Add PyBuffer tests, documentation, and async I/O support#30
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- test/py_buffer_SUITE.erl: Common Test suite with 13 tests for: - Basic buffer creation (with/without content length) - Write/read cycle, readline, readlines - Seek/tell position tracking - Fast find with memchr/memmem - Zero-copy memoryview access - Line iteration, closed/empty buffer handling - Auto-conversion when passing buffer ref to Python - GC and reference counting verification - docs/buffer.md: Documentation covering: - Erlang API (new, write, close) - Python API (file-like methods, buffer protocol, find) - Architecture diagram and memory layout - Performance tips and examples - examples/py_buffer_example.erl: Working escript demonstrating: - Basic buffer usage - HTTP body streaming simulation - File-like interface methods - Zero-copy memoryview access - Line iteration for CSV-like data - CHANGELOG.md: Added PyBuffer API entry under 2.2.0 - docs/getting-started.md: Added Zero-Copy Buffers section with link to buffer.md
- read_nonblock(size=-1): Read available bytes immediately, never blocks - readable_amount(): Return bytes available without blocking - at_eof(): Check if at EOF with no more data These methods enable async I/O patterns where Python code needs to check for available data without blocking, suitable for asyncio integration. Tests demonstrate Erlang streaming data while Python reads asynchronously.
Memory leaks:
- Py_BuildValue("()") in readlines and iternext was never DECREF'd
- Now uses PyTuple_New(0) with proper cleanup
Deadlock prevention:
- read/readline/read_nonblock now copy data while holding mutex,
then release mutex before calling Python APIs (PyBytes_FromStringAndSize)
- This avoids holding mutex while reacquiring GIL, which could deadlock
with other functions (find, readable_amount, etc.) that hold GIL
while acquiring mutex
Integer overflow:
- Added SIZE_MAX check before computing required capacity in py_buffer_write
- c_src/py_buffer.h: Header with resource struct and function declarations - src/py_buffer.erl: Erlang API module (new/0,1, write/2, close/1) - c_src/py_convert.c: Auto-conversion of buffer refs to PyBuffer objects - c_src/py_nif.c: NIF registration and resource type initialization - src/py_nif.erl: NIF function exports
PyBuffer was only registered in the main interpreter, causing ImportError when using subinterpreters (Python 3.12+). Add PyBuffer_register_with_module() calls in: - py_subinterp_pool.c: for shared-GIL subinterpreter pool - py_subinterp_thread.c: for OWN_GIL subinterpreter threads
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Summary
Non-blocking methods added
read_nonblock(size=-1)- Read available bytes immediatelyreadable_amount()- Bytes available without blockingat_eof()- Check if at EOF with no data remainingTests
Tests include Erlang streaming data while Python reads asynchronously, verifying the producer-consumer pattern works correctly.