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MON 274B (octal) - GetFileIndexes (FOBJN)

Gets the directory index, the user index, the object index, and the next-version object index of a file, identified by name. These are the indexes that address the file inside the SINTRAN III File System. Unlike MON 217B GetAllFileIndexes, the file need not be open - the worker resolves the name against the directory itself.

Status: GOTAB dispatch head byte-proven as fall-through (GOTAB[274B] = 000000, no per-call stub); the FOBJN worker body is real SINTRAN L bytes and builds the returned index quadruple with the same byte sequence used by the GUIOI worker (MON 217B). The exact MON 274 -> worker link crosses an uncarved kernel bridge (see Honest caveats). All addresses/values are octal.

Dispatch path

flowchart LR
    A["User program<br/>MON 274B"] --> B["ENT14 level-14<br/>T = MON number"]
    B --> C["GOTAB[274B] = 000000<br/>(byte-proven: fall-through)"]
    C -.uncarved MFELL / CALLPROC.-> E["FOBJN find-by-name worker<br/>006-S3FS :111210B"]
    E --> F["directory scan +<br/>index-quadruple build<br/>006-S3FS :111411B"]
    class A blue
    class B,C blue
    class E,F green
    classDef blue fill:#E3F2FD,stroke:#0D47A1,color:#0D47A1
    classDef teal fill:#E0F7FA,stroke:#00838F,color:#00838F
    classDef green fill:#E8F5E9,stroke:#2E7D32,color:#2E7D32

The GOTAB slot is zero, so there is no per-call entry stub. The dashed hop (C -> E) is the resident MFELL/CALLPROC fall-through second-level dispatch - it is not present in any carved segment, so it is the one link that cannot be followed statically.

Code location (dispatch path)

Every row is a real region you can open. Byte offset is the 006-S3FS.hex byte offset.

Role Segment (full disasm) Addr range (octal) Byte offset Symbol Verdict
GOTAB[274] dispatch word commoncode.asm - .hex 071527B (1 word) 59054 GOTAB+274 = 000000 VERIFIED (fall-through)
resident MFELL/CALLPROC bridge - (uncarved) - - CALLPROC UNVERIFIED
FOBJN find-by-name worker (+ FOPFN sibling entry) 006-S3FS.asm - .hex 111210B-111500B (185w) 52496 FOBJN real bytes; link MISATTRIBUTED
index-quadruple build 006-S3FS.asm - .hex 111411B-111431B 52754 (inside FOBJN) real bytes - VERIFIED

Verify by hand: grep '^111210 ' ../../segments-ref/006-S3FS/006-S3FS.hex -> byte offset 52496; then dd if=../../../segments/006-S3FS.bin bs=1 skip=52496 count=8 | od -An -tx1 -> f8 90 a8 02 f8 10 22 36 (= octal 174220 124002 174020 021066 = BSET ONE SSK / JMP 2 / BSET ZRO SSK (FOPFN) / STD I 66, the FOBJN entry).

The GOTAB slot itself: dd if=../../../resident/SINTRAN-DATA_commoncode.bin bs=1 skip=59054 count=2 | od -An -tx1 -> 00 00 (= 000000, fall-through).

Instruction walkthrough

Full listing: 274B-GetFileIndexes.ASM. There is no F16xx/F17xx stub because GOTAB[274] = 0.

Mode-select entry (111210-111213) - FOBJN (111210 BSET ONE SSK) and its sibling FOPFN (111212 BSET ZRO SSK) set/clear the STS K flag, then both merge at 111213 STD I 66 which stashes the caller's parameter double-word and 111216 SAB 122 builds a 122-word local frame. The K flag is turned into an open-flag word at 111220-111225 (BSKP ONE SSK -> STA ,B 121).

Name parse + directory resolve (111226-111254) - 111230 STA ,B 113 records the file-name buffer pointer; 111232 JPL I 53 parses the name; the following calls resolve the default directory / user for the parsed name.

Directory walk (111350-111401) - the loop reads directory entries, compares the entry's dir index (111362 LDA ,X 15) and user index (111366 LDA ,X 16) against the parsed target, advances by 111400 AAX 2, and ends when the table pointer wraps (111352 SKP IF DX UEQ ST).

Index-quadruple build (111411-111431) - the returned words are packed with the same shape as GUIOI (MON 217B): the dir index is shifted into the left byte and the user index into the right byte of the INDEX word (111415-111423 SHA ZIN 10 / SHA ZIN SHR 10 / RADD ST DA / STA ,B 1); the object index goes to B+3 (111414) and the next-version object index to B+2 (111424-111430). 111431 MIN ,B 4 bumps the success flag. This identical packing sequence is the byte-level proof that FOBJN is the GetFileIndexes worker.

Finish (111432-111500) - the epilogue restores state and every path funnels into the resident return 111440 JMP I 40 -> 111500 = 003776.

Parameter / register contract

Reg / field Dir Meaning Verdict
entry point in 111210B = FOBJN worker entry (fall-through, no stub) VERIFIED (bytes)
STS K flag in mode select: FOBJN sets it, FOPFN clears it (BSET ONE/ZRO SSK) VERIFIED (bytes)
X (manual) in address of the file-name string inferred (manual MAC example)
local frame B internal SAB 122 = 122-word working frame VERIFIED (bytes)
B+121 internal open-flag derived from K (BSKP ONE SSK) VERIFIED (bytes)
T (manual) out INDEX: directory index (left byte) + user index (right byte) inferred (manual MAC example)
A (manual) out object index (OBJIX) inferred (manual MAC example)
D (manual) out object index of the next file version (NEXTO) inferred (manual MAC example)
B+1 out INDEX word (dir/user), built at 111423 VERIFIED (bytes)
B+2 out next-object index, built at 111430 VERIFIED (bytes); role inferred
B+3 out object index, stored at 111414 VERIFIED (bytes); role inferred
error at 111402 out not-found error number (LDA 71) VERIFIED (bytes); mapping inferred

The user-visible X-in / T/A/D-out convention lives in the caller-side MON 274 wrapper and the uncarved MFELL/CALLPROC frame, so the precise user-register-to-field assignment is inferred from the manual (274B_GetFileIndexes.yaml), not byte-proven here.

Pseudo-code (for an emulator)

See 274B-GetFileIndexes.pseudo.c - a pseudo-C model of the handler for emulator authors. Control flow and the index-quadruple build are byte-verified; the index-field roles and error-number meanings are inferred from the call structure, the manual, and the identical GUIOI packing.

Every instruction in the model is translated per the canonical ND100-INSTRUCTION-SEMANTICS.md (bare LDA disp = mem[P+disp]; RADD CLD Sx Dy = Dy = Sx; BSET/BSKP on STS bit K = STS bit2; SHA ZIN/SHA ZIN SHR logical shifts; MIN ,B 4 success bump).

Honest caveats

What is byte-proven: GOTAB[274B] = 000000 (level-14 dispatch, a fall-through with no per-call vector); the FOBJN worker body at 111210B in 006-S3FS is real code (entry bytes 174220 124002 174020 021066 match the disassembly); and it belongs to the file-index family - it packs a directory/user/object/next-object index quadruple into the caller frame using the identical SHA ZIN byte-pack sequence as GUIOI (111411-111431).

What is NOT proven: the link from the zero GOTAB slot to the FOBJN worker. Because the vector is zero there is no stub to disassemble and no pointer to dereference; dispatch drops into the resident MFELL/CALLPROC second-level path, which lives in an uncarved overlay. So the MON 274 -> FOBJN attribution rests on the FOBJN symbol name + its index-quadruple behaviour + the matching by-name (file-need-not-be-open) contract, not a followed pointer - hence MISATTRIBUTED in the strict sense. Confirming the link needs a live trace: issue a real MON 274, single-step the level-14 fall-through into the resident CALLPROC dispatch, and confirm P lands on FOBJN = 111210.

Region bound: the FOBJN body is bounded strictly to the next symbol SDRUS = 111501B (185 words); its shared body closes on the 003776 resident-return link cell at 111500.

Several link-cell contents (031075, 031310, 031312, 031313, 031316, 031470, 031474, 031476, 031477) match no FILSYS-SYMBOLS entry; their low addresses suggest resident-monitor / directory-primitive routines outside the file-system segment and are not resolved here.

Method: ../../../../../EXTRACTING-RESIDENT-CODE.md - dispatch reality: ../../TASK-05-mismatches.md - master map: ../../MON-CALL-INDEX.md.