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zero-alloc audio pipeline: pointer-based IO from ring buffer to stdout

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Replace Data/AudioPacket allocations with raw pointer callbacks through
the entire audio pipeline. Ring buffer hands out direct pointers (or
linearizes into a pre-allocated scratch buffer on wrap-around), converter
accepts/emits pointers via its cached buffers, and output handler writes
to stdout via write(2) with EINTR handling.

Remove AudioPacket (dead code), --flush flag (no-op with raw write(2)).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
Nick Payne
2026-03-07 07:14:16 +00:00
parent 65c2d58c82
commit a1eb465142
9 changed files with 122 additions and 174 deletions
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Tests/AudioTeeCoreTests/AudioBufferTests.swift
+39 -32
View File
@@ -44,6 +44,15 @@ final class AudioBufferTests: XCTestCase {
}
}
/// Collects chunks from the buffer as Data objects for test verification.
private func collectChunks(from buffer: AudioBuffer) -> [Data] {
var chunks: [Data] = []
buffer.processChunks { pointer, count in
chunks.append(Data(bytes: pointer, count: count))
}
return chunks
}
// MARK: - Basic append + processChunks
func testSingleChunkExtraction() {
@@ -55,10 +64,10 @@ final class AudioBufferTests: XCTestCase {
let data = makeData(byte: 0xAB, count: chunkSize)
appendData(data, to: buffer)
let packets = buffer.processChunks()
XCTAssertEqual(packets.count, 1)
XCTAssertEqual(packets[0].data.count, chunkSize)
XCTAssertEqual(packets[0].data, data)
let chunks = collectChunks(from: buffer)
XCTAssertEqual(chunks.count, 1)
XCTAssertEqual(chunks[0].count, chunkSize)
XCTAssertEqual(chunks[0], data)
}
func testMultipleChunksExtracted() {
@@ -69,11 +78,11 @@ final class AudioBufferTests: XCTestCase {
// Append 2.5 chunks worth
appendData(makeData(byte: 0x01, count: chunkSize * 2 + chunkSize / 2), to: buffer)
let packets = buffer.processChunks()
let chunks = collectChunks(from: buffer)
// Should get 2 complete chunks, remainder stays in buffer
XCTAssertEqual(packets.count, 2)
XCTAssertEqual(packets[0].data.count, chunkSize)
XCTAssertEqual(packets[1].data.count, chunkSize)
XCTAssertEqual(chunks.count, 2)
XCTAssertEqual(chunks[0].count, chunkSize)
XCTAssertEqual(chunks[1].count, chunkSize)
}
func testInsufficientDataReturnsNoChunks() {
@@ -84,8 +93,8 @@ final class AudioBufferTests: XCTestCase {
// Append less than one chunk
appendData(makeData(byte: 0xFF, count: chunkSize - 1), to: buffer)
let packets = buffer.processChunks()
XCTAssertEqual(packets.count, 0)
let chunks = collectChunks(from: buffer)
XCTAssertEqual(chunks.count, 0)
}
// MARK: - Wrap-around
@@ -103,7 +112,7 @@ final class AudioBufferTests: XCTestCase {
for _ in 0..<33 {
appendData(makeData(byte: 0x00, count: chunkSize), to: buffer)
}
let drained = buffer.processChunks()
let drained = collectChunks(from: buffer)
XCTAssertEqual(drained.count, 33)
// Next write of 4800 bytes starts at 158400. 158400 + 4800 = 163200 > 160000.
@@ -117,9 +126,9 @@ final class AudioBufferTests: XCTestCase {
XCTAssertEqual(wrappingData.count, chunkSize)
appendData(wrappingData, to: buffer)
let packets = buffer.processChunks()
XCTAssertEqual(packets.count, 1)
XCTAssertEqual(packets[0].data, wrappingData)
let chunks = collectChunks(from: buffer)
XCTAssertEqual(chunks.count, 1)
XCTAssertEqual(chunks[0], wrappingData)
}
func testWrapAroundRead() {
@@ -133,7 +142,7 @@ final class AudioBufferTests: XCTestCase {
for _ in 0..<33 {
appendData(makeData(byte: 0x00, count: chunkSize), to: buffer)
}
_ = buffer.processChunks()
_ = collectChunks(from: buffer)
// Write one chunk starting at 158400. The write itself wraps (tested above),
// but crucially the READ will also wrap: readIndex = 158400,
@@ -145,9 +154,9 @@ final class AudioBufferTests: XCTestCase {
crossBoundaryData.append(makeData(byte: 0xDD, count: 3200))
appendData(crossBoundaryData, to: buffer)
let packets = buffer.processChunks()
XCTAssertEqual(packets.count, 1)
XCTAssertEqual(packets[0].data, crossBoundaryData)
let chunks = collectChunks(from: buffer)
XCTAssertEqual(chunks.count, 1)
XCTAssertEqual(chunks[0], crossBoundaryData)
}
// MARK: - Overflow guard
@@ -164,13 +173,13 @@ final class AudioBufferTests: XCTestCase {
appendData(makeData(byte: 0x02, count: 100), to: buffer)
// Drain and verify we only got the original data
let packets = buffer.processChunks()
let totalBytes = packets.reduce(0) { $0 + $1.data.count }
let chunks = collectChunks(from: buffer)
let totalBytes = chunks.reduce(0) { $0 + $1.count }
XCTAssertEqual(totalBytes, maxBuffer)
// Every byte should be 0x01, not 0x02
for packet in packets {
XCTAssertTrue(packet.data.allSatisfy { $0 == 0x01 })
for chunk in chunks {
XCTAssertTrue(chunk.allSatisfy { $0 == 0x01 })
}
}
@@ -187,26 +196,24 @@ final class AudioBufferTests: XCTestCase {
appendData(makeData(byte: UInt8(i), count: callbackSize), to: buffer)
}
let packets = buffer.processChunks()
XCTAssertEqual(packets.count, 1)
XCTAssertEqual(packets[0].data.count, chunkSize)
let chunks = collectChunks(from: buffer)
XCTAssertEqual(chunks.count, 1)
XCTAssertEqual(chunks[0].count, chunkSize)
// Verify the data is in the correct order
for i in 0..<10 {
let slice = packets[0].data.subdata(in: (i * callbackSize)..<((i + 1) * callbackSize))
let slice = chunks[0].subdata(in: (i * callbackSize)..<((i + 1) * callbackSize))
XCTAssertTrue(slice.allSatisfy { $0 == UInt8(i) })
}
}
// MARK: - Packet metadata
// MARK: - Chunk size
func testChunkDurationIsCorrect() {
func testBytesPerChunkIsCorrect() {
let format = makeFormat()
let buffer = AudioBuffer(format: format, chunkDuration: 0.1)
appendData(makeData(byte: 0x00, count: 3200), to: buffer)
let packets = buffer.processChunks()
XCTAssertEqual(packets[0].duration, 0.1, accuracy: 0.001)
// 16kHz * 0.1s * 2 bytes/frame = 3200
XCTAssertEqual(buffer.bytesPerChunk, 3200)
}
}