From 220707d9ee5594c782460272dd7385ff9b947cb4 Mon Sep 17 00:00:00 2001
From: Alejandro Cabeza Romero <alex93cabeza@gmail.com>
Date: Fri, 24 Apr 2026 13:47:43 +0200
Subject: [PATCH] Simplify guard.

---
 .../src/native/witness_input.rs               | 37 ++++++-------------
 1 file changed, 11 insertions(+), 26 deletions(-)

diff --git a/rust/logos-blockchain-circuits-types/src/native/witness_input.rs b/rust/logos-blockchain-circuits-types/src/native/witness_input.rs
index 3f6f7be..00843db 100644
--- a/rust/logos-blockchain-circuits-types/src/native/witness_input.rs
+++ b/rust/logos-blockchain-circuits-types/src/native/witness_input.rs
@@ -1,4 +1,4 @@
-use std::ffi::{c_char, CString, NulError};
+use std::ffi::{CString, NulError};
 use crate::ffi;
 
 /// Input for witness generators
@@ -6,41 +6,36 @@ pub struct WitnessInput {
     /// The circuit's dat file contents.
     dat: Vec<u8>,
     /// The JSON string containing the circuit inputs.
-    inputs_json: String,
+    inputs_json: CString,
 }
 
 impl WitnessInput {
-    #[must_use]
-    pub const fn new(dat: Vec<u8>, inputs_json: String) -> Self {
-        Self { dat, inputs_json }
+    pub fn new(dat: Vec<u8>, inputs_json: String) -> Result<Self, NulError> {
+        let inputs_json = CString::new(inputs_json)?;
+        Ok(Self { dat, inputs_json })
     }
 
     /// Borrows this value as a temporary FFI-compatible view.
-    ///
-    /// Returns an error if `inputs_json` contains an interior null byte.
-    pub fn as_ffi(&'_ self) -> Result<WitnessInputFfiGuard<'_>, NulError> {
+    pub fn as_ffi(&'_ self) -> WitnessInputFfiGuard<'_> {
         WitnessInputFfiGuard::new(self)
     }
 }
 
-/// Temporary FFI view of a [`WitnessInput`], valid for the lifetime of the source.
-///
-/// Owns the C string allocation of `WitnessInput::inputs_json` and ensures it is freed when
-/// dropped.
+/// Temporary FFI view of a [`WitnessInput`], which makes [`ffi::WitnessInput`] lifetime-aware.
 pub struct WitnessInputFfiGuard<'a> {
     ffi: ffi::WitnessInput,
     _lifetime: std::marker::PhantomData<&'a WitnessInput>,
 }
 
 impl<'a> WitnessInputFfiGuard<'a> {
-    fn new(inner: &'a WitnessInput) -> Result<Self, NulError> {
+    fn new(inner: &'a WitnessInput) -> Self {
         let dat = ffi::ConstBytes { data: inner.dat.as_ptr(), size: inner.dat.len() };
-        let inputs_json = CString::new(inner.inputs_json.clone())?.into_raw(); // TODO CLEANER?
+        let inputs_json = inner.inputs_json.as_ptr();
         let ffi = ffi::WitnessInput { dat, inputs_json };
-        Ok(Self {
+        Self {
             ffi,
             _lifetime: std::marker::PhantomData,
-        })
+        }
     }
 }
 
@@ -49,13 +44,3 @@ impl<'a> AsRef<ffi::WitnessInput> for WitnessInputFfiGuard<'a> {
         &self.ffi
     }
 }
-
-impl<'a> Drop for WitnessInputFfiGuard<'a> {
-    fn drop(&mut self) {
-        if !self.ffi.inputs_json.is_null() {
-            drop(unsafe {
-                CString::from_raw(self.ffi.inputs_json as *mut c_char)
-            })
-        }
-    }
-}