allow decoding money as f64

for precise money handling, you should still use decimal types

but allowing decoding all mssql types to native rust types makes things
easier

Author: lovasoa

sqlx-core/src/mssql/types/decimal_tools.rs

@@ -13,6 +13,8 @@ pub(crate) fn decode_money_bytes(bytes: &[u8]) -> Result<i64, BoxDynError> {
     };
     Ok(amount)
 }
+
+/// Returns
 pub(crate) fn decode_numeric_bytes(bytes: &[u8]) -> Result<(i8, u128), BoxDynError> {
     if bytes.is_empty() {
         return Err(err_protocol!("numeric bytes cannot be empty").into());

sqlx-core/src/mssql/types/float.rs

@@ -1,5 +1,6 @@
 use byteorder::{ByteOrder, LittleEndian};
 
+use super::decimal_tools::{decode_money_bytes, decode_numeric_bytes};
 use crate::decode::Decode;
 use crate::encode::{Encode, IsNull};
 use crate::error::BoxDynError;
@@ -46,6 +47,9 @@ impl Type<Mssql> for f64 {
                 | DataType::DecimalN
                 | DataType::Numeric
                 | DataType::NumericN
+                | DataType::MoneyN
+                | DataType::Money
+                | DataType::SmallMoney
         )
     }
 }
@@ -74,6 +78,13 @@ impl Decode<'_, Mssql> for f64 {
             DataType::Numeric | DataType::NumericN | DataType::Decimal | DataType::DecimalN => {
                 decode_numeric(value.as_bytes()?, precision, scale)
             }
+            DataType::MoneyN | DataType::Money | DataType::SmallMoney => {
+                let numerator = decode_money_bytes(value.as_bytes()?)?;
+                let denominator = 10_000;
+                let integer_part = (numerator / denominator) as f64;
+                let fractional_part = (numerator % denominator) as f64 / denominator as f64;
+                Ok(integer_part + fractional_part)
+            }
             _ => Err(err_protocol!(
                 "Decoding {:?} as a float failed because type {:?} is not implemented",
                 value,
@@ -86,17 +97,16 @@ impl Decode<'_, Mssql> for f64 {
 
 #[allow(clippy::cast_precision_loss)]
 fn decode_numeric(bytes: &[u8], _precision: u8, mut scale: u8) -> Result<f64, BoxDynError> {
-    let sign = if bytes[0] == 0 { -1. } else { 1. };
-    let rest = &bytes[1..];
-    let mut fixed_bytes = [0u8; 16];
-    fixed_bytes[0..rest.len()].copy_from_slice(rest);
-    let mut numerator = u128::from_le_bytes(fixed_bytes);
+    let (sign, mut numerator) = decode_numeric_bytes(bytes)?;
+
     while numerator % 10 == 0 && scale > 0 {
         numerator /= 10;
         scale -= 1;
     }
     let denominator = 10u128.pow(scale as u32);
     let integer_part = (numerator / denominator) as f64;
     let fractional_part = (numerator % denominator) as f64 / denominator as f64;
-    Ok(sign * (integer_part + fractional_part))
+    let absolute = integer_part + fractional_part;
+    let positive = sign == 1;
+    Ok(if positive { absolute } else { -absolute })
 }

tests/mssql/types.rs

@@ -253,6 +253,23 @@ mod decimal {
         "CAST('214748.3647' AS SMALLMONEY)" == Decimal::from_str_exact("214748.3647").unwrap(),
         "CAST('-214748.3648' AS SMALLMONEY)" == Decimal::from_str_exact("-214748.3648").unwrap(),
     ));
+
+    test_type!(money_precision_tests_f64<f64>(
+        Mssql,
+        "CAST('0.0000' AS MONEY)" == 0.0000,
+        "CAST('0.0001' AS MONEY)" == 0.0001,
+        "CAST('-0.0001' AS MONEY)" == -0.0001,
+        "CAST('0.9999' AS MONEY)" == 0.9999,
+        "CAST('-0.9999' AS MONEY)" == -0.9999,
+        "CAST('1.0000' AS MONEY)" == 1.0000,
+        "CAST('-1.0000' AS MONEY)" == -1.0000,
+        "CAST('2.15' AS MONEY)" == 2.15,
+        "CAST('214748.3647' AS SMALLMONEY)" == 214748.3647,
+        "CAST('922337203685477.5807' AS MONEY)" == 922337203685477.5807,
+        "CAST('-922337203685477.5808' AS MONEY)" == -922337203685477.5808,
+        "CAST('214748.3647' AS SMALLMONEY)" == 214748.3647,
+        "CAST('-214748.3648' AS SMALLMONEY)" == -214748.3648,
+    ));
 }
 
 #[cfg(feature = "bigdecimal")]