{"record":{"id":"8c62404aeaa538cc","repo":"can1357/oh-my-pi","slug":"unsupported-xz-stream-flags","errorCode":null,"errorMessage":"Unsupported XZ stream flags","messagePattern":"Unsupported XZ stream flags","errorType":"exception","errorClass":"ArchiveError","httpStatus":null,"severity":"error","filePath":"packages/utils/src/ar/codecs/xz.ts","lineNumber":125,"sourceCode":"\t\tthrow new ArchiveError(\"Invalid XZ stream: size is not a multiple of four bytes\");\n\tconst streams: XzStream[] = [];\n\tlet end = bytes.byteLength;\n\twhile (end > 0) {\n\t\tlet padding = 0;\n\t\twhile (end >= 4 && bytes[end - 1] === 0 && bytes[end - 2] === 0 && bytes[end - 3] === 0 && bytes[end - 4] === 0) {\n\t\t\tend -= 4;\n\t\t\tpadding += 4;\n\t\t}\n\t\tif (end === 0) throw new ArchiveError(\"Invalid XZ stream: padding without a stream\");\n\t\tif (end < 24) throw new ArchiveError(\"Invalid XZ stream: truncated stream framing\");\n\t\tconst footerStart = end - 12;\n\t\tif (bytes[footerStart + 10] !== 0x59 || bytes[footerStart + 11] !== 0x5a)\n\t\t\tthrow new ArchiveError(\"Invalid XZ stream: footer magic mismatch\");\n\t\tif (crc32(bytes.subarray(footerStart + 4, footerStart + 10)) !== read32LE(bytes, footerStart))\n\t\t\tthrow new ArchiveError(\"Invalid XZ stream: footer CRC32 mismatch\");\n\t\tconst flag0 = bytes[footerStart + 8]!;\n\t\tconst flag1 = bytes[footerStart + 9]!;\n\t\tif (flag0 !== 0 || (flag1 & 0xf0) !== 0) throw new ArchiveError(\"Unsupported XZ stream flags\");\n\t\tconst checkId = flag1 & 0x0f;\n\t\tcheckSize(checkId);\n\t\tconst indexSize = (read32LE(bytes, footerStart + 4) + 1) * 4;\n\t\tif (!Number.isSafeInteger(indexSize) || indexSize > footerStart)\n\t\t\tthrow new ArchiveError(\"Invalid XZ stream: backward index size is invalid\");\n\t\tconst indexStart = footerStart - indexSize;\n\t\tconst records = parseIndex(bytes, indexStart, indexSize);\n\t\tlet blocksSize = 0;\n\t\tfor (const record of records) {\n\t\t\tblocksSize += Math.ceil(record.unpaddedSize / 4) * 4;\n\t\t\tif (!Number.isSafeInteger(blocksSize)) throw new ArchiveError(\"XZ stream uses sizes too large to read safely\");\n\t\t}\n\t\tconst start = indexStart - blocksSize - 12;\n\t\tif (start < 0 || start + 12 > bytes.byteLength || !equalBytes(bytes.subarray(start, start + 6), XZ_MAGIC)) {\n\t\t\tthrow new ArchiveError(\"Invalid XZ stream: header position or magic is invalid\");\n\t\t}\n\t\tif (bytes[start + 6] !== flag0 || bytes[start + 7] !== flag1)\n\t\t\tthrow new ArchiveError(\"Invalid XZ stream: header and footer flags differ\");","sourceCodeStart":107,"sourceCodeEnd":143,"githubUrl":"https://github.com/can1357/oh-my-pi/blob/969062200754ea02cfac922e5ebb8c608c079e15/packages/utils/src/ar/codecs/xz.ts#L107-L143","documentation":"XZ stream flags occupy two bytes in the footer: the first must be 0x00 (reserved, must be zero) and the high nibble of the second must be 0x00 (reserved). discoverStreams() rejects any footer with reserved bits set, since such a stream does not conform to the XZ specification and its meaning is undefined.","triggerScenarios":"A footer whose flag byte at footerStart+8 is non-zero or whose flag byte at footerStart+9 has any of the upper 4 bits set — produced by a non-conformant compressor, a corrupted footer, or misaligned parsing reading wrong bytes as flags.","commonSituations":"Archives produced by broken or experimental XZ encoders, corruption during transfer/storage, or a hand-built XZ stream with wrong flag bytes.","solutions":["Re-compress with a standard tool (xz/zstd-compatible xz encoder) to regenerate a conformant footer","Verify the file with xz -t to see if the file itself is invalid","Re-download/restore the file if corruption is suspected","If you build XZ streams programmatically, write 0x00 for flag0 and keep flag1's high nibble zero"],"exampleFix":"// before\nfooter[8] = 0x01; // reserved flag bit set\n// after\nfooter[8] = 0x00; // spec: reserved byte must be 0\nfooter[9] &= 0x0f; // keep only check ID in low nibble","handlingStrategy":"try-catch","validationCode":"// The library surfaces this as a non-conformant stream; nothing to pre-check\n// beyond ensuring the file comes from a standard xz encoder.","typeGuard":"null","tryCatchPattern":"try {\n  await xzDecode(bytes);\n} catch (err) {\n  if (err instanceof ArchiveError && err.message.includes(\"Unsupported XZ stream flags\")) {\n    throw new Error(\"Archive produced by a non-conformant XZ encoder — re-compress with standard xz\");\n  }\n  throw err;\n}","preventionTips":["Compress only with spec-conformant tools (xz, 7-Zip)","Reject archives from unknown/untrusted encoders","Re-encode any archive that fails xz -t"],"tags":["xz","archive","spec-violation","validation"],"backgroundTag":"invalid-archive-format","analyzedSha":"969062200754ea02cfac922e5ebb8c608c079e15","analyzedAt":"2026-08-31T10:29:35.737Z","schemaVersion":2},"datasetVersion":"2026-08-31T14:17:45.589Z"}