8 c9 ca cb cc cd ce cf d0 d1 d2 d3 d4 d5 d6 d7 d8 d9 da db dc dd de df \
            e0 e1 e2 e3 e4 e5 e6 e7 e8 e9 ea eb ec ed ee ef f0 f1 f2 f3 f4 f5 f6 f7 f8 f9 fa fb fc fd fe ff ]
            """
        XCTAssertEqual(expected, actual)

Review comment (bug):
Can we very specifically look at the 2nd test in `testShrinkBufferCapacityWithLeadingUnwrittenBytes` and the comments and make sure it is what is expected. Or if I am testing implementation detail that should not fail if the function changes?

Code after:
        XCTAssertFalse(buffer.shrinkBufferCapacity(to: desiredCapacity))
        XCTAssertEqual(buffer.capacity, 2048)

        // If desired capacity is greater than or equal the readable bytes and less than buffer capacity, should shrink
        buffer.clear()
        buffer.writeString(String(repeating: "x", count: desiredCapacity))
        XCTAssertEqual(buffer.capacity, 2048)
        XCTAssertTrue(buffer.shrinkBufferCapacity(to: desiredCapacity))
        XCTAssertEqual(buffer.capacity, 1024)
    }

    func testShrinkBufferCapacityWithLeadingUnwrittenBytes() {
        var buffer = self.allocator.buffer(capacity: 16384)
        buffer.moveWriterIndex(to: 16000)
        buffer.moveReaderIndex(to: 16000)
        buffer.writeString("WW")
        buffer.shrinkBufferCapacity(to: 4)
        XCTAssertEqual("WW", String(buffer: buffer))

        // If readable bytes is exactly the same as buffer capacity shrunken to
        buffer = self.allocator.buffer(capacity: 16)
        buffer.moveWriterIndex(to: 8)
        buffer.moveReaderIndex(to: 8)
        buffer.writeString("WWWWWWWW")  // 8 bytes written
        buffer.shrinkBufferCapacity(to: 4)  // Invisible padding makes this 8 bytes
        XCTAssertEqual("WWWWWWWW", String(buffer: buffer))  // All 8 bytes are returned!
    }

    func testExpansionOfCapacityWithPadding() throws {
        XCTAssertEqual(ByteBuffer.roundUpToUsableCapacity(12), 16)
        XCTAssertEqual(ByteBuffer.roundUpToUsableCapacity(0), 0)
        XCTAssertEqual(ByteBuffer.roundUpToUsableCapacity(UInt32.min), 0)
        XCTAssertEqual(ByteBuffer.roundUpToUsableCapacity(UInt32.max), UInt32.max)
    }

    func testDumpBytesFormat() throws {
        self.buf.clear()
        for f in UInt8.min...UInt8.max {
            self.buf.writeInteger(f)
        }
        let actual = self.buf._storage.dumpBytes(slice: self.buf._slice, offset: 0, length: self.buf.readableBytes)
        let expected = """
            [ 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f \
            20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f \
            40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f 50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f \
            60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f 70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f \
            80 81 82 83 84 85 86 87 88 89 8a 8b 8c 8d 8e 8f 90 91 92 93 94 95 96 97 98 99 9a 9b 9c 9d 9e 9f \
            a0 a1 a2 a3 a4 a5 a6 a7 a8 a9 aa ab ac ad ae af b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 ba bb bc bd be bf \
            c0 c1 c2 c3 c4 c5 c6 c7 c8 c9 ca cb cc cd ce cf d0 d1 d2 d3 d4 d5 d6 d7 d8 d9 da db dc dd de df \
            e0 e1 e2 e3 e4 e5 e6 e7 e8 e9 ea eb ec ed ee ef f0 f1 f2 f3 f4 f5 f6 f7 f8 f9 fa fb fc fd fe ff ]
            """