FA-52402 / Raster memory layout / Member archive

Indexed Nibble Records: Scanline checksum omitted or mistaken for per-byte data · case 02

The returned physical layout descriptor disagrees with the declared buffer mapping at row_pitch.

Member previewVariant 2 · 3 implementations · 6 checks per implementation

Case contract

An indexed image has a palette of three-byte entries, a two-byte palette-count field, and high-nibble-first pixels. Each scanline starts with a one-byte checksum. Odd final low nibbles are padding. Return the named intermediate layout descriptor and final address fields; all quantities are integer byte offsets unless explicitly stated.

Why this case matters

Offline raster resource, upload, readback, and storage-layout regression model.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
layout fixture 1	`{"allocation_end": 60, "byte_address": 55, "image_origin": 54, "keep_mask": 15, "packed_bytes": 3, "palette_bytes": 20, "row_pitch": 3, "shift": 4, "tail_mask": 240, "written_byte": 35}`	`{"allocation_end": 62, "byte_address": 55, "image_origin": 54, "keep_mask": 15, "packed_bytes": 3, "palette_bytes": 20, "row_pitch": 4, "shift": 4, "tail_mask": 240, "written_byte": 35}`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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