move decode_struct_field and encode_struct_field to sqlx-core

sqlx-core/src/postgres/mod.rs

@@ -29,4 +29,4 @@ pub type PgPool = crate::pool::Pool<PgConnection>;
 make_query_as!(PgQueryAs, Postgres, PgRow);
 impl_map_row_for_row!(Postgres, PgRow);
 impl_column_index_for_row!(Postgres);
-impl_from_row_for_tuples!(Postgres, PgRow);
+impl_from_row_for_tuples!(Postgres, PgRow);

sqlx-core/src/postgres/types/mod.rs

@@ -12,6 +12,7 @@ mod bytes;
 mod float;
 mod int;
 mod str;
+pub mod r#struct;
 
 #[cfg(feature = "chrono")]
 mod chrono;

sqlx-core/src/postgres/types/struct.rs

@@ -0,0 +1,59 @@
+use crate::decode::{Decode, DecodeError};
+use crate::encode::Encode;
+use crate::postgres::protocol::TypeId;
+use crate::postgres::types::PgTypeInfo;
+use crate::types::HasSqlType;
+use crate::Postgres;
+use std::convert::TryInto;
+
+/// read a struct field and advance the buffer
+pub fn decode_struct_field<T: Decode<Postgres>>(buf: &mut &[u8]) -> Result<T, DecodeError>
+where
+    Postgres: HasSqlType<T>,
+{
+    if buf.len() < 8 {
+        return Err(DecodeError::Message(std::boxed::Box::new(
+            "Not enough data sent",
+        )));
+    }
+
+    let oid = u32::from_be_bytes(std::convert::TryInto::try_into(&buf[0..4]).unwrap());
+    if oid != <Postgres as HasSqlType<T>>::type_info().oid() {
+        return Err(DecodeError::Message(std::boxed::Box::new("Invalid oid")));
+    }
+
+    let len = u32::from_be_bytes(buf[4..8].try_into().unwrap()) as usize;
+
+    if buf.len() < 8 + len {
+        return Err(DecodeError::Message(std::boxed::Box::new(
+            "Not enough data sent",
+        )));
+    }
+
+    let raw = &buf[8..8 + len];
+    let value = T::decode(raw)?;
+
+    *buf = &buf[8 + len..];
+
+    Ok(value)
+}
+
+pub fn encode_struct_field<T: Encode<Postgres>>(buf: &mut Vec<u8>, value: &T)
+where
+    Postgres: HasSqlType<T>,
+{
+    // write oid
+    let info = <Postgres as HasSqlType<T>>::type_info();
+    buf.extend(&info.oid().to_be_bytes());
+
+    // write zeros for length
+    buf.extend(&[0; 4]);
+
+    let start = buf.len();
+    value.encode(buf);
+    let end = buf.len();
+    let size = end - start;
+
+    // replaces zeros with actual length
+    buf[start - 4..start].copy_from_slice(&(size as u32).to_be_bytes());
+}

sqlx-macros/src/derives/decode.rs

@@ -161,35 +161,16 @@ fn expand_derive_decode_struct(
         }
         let (impl_generics, _, where_clause) = generics.split_for_impl();
 
-        let mut reads: Vec<Vec<Stmt>> = Vec::new();
+        let mut reads: Vec<Stmt> = Vec::new();
         let mut names: Vec<Ident> = Vec::new();
         for field in fields {
             let id = &field.ident;
             names.push(id.clone().unwrap());
             let ty = &field.ty;
             reads.push(parse_quote!(
-            if buf.len() < 8 {
-                return Err(sqlx::decode::DecodeError::Message(std::boxed::Box::new("Not enough data sent")));
-            }
-
-            let oid = u32::from_be_bytes(std::convert::TryInto::try_into(&buf[0..4]).unwrap());
-            if oid != <sqlx::Postgres as sqlx::types::HasSqlType<#ty>>::type_info().oid() {
-                return Err(sqlx::decode::DecodeError::Message(std::boxed::Box::new("Invalid oid")));
-            }
-
-            let len = u32::from_be_bytes(std::convert::TryInto::try_into(&buf[4..8]).unwrap()) as usize;
-
-            if buf.len() < 8 + len {
-                return Err(sqlx::decode::DecodeError::Message(std::boxed::Box::new("Not enough data sent")));
-            }
-
-            let raw = &buf[8..8+len];
-            let #id = <#ty as sqlx::decode::Decode<sqlx::Postgres>>::decode(raw)?;
-
-            let buf = &buf[8+len..];
-        ));
+                let #id = sqlx::postgres::decode_struct_field::<#ty>(&mut buf)?;
+            ));
         }
-        let reads = reads.into_iter().flatten();
 
         tts.extend(quote!(
         impl #impl_generics sqlx::decode::Decode<sqlx::Postgres> for #ident#ty_generics #where_clause {
@@ -202,7 +183,7 @@ fn expand_derive_decode_struct(
                 if column_count != #column_count {
                     return Err(sqlx::decode::DecodeError::Message(std::boxed::Box::new("Invalid column count")));
                 }
-                let buf = &buf[4..];
+                let mut buf = &buf[4..];
 
                 #(#reads)*
 

sqlx-macros/src/derives/encode.rs

@@ -6,8 +6,8 @@ use quote::quote;
 use syn::punctuated::Punctuated;
 use syn::token::Comma;
 use syn::{
-    parse_quote, Block, Data, DataEnum, DataStruct, DeriveInput, Expr, Field, Fields, FieldsNamed,
-    FieldsUnnamed, Variant,
+    parse_quote, Data, DataEnum, DataStruct, DeriveInput, Expr, Field, Fields, FieldsNamed,
+    FieldsUnnamed, Stmt, Variant,
 };
 
 pub fn expand_derive_encode(input: &DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
@@ -160,26 +160,12 @@ fn expand_derive_encode_struct(
         }
         let (impl_generics, _, where_clause) = generics.split_for_impl();
 
-        let mut writes: Vec<Block> = Vec::new();
+        let mut writes: Vec<Stmt> = Vec::new();
         for field in fields {
             let id = &field.ident;
-            let ty = &field.ty;
-            writes.push(parse_quote!({
-                // write oid
-                let info = <sqlx::Postgres as sqlx::types::HasSqlType<#ty>>::type_info();
-                buf.extend(&info.oid().to_be_bytes());
-
-                // write zeros for length
-                buf.extend(&[0; 4]);
-
-                let start = buf.len();
-                sqlx::encode::Encode::<sqlx::Postgres>::encode(&self. #id, buf);
-                let end = buf.len();
-                let size = end - start;
-
-                // replaces zeros with actual length
-                buf[start-4..start].copy_from_slice(&(size as u32).to_be_bytes());
-            }));
+            writes.push(parse_quote!(
+                sqlx::postgres::encode_struct_field(buf, &self. #id);
+            ));
         }
 
         let mut sizes: Vec<Expr> = Vec::new();