GPT-6.1 Sol (effort default (no reasoning-effort override) · thinking on) on Implement a reader/writer for a documented chunked binary container (LEB128 lengths, CRC-32, zlib chunks, critical vs ancillary)

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{"type": "item.completed", "item": {"id": "item_0", "type": "agent_message", "text": "I\u2019ll read the format specification and existing code, implement both functions, then verify the behavior and error offsets.\n"}}
{"type": "item.started", "item": {"id": "item_1", "type": "command_execution", "command": "/bin/bash -lc \"pwd; rg --files -g 'AGENTS.md' -g 'FORMAT.md' -g 'chnk.py' -g '*test*'\"", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
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{"type": "item.started", "item": {"id": "item_2", "type": "command_execution", "command": "/bin/bash -lc 'cat FORMAT.md chnk.py'", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_2", "type": "command_execution", "command": "/bin/bash -lc 'cat FORMAT.md chnk.py'", "aggregated_output": "# CHNK container format, version 1\nAll multi-byte fixed-width integers are big-endian.\n## Header (6 bytes)\n`43 48 4E 4B` (ASCII \"CHNK\"), then 1 byte version (must be 1), then 1 byte flags. Flag bit 0 (`0x01`): every chunk carries a CRC. Bits 1-7 must be 0.\n## Chunks (repeated until the END chunk)\n- type: 4 bytes, each an ASCII letter `A-Z`/`a-z` or space (0x20); first byte must be a letter.\n- length: unsigned LEB128 varint (7 bits per byte, least-significant group first, high bit = continuation; at most 5 bytes; must be minimal: in a varint of 2 or more bytes the last byte must not be `0x00`; the value 0 is the single byte `00`; more than 5 bytes is an error).\n- payload: `length` bytes.\n- crc: present only if header flag bit 0 is set; 4 bytes, CRC-32 (zlib.crc32) of type bytes + payload.\n## Chunk types\n- `META`: UTF-8 text, lines separated by `\\n`, each `key=value` (split at first `=`; key non-empty). Several META chunks merge; a later key overrides. Must appear before the first data chunk.\n- `DATA`: raw payload bytes. `DATZ`: zlib-compressed payload (decompressed bytes are appended). The file's data is the concatenation of all data chunks in order.\n- `END ` (with trailing space): length must be 0, must be the last chunk; nothing may follow it.\n- Any other type: if its first letter is uppercase it is *critical* -> error; if lowercase it is *ancillary* -> skipped (its CRC is still verified).\n## Errors\nReader raises `FormatError(msg, offset)` (attribute `.offset`): for file-header errors the offset of that header field (magic 0, version 4, flags 5); for **every** error inside a chunk - bad type, bad/overlong varint, truncated length/payload/CRC, CRC mismatch, bad META (invalid UTF-8 or bad line), META after data, unknown critical chunk, bad zlib data, END length != 0 - the offset of the first byte of that chunk's type field for: bad magic (offset 0), unsupported version (4), reserved flag bits (5), truncated input (offset of the chunk being read), invalid type bytes, non-minimal/overlong varint, CRC mismatch, bad META line, META after data, unknown critical chunk, bad zlib data, END length != 0, missing END (offset = length of the input), data after END (offset = first byte after the END chunk).\n## Writer\n`write(meta: dict[str,str], data: bytes, chunk_size=65536, compress=False, crc=True) -> bytes`: header; one META chunk if meta is non-empty (keys sorted, `key=value` lines joined by `\\n`, no trailing newline); data split into chunks of at most `chunk_size` bytes (each compressed separately with `zlib.compress(level=6)` as `DATZ` if `compress`, else `DATA`; no data chunk when data is empty); then `END `.\n\"\"\"CHNK reader/writer - implement per FORMAT.md\"\"\"\nclass FormatError(Exception):\n    def __init__(self, msg, offset):\n        super().__init__(f\"{msg} at byte {offset}\"); self.offset = offset\n\ndef read(buf):\n    \"\"\"-> {\"meta\": dict, \"data\": bytes, \"skipped\": [ancillary chunk types as str, in order]}\"\"\"\n    raise NotImplementedError\n\ndef write(meta, data, chunk_size=65536, compress=False, crc=True):\n    raise NotImplementedError\n", "exit_code": 0, "status": "completed"}}
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{"type": "item.completed", "item": {"id": "item_5", "type": "agent_message", "text": "Both functions are implemented. I\u2019m now checking malformed inputs, error offsets, and the writer\u2019s exact bytes, including CRCs and compressed chunks.\n"}}
{"type": "item.started", "item": {"id": "item_6", "type": "command_execution", "command": "/bin/bash -lc \"cat > test_chnk.py <<'PY'\nimport unittest\nimport zlib\n\nfrom chnk import FormatError, read, write\n\n\nHEADER = b'CHNK\\\\x01\\\\x00'\n\n\ndef chunk(kind, payload=b'', crc=False):\n    n = len(payload)\n    length = bytearray()\n    while n >= 128:\n        length.append((n & 127) | 128)\n        n >>= 7\n    length.append(n)\n    result = kind + length + payload\n    if crc:\n        result += (zlib.crc32(kind + payload) & 0xffffffff).to_bytes(4, 'big')\n    return result\n\n\nclass ChnkTests(unittest.TestCase):\n    def assert_error(self, raw, offset):\n        with self.assertRaises(FormatError) as caught:\n            read(raw)\n        self.assertEqual(caught.exception.offset, offset)\n\n    def test_header_errors(self):\n        for raw, offset in [(b'', 0), (b'CHN', 0), (b'NOPE', 0),\n                            (b'CHNK', 4), (b'CHNK\\\\x02', 4),\n                            (b'CHNK\\\\x01', 5), (b'CHNK\\\\x01\\\\x02', 5)]:\n            with self.subTest(raw=raw):\n                self.assert_error(raw, offset)\n\n    def test_chunk_errors_at_each_position(self):\n        malformed = [b'D', b'1ATA\\\\x00', b'DA\\\\xffA\\\\x00', b'DATA',\n                     b'DATA\\\\x80', b'DATA\\\\x80\\\\x00',\n                     b'DATA' + b'\\\\x80' * 5, b'DATA\\\\x02x',\n                     chunk(b'META', b'\\\\xff'), chunk(b'META', b'=value'),\n                     chunk(b'META', b'bad'), chunk(b'META', b'a=b\\\\n'),\n                     chunk(b'WHAT'), chunk(b'END ', b'x'),\n                     chunk(b'DATZ', b'bad'),\n                     chunk(b'DATZ', zlib.compress(b'abc')[:-1])]\n        for prefix in [b'', chunk(b'also', b'ignored')]:\n            for bad in malformed:\n                with self.subTest(prefix=prefix, bad=bad):\n                    self.assert_error(HEADER + prefix + bad, 6 + len(prefix))\n        self.assert_error(HEADER + chunk(b'DATA') + chunk(b'META', b'a=b'), 11)\n\n    def test_crc_errors(self):\n        header = b'CHNK\\\\x01\\\\x01'\n        for kind in [b'DATA', b'also', b'END ']:\n            valid = chunk(kind, crc=True)\n            for missing in range(1, 5):\n                self.assert_error(header + valid[:-missing], 6)\n            self.assert_error(header + valid[:-1] + bytes([valid[-1] \"'^ 1]), 6)\n\n    def test_end_errors(self):\n        self.assert_error(HEADER, 6)\n        raw = HEADER + chunk(b'\"'DATA', b'x')\n        self.assert_error(raw, len(raw))\n        raw = HEADER + chunk(b'END ')\n        self.assert_error(raw + b'x', len(raw))\n\n    def test_merge_skip_and_mixed_data(self):\n        raw = HEADER + chunk(b'META', 'a=old\\\\nb=\u00e9'.encode())\n        raw += chunk(b'abc ', b'ignored') + chunk(b'META', b'a=new=ok')\n        raw += chunk(b'DATA', b'raw') + chunk(b'DATZ', zlib.compress(b'zip'))\n        raw += chunk(b'END ')\n        self.assertEqual(read(raw), {'meta': {'a': 'new=ok', 'b': '\u00e9'},\n                                     'data': b'rawzip', 'skipped': ['abc ']})\n\n    def test_writer_exact_and_roundtrip(self):\n        for crc in [False, True]:\n            for compress in [False, True]:\n                for data in [b'', b'a', bytes(range(256)) * 4]:\n                    with self.subTest(crc=crc, compress=compress, size=len(data)):\n                        meta = {'z': 'last', 'a': '\u00e9=x'}\n                        expected = b'CHNK\\\\x01' + bytes([crc])\n                        expected += chunk(b'META', 'a=\u00e9=x\\\\nz=last'.encode(), crc)\n                        for pos in range(0, len(data), 127):\n                            payload = data[pos:pos + 127]\n                            expected += chunk(b'DATZ' if compress else b'DATA',\n                                              zlib.compress(payload, level=6) if compress else payload,\n                                              crc)\n                        expected += chunk(b'END ', crc=crc)\n                        actual = write(meta, data, chunk_size=127, compress=compress, crc=crc)\n                        self.assertEqual(actual, expected)\n                        self.assertEqual(read(actual), {'meta': meta, 'data': data, 'skipped': []})\n        self.assertEqual(write({}, b'', crc=False), HEADER + chunk(b'END '))\n\n    def test_five_byte_length_is_not_limited_to_32_bits(self):\n        self.assert_error(HEADER + b'DATA\\\\xff\\\\xff\\\\xff\\\\xff\\\\x7f', 6)\n\n    def test_invalid_chunk_size(self):\n        for size in [0, -1]:\n            with self.assertRaises(ValueError):\n                write({}, b'x', chunk_size=size)\n\n\nif __name__ == '__main__':\n    unittest.main()\nPY\npython -m unittest -v\"", "aggregated_output": "", "exit_code": null, "status": "in_progress"}}
{"type": "item.completed", "item": {"id": "item_6", "type": "command_execution", "command": "/bin/bash -lc \"cat > test_chnk.py <<'PY'\nimport unittest\nimport zlib\n\nfrom chnk import FormatError, read, write\n\n\nHEADER = b'CHNK\\\\x01\\\\x00'\n\n\ndef chunk(kind, payload=b'', crc=False):\n    n = len(payload)\n    length = bytearray()\n    while n >= 128:\n        length.append((n & 127) | 128)\n        n >>= 7\n    length.append(n)\n    result = kind + length + payload\n    if crc:\n        result += (zlib.crc32(kind + payload) & 0xffffffff).to_bytes(4, 'big')\n    return result\n\n\nclass ChnkTests(unittest.TestCase):\n    def assert_error(self, raw, offset):\n        with self.assertRaises(FormatError) as caught:\n            read(raw)\n        self.assertEqual(caught.exception.offset, offset)\n\n    def test_header_errors(self):\n        for raw, offset in [(b'', 0), (b'CHN', 0), (b'NOPE', 0),\n                            (b'CHNK', 4), (b'CHNK\\\\x02', 4),\n                            (b'CHNK\\\\x01', 5), (b'CHNK\\\\x01\\\\x02', 5)]:\n            with self.subTest(raw=raw):\n                self.assert_error(raw, offset)\n\n    def test_chunk_errors_at_each_position(self):\n        malformed = [b'D', b'1ATA\\\\x00', b'DA\\\\xffA\\\\x00', b'DATA',\n                     b'DATA\\\\x80', b'DATA\\\\x80\\\\x00',\n                     b'DATA' + b'\\\\x80' * 5, b'DATA\\\\x02x',\n                     chunk(b'META', b'\\\\xff'), chunk(b'META', b'=value'),\n                     chunk(b'META', b'bad'), chunk(b'META', b'a=b\\\\n'),\n                     chunk(b'WHAT'), chunk(b'END ', b'x'),\n                     chunk(b'DATZ', b'bad'),\n                     chunk(b'DATZ', zlib.compress(b'abc')[:-1])]\n        for prefix in [b'', chunk(b'also', b'ignored')]:\n            for bad in malformed:\n                with self.subTest(prefix=prefix, bad=bad):\n                    self.assert_error(HEADER + prefix + bad, 6 + len(prefix))\n        self.assert_error(HEADER + chunk(b'DATA') + chunk(b'META', b'a=b'), 11)\n\n    def test_crc_errors(self):\n        header = b'CHNK\\\\x01\\\\x01'\n        for kind in [b'DATA', b'also', b'END ']:\n            valid = chunk(kind, crc=True)\n            for missing in range(1, 5):\n                self.assert_error(header + valid[:-missing], 6)\n            self.assert_error(header + valid[:-1] + bytes([valid[-1] \"'^ 1]), 6)\n\n    def test_end_errors(self):\n        self.assert_error(HEADER, 6)\n        raw = HEADER + chunk(b'\"'DATA', b'x')\n        self.assert_error(raw, len(raw))\n        raw = HEADER + chunk(b'END ')\n        self.assert_error(raw + b'x', len(raw))\n\n    def test_merge_skip_and_mixed_data(self):\n        raw = HEADER + chunk(b'META', 'a=old\\\\nb=\u00e9'.encode())\n        raw += chunk(b'abc ', b'ignored') + chunk(b'META', b'a=new=ok')\n        raw += chunk(b'DATA', b'raw') + chunk(b'DATZ', zlib.compress(b'zip'))\n        raw += chunk(b'END ')\n        self.assertEqual(read(raw), {'meta': {'a': 'new=ok', 'b': '\u00e9'},\n                                     'data': b'rawzip', 'skipped': ['abc ']})\n\n    def test_writer_exact_and_roundtrip(self):\n        for crc in [False, True]:\n            for compress in [False, True]:\n                for data in [b'', b'a', bytes(range(256)) * 4]:\n                    with self.subTest(crc=crc, compress=compress, size=len(data)):\n                        meta = {'z': 'last', 'a': '\u00e9=x'}\n                        expected = b'CHNK\\\\x01' + bytes([crc])\n                        expected += chunk(b'META', 'a=\u00e9=x\\\\nz=last'.encode(), crc)\n                        for pos in range(0, len(data), 127):\n                            payload = data[pos:pos + 127]\n                            expected += chunk(b'DATZ' if compress else b'DATA',\n                                              zlib.compress(payload, level=6) if compress else payload,\n                                              crc)\n                        expected += chunk(b'END ', crc=crc)\n                        actual = write(meta, data, chunk_size=127, compress=compress, crc=crc)\n                        self.assertEqual(actual, expected)\n                        self.assertEqual(read(actual), {'meta': meta, 'data': data, 'skipped': []})\n        self.assertEqual(write({}, b'', crc=False), HEADER + chunk(b'END '))\n\n    def test_five_byte_length_is_not_limited_to_32_bits(self):\n        self.assert_error(HEADER + b'DATA\\\\xff\\\\xff\\\\xff\\\\xff\\\\x7f', 6)\n\n    def test_invalid_chunk_size(self):\n        for size in [0, -1]:\n            with self.assertRaises(ValueError):\n                write({}, b'x', chunk_size=size)\n\n\nif __name__ == '__main__':\n    unittest.main()\nPY\npython -m unittest -v\"", "aggregated_output": "/bin/bash: line 106: python: command not found\n", "exit_code": 127, "status": "failed"}}
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{"type": "item.completed", "item": {"id": "item_7", "type": "command_execution", "command": "/bin/bash -lc 'python3 -m unittest -v'", "aggregated_output": "test_chunk_errors_at_each_position (test_chnk.ChnkTests.test_chunk_errors_at_each_position) ... ok\ntest_crc_errors (test_chnk.ChnkTests.test_crc_errors) ... ok\ntest_end_errors (test_chnk.ChnkTests.test_end_errors) ... ok\ntest_five_byte_length_is_not_limited_to_32_bits (test_chnk.ChnkTests.test_five_byte_length_is_not_limited_to_32_bits) ... ok\ntest_header_errors (test_chnk.ChnkTests.test_header_errors) ... ok\ntest_invalid_chunk_size (test_chnk.ChnkTests.test_invalid_chunk_size) ... ok\ntest_merge_skip_and_mixed_data (test_chnk.ChnkTests.test_merge_skip_and_mixed_data) ... ok\ntest_writer_exact_and_roundtrip (test_chnk.ChnkTests.test_writer_exact_and_roundtrip) ... ok\n\n----------------------------------------------------------------------\nRan 8 tests in 0.002s\n\nOK\n", "exit_code": 0, "status": "completed"}}
{"type": "item.completed", "item": {"id": "item_8", "type": "agent_message", "text": "Implemented `read()` and `write()` in `chnk.py`, preserving `FormatError(msg, offset)` and enforcing the documented format and error offsets.\n\nAdded tests for malformed input, CRCs, metadata, compression, and exact writer output. All 8 tests pass with `python3 -m unittest -v`."}}
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