feat: Hook up check_id host function

crates/xrpl-host-functions/src/lib.rs

@@ -247,6 +247,13 @@ host_functions! {
     #[wasm_name = "amm_id"]
     fn amm_keylet(&self, asset1: &[u8], asset2: &[u8], out: &mut [u8]) -> HostResult<usize>;
 
+    /// The 32-byte keylet of a `Check`, computed from a 20-byte account id and its
+    /// sequence number. `seq` is the guest's `u32` carried as its `i32` bit pattern.
+    /// Reads the account region and writes the keylet.
+    #[gas = 350]
+    #[wasm_name = "check_id"]
+    fn check_keylet(&self, account: &[u8], seq: i32, out: &mut [u8]) -> HostResult<usize>;
+
     /// The XRPL `sha512Half` of `data`: the first [`HASH_LEN`] bytes of its SHA-512.
     #[gas = 2000]
     #[wasm_name = "sha512_half"]

crates/xrpl-host-functions/tests/generated_abi.rs

@@ -190,6 +190,14 @@ impl HostFunctions for FakeHost {
         put(out, &[asset1.len() as u8; HASH_LEN])
     }
 
+    /// A keylet from an account and a sequence; `InvalidAccount` on an empty account.
+    fn check_keylet(&self, account: &[u8], _seq: i32, out: &mut [u8]) -> HostResult<usize> {
+        if account.is_empty() {
+            return Err(HostError::InvalidAccount);
+        }
+        put(out, &[account[0]; HASH_LEN])
+    }
+
     fn sha512_half(&self, data: &[u8], out: &mut [u8]) -> HostResult<usize> {
         let mut digest = [0; HASH_LEN];
         digest[0] = data.len() as u8;
@@ -288,6 +296,12 @@ fn the_trait_is_implementable() {
         host.amm_keylet(&[1; 20], &[1; 20], &mut out),
         Err(HostError::InvalidParams)
     );
+    assert_eq!(host.check_keylet(&[7; 20], 5, &mut out), Ok(HASH_LEN));
+    assert_eq!(out[0], 7);
+    assert_eq!(
+        host.check_keylet(&[], 5, &mut out),
+        Err(HostError::InvalidAccount)
+    );
     assert_eq!(host.sha512_half(b"abc", &mut out), Ok(HASH_LEN));
     assert_eq!(out[0], 3);
     assert_eq!(host.trace("hello", b"xy", true), Ok(()));
@@ -376,6 +390,7 @@ fn the_spec_table_matches_the_declarations() {
             ("check_sig", 300),
             ("accountroot_id", 350),
             ("amm_id", 450),
+            ("check_id", 350),
             ("sha512_half", 2000),
             ("trace", 500),
             ("trace_num", 500),

crates/xrpl-wasm-vm-ffi/src/lib.rs

@@ -268,6 +268,10 @@ mod ffi {
         #[cxx_name = "ammKeylet"]
         fn amm_keylet(self: &HostContext, asset1: &[u8], asset2: &[u8], out: &mut [u8]) -> i32;
 
+        #[namespace = "xrpl"]
+        #[cxx_name = "checkKeylet"]
+        fn check_keylet(self: &HostContext, account: &[u8], seq: i32, out: &mut [u8]) -> i32;
+
         #[namespace = "xrpl"]
         #[cxx_name = "sha512Half"]
         fn sha512_half(self: &HostContext, data: &[u8], out: &mut [u8]) -> i32;
@@ -423,6 +427,10 @@ impl HostFunctions for CxxHost<'_> {
         bytes_written(self.ctx.amm_keylet(asset1, asset2, out))
     }
 
+    fn check_keylet(&self, account: &[u8], seq: i32, out: &mut [u8]) -> HostResult<usize> {
+        bytes_written(self.ctx.check_keylet(account, seq, out))
+    }
+
     fn sha512_half(&self, data: &[u8], out: &mut [u8]) -> HostResult<usize> {
         bytes_written(self.ctx.sha512_half(data, out))
     }

crates/xrpl-wasm-vm/src/abi.rs

@@ -271,6 +271,9 @@ mod tests {
         fn amm_keylet(&self, _asset1: &[u8], _asset2: &[u8], _out: &mut [u8]) -> HostResult<usize> {
             unreachable!("no unit test in this module calls the host")
         }
+        fn check_keylet(&self, _account: &[u8], _seq: i32, _out: &mut [u8]) -> HostResult<usize> {
+            unreachable!("no unit test in this module calls the host")
+        }
         fn sha512_half(&self, _data: &[u8], _out: &mut [u8]) -> HostResult<usize> {
             unreachable!("no unit test in this module calls the host")
         }

crates/xrpl-wasm-vm/src/register.rs

@@ -363,6 +363,25 @@ pub(crate) fn register_host_functions(
                     })
                 },
             ),
+            HostFunctionSpec::CheckKeylet => linker.func_wrap(
+                HOST_MODULE,
+                op.wasm_name(),
+                |mut caller: Caller<'_, VmState<'_>>,
+                 acc_ptr: i32,
+                 acc_len: i32,
+                 seq: i32,
+                 out_ptr: i32,
+                 out_len: i32|
+                 -> Result<i32, wasmi::Error> {
+                    charged(&mut caller, HostFunctionSpec::CheckKeylet, |c| {
+                        let out = Region::new(out_ptr, out_len);
+                        let account = Region::new(acc_ptr, acc_len);
+                        write_buffered(c, out, |host, data, buf| {
+                            host.check_keylet(account.read(data)?, seq, buf)
+                        })
+                    })
+                },
+            ),
             HostFunctionSpec::Sha512Half => linker.func_wrap(
                 HOST_MODULE,
                 op.wasm_name(),

crates/xrpl-wasm-vm/tests/budgets.rs

@@ -154,6 +154,11 @@ fn call_for(op: HostFunctionSpec) -> Call {
             "(call $amm_id (i32.const 0) (i32.const 20) (i32.const 24) (i32.const 40) (i32.const 0) (i32.const 32))",
             6,
         ),
+        HostFunctionSpec::CheckKeylet => (
+            import::CHECK_ID,
+            "(call $check_id (i32.const 0) (i32.const 20) (i32.const 5) (i32.const 32) (i32.const 32))",
+            5,
+        ),
         HostFunctionSpec::Sha512Half => (
             import::SHA512_HALF,
             "(call $sha512_half (i32.const 0) (i32.const 4) (i32.const 0) (i32.const 32))",

crates/xrpl-wasm-vm/tests/host_calls.rs

@@ -414,6 +414,23 @@ fn amm_id_reads_two_assets_and_writes_the_keylet() {
     assert_eq!(*host.amm_keylets_asked.borrow(), vec![(asset1, asset2)]);
 }
 
+/// A keylet getter that reads an account region and also takes a scalar seq: both
+/// reach the host keyed together, and the keylet lands where the guest asked.
+#[test]
+fn check_id_reads_the_account_and_seq_and_writes_the_keylet() {
+    // Guest memory is zeroed, so a 20-byte account read is all zeros.
+    let account = vec![0u8; 20];
+    let host =
+        FakeHost::new().answering_check_keylet(account.clone(), 5, support::Answer::filler(32));
+
+    let wat = module(
+        &[import::CHECK_ID, ONE_PAGE],
+        "(call $check_id (i32.const 0) (i32.const 20) (i32.const 5) (i32.const 64) (i32.const 64))",
+    );
+    assert_eq!(status(&wat, &host), 32, "the 32-byte keylet length");
+    assert_eq!(*host.check_keylets_asked.borrow(), vec![(account, 5)]);
+}
+
 /// A leading scalar parameter reaches the host as declared.
 #[test]
 fn home_le_field_passes_the_field_selector_through() {

crates/xrpl-wasm-vm/tests/preflight.rs

@@ -98,7 +98,7 @@ fn a_disabled_feature_does_not_pass() {
 
 /// Every host function the ABI declares, spelled as a guest imports it. The count
 /// is asserted against the ABI so a function added to it cannot be left out here.
-const ALL_IMPORTS: [&str; 24] = [
+const ALL_IMPORTS: [&str; 25] = [
     import::LDGR_INDEX,
     import::PARENT_LDGR_TIME,
     import::PARENT_LDGR_HASH,
@@ -120,6 +120,7 @@ const ALL_IMPORTS: [&str; 24] = [
     import::CHECK_SIG,
     import::ACCOUNTROOT_ID,
     import::AMM_ID,
+    import::CHECK_ID,
     import::SHA512_HALF,
     import::TRACE,
     import::TRACE_NUM,

crates/xrpl-wasm-vm/tests/support/mod.rs

@@ -189,6 +189,11 @@ pub struct FakeHost {
     pub amm_keylets: HashMap<(Vec<u8>, Vec<u8>), Answer>,
     /// Every (asset1, asset2) pair `amm_keylet` was asked for.
     pub amm_keylets_asked: RefCell<Vec<(Vec<u8>, Vec<u8>)>>,
+    /// What `check_keylet` answers, by (account bytes, seq). An unlisted key answers
+    /// `InvalidAccount`.
+    pub check_keylets: HashMap<(Vec<u8>, i32), Answer>,
+    /// Every (account, seq) `check_keylet` was asked for.
+    pub check_keylets_asked: RefCell<Vec<(Vec<u8>, i32)>>,
     /// What `sha512_half` answers, whatever it is given.
     pub digest: Answer,
     /// Every field selector `get_current_ledger_obj_field` was asked for.
@@ -247,6 +252,8 @@ impl Default for FakeHost {
             account_keylets_asked: RefCell::new(Vec::new()),
             amm_keylets: HashMap::new(),
             amm_keylets_asked: RefCell::new(Vec::new()),
+            check_keylets: HashMap::new(),
+            check_keylets_asked: RefCell::new(Vec::new()),
             digest: Answer::filler(32),
             fields_asked: RefCell::new(Vec::new()),
             digested: RefCell::new(Vec::new()),
@@ -380,6 +387,16 @@ impl FakeHost {
         self
     }
 
+    pub fn answering_check_keylet(
+        mut self,
+        account: Vec<u8>,
+        seq: i32,
+        answer: Answer,
+    ) -> FakeHost {
+        self.check_keylets.insert((account, seq), answer);
+        self
+    }
+
     pub fn answering_digest(mut self, answer: Answer) -> FakeHost {
         self.digest = answer;
         self
@@ -566,6 +583,16 @@ impl HostFunctions for FakeHost {
         }
     }
 
+    fn check_keylet(&self, account: &[u8], seq: i32, out: &mut [u8]) -> HostResult<usize> {
+        self.check_keylets_asked
+            .borrow_mut()
+            .push((account.to_vec(), seq));
+        match self.check_keylets.get(&(account.to_vec(), seq)) {
+            Some(answer) => answer.fill(out),
+            None => Err(HostError::InvalidAccount),
+        }
+    }
+
     fn sha512_half(&self, data: &[u8], out: &mut [u8]) -> HostResult<usize> {
         self.digested.borrow_mut().push(data.to_vec());
         self.digest.fill(out)
@@ -627,6 +654,7 @@ pub mod import {
     pub const CHECK_SIG: &str = r#"(import "host_lib" "check_sig" (func $check_sig (param i32 i32 i32 i32 i32 i32) (result i32)))"#;
     pub const ACCOUNTROOT_ID: &str = r#"(import "host_lib" "accountroot_id" (func $accountroot_id (param i32 i32 i32 i32) (result i32)))"#;
     pub const AMM_ID: &str = r#"(import "host_lib" "amm_id" (func $amm_id (param i32 i32 i32 i32 i32 i32) (result i32)))"#;
+    pub const CHECK_ID: &str = r#"(import "host_lib" "check_id" (func $check_id (param i32 i32 i32 i32 i32) (result i32)))"#;
     pub const SHA512_HALF: &str = r#"(import "host_lib" "sha512_half" (func $sha512_half (param i32 i32 i32 i32) (result i32)))"#;
     pub const TRACE: &str =
         r#"(import "host_lib" "trace" (func $trace (param i32 i32 i32 i32 i32) (result i32)))"#;

include/xrpl/tx/wasm/HostContext.h

@@ -133,6 +133,14 @@ public:
         rust::Slice<std::uint8_t const> asset2,
         rust::Slice<std::uint8_t> out) const noexcept;
 
+    // The account id must be 20 bytes, else `InvalidParams`. `seq` carries the guest's
+    // u32 as its i32 bit pattern. Writes the 32-byte keylet.
+    [[nodiscard]] std::int32_t
+    checkKeylet(
+        rust::Slice<std::uint8_t const> account,
+        std::int32_t seq,
+        rust::Slice<std::uint8_t> out) const noexcept;
+
     [[nodiscard]] std::int32_t
     sha512Half(rust::Slice<std::uint8_t const> data, rust::Slice<std::uint8_t> out) const noexcept;
 

src/libxrpl/tx/wasm/HostContext.cpp

@@ -485,6 +485,26 @@ HostContext::ammKeylet(
     });
 }
 
+std::int32_t
+HostContext::checkKeylet(
+    rust::Slice<std::uint8_t const> account,
+    std::int32_t seq,
+    rust::Slice<std::uint8_t> out) const noexcept
+{
+    return guarded(hostFunctions_.getJournal(), kHostInternal, [&] {
+        if (account.size() != AccountID::size())
+            return hfErrorToInt(HostFunctionError::InvalidParams);
+
+        // The guest's u32 seq arrives as its i32 bit pattern; recover it.
+        auto const value = hostFunctions_.checkKeylet(
+            AccountID::fromVoid(account.data()), static_cast<std::uint32_t>(seq));
+        if (!value)
+            return hfErrorToInt(value.error());
+
+        return answer(out, value->data(), value->size());
+    });
+}
+
 std::int32_t
 HostContext::sha512Half(rust::Slice<std::uint8_t const> data, rust::Slice<std::uint8_t> out)
     const noexcept