Add extension builder trait.

Cargo.toml

@@ -5,7 +5,7 @@ members = [
     "group",
     "pairing",
     "zcash_client_backend",
-    "zcash_extensions_api",
+    "zcash_extensions",
     "zcash_history",
     "zcash_primitives",
     "zcash_proofs",

zcash_extensions_api/Cargo.toml → zcash_extensions/Cargo.toml

@@ -1,11 +1,13 @@
 [package]
-name = "zcash_extensions_api"
+name = "zcash_extensions"
 description = "TBD"
 version = "0.0.0"
-authors = ["Jack Grigg <jack@z.cash>"]
+authors = ["Jack Grigg <jack@z.cash>", "Kris Nuttycombe <kris@z.cash>"]
 homepage = "https://github.com/zcash/librustzcash"
 repository = "https://github.com/zcash/librustzcash"
 license = "MIT OR Apache-2.0"
 edition = "2018"
 
 [dependencies]
+blake2b_simd = "0.5"
+zcash_primitives = { version = "0.2", path = "../zcash_primitives" }

zcash_primitives/src/consensus/extensions/transparent.rs → zcash_extensions/src/consensus/transparent.rs

@@ -1,11 +1,11 @@
 //! Consensus logic for Transparent Zcash Extensions.
 
 use std::convert::TryFrom;
-use zcash_extensions_api::transparent::{Error, Extension, Precondition, Witness};
+use zcash_primitives::transaction::components::TzeOut;
+use zcash_primitives::transaction::Transaction;
+use zcash_primitives::extensions::transparent::{Error, Extension, Precondition, Witness};
 
-use crate::extensions::transparent::demo;
-use crate::transaction::components::TzeOut;
-use crate::transaction::Transaction;
+use crate::transparent::demo;
 
 /// The set of programs that have assigned type IDs within the Zcash consensus rules.
 #[derive(Debug, Clone, Copy)]

zcash_extensions/src/lib.rs

@@ -0,0 +1,3 @@
+pub mod transparent;
+pub mod consensus;
+

zcash_extensions/src/transparent.rs

@@ -0,0 +1,3 @@
+//! Zcash transparent extensions.
+
+pub mod demo;

zcash_primitives/src/extensions/transparent/demo.rs → zcash_extensions/src/transparent/demo.rs

@@ -21,9 +21,9 @@
 use blake2b_simd::Params;
 use std::convert::TryFrom;
 use std::fmt;
-use zcash_extensions_api::transparent::{Extension, FromPayload, ToPayload};
 
-use crate::transaction::components::TzeOut;
+use zcash_primitives::transaction::components::{OutPoint, TzeOut, amount::Amount};
+use zcash_primitives::extensions::transparent::{Extension, FromPayload, ToPayload, ExtensionTxBuilder};
 
 mod open {
     pub const MODE: usize = 0;
@@ -273,6 +273,94 @@ impl<C: Context> Extension<C> for Program {
     }
 }
 
+fn builder_hashes(preimage_1: &[u8; 32], preimage_2: &[u8; 32]) -> ([u8; 32], [u8; 32]) {
+    let hash_2 = {
+        let mut hash = [0; 32];
+        hash.copy_from_slice(Params::new().hash_length(32).hash(preimage_2).as_bytes());
+        hash
+    };
+
+    let hash_1 = {
+        let mut hash = [0; 32];
+        hash.copy_from_slice(
+            Params::new()
+                .hash_length(32)
+                .to_state()
+                .update(preimage_1)
+                .update(&hash_2)
+                .finalize()
+                .as_bytes(),
+        );
+        hash
+    };
+
+    (hash_1, hash_2)
+}
+
+pub struct DemoBuilder<'a, B> { 
+    txn_builder: &'a mut B,
+    extension_id: usize,
+}
+
+impl<'a, B: ExtensionTxBuilder<'a>> DemoBuilder<'a, B> {
+    pub fn demo_open(
+        &mut self, 
+        value: Amount, 
+        preimage_1: [u8; 32], 
+        preimage_2: [u8; 32]
+    ) -> Result<(), B::BuildError> {
+        let (hash_1, _) = builder_hashes(&preimage_1, &preimage_2);
+
+        // Call through to the generic builder.
+        self.txn_builder.add_tze_output(
+            self.extension_id, 
+            value, 
+            &Precondition::open(hash_1),
+        )
+    }
+
+    pub fn demo_transfer_to_close(
+        &mut self, 
+        prevout: (OutPoint, TzeOut),
+        transfer_amount: Amount,
+        preimage_1: [u8; 32], 
+        preimage_2: [u8; 32]
+    ) -> Result<(), B::BuildError> {
+        let (_, hash_2) = builder_hashes(&preimage_1, &preimage_2);
+
+        // should we eagerly validate the relationship between prevout.1 and preimage_1?
+        self.txn_builder.add_tze_input(
+            self.extension_id,
+            prevout,
+            move |_| Ok(Witness::open(preimage_1))
+        )?;
+
+        self.txn_builder.add_tze_output(
+            self.extension_id, 
+            transfer_amount, // can this be > prevout.1.value?
+            &Precondition::close(hash_2)
+        )
+    }
+
+    pub fn demo_close(
+        &mut self, 
+        prevout: (OutPoint, TzeOut), 
+        preimage: [u8; 32]
+    ) -> Result<(), B::BuildError> {
+        let hash_2 = {
+            let mut hash = [0; 32];
+            hash.copy_from_slice(Params::new().hash_length(32).hash(&preimage).as_bytes());
+            hash
+        };
+
+        self.txn_builder.add_tze_input(
+            self.extension_id,
+            prevout,
+            move |_| Ok(Witness::close(hash_2))
+        )
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use blake2b_simd::Params;
@@ -382,31 +470,52 @@ mod tests {
             hash
         };
 
-        let mut mtx_a = TransactionData::nu4();
-        mtx_a.tze_outputs.push(TzeOut {
+        //
+        // Opening transaction
+        //
+
+        let out_a = TzeOut {
             value: Amount::from_u64(1).unwrap(),
             precondition: tze::Precondition::from(0, &Precondition::open(hash_1)),
-        });
+        };
+
+        println!("{:x?}", precondition.payload);
+
+        let mut mtx_a = TransactionData::nu4();
+        mtx_a.tze_outputs.push(out_a);
         let tx_a = mtx_a.freeze().unwrap();
 
-        let mut mtx_b = TransactionData::nu4();
-        mtx_b.tze_inputs.push(TzeIn {
+        // 
+        // Transfer
+        //
+
+        let in_b = TzeIn {
             prevout: OutPoint::new(tx_a.txid().0, 0),
             witness: tze::Witness::from(0, &Witness::open(preimage_1)),
-        });
-        mtx_b.tze_outputs.push(TzeOut {
+        };
+        let out_b = TzeOut {
             value: Amount::from_u64(1).unwrap(),
             precondition: tze::Precondition::from(0, &Precondition::close(hash_2)),
-        });
+        };
+        let mut mtx_b = TransactionData::nu4();
+        mtx_b.tze_inputs.push(in_b);
+        mtx_b.tze_outputs.push(out_b);
         let tx_b = mtx_b.freeze().unwrap();
 
-        let mut mtx_c = TransactionData::nu4();
-        mtx_c.tze_inputs.push(TzeIn {
+        // 
+        // Closing transaction
+        //
+
+        let in_c = TzeIn {
             prevout: OutPoint::new(tx_b.txid().0, 0),
             witness: tze::Witness::from(0, &Witness::close(preimage_2)),
-        });
+        };
+
+        let mut mtx_c = TransactionData::nu4();
+        mtx_c.tze_inputs.push(in_c);
         let tx_c = mtx_c.freeze().unwrap();
 
+
         // Verify tx_b
         {
             let ctx = Ctx { tx: &tx_b };

zcash_primitives/Cargo.toml

@@ -29,7 +29,6 @@ ripemd160 = { version = "0.8", optional = true }
 secp256k1 = { version = "=0.15.0", optional = true }
 sha2 = "0.8"
 subtle = "2.2.1"
-zcash_extensions_api = { version = "0.0", path = "../zcash_extensions_api" }
 
 [dev-dependencies]
 criterion = "0.3"

zcash_primitives/src/consensus.rs

@@ -3,8 +3,6 @@
 use std::convert::TryFrom;
 use std::fmt;
 
-pub mod extensions;
-
 /// Zcash consensus parameters.
 pub trait Parameters {
     fn activation_height(nu: NetworkUpgrade) -> Option<u32>;

zcash_primitives/src/extensions.rs

@@ -1,3 +1 @@
-//! Zcash extensions.
-
 pub mod transparent;