From aa41e096553e534b68ae3961b0f058b9478b47f9 Mon Sep 17 00:00:00 2001
From: Danny Willems <be.danny.willems@gmail.com>
Date: Mon, 30 Dec 2024 20:44:21 +0100
Subject: [PATCH] o1vm/riscv32im: helper to read a uint32 from memory

---
 o1vm/src/interpreters/riscv32im/witness.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/o1vm/src/interpreters/riscv32im/witness.rs b/o1vm/src/interpreters/riscv32im/witness.rs
index 256de81687..d6085922ad 100644
--- a/o1vm/src/interpreters/riscv32im/witness.rs
+++ b/o1vm/src/interpreters/riscv32im/witness.rs
@@ -945,4 +945,15 @@ impl<Fp: Field> Env<Fp> {
     pub fn normalized_instruction_counter(&self) -> u64 {
         self.instruction_counter / MAX_ACC
     }
+
+    /// Get a u32 from memory, starting from address `addr`.
+    pub fn get_uint32(&mut self, addr: u32) -> u32 {
+        let page = addr >> PAGE_ADDRESS_SIZE;
+        let page_address = (addr & PAGE_ADDRESS_MASK) as usize;
+        let memory_page_idx = self.get_memory_page_index(page);
+        let value = self.memory[memory_page_idx].1[page_address..page_address + 4]
+            .try_into()
+            .expect("get_uint32 values fit in a u32");
+        u32::from_be_bytes(value)
+    }
 }