update uf library to latest head, add readme

.gitignore

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 testext
 test/python/__pycache__/
 .Rhistory
+cache_w*.bin

README.md

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+# DuckDB UltrafastSecp256k1 Extension
+
+A DuckDB extension for Bitcoin Silent Payments (BIP-352) scanning using [UltrafastSecp256k1](https://github.com/shrec/UltrafastSecp256k1). Supports both CPU and optional NVIDIA GPU acceleration.
+
+## Features
+
+- **BIP-352 scanning**: Full Silent Payments pipeline (scalar multiply, tagged hash, generator multiply, point addition, prefix matching)
+- **Label support**: Tests both base output and label-tweaked variants
+- **CPU + GPU**: CPU-only by default, with optional CUDA acceleration for NVIDIA GPUs (Ampere+)
+- **Batch processing**: Configurable batch sizes for optimal throughput
+- **Automatic backend selection**: Detects available GPUs and selects the best backend
+
+## Building
+
+### Prerequisites
+
+- CMake 3.18+
+- C++ compiler with C++20 support
+- OpenSSL
+- Git
+
+For GPU support (optional):
+- NVIDIA GPU with compute capability 8.0+ (Ampere, Ada Lovelace, Hopper, Blackwell)
+- CUDA Toolkit 12.8+
+
+### Build steps
+
+```bash
+git clone --recursive https://github.com/sparrowwallet/duckdb-ufsecp-extension.git
+cd duckdb-ufsecp-extension
+```
+
+CPU-only build:
+```bash
+GEN=ninja make
+```
+
+With CUDA GPU support:
+```bash
+UFSECP_ENABLE_CUDA=ON GEN=ninja make
+```
+
+Run tests:
+```bash
+GEN=ninja make test
+```
+
+The compiled extension is at `build/release/extension/ufsecp/ufsecp.duckdb_extension`.
+The compiled DuckDB binary at `build/release/duckdb` loads the extension automatically.
+
+### Loading the extension
+
+```sql
+LOAD 'path/to/ufsecp.duckdb_extension';
+```
+
+## Functions
+
+### `ufsecp_scan(input_table, scan_private_key, spend_public_key, label_keys, [backend, batch_size])`
+
+Scans a table of transactions for BIP-352 Silent Payments matches.
+
+**Parameters:**
+- `input_table` (TABLE): Input table with columns:
+  - `txid` (BLOB): 32-byte transaction ID
+  - `height` (INTEGER): Block height
+  - `tweak_key` (BLOB): 64-byte uncompressed EC point (32-byte x || 32-byte y, little-endian)
+  - `outputs` (BIGINT[]): Array of output prefix values (first 8 bytes of x-coordinates as big-endian integers)
+- `scan_private_key` (BLOB): 32-byte scan private key (little-endian)
+- `spend_public_key` (BLOB): 64-byte uncompressed spend public key (32-byte x || 32-byte y, little-endian)
+- `label_keys` (LIST[BLOB]): Array of 64-byte uncompressed label public keys (can be empty)
+- `backend` (VARCHAR, optional): `'cpu'`, `'gpu'`, or `'auto'` (default: `'auto'`)
+- `batch_size` (INTEGER, optional): Rows per processing batch (default: 300000)
+
+**Returns:** TABLE with columns:
+- `txid` (BLOB): Transaction ID of matching transaction
+- `height` (INTEGER): Block height of matching transaction
+- `tweak_key` (BLOB): Tweak key that produced the match
+
+**Example:**
+```sql
+SELECT hex(txid), height
+FROM ufsecp_scan(
+    (SELECT txid, height, tweak_key, outputs FROM tweak),
+    from_hex('0f694e068028a717f8af6b9411f9a133dd3565258714cc226594b34db90c1f2c'),
+    from_hex('36cf8fcd4d4890ab6c1083aeb5b50c260c20acda7839120e3575836f6d85c95ce0d705e31ff9fdcce67a8f3598871c6dfbe6bcde8a51cb7b48b0f95be0ea94de'),
+    [from_hex('cd63f9212a2deebde8a71e9ea23f6f958c47c41d2ed74b9617fe6fb554d1524e292fabddbdcbb643eafc328875c46d75a1d697b2b31c42d38aa93f85eab34bc1')]
+);
+```
+
+### `ufsecp_backend()`
+
+Returns a string describing the active backend.
+
+```sql
+SELECT ufsecp_backend();
+-- 'cpu', 'gpu (2 devices)', or 'cpu (CUDA compiled, no GPU detected)'
+```
+
+## Precomputed table cache
+
+UltrafastSecp256k1 generates a ~244 MB precomputed lookup table (`cache_w18.bin`) on first use for fast fixed-scalar multiplication. This file is written to the current working directory by default.
+
+To control the cache location, set the environment variable before loading the extension:
+
+```bash
+export SECP256K1_CACHE_DIR=/path/to/cache/directory
+```
+
+Or set the exact file path:
+
+```bash
+export SECP256K1_CACHE_PATH=/path/to/cache_w18.bin
+```
+
+## Dependencies
+
+- [UltrafastSecp256k1](https://github.com/shrec/UltrafastSecp256k1): High-performance secp256k1 library
+- [DuckDB](https://duckdb.org/): In-process analytical database
+- OpenSSL
+- NVIDIA CUDA Runtime (optional, for GPU acceleration)
+
+## License
+
+MIT License — see [LICENSE](LICENSE) for details.

UltrafastSecp256k1

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-Subproject commit 2db7109e2816b6e0c6bb3849ff85ccb73008e636
+Subproject commit 1dcdb8d24f26ce5e36fe802bd60fe75a042f14ea