PARAM.SFO and param.json, and eleven files that disagreed with the source

New crate, selfish-title: the binary key-value table every package carries, and the JSON the current generation writes into a title directory. Both read, both written.

A citable source turned up for the first time on the first look - pfd_sfo_tools, which is a reader and a writer, plus ps5upload as an independent second reading in another language. Compare that with the package, which still has no writer and is still blocked.

The three real packages parse

Twenty-nine keys each, and the titles are what they should be:

Store-R2-PS5           TITLE_ID NPXS39041   TITLE "Store (PS5)"
PS5_ITEM00001_v1.14    TITLE_ID ITEM00001   TITLE "Itemzflow Game Manager (PS5)"
PS5_LAPY20011_v1.05    TITLE_ID LAPY20011   TITLE "PS5-Xplorer"

PARAM.SFO is a package entry rather than a file inside the filesystem, so extracting a package does not produce it. selfish title takes a package, a bare .sfo, or a param.json and works out which by content.

Then the round trip failed, three times, and each failure was a real fact

--round-trip writes the parsed table back and compares byte for byte. Three rounds:

Four bytes too long. The cited writer pads the key table so the whole file is a multiple of sixteen. No real file does - the three packages are 1868 bytes, which is not a multiple of sixteen at all.

Three bytes too short. Removing the padding entirely was also wrong. Six more files were pulled in - two PS4 toolchain samples and six PS3 titles and saves, nine distinct files, seven distinct key-table lengths - and the rule fell out cleanly: the key table is padded to a multiple of four, and the file itself is not padded. Seven for seven. (D019)

One byte too long, on a PS3 save. 0x0004 is UTF-8 without a terminator and the first version wrote every string as terminated. The difference showed up in a format code fifty-five bytes in. Now a separate value variant, so a value cannot be held next to a format it disagrees with. (D020)

Eleven of eleven now round-trip byte-identical, across three console generations.

What that says about the method

None of the three would have been caught by parsing. Two are gaps a reader skips by construction, and the third produces a string that is correct in every way except its length. Writing bytes and diffing them is the only thing that finds this class, and it needed real files - the synthetic ones agreed with the wrong rule perfectly.

param.json keeps what it does not understand

Four fields have grounds - titleId, applicationCategoryType, and titleName under the locale that defaultLanguage names. A real file carries dozens more, all store metadata with no citable meaning here. Modelled as named accessors over the parsed document rather than a struct: a struct drops the unknown keys, and every real file would come back shorter than it went in.

The title name is deliberately not one field. localizedParameters is a map, and taking the first entry gives a Japanese title for a title that ships in twelve languages - right shape, wrong answer, no error.