Switch to smart_str API

[ndossche]

This is the same as kjdev/php-ext-brotli#83, but for zstd.

Summary by CodeRabbit

• Refactor
  • Updated the ZSTD extension implementation to use modern PHP APIs for improved code quality and maintainability.
  • Enhanced compatibility support for older PHP versions while maintaining support for newer versions.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 6bf34dc7-264e-4373-82ba-f911c77b3039

📥 Commits

Reviewing files that changed from the base of the PR and between d6d26eb and 05f5d05.

📒 Files selected for processing (1)

• zstd.c

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📝 Walkthrough

Walkthrough

This PR upgrades the PHP ZSTD extension to use the modern smart_str API instead of the deprecated smart_string buffer type. A compatibility helper was added for older PHP versions, header includes were reordered, and all compression/decompression functions (one-shot and incremental) were updated to initialize, append to, free, and extract results from smart_str buffers.

Changes

ZSTD smart_str API migration

Layer / File(s)	Summary
Infrastructure and compatibility setup zstd.c	Headers reordered to include zend_smart_str.h before APCu conditional blocks. Added inline smart_str_extract() helper guarded by PHP_VERSION_ID < 70200 to safely extract the owned zend_string from a smart_str buffer or return an empty allocated string for older PHP versions.
Compression functions: buffer and return migration zstd.c	Updated zstd_compress, zstd_compress_dict, and zstd_compress_add to replace smart_string with smart_str for output accumulation. Error paths now free the smart_str, output is appended via smart_str_appendl, and functions return via RETVAL_STR(smart_str_extract(&out)).
Decompression functions: buffer and return migration zstd.c	Updated zstd_uncompress, zstd_uncompress_dict, and zstd_uncompress_add to replace smart_string with smart_str for output accumulation. Error paths free the smart_str and emit appropriate warnings, output is appended via smart_str_appendl, and functions return via RETVAL_STR(smart_str_extract(&out)).

Possibly related PRs

• kjdev/php-ext-zstd#86: Both PRs refactor the same output buffering logic in zstd.c to use PHP smart-string APIs; this PR switches to the newer smart_str with a compatibility helper, while #86 rewrites the same functions using smart_string.
• kjdev/php-ext-zstd#88: Both PRs modify header inclusion and add compatibility for different PHP versions to support the smart_str/zend_smart_str API at the same integration points.
• kjdev/php-ext-zstd#79: The incremental compression/decompression functions updated in this PR (zstd_compress_add, zstd_uncompress_add) are the same functions introduced in #79, so the smart_str migration directly applies to that feature.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 The buffers, they whispered of times long past,
So we swapped out the old for the new built to last,
With smart_str extracted and compatibility tight,
Compression flows onward—hooray! All is right! 🎉

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'Switch to smart_str API' accurately and concisely describes the primary change in the changeset, which updates the PHP ZSTD extension to use the smart_str API instead of the older smart_string API.
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.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[kjdev]

Thanks.