MOD: Reduce unsafe in record version conversions

CHANGELOG.md

@@ -21,6 +21,7 @@
 - Relaxed `DecodeRecord` trait constraint on `StreamIterDecoder`'s inner decoder
 - Added `DbnMetadata` implementation for `StreamInnerDecoder` if the inner decoder
   implements `DbnMetadata`
+- Eliminate `unsafe` in `From` implementations for record structs from different versions
 
 ## 0.25.0 - 2024-12-17
 

rust/dbn/src/compat.rs

@@ -118,15 +118,15 @@ unsafe fn upgrade_record<'a, T, U>(
 ) -> RecordRef<'a>
 where
     T: HasRType,
-    U: HasRType + for<'b> From<&'b T>,
+    U: AsRef<[u8]> + HasRType + for<'b> From<&'b T>,
 {
     if ts_out {
         let rec = transmute_record_bytes::<WithTsOut<T>>(input).unwrap();
         let upgraded = WithTsOut::new(U::from(&rec.rec), rec.ts_out);
-        std::ptr::copy_nonoverlapping(&upgraded, compat_buffer.as_mut_ptr().cast(), 1);
+        compat_buffer[..upgraded.as_ref().len()].copy_from_slice(upgraded.as_ref());
     } else {
         let upgraded = U::from(transmute_record_bytes::<T>(input).unwrap());
-        std::ptr::copy_nonoverlapping(&upgraded, compat_buffer.as_mut_ptr().cast(), 1);
+        compat_buffer[..upgraded.as_ref().len()].copy_from_slice(upgraded.as_ref());
     }
     RecordRef::new(compat_buffer)
 }

rust/dbn/src/record/conv.rs

@@ -101,6 +101,7 @@ pub unsafe fn transmute_record_mut<T: HasRType>(header: &mut RecordHeader) -> Op
 /// This function returns an error if `s` contains more than N - 1 characters. The last
 /// character is reserved for the null byte.
 pub fn str_to_c_chars<const N: usize>(s: &str) -> Result<[c_char; N]> {
+    let s = s.as_bytes();
     if s.len() > (N - 1) {
         return Err(Error::encode(format!(
             "string cannot be longer than {}; received str of length {}",
@@ -109,9 +110,10 @@ pub fn str_to_c_chars<const N: usize>(s: &str) -> Result<[c_char; N]> {
         )));
     }
     let mut res = [0; N];
-    for (i, byte) in s.as_bytes().iter().enumerate() {
-        res[i] = *byte as c_char;
-    }
+    res[..s.len()].copy_from_slice(
+        // Safety: checked length of string and okay to interpret `u8` as `c_char`.
+        unsafe { std::mem::transmute::<&[u8], &[c_char]>(s) },
+    );
     Ok(res)
 }
 

rust/dbn/src/v2.rs

@@ -83,14 +83,7 @@ impl From<&v1::InstrumentDefMsg> for InstrumentDefMsg {
             tick_rule: old.tick_rule,
             ..Default::default()
         };
-        // Safety: SYMBOL_CSTR_LEN_V1 is less than SYMBOL_CSTR_LEN
-        unsafe {
-            std::ptr::copy_nonoverlapping(
-                old.raw_symbol.as_ptr(),
-                res.raw_symbol.as_mut_ptr(),
-                v1::SYMBOL_CSTR_LEN,
-            );
-        }
+        res.raw_symbol[..v1::SYMBOL_CSTR_LEN].copy_from_slice(old.raw_symbol.as_slice());
         res
     }
 }
@@ -106,10 +99,7 @@ impl From<&v1::ErrorMsg> for ErrorMsg {
             ),
             ..Default::default()
         };
-        // Safety: new `err` is longer than older
-        unsafe {
-            std::ptr::copy_nonoverlapping(old.err.as_ptr(), new.err.as_mut_ptr(), new.err.len());
-        }
+        new.err[..old.err.len()].copy_from_slice(old.err.as_slice());
         new
     }
 }
@@ -127,19 +117,9 @@ impl From<&v1::SymbolMappingMsg> for SymbolMappingMsg {
             end_ts: old.end_ts,
             ..Default::default()
         };
-        // Safety: SYMBOL_CSTR_LEN_V1 is less than SYMBOL_CSTR_LEN
-        unsafe {
-            std::ptr::copy_nonoverlapping(
-                old.stype_in_symbol.as_ptr(),
-                res.stype_in_symbol.as_mut_ptr(),
-                v1::SYMBOL_CSTR_LEN,
-            );
-            std::ptr::copy_nonoverlapping(
-                old.stype_out_symbol.as_ptr(),
-                res.stype_out_symbol.as_mut_ptr(),
-                v1::SYMBOL_CSTR_LEN,
-            );
-        }
+        res.stype_in_symbol[..v1::SYMBOL_CSTR_LEN].copy_from_slice(old.stype_in_symbol.as_slice());
+        res.stype_out_symbol[..v1::SYMBOL_CSTR_LEN]
+            .copy_from_slice(old.stype_out_symbol.as_slice());
         res
     }
 }
@@ -155,10 +135,7 @@ impl From<&v1::SystemMsg> for SystemMsg {
             ),
             ..Default::default()
         };
-        // Safety: new `msg` is longer than older
-        unsafe {
-            std::ptr::copy_nonoverlapping(old.msg.as_ptr(), new.msg.as_mut_ptr(), new.msg.len());
-        }
+        new.msg[..old.msg.len()].copy_from_slice(old.msg.as_slice());
         new
     }
 }

rust/dbn/src/v3/methods.rs

@@ -4,10 +4,10 @@ use crate::{
     pretty::px_to_f64,
     record::{c_chars_to_str, ts_to_dt},
     rtype, v1, v2, Error, InstrumentClass, MatchAlgorithm, RecordHeader, Result,
-    SecurityUpdateAction, Side, UserDefinedInstrument, UNDEF_PRICE,
+    SecurityUpdateAction, UserDefinedInstrument,
 };
 
-use super::{InstrumentDefMsg, SYMBOL_CSTR_LEN};
+use super::InstrumentDefMsg;
 
 impl From<&v1::InstrumentDefMsg> for InstrumentDefMsg {
     fn from(old: &v1::InstrumentDefMsg) -> Self {
@@ -74,31 +74,9 @@ impl From<&v1::InstrumentDefMsg> for InstrumentDefMsg {
             contract_multiplier_unit: old.contract_multiplier_unit,
             flow_schedule_type: old.flow_schedule_type,
             tick_rule: old.tick_rule,
-            // Set later
-            raw_symbol: [0; SYMBOL_CSTR_LEN],
-            leg_count: 0,
-            leg_index: 0,
-            leg_price: UNDEF_PRICE,
-            leg_delta: UNDEF_PRICE,
-            leg_instrument_id: 0,
-            leg_ratio_price_numerator: 0,
-            leg_ratio_price_denominator: 0,
-            leg_ratio_qty_numerator: 0,
-            leg_ratio_qty_denominator: 0,
-            leg_underlying_id: 0,
-            leg_raw_symbol: [0; SYMBOL_CSTR_LEN],
-            leg_instrument_class: 0,
-            leg_side: Side::None as c_char,
-            _reserved: Default::default(),
+            ..Default::default()
         };
-        // Safety: SYMBOL_CSTR_LEN_V1 is less than SYMBOL_CSTR_LEN
-        unsafe {
-            std::ptr::copy_nonoverlapping(
-                old.raw_symbol.as_ptr(),
-                res.raw_symbol.as_mut_ptr(),
-                v1::SYMBOL_CSTR_LEN,
-            );
-        }
+        res.raw_symbol[..v1::SYMBOL_CSTR_LEN].copy_from_slice(old.raw_symbol.as_slice());
         res
     }
 }
@@ -169,20 +147,7 @@ impl From<&v2::InstrumentDefMsg> for InstrumentDefMsg {
             flow_schedule_type: old.flow_schedule_type,
             tick_rule: old.tick_rule,
             raw_symbol: old.raw_symbol,
-            leg_count: 0,
-            leg_index: 0,
-            leg_price: UNDEF_PRICE,
-            leg_delta: UNDEF_PRICE,
-            leg_instrument_id: 0,
-            leg_ratio_price_numerator: 0,
-            leg_ratio_price_denominator: 0,
-            leg_ratio_qty_numerator: 0,
-            leg_ratio_qty_denominator: 0,
-            leg_underlying_id: 0,
-            leg_raw_symbol: [0; SYMBOL_CSTR_LEN],
-            leg_instrument_class: 0,
-            leg_side: Side::None as c_char,
-            _reserved: Default::default(),
+            ..Default::default()
         }
     }
 }