Rob Hogan
c085180264
Summary: Pull Request resolved: https://github.com/facebook/react-native/pull/45426 The initial implementation of `Network.loadNetworkResource` and the accompanying `IO.read` (D54202854) base64-encodes all data as if it is binary. This is the more general case, and we'll continue to base64-encode non-text resources. In the common case of text resources (particularly JS and JSON), it'd be preferable to do as Chrome does and send UTF-8 over the wire directly. This has a few performance benefits: - Less CPU and RAM footprint on device (UTF-8 truncation is constant-time, fast, and in-place), similarly less decoding for the frontend. - 25% less data per chunk (base64 encodes 3 bytes as 4 characters), implies up to 25% fewer network round trips for large resources. It also has the benefit of being human-readable in the CDP protocol inspector. ## Determining whether data is text We use exactly Chromium's heuristic for this (code pointers in comments), which is based only on the `Content-Type` header, and assuming any text mime type is UTF-8. ## UTF-8 truncation The slight implementation complexity here is that `IO.read` requests may specify a maximum number of bytes, and so we must slice a raw buffer up into valid UTF-8 sequences. This turns out to be fairly simple and cheap: 1. Naively truncate the buffer, inspect the last byte 2. If the last byte has topmost bit =0, it's ASCII (single byte) and we're done. 3. Otherwise, look back at most 3 bytes to find the first byte of the code point (topmost bits 11), counting the number of "continuationBytes" at the end of our buffer. If we don't find one within 3 bytes then the string isn't UTF-8 - throw. 4. Read the code point length, which is encoded into the first byte. 5. Resize to remove the last code point fragment, unless it terminates correctly exactly at the end of our buffer. ## Edge cases + divergence from Chrome Chrome's behaviour here in at least one case is questionable and we intentionally differ: - If a response has header "content-type: text/plain" but content eg`0x80` (not valid UTF-8), Chrome will respond to an `IO.read` with `{ "data": "", "base64Encoded": false, "eof": false }`, ie an empty string, but will move its internal pointer such that the next or some subsequent `IO.read` will have `"eof": true`. To the client, this is indistinguishable from a successfully received resource, when in fact it is effectively corrupted. - Instead, we respond with a CDP error to the `IO.read`. We do not immediately cancel the request or discard data, since not all `IO.read` errors are necessarily fatal. I've verified that CDT sends `IO.close` after an error, so we'll clean up that way (this isn't strictly guaranteed by any spec, but nor is `IO.close` after a resource is successfully consumed). Changelog: [General][Added] Debugger: Support text responses to CDP `IO.read` requests Reviewed By: hoxyq Differential Revision: D58323790 fbshipit-source-id: def8bf8426266f16bb305d836a6efe8927a9dfc4
React Native
Learn once, write anywhere:
Build mobile apps with React.
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React Native brings React's declarative UI framework to iOS and Android. With React Native, you use native UI controls and have full access to the native platform.
- Declarative. React makes it painless to create interactive UIs. Declarative views make your code more predictable and easier to debug.
- Component-Based. Build encapsulated components that manage their state, then compose them to make complex UIs.
- Developer Velocity. See local changes in seconds. Changes to JavaScript code can be live reloaded without rebuilding the native app.
- Portability. Reuse code across iOS, Android, and other platforms.
React Native is developed and supported by many companies and individual core contributors. Find out more in our ecosystem overview.
Contents
- Requirements
- Building your first React Native app
- Documentation
- Upgrading
- How to Contribute
- Code of Conduct
- License
📋 Requirements
React Native apps may target iOS 13.4 and Android 6.0 (API 23) or newer. You may use Windows, macOS, or Linux as your development operating system, though building and running iOS apps is limited to macOS. Tools like Expo can be used to work around this.
🎉 Building your first React Native app
Follow the Getting Started guide. The recommended way to install React Native depends on your project. Here you can find short guides for the most common scenarios:
📖 Documentation
The full documentation for React Native can be found on our website.
The React Native documentation discusses components, APIs, and topics that are specific to React Native. For further documentation on the React API that is shared between React Native and React DOM, refer to the React documentation.
The source for the React Native documentation and website is hosted on a separate repo, @facebook/react-native-website.
🚀 Upgrading
Upgrading to new versions of React Native may give you access to more APIs, views, developer tools, and other goodies. See the Upgrading Guide for instructions.
React Native releases are discussed in this discussion repo.
👏 How to Contribute
The main purpose of this repository is to continue evolving React Native core. We want to make contributing to this project as easy and transparent as possible, and we are grateful to the community for contributing bug fixes and improvements. Read below to learn how you can take part in improving React Native.
Code of Conduct
Facebook has adopted a Code of Conduct that we expect project participants to adhere to. Please read the full text so that you can understand what actions will and will not be tolerated.
Contributing Guide
Read our Contributing Guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to React Native.
Open Source Roadmap
You can learn more about our vision for React Native in the Roadmap.
Good First Issues
We have a list of good first issues that contain bugs which have a relatively limited scope. This is a great place to get started, gain experience, and get familiar with our contribution process.
Discussions
Larger discussions and proposals are discussed in @react-native-community/discussions-and-proposals.
📄 License
React Native is MIT licensed, as found in the LICENSE file.
React Native documentation is Creative Commons licensed, as found in the LICENSE-docs file.