# TypedArray TimeSamples Implementation Summary

## Overview

Successfully implemented `TypedArray<T>` support for TimeSamples array values with ValueRep-based deduplication in the Crate binary format reader.

## Changes Made

### 1. Updated Deduplication Cache (`src/crate-reader.hh`)

Replaced `std::vector<T>` with `TypedArray<T>` for POD array dedup maps:

```cpp
// Before:
std::unordered_map<crate::ValueRep, std::vector<int32_t>, crate::ValueRep::Hash> _dedup_int32_array;

// After:
std::unordered_map<crate::ValueRep, TypedArray<int32_t>, crate::ValueRep::Hash> _dedup_int32_array;
```

**Affected Types:**
- Integer arrays: `int32_t[]`, `uint32_t[]`, `int64_t[]`, `uint64_t[]`
- Floating point arrays: `half[]`, `float[]`, `double[]`

**Unchanged (still using std::vector):**
- Composite types: `half2[]`, `float2[]`, `double2[]`, `quat*[]`, `matrix*[]`
- These use `ReadArray<T>()` which returns `std::vector<T>`

### 2. Added TypedArray Overloads (`src/timesamples.hh`)

Added new template overloads to accept `TypedArray<T>`:

```cpp
template<typename T>
bool add_array_sample_pod(double t, const TypedArray<T>& value,
                          std::string *err = nullptr,
                          size_t expected_total_samples = 0);

template<typename T>
bool add_matrix_array_sample_pod(double t, const TypedArray<T>& value,
                                  std::string *err = nullptr,
                                  size_t expected_total_samples = 0);
```

### 3. Updated Helper Functions (`src/crate-reader-timesamples.cc`)

Added TypedArray overloads for array sample helpers:

```cpp
template <typename T>
typename std::enable_if<is_pod_type<T>::value, bool>::type
add_array_sample_to_timesamples(value::TimeSamples *d, double time,
                                const TypedArray<T> &arrval, std::string *err,
                                size_t expected_total_samples = 0);
```

### 4. Updated UnpackTimeSampleValue Functions

Modified array unpacking to use TypedArray:

| Function | Type | Read Method | Dedup Storage |
|----------|------|-------------|---------------|
| `UnpackTimeSampleValue_INT32` | `int32_t[]` | `ReadIntArrayTyped` | `TypedArray<int32_t>` |
| `UnpackTimeSampleValue_UINT32` | `uint32_t[]` | `ReadIntArrayTyped` | `TypedArray<uint32_t>` |
| `UnpackTimeSampleValue_INT64` | `int64_t[]` | `ReadIntArrayTyped` | `TypedArray<int64_t>` |
| `UnpackTimeSampleValue_UINT64` | `uint64_t[]` | `ReadIntArrayTyped` | `TypedArray<uint64_t>` |
| `UnpackTimeSampleValue_HALF` | `half[]` | `ReadHalfArray` → convert | `TypedArray<half>` |
| `UnpackTimeSampleValue_FLOAT` | `float[]` | `ReadFloatArrayTyped` | `TypedArray<float>` |
| `UnpackTimeSampleValue_DOUBLE` | `double[]` | `ReadDoubleArrayTyped` | `TypedArray<double>` |

## Benefits

### 1. Memory Efficiency
- **Deduplication**: When the same `ValueRep` appears multiple times in TimeSamples, the decoded array is cached and reused
- **Reduced allocations**: Shared arrays avoid duplicate memory allocations
- **Compact storage**: TypedArray uses packed pointer representation

### 2. Performance
- **Faster parsing**: Cached arrays avoid redundant file I/O operations
- **No decompression overhead**: Repeated compressed arrays are decompressed once
- **Cache-friendly**: POD TimeSamples storage is contiguous in memory

### 3. Code Quality
- **Backward compatible**: All existing `std::vector<T>` overloads continue to work
- **Type safe**: Template specialization ensures POD types only
- **Future ready**: TypedArray supports mmap views for zero-copy access

## Test Coverage

Created comprehensive feature test in `tests/feat/typed-array-timesamples/`:

```bash
cd tests/feat/typed-array-timesamples
make test
```

**Test Cases:**
1. TypedArray deduplication for POD array types
2. std::vector backward compatibility
3. Scalar value storage
4. Multiple type support (int, uint, int64, uint64, float, double)

**Results:** ✅ All 12 tests passed

## Example Usage

```cpp
// In Crate reader, when same ValueRep appears multiple times:
TypedArray<int32_t> v;

// First occurrence - read from file
if (!ReadIntArrayTyped(rep.IsCompressed(), &v)) {
    return false;
}
_dedup_int32_array[rep] = v;  // Cache it

// Second occurrence - reuse cached value
auto it = _dedup_int32_array.find(rep);
if (it != _dedup_int32_array.end()) {
    v = it->second;  // No file I/O!
}

// Add to TimeSamples (uses POD optimization)
add_array_sample_to_timesamples<int32_t>(&dst, time, v, &err);
```

## Implementation Notes

### Non-POD Path Fallback

When POD optimization is disabled, TypedArray is converted to std::vector:

```cpp
if (d->is_using_pod()) {
    return d->add_array_sample_pod<T>(time, arrval, err, expected_total_samples);
} else {
    // Convert TypedArray to std::vector for non-POD path
    std::vector<T> vec(arrval.data(), arrval.data() + arrval.size());
    return d->add_sample(time, value::Value(vec), err);
}
```

### TypedArray Construction

TypedArray requires a TypedArrayImpl pointer:

```cpp
// Convert std::vector to TypedArray
std::vector<T> temp_v;
ReadSomeArray(&temp_v);

TypedArray<T> arr(new TypedArrayImpl<T>(temp_v.data(), temp_v.size()));
```

## Files Modified

1. `src/crate-reader.hh` - Dedup cache type changes (lines 544-594)
2. `src/timesamples.hh` - TypedArray overloads (lines 1153-1215)
3. `src/crate-reader-timesamples.cc` - Array unpacking updates
   - Helper functions (lines 549-640)
   - INT32 (line 793)
   - UINT32 (line 2614)
   - INT64 (line 2699)
   - UINT64 (line 2784)
   - HALF (line 886)
   - FLOAT (line 1288)
   - DOUBLE (line 2873)

## Build Verification

```bash
# Main build
cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build --target test_tinyusdz -j8

# Feature test
cd tests/feat/typed-array-timesamples
make test
```

Both builds successful ✅

## Future Enhancements

Potential improvements:

1. **Composite type support**: Extend TypedArray to half2, float2, double2, etc.
2. **Mmap integration**: Use TypedArray views for memory-mapped crate data
3. **Hash-based dedup**: Use array content hash instead of ValueRep for better dedup
4. **Streaming support**: Lazy loading of large arrays via TypedArray views

## References

- TypedArray implementation: `src/typed-array.hh`
- POD TimeSamples: `src/timesamples.hh`
- Crate format reader: `src/crate-reader-timesamples.cc`
- ValueRep deduplication: Recent commit `8afae37e`
