Fix string verbatim reply to work correctly. (#315)

Current behaviour is to append to format to the data. This is wrong because the format need to pass separately to Redis. Also, a wrong RedisModuleAPI was used, we need to use the API that allows to pass the format (otherwise Redis uses the default `txt` format).

src/context/call_reply.rs

@@ -7,7 +7,7 @@ use std::{
     ptr::NonNull,
 };
 
-use crate::raw::*;
+use crate::{raw::*, RedisError};
 
 pub struct StringCallReply<'root> {
     reply: NonNull<RedisModuleCallReply>,
@@ -531,13 +531,48 @@ pub struct VerbatimStringCallReply<'root> {
     _dummy: PhantomData<&'root ()>,
 }
 
+/// RESP3 state that the verbatim string format must be of length 3.
+const VERBATIM_FORMAT_LENGTH: usize = 3;
+/// The string format of a verbatim string ([VerbatimStringCallReply]).
+#[repr(transparent)]
+#[derive(Debug, Default, Copy, Clone, PartialEq)]
+pub struct VerbatimStringFormat(pub [c_char; VERBATIM_FORMAT_LENGTH]);
+
+impl TryFrom<&str> for VerbatimStringFormat {
+    type Error = RedisError;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        if value.len() != 3 {
+            return Err(RedisError::String(format!(
+                "Verbatim format length must be {VERBATIM_FORMAT_LENGTH}."
+            )));
+        }
+        let mut res = VerbatimStringFormat::default();
+        value
+            .chars()
+            .into_iter()
+            .take(3)
+            .enumerate()
+            .try_for_each(|(i, c)| {
+                if c as u32 >= 127 {
+                    return Err(RedisError::String(
+                        "Verbatim format must contains only ASCI values.".to_owned(),
+                    ));
+                }
+                res.0[i] = c as c_char;
+                Ok(())
+            })?;
+        Ok(res)
+    }
+}
+
 impl<'root> VerbatimStringCallReply<'root> {
     /// Return the verbatim string value of the [VerbatimStringCallReply] as a tuple.
     /// The first entry represents the format, the second entry represent the data.
     /// Return None if the format is not a valid utf8
-    pub fn to_parts(&self) -> Option<(String, Vec<u8>)> {
-        self.as_parts()
-            .map(|(format, data)| (format.to_string(), data.to_vec()))
+    pub fn to_parts(&self) -> Option<(VerbatimStringFormat, Vec<u8>)> {
+        let (format, data) = self.as_parts()?;
+        Some((format.try_into().ok()?, data.to_vec()))
     }
 
     /// Borrow the verbatim string value of the [VerbatimStringCallReply] as a tuple.

src/context/mod.rs

@@ -425,15 +425,12 @@ impl Context {
                 raw::reply_with_big_number(self.ctx, s.as_ptr().cast::<c_char>(), s.len())
             }
 
-            Ok(RedisValue::VerbatimString((format, mut data))) => {
-                let mut final_data = format.as_bytes().to_vec();
-                final_data.append(&mut data);
-                raw::reply_with_verbatim_string(
-                    self.ctx,
-                    final_data.as_ptr().cast::<c_char>(),
-                    final_data.len(),
-                )
-            }
+            Ok(RedisValue::VerbatimString((format, data))) => raw::reply_with_verbatim_string(
+                self.ctx,
+                data.as_ptr().cast(),
+                data.len(),
+                format.0.as_ptr().cast(),
+            ),
 
             Ok(RedisValue::BulkRedisString(s)) => raw::reply_with_string(self.ctx, s.inner),
 

src/raw.rs

@@ -435,8 +435,9 @@ pub fn reply_with_verbatim_string(
     ctx: *mut RedisModuleCtx,
     s: *const c_char,
     len: size_t,
+    format: *const c_char,
 ) -> Status {
-    unsafe { RedisModule_ReplyWithVerbatimString.unwrap()(ctx, s, len).into() }
+    unsafe { RedisModule_ReplyWithVerbatimStringType.unwrap()(ctx, s, len, format).into() }
 }
 
 // Sets the expiry on a key.

src/redisvalue.rs

@@ -1,4 +1,7 @@
-use crate::{context::call_reply::CallResult, CallReply, RedisError, RedisString};
+use crate::{
+    context::call_reply::{CallResult, VerbatimStringFormat},
+    CallReply, RedisError, RedisString,
+};
 use std::{
     collections::{HashMap, HashSet},
     hash::Hash,
@@ -24,7 +27,7 @@ pub enum RedisValue {
     Bool(bool),
     Float(f64),
     BigNumber(String),
-    VerbatimString((String, Vec<u8>)),
+    VerbatimString((VerbatimStringFormat, Vec<u8>)),
     Array(Vec<RedisValue>),
     StaticError(&'static str),
     Map(HashMap<RedisValueKey, RedisValue>),