swiftlang / swiftlang/swift-java

[JExtract] Translate String to a imported type

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feature:jextract
Dominant language
Swift
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Merged PRs (30d)
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Description

Swift.String should be translated to an imported String type instead of java.lang.String, just like Foundation.Data.

In JExtract/FFM, String is currently translated to java.lang.String and lowered to C-string (UnsafePointer<Int8>).
That works for parameters, but is making passing String value between Swift and Java more expensive than it should be. Also it does not work well for API returning String because the client has to manually free the memory.

For example, using this interface,

public func getSomeString() -> String
public func receiveString(str: String)

In Java:

var str = MyLib.getSomeString()
receiveString(str)

This receiving and passing string value should not cause copy.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start in the JExtract/FFM translation logic and compare the existing Foundation.Data handling with the current Swift.String mapping. Trace the generated Java and Swift-facing representations for getSomeString and receiveString. Done means imported String values can be returned and passed without the current C-string conversion, unnecessary copying, or manual freeing.

Written by the indexing model from the issue text.

Assessment

Tech stack
java, swift
Domain
devtools
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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