From 9d7de214d7a8e7ee53bc687a700f18c428df4cff Mon Sep 17 00:00:00 2001
From: Akilan <me@akilan.io>
Date: Tue, 31 Mar 2026 16:15:40 +0100
Subject: [PATCH] added add delta

---
 CHERICC_Fat.bsv | 10 ++++++++++
 CHERICap.bsv    |  1 +
 2 files changed, 11 insertions(+)

diff --git a/CHERICC_Fat.bsv b/CHERICC_Fat.bsv
index e85b175..49dcc12 100644
--- a/CHERICC_Fat.bsv
+++ b/CHERICC_Fat.bsv
@@ -38,6 +38,7 @@ export CapReg;
 export CapPipe;
 
 export encodeDelta;
+export addDelta;
 export decodeDelta;
 
 export CapFat;
@@ -1185,6 +1186,7 @@ instance CHERICap #(CapMem, OTypeW, FlagsW, CapAddrW, CapW, TSub #(MW, 3));
   function isDerivable = error ("isDerivable not implemented for CapMem");
 
   function encodeDelta (cap, delta) = error ("encode delta not implemented");
+  function addDelta (cap, delta) = error ("addDelta not implemented");
   function decodeDelta (cap) = error ("decode delta not implemented");
 
 endinstance
@@ -1342,6 +1344,7 @@ instance CHERICap #(CapReg, OTypeW, FlagsW, CapAddrW, CapW, TSub #(MW, 3));
   function setBoundsCombined (cap, length) = error ("setBoundsCombined not implemented for CapReg");
 
   function encodeDelta (cap, delta) = error ("encode delta not implemented");
+  function addDelta (cap, delta) = error ("addDelta not implemented");
   function decodeDelta (cap) = error ("decode delta not implemented");
 
   //function setBounds = error ("setBounds not implemented for CapReg");
@@ -1428,6 +1431,13 @@ instance CHERICap #(CapPipe, OTypeW, FlagsW, CapAddrW, CapW, TSub#(MW, 3));
     cap.capFat.address = {d, va_bits};
     return cap;
   endfunction
+
+  function addDelta(cap, delta);
+    Bit#(25) d = truncate(delta);
+    cap.capFat.address = cap.capFat.address + zeroExtend(delta);
+    return cap;
+  endfunction
+
   
   // Extract the delta stored in bits 63:39 of the address
   function decodeDelta(cap);
diff --git a/CHERICap.bsv b/CHERICap.bsv
index e4bea27..e81635f 100644
--- a/CHERICap.bsv
+++ b/CHERICap.bsv
@@ -173,6 +173,7 @@ typeclass CHERICap #( type capT              // type of the CHERICap capability
   function capT setFlags (capT cap, Bit #(flgW) flags);
 
   function capT encodeDelta(capT cap, Bit #(64) delta);
+  function capT addDelta(capT cap, Bit #(25) delta);
 
   function Bit #(25) decodeDelta(capT cap);