Added descriptorpubkeyctx example

Author: sanket1729

Cargo.toml

@@ -37,3 +37,6 @@ name = "verify_tx"
 
 [[example]]
 name = "psbt"
+
+[[example]]
+name = "xpub_descriptors"

examples/xpub_descriptors.rs

@@ -0,0 +1,68 @@
+// Miniscript
+// Written in 2019 by
+//     Andrew Poelstra <apoelstra@wpsoftware.net>
+//
+// To the extent possible under law, the author(s) have dedicated all
+// copyright and related and neighboring rights to this software to
+// the public domain worldwide. This software is distributed without
+// any warranty.
+//
+// You should have received a copy of the CC0 Public Domain Dedication
+// along with this software.
+// If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
+//
+
+//! Example: Parsing a xpub and getting address
+
+extern crate miniscript;
+
+use miniscript::bitcoin::{self, secp256k1};
+use miniscript::{Descriptor, DescriptorPublicKey, DescriptorPublicKeyCtx};
+
+use bitcoin::util::bip32;
+
+use std::str::FromStr;
+fn main() {
+    // For deriving from descriptors, we need to provide a secp context
+    let secp_ctx = secp256k1::Secp256k1::verification_only();
+    // Child number to derive public key
+    // This is used only when xpub is wildcard
+    let child_number = bip32::ChildNumber::from_normal_idx(0).unwrap();
+    let desc_ctx = DescriptorPublicKeyCtx::new(&secp_ctx, child_number);
+    // P2WSH and single xpubs
+    let addr_one = Descriptor::<DescriptorPublicKey>::from_str(
+            "wsh(sortedmulti(1,xpub661MyMwAqRbcFW31YEwpkMuc5THy2PSt5bDMsktWQcFF8syAmRUapSCGu8ED9W6oDMSgv6Zz8idoc4a6mr8BDzTJY47LJhkJ8UB7WEGuduB,xpub69H7F5d8KSRgmmdJg2KhpAK8SR3DjMwAdkxj3ZuxV27CprR9LgpeyGmXUbC6wb7ERfvrnKZjXoUmmDznezpbZb7ap6r1D3tgFxHmwMkQTPH))",
+        )
+        .unwrap()
+        .address(bitcoin::Network::Bitcoin, desc_ctx).unwrap();
+
+    let addr_two = Descriptor::<DescriptorPublicKey>::from_str(
+            "wsh(sortedmulti(1,xpub69H7F5d8KSRgmmdJg2KhpAK8SR3DjMwAdkxj3ZuxV27CprR9LgpeyGmXUbC6wb7ERfvrnKZjXoUmmDznezpbZb7ap6r1D3tgFxHmwMkQTPH,xpub661MyMwAqRbcFW31YEwpkMuc5THy2PSt5bDMsktWQcFF8syAmRUapSCGu8ED9W6oDMSgv6Zz8idoc4a6mr8BDzTJY47LJhkJ8UB7WEGuduB))",
+        )
+        .unwrap()
+        .address(bitcoin::Network::Bitcoin, desc_ctx).unwrap();
+    let expected = bitcoin::Address::from_str(
+        "bc1qpq2cfgz5lktxzr5zqv7nrzz46hsvq3492ump9pz8rzcl8wqtwqcspx5y6a",
+    )
+    .unwrap();
+    assert_eq!(addr_one, expected);
+    assert_eq!(addr_two, expected);
+
+    // P2WSH-P2SH and ranged xpubs
+    let addr_one = Descriptor::<DescriptorPublicKey>::from_str(
+            "sh(wsh(sortedmulti(1,xpub661MyMwAqRbcFW31YEwpkMuc5THy2PSt5bDMsktWQcFF8syAmRUapSCGu8ED9W6oDMSgv6Zz8idoc4a6mr8BDzTJY47LJhkJ8UB7WEGuduB/1/0/*,xpub69H7F5d8KSRgmmdJg2KhpAK8SR3DjMwAdkxj3ZuxV27CprR9LgpeyGmXUbC6wb7ERfvrnKZjXoUmmDznezpbZb7ap6r1D3tgFxHmwMkQTPH/0/0/*)))",
+        )
+        .unwrap()
+        .derive(bitcoin::util::bip32::ChildNumber::from_normal_idx(5).unwrap())
+        .address(bitcoin::Network::Bitcoin, desc_ctx).unwrap();
+
+    let addr_two = Descriptor::<DescriptorPublicKey>::from_str(
+            "sh(wsh(sortedmulti(1,xpub69H7F5d8KSRgmmdJg2KhpAK8SR3DjMwAdkxj3ZuxV27CprR9LgpeyGmXUbC6wb7ERfvrnKZjXoUmmDznezpbZb7ap6r1D3tgFxHmwMkQTPH/0/0/*,xpub661MyMwAqRbcFW31YEwpkMuc5THy2PSt5bDMsktWQcFF8syAmRUapSCGu8ED9W6oDMSgv6Zz8idoc4a6mr8BDzTJY47LJhkJ8UB7WEGuduB/1/0/*)))",
+        )
+        .unwrap()
+        .derive(bitcoin::util::bip32::ChildNumber::from_normal_idx(5).unwrap())
+        .address(bitcoin::Network::Bitcoin, desc_ctx).unwrap();
+    let expected = bitcoin::Address::from_str("325zcVBN5o2eqqqtGwPjmtDd8dJRyYP82s").unwrap();
+    assert_eq!(addr_one, expected);
+    assert_eq!(addr_two, expected);
+}