---
phase: 09-kotlin-decoder-update
plan: 01
subsystem: decoder
tags: [kotlin, android, directory-support, binary-format, permissions, cross-validation]

# Dependency graph
requires:
  - phase: 08-rust-directory-archiver
    provides: v1.1 Rust archiver with directory traversal, entry_type/permissions in TOC
provides:
  - v1.1-compatible Kotlin decoder with directory support and permission restoration
  - Cross-validation test script with 8 test cases (5 original + 3 directory)
affects: [10-hardening, 11-polish]

# Tech tracking
tech-stack:
  added: []
  patterns: [applyPermissions pattern using Java File API owner/everyone distinction, directory-first extraction with parent directory creation]

key-files:
  created: []
  modified:
    - kotlin/ArchiveDecoder.kt
    - kotlin/test_decoder.sh

key-decisions:
  - "Java File API owner/everyone permission model sufficient for KOT-07 (no group-level granularity)"
  - "Directory entries processed before file entries naturally via DFS preorder parent-before-child ordering"
  - "Permission application: set everyone flags first (ownerOnly=false), then override owner-only (ownerOnly=true)"

patterns-established:
  - "applyPermissions(): extract POSIX mode bits and map to Java File setReadable/setWritable/setExecutable"
  - "Entry type dispatch: directory entries skip crypto pipeline entirely, file entries ensure parent dirs exist"

requirements-completed: [KOT-05, KOT-06, KOT-07]

# Metrics
duration: 2min
completed: 2026-02-26
---

# Phase 9 Plan 01: Kotlin Decoder Update Summary

**v1.1 Kotlin decoder with directory hierarchy creation, empty directory support, and POSIX permission restoration via Java File API**

## Performance

- **Duration:** 2 min
- **Started:** 2026-02-26T19:03:18Z
- **Completed:** 2026-02-26T19:05:44Z
- **Tasks:** 2
- **Files modified:** 2

## Accomplishments
- Updated TocEntry data class with entryType (0=file, 1=directory) and permissions (12-bit POSIX mode_t) fields
- Kotlin decoder now parses v1.1 TOC entries (104 + name_length bytes) with entry_type and permissions
- Directory entries create full hierarchy via mkdirs() without attempting decryption
- File entries with relative paths create parent directories before writing
- Permissions restored via Java File API (setReadable/setWritable/setExecutable with owner/everyone distinction)
- Test script expanded from 5 to 8 test cases with nested directory, empty directory, and mixed file/directory tests

## Task Commits

Each task was committed atomically:

1. **Task 1: Update ArchiveDecoder.kt for v1.1 format with directory support** - `a01b260` (feat)
2. **Task 2: Update test_decoder.sh with directory test cases** - `27fb392` (test)

## Files Created/Modified
- `kotlin/ArchiveDecoder.kt` - v1.1 decoder: entryType/permissions parsing, directory handling, permission restoration
- `kotlin/test_decoder.sh` - 3 new directory test cases (nested dirs, empty dir, mixed files+dirs)

## Decisions Made
- Used Java File API owner/everyone permission model (no Java NIO PosixFilePermission) per KOT-07 spec
- Permission application order: set everyone flags first (ownerOnly=false), then owner-only overrides (ownerOnly=true) to correctly handle cases where owner has permissions but others do not
- Entry size formula updated from 101 to 104 + name_length consistently

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered
None - all tasks completed without issues.

## User Setup Required
None - no external service configuration required.

## Next Phase Readiness
- Kotlin decoder fully compatible with v1.1 format produced by Rust archiver
- Cross-validation test script ready with 8 test cases covering files, directories, empty dirs, and mixed content
- Ready for Phase 10 (hardening) or Phase 11 (polish)

## Self-Check: PASSED

- [x] kotlin/ArchiveDecoder.kt exists
- [x] kotlin/test_decoder.sh exists
- [x] 09-01-SUMMARY.md exists
- [x] Commit a01b260 (Task 1) verified
- [x] Commit 27fb392 (Task 2) verified

---
*Phase: 09-kotlin-decoder-update*
*Completed: 2026-02-26*