From c24d991a7e87d60e4966583d0254607b9e49aa7c Mon Sep 17 00:00:00 2001
From: Mike Hearn <mike@r3cev.com>
Date: Thu, 25 Feb 2016 19:23:00 +0100
Subject: [PATCH] Introduce a NamedByHash interface, for things that are
 identified via secure hash.

---
 core/src/main/kotlin/core/Structures.kt   | 25 ++++++++++++++++++++++-
 core/src/main/kotlin/core/Transactions.kt | 10 +++++----
 2 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/core/src/main/kotlin/core/Structures.kt b/core/src/main/kotlin/core/Structures.kt
index 498e4ea4ef..73aa3d45c4 100644
--- a/core/src/main/kotlin/core/Structures.kt
+++ b/core/src/main/kotlin/core/Structures.kt
@@ -12,9 +12,16 @@ import core.crypto.SecureHash
 import core.crypto.toStringShort
 import core.serialization.OpaqueBytes
 import core.serialization.serialize
+import java.io.InputStream
 import java.security.PublicKey
 import java.time.Duration
 import java.time.Instant
+import java.util.jar.JarInputStream
+
+/** Implemented by anything that can be named by a secure hash value (e.g. transactions, attachments). */
+interface NamedByHash {
+    val id: SecureHash
+}
 
 /**
  * A contract state (or just "state") contains opaque data used by a contract program. It can be thought of as a disk
@@ -146,4 +153,20 @@ interface ContractFactory {
     operator fun <T : Contract> get(hash: SecureHash): T
 }
 
-class UnknownContractException : Exception()
\ No newline at end of file
+class UnknownContractException : Exception()
+
+/**
+ * An attachment is a ZIP (or an optionally signed JAR) that contains one or more files. Attachments are meant to
+ * contain public static data which can be referenced from transactions and utilised from contracts. Good examples
+ * of how attachments are meant to be used include:
+ *
+ * - Calendar data
+ * - Fixes (e.g. LIBOR)
+ * - Smart contract code
+ * - Legal documents
+ * - Facts generated by oracles which might be reused a lot
+ */
+interface Attachment : NamedByHash {
+    fun open(): InputStream
+    fun openAsJAR() = JarInputStream(open())
+}
\ No newline at end of file
diff --git a/core/src/main/kotlin/core/Transactions.kt b/core/src/main/kotlin/core/Transactions.kt
index 54ac529403..35eb09f975 100644
--- a/core/src/main/kotlin/core/Transactions.kt
+++ b/core/src/main/kotlin/core/Transactions.kt
@@ -57,12 +57,13 @@ import java.util.*
 /** Transaction ready for serialisation, without any signatures attached. */
 data class WireTransaction(val inputs: List<StateRef>,
                            val outputs: List<ContractState>,
-                           val commands: List<Command>) {
+                           val commands: List<Command>) : NamedByHash {
 
     // Cache the serialised form of the transaction and its hash to give us fast access to it.
     @Volatile @Transient private var cachedBits: SerializedBytes<WireTransaction>? = null
     val serialized: SerializedBytes<WireTransaction> get() = cachedBits ?: serialize().apply { cachedBits = this }
-    val id: SecureHash get() = serialized.hash
+    override val id: SecureHash get() = serialized.hash
+
     companion object {
         fun deserialize(bits: SerializedBytes<WireTransaction>): WireTransaction {
             val wtx = bits.deserialize()
@@ -98,14 +99,15 @@ data class WireTransaction(val inputs: List<StateRef>,
 }
 
 /** Container for a [WireTransaction] and attached signatures. */
-data class SignedTransaction(val txBits: SerializedBytes<WireTransaction>, val sigs: List<DigitalSignature.WithKey>) {
+data class SignedTransaction(val txBits: SerializedBytes<WireTransaction>,
+                             val sigs: List<DigitalSignature.WithKey>) : NamedByHash {
     init { check(sigs.isNotEmpty()) }
 
     /** Lazily calculated access to the deserialised/hashed transaction data. */
     val tx: WireTransaction by lazy { WireTransaction.deserialize(txBits) }
 
     /** A transaction ID is the hash of the [WireTransaction]. Thus adding or removing a signature does not change it. */
-    val id: SecureHash get() = txBits.hash
+    override val id: SecureHash get() = txBits.hash
 
     /**
      * Verifies the given signatures against the serialized transaction data. Does NOT deserialise or check the contents