4 ms·
I'm almost positive that he didn't use thinking mode, because I've asked GPT-5 thinking his question verbatim in 10 parallel threads and it said "you can't" and
by yelirekim 1y ago
I'm almost positive that he didn't use thinking mode, because I've asked GPT-5 thinking his question verbatim in 10 parallel threads and it said "you can't" and thoroughly explained why every time. Below is the first response I got back.
---
Short answer: you can’t. iOS doesn’t ship a Zstandard encoder/decoder. Apple’s built-in `Compression` framework only exposes LZFSE, LZ4(/RAW), zlib/DEFLATE, and LZMA—no ZSTD knob to turn. ([Microsoft Learn][1], [Apple Developer][2])
If you’re okay with a built-in alternative that’s “zstd-ish” in speed/ratio, use LZFSE via `Compression`’s streaming API. Here’s a minimal streaming compressor you can drop in; it takes chunks of `Data` and yields compressed chunks (no third-party code):
```swift
import Compression
final class StreamCompressor {
private var stream = compression_stream()
private let algo: compression_algorithm
private var isInitialized = false
init(algorithm: compression_algorithm = COMPRESSION_LZFSE) {
self.algo = algorithm
}
func append(_ input: Data, isFinal: Bool, outChunkSize: Int = 64 * 1024) -> [Data] {
if !isInitialized {
let status = compression_stream_init(&stream, COMPRESSION_STREAM_ENCODE, algo)
precondition(status != COMPRESSION_STATUS_ERROR, "compression_stream_init failed")
isInitialized = true
}
var outputs: [Data] = []
input.withUnsafeBytes { (srcBuf: UnsafeRawBufferPointer) in
var flags: Int32 = isFinal ? Int32(COMPRESSION_STREAM_FINALIZE.rawValue) : 0
stream.src_ptr = srcBuf.bindMemory(to: UInt8.self).baseAddress
stream.src_size = srcBuf.count
var out = Data(count: outChunkSize)
out.withUnsafeMutableBytes { dstBuf in
while true {
stream.dst_ptr = dstBuf.bindMemory(to: UInt8.self).baseAddress
stream.dst_size = dstBuf.count
let status = compression_stream_process(&stream, flags)
let produced = dstBuf.count - stream.dst_size
if produced > 0 {
outputs.append(Data(bytes: dstBuf.baseAddress!, count: produced))
}
if status == COMPRESSION_STATUS_OK && stream.src_size == 0 && stream.dst_size > 0 {
break // need more input to continue
} else if status == COMPRESSION_STATUS_OK && stream.dst_size == 0 {
// output buffer filled; loop to drain more
continue
} else if status == COMPRESSION_STATUS_END {
break
} else if status == COMPRESSION_STATUS_ERROR {
preconditionFailure("compression_stream_process failed")
} else {
// Shouldn’t happen
break
}
}
}
}
return outputs
}
deinit {
if isInitialized {
compression_stream_destroy(&stream)
}
}
}
```
Usage:
```swift
let compressor = StreamCompressor(algorithm: COMPRESSION_LZFSE)
var compressed: [Data] = []
for (i, chunk) in chunks.enumerated() {
let final = i == chunks.count - 1
compressed.append(contentsOf: compressor.append(chunk, isFinal: final))
}
// `compressed` now contains the zstd-adjacent (LZFSE) stream
```
If you truly need the ZSTD format (interop requirement), you’ll have to ship the reference C library (`libzstd`) in your app (static link it and call through a tiny Swift wrapper). That’s still “third-party,” even if you vendor the sources instead of using SPM/CocoaPods. There is no system-provided ZSTD on iOS today. ([GitHub][3])
tl;dr: iOS doesn’t expose ZSTD. Use `Compression` with LZFSE for built-in streaming, or vendor `libzstd` and bridge to it if you must emit/ingest ZSTD. ([Microsoft Learn][1], [Apple Developer][2], [GitHub][3])
[1]: https://learn.microsoft.com/en-us/dotnet/api/compression.compressionalgorithm?view=xamarin-ios-sdk-12&utm_source=chatgpt.com https://learn.microsoft.com/en-us/dotnet/api/compression.com... "CompressionAlgorithm Enum (Compression)"
[2]: https://developer.apple.com/documentation/compression/compression_lzfse?utm_source=chatgpt.com https://developer.apple.com/documentation/compression/compre... "COMPRESSION_LZFSE | Apple Developer Documentation"
[3]: https://github.com/facebook/zstd?utm_source=chatgpt.com https://github.com/facebook/zstd?utm_source=chatgpt.com "facebook/zstd: Zstandard - Fast real-time compression ..."