Hint IO in the SDK

Cargo.toml

@@ -2,14 +2,15 @@
 exclude = ["examples"]
 members = [
   "ceno_emul",
-  "examples-builder",
+  "ceno_host",
   "ceno_rt",
+  "ceno_zkvm",
+  "examples-builder",
   "mpcs",
   "multilinear_extensions",
+  "poseidon",
   "sumcheck",
   "transcript",
-  "ceno_zkvm",
-  "poseidon",
 ]
 resolver = "2"
 
@@ -23,6 +24,7 @@ repository = "https://github.com/scroll-tech/ceno"
 version = "0.1.0"
 
 [workspace.dependencies]
+anyhow = { version = "1.0", default-features = false }
 ark-std = "0.4"
 cfg-if = "1.0"
 criterion = { version = "0.5", features = ["html_reports"] }

ceno_emul/Cargo.toml

@@ -10,7 +10,7 @@ repository.workspace = true
 version.workspace = true
 
 [dependencies]
-anyhow = { version = "1.0", default-features = false }
+anyhow.workspace = true
 elf = "0.7"
 itertools.workspace = true
 num-derive.workspace = true

ceno_emul/src/addr.rs

@@ -16,6 +16,7 @@
 
 use std::{
     fmt,
+    iter::Step,
     ops::{self, Range},
 };
 
@@ -106,6 +107,18 @@ impl WordAddr {
     }
 }
 
+impl Step for WordAddr {
+    fn steps_between(start: &Self, end: &Self) -> (usize, Option<usize>) {
+        u32::steps_between(&start.0, &end.0)
+    }
+    fn forward_checked(start: Self, count: usize) -> Option<Self> {
+        u32::forward_checked(start.0, count).map(Self)
+    }
+    fn backward_checked(start: Self, count: usize) -> Option<Self> {
+        u32::backward_checked(start.0, count).map(Self)
+    }
+}
+
 impl fmt::Debug for ByteAddr {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "0x{:08x}", self.0)

ceno_emul/src/host_utils.rs

@@ -0,0 +1,32 @@
+use std::iter::from_fn;
+
+use crate::{ByteAddr, EmuContext, VMState, WordAddr};
+
+const WORD_SIZE: usize = 4;
+const INFO_OUT_ADDR: WordAddr = ByteAddr(0xC000_0000).waddr();
+
+pub fn read_all_messages(state: &VMState) -> Vec<String> {
+    let mut offset: WordAddr = WordAddr::from(0);
+    from_fn(move || match read_message(state, offset) {
+        out if out.is_empty() => None,
+        out => {
+            offset += out.len().div_ceil(WORD_SIZE) as u32 + 1;
+            Some(out)
+        }
+    })
+    .collect()
+}
+
+fn read_message(state: &VMState, offset: WordAddr) -> String {
+    let out_addr = INFO_OUT_ADDR + offset;
+    let byte_len = state.peek_memory(out_addr) as usize;
+
+    String::from_utf8_lossy(
+        &(out_addr + 1_usize..)
+            .map(|memory| state.peek_memory(memory))
+            .flat_map(u32::to_le_bytes)
+            .take(byte_len)
+            .collect::<Vec<_>>(),
+    )
+    .to_string()
+}

ceno_emul/src/lib.rs

@@ -1,4 +1,5 @@
 #![deny(clippy::cargo)]
+#![feature(step_trait)]
 mod addr;
 pub use addr::*;
 
@@ -19,3 +20,5 @@ pub use elf::Program;
 
 mod rv32im_encode;
 pub use rv32im_encode::encode_rv32;
+
+pub mod host_utils;

ceno_emul/tests/test_elf.rs

@@ -1,5 +1,8 @@
 use anyhow::Result;
-use ceno_emul::{ByteAddr, CENO_PLATFORM, EmuContext, InsnKind, Platform, StepRecord, VMState};
+use ceno_emul::{
+    CENO_PLATFORM, EmuContext, InsnKind, Platform, StepRecord, VMState,
+    host_utils::read_all_messages,
+};
 
 #[test]
 fn test_ceno_rt_mini() -> Result<()> {
@@ -65,10 +68,10 @@ fn test_ceno_rt_io() -> Result<()> {
 
     let all_messages = read_all_messages(&state);
     for msg in &all_messages {
-        print!("{}", String::from_utf8_lossy(msg));
+        print!("{msg}");
     }
-    assert_eq!(&all_messages[0], "📜📜📜 Hello, World!\n".as_bytes());
-    assert_eq!(&all_messages[1], "🌏🌍🌎\n".as_bytes());
+    assert_eq!(&all_messages[0], "📜📜📜 Hello, World!\n");
+    assert_eq!(&all_messages[1], "🌏🌍🌎\n");
     Ok(())
 }
 
@@ -77,34 +80,3 @@ fn run(state: &mut VMState) -> Result<Vec<StepRecord>> {
     eprintln!("Emulator ran for {} steps.", steps.len());
     Ok(steps)
 }
-
-const WORD_SIZE: usize = 4;
-const INFO_OUT_ADDR: u32 = 0xC000_0000;
-
-fn read_all_messages(state: &VMState) -> Vec<Vec<u8>> {
-    let mut all_messages = Vec::new();
-    let mut word_offset = 0;
-    loop {
-        let out = read_message(state, word_offset);
-        if out.is_empty() {
-            break;
-        }
-        word_offset += out.len().div_ceil(WORD_SIZE) as u32 + 1;
-        all_messages.push(out);
-    }
-    all_messages
-}
-
-fn read_message(state: &VMState, word_offset: u32) -> Vec<u8> {
-    let out_addr = ByteAddr(INFO_OUT_ADDR).waddr() + word_offset;
-    let byte_len = state.peek_memory(out_addr);
-    let word_len_up = byte_len.div_ceil(4);
-
-    let mut info_out = Vec::with_capacity(WORD_SIZE * word_len_up as usize);
-    for i in 1..1 + word_len_up {
-        let value = state.peek_memory(out_addr + i);
-        info_out.extend_from_slice(&value.to_le_bytes());
-    }
-    info_out.truncate(byte_len as usize);
-    info_out
-}

ceno_host/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+categories.workspace = true
+description = "Support for the host port of a Ceno application"
+edition.workspace = true
+keywords.workspace = true
+license.workspace = true
+name = "ceno_host"
+readme.workspace = true
+repository.workspace = true
+version.workspace = true
+
+[dependencies]
+anyhow.workspace = true
+ceno_emul = { path = "../ceno_emul" }
+itertools.workspace = true
+rkyv = { version = "0.8.9", default-features = false, features = ["alloc", "bytecheck"] }
+
+[dev-dependencies]
+rand.workspace = true