decoder: Faster decoding temp/memory streams

[JakubOnderka]

Summary by CodeRabbit

• New Features

  • Improved JSON decoding from memory-backed and temporary streams, reducing unnecessary data copying.
  • Added support for decoding filtered stream content, including transformations such as converting uppercase JSON booleans to lowercase.

• Bug Fixes

  • Temporary and memory stream request bodies now decode correctly when stream filters modify their contents.

• Tests

  • Added coverage for filtered memory and temporary streams.

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: bbb61e3e-e58c-4b2f-8273-e9a4d05e0e51

📥 Commits

Reviewing files that changed from the base of the PR and between ba536cc and e29a3c1.

📒 Files selected for processing (4)

• php_simdjson.cpp
• src/simdjson_decoder.cpp
• tests/decode_stream_memory.phpt
• tests/decode_stream_temp.phpt

📝 Walkthrough

Walkthrough

Changes

Stream decoding

Layer / File(s)	Summary
Buffer extraction and reallocation contract src/simdjson_decoder_defs.h, src/simdjson_decoder.cpp, php_simdjson.cpp	The reallocation check is externally declared. A helper extracts memory buffers from eligible temporary streams.
Direct stream decoding integration php_simdjson.cpp	Memory and temporary streams use direct parsing when possible. The existing fallback remains available. Request-body decoding uses the shared helper.
Filtered stream coverage tests/decode_stream_memory.phpt, tests/decode_stream_temp.phpt	Tests verify filtered memory and temporary streams decode uppercase boolean input successfully.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Caller
  participant simdjson_decode_from_stream
  participant MemoryBufferHelper
  participant simdjsonParser
  Caller->>simdjson_decode_from_stream: decode stream
  simdjson_decode_from_stream->>MemoryBufferHelper: inspect stream buffer
  MemoryBufferHelper-->>simdjson_decode_from_stream: return buffer or NULL
  simdjson_decode_from_stream->>simdjsonParser: parse buffer directly
  simdjsonParser-->>Caller: return decoded value or JSON error

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Possibly related PRs

• JakubOnderka/simdjson_php#57: Both changes modify stream-buffer handling in simdjson_decode_from_stream.
• JakubOnderka/simdjson_php#67: This PR extends the memory-stream fast path with a shared helper.
• JakubOnderka/simdjson_php#75: Both changes modify simdjson_realloc_needed.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: faster decoding for temporary and memory-backed streams.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch updates-copilot

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[Copilot]

Pull request overview

Adds zero-copy decoding for unfiltered memory-backed streams on PHP 8.2+.

Changes:

• Directly parses eligible memory and temporary stream buffers.
• Falls back for filtered or file-backed streams.
• Adds filtered-stream regression tests.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
php_simdjson.cpp	Implements stream fast path and buffer helper.
src/simdjson_decoder.cpp	Exposes padding-check helper.
src/simdjson_decoder_defs.h	Declares the helper.
tests/decode_stream_memory.phpt	Tests filtered memory streams.
tests/decode_stream_temp.phpt	Tests filtered temporary streams.

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