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hakorune/docs/development/current
nyash-codex 61dc4dec9b feat(filebox): Phase 108 FileBox write/write_all implementation
Implement write functionality for FileBox following Phase 108 specification,
completing the read/write pipeline via Ring0.FsApi.

## Implementation Summary

### Task 2: FsApi / Ring0FsFileIo write implementation
- Added write() method to FileIo trait
- Implemented write() in Ring0FsFileIo (truncate mode via Ring0.FsApi.write_all)
- Updated FileCaps to { read: true, write: true } for standard profile
- Added write() stub to CoreRoFileIo (returns Unsupported)

### Task 3: FileBox write/write_all implementation
- Updated FileBox.write_all() to delegate to provider.write()
- Updated FileBox.write() to convert content to text and call provider.write()
- UTF-8 conversion via String::from_utf8_lossy (text-oriented design)
- Returns "OK" on success, "Error: ..." on failure

### Task 4: Test coverage
- Round-trip test (write → read):  PASS
- Truncate mode verification:  PASS
- Write without open error:  PASS
- Read-only provider rejection:  PASS
- Auto-registration test updated:  PASS

### Task 5: Documentation updates
- phase107_fsapi_fileio_bridge.md: Added Phase 108 section
- core_boxes_design.md: Updated Ring0.FsApi relationship section
- CURRENT_TASK.md: Added Phase 108 completion entry

## Design Decisions (from phase108_filebox_write_semantics.md)

- **Write mode**: truncate (overwrite existing file each time)
- **Text-oriented**: UTF-8 conversion via from_utf8_lossy
- **Append mode**: Planned for Phase 109+
- **Error handling**: FileError::Io for failures, Fail-Fast on caps.write=false

## Test Results

```
cargo test --release --lib filebox
test result: ok. 5 passed; 0 failed; 1 ignored
```

All FileBox tests pass, including Phase 107 compatibility tests.

## Pipeline Complete

```
FileBox.write(content)
    ↓
FileBox.write_all(buf)
    ↓
provider.write(text) ← Ring0FsFileIo implementation
    ↓
Ring0.FsApi.write_all()
    ↓
std::fs::write()
```

## Next Steps (Backlog)

- Phase 109: minimal/no-fs profile
- Phase 110: FileHandleBox (multiple files simultaneously)
- Phase 111: append mode implementation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
2025-12-03 18:40:33 +09:00
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