Merge pull request #1263 from serde-rs/integer128

Add Serde impls for i128 and u128

serde/src/de/from_primitive.rs

@@ -178,3 +178,91 @@ impl_from_primitive_for_uint!(u32);
 impl_from_primitive_for_uint!(u64);
 impl_from_primitive_for_float!(f32);
 impl_from_primitive_for_float!(f64);
+
+serde_if_integer128! {
+    impl FromPrimitive for i128 {
+        #[inline]
+        fn from_i8(n: i8) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_i16(n: i16) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_i32(n: i32) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_i64(n: i64) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_u8(n: u8) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_u16(n: u16) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_u32(n: u32) -> Option<Self> {
+            Some(n as i128)
+        }
+        #[inline]
+        fn from_u64(n: u64) -> Option<Self> {
+            Some(n as i128)
+        }
+    }
+
+    impl FromPrimitive for u128 {
+        #[inline]
+        fn from_i8(n: i8) -> Option<Self> {
+            if n >= 0 {
+                Some(n as u128)
+            } else {
+                None
+            }
+        }
+        #[inline]
+        fn from_i16(n: i16) -> Option<Self> {
+            if n >= 0 {
+                Some(n as u128)
+            } else {
+                None
+            }
+        }
+        #[inline]
+        fn from_i32(n: i32) -> Option<Self> {
+            if n >= 0 {
+                Some(n as u128)
+            } else {
+                None
+            }
+        }
+        #[inline]
+        fn from_i64(n: i64) -> Option<Self> {
+            if n >= 0 {
+                Some(n as u128)
+            } else {
+                None
+            }
+        }
+        #[inline]
+        fn from_u8(n: u8) -> Option<Self> {
+            Some(n as u128)
+        }
+        #[inline]
+        fn from_u16(n: u16) -> Option<Self> {
+            Some(n as u128)
+        }
+        #[inline]
+        fn from_u32(n: u32) -> Option<Self> {
+            Some(n as u128)
+        }
+        #[inline]
+        fn from_u64(n: u64) -> Option<Self> {
+            Some(n as u128)
+        }
+    }
+}

serde/src/de/impls.rs

@@ -166,6 +166,92 @@ impl_deserialize_num!(usize, deserialize_u64, integer);
 impl_deserialize_num!(f32, deserialize_f32, integer, float);
 impl_deserialize_num!(f64, deserialize_f64, integer, float);
 
+serde_if_integer128! {
+    impl<'de> Deserialize<'de> for i128 {
+        #[inline]
+        fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where
+            D: Deserializer<'de>,
+        {
+            struct PrimitiveVisitor;
+
+            impl<'de> Visitor<'de> for PrimitiveVisitor {
+                type Value = i128;
+
+                fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("i128")
+                }
+
+                impl_deserialize_num!(integer i128);
+
+                #[inline]
+                fn visit_i128<E>(self, v: i128) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    Ok(v)
+                }
+
+                #[inline]
+                fn visit_u128<E>(self, v: u128) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    if v <= i128::max_value() as u128 {
+                        Ok(v as i128)
+                    } else {
+                        Err(Error::invalid_value(Unexpected::Other("u128"), &self))
+                    }
+                }
+            }
+
+            deserializer.deserialize_i128(PrimitiveVisitor)
+        }
+    }
+
+    impl<'de> Deserialize<'de> for u128 {
+        #[inline]
+        fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where
+            D: Deserializer<'de>,
+        {
+            struct PrimitiveVisitor;
+
+            impl<'de> Visitor<'de> for PrimitiveVisitor {
+                type Value = u128;
+
+                fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                    formatter.write_str("u128")
+                }
+
+                impl_deserialize_num!(integer u128);
+
+                #[inline]
+                fn visit_i128<E>(self, v: i128) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    if v >= 0 {
+                        Ok(v as u128)
+                    } else {
+                        Err(Error::invalid_value(Unexpected::Other("i128"), &self))
+                    }
+                }
+
+                #[inline]
+                fn visit_u128<E>(self, v: u128) -> Result<Self::Value, E>
+                where
+                    E: Error,
+                {
+                    Ok(v)
+                }
+            }
+
+            deserializer.deserialize_u128(PrimitiveVisitor)
+        }
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 struct CharVisitor;

serde/src/de/mod.rs

@@ -52,8 +52,8 @@
 //!
 //!  - **Primitive types**:
 //!    - bool
-//!    - i8, i16, i32, i64, isize
+//!    - i8, i16, i32, i64, i128, isize
-//!    - u8, u16, u32, u64, usize
+//!    - u8, u16, u32, u64, u128, usize
 //!    - f32, f64
 //!    - char
 //!  - **Compound types**:
@@ -757,7 +757,7 @@ where
 /// Serde.
 ///
 /// The role of this trait is to define the deserialization half of the Serde
-/// data model, which is a way to categorize every Rust data type into one of 27
+/// data model, which is a way to categorize every Rust data type into one of 29
 /// possible types. Each method of the `Serializer` trait corresponds to one of
 /// the types of the data model.
 ///
@@ -767,10 +767,10 @@ where
 ///
 /// The types that make up the Serde data model are:
 ///
-///  - **12 primitive types**
+///  - **14 primitive types**
 ///    - bool
-///    - i8, i16, i32, i64
+///    - i8, i16, i32, i64, i128
-///    - u8, u16, u32, u64
+///    - u8, u16, u32, u64, u128
 ///    - f32, f64
 ///    - char
 ///  - **string**
@@ -884,6 +884,20 @@ pub trait Deserializer<'de>: Sized {
     where
         V: Visitor<'de>;
 
+    serde_if_integer128! {
+        /// Hint that the `Deserialize` type is expecting an `i128` value.
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default behavior unconditionally returns an error.
+        fn deserialize_i128<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+        where
+            V: Visitor<'de>
+        {
+            let _ = visitor;
+            Err(Error::custom("i128 is not supported"))
+        }
+    }
+
     /// Hint that the `Deserialize` type is expecting a `u8` value.
     fn deserialize_u8<V>(self, visitor: V) -> Result<V::Value, Self::Error>
     where
@@ -904,6 +918,20 @@ pub trait Deserializer<'de>: Sized {
     where
         V: Visitor<'de>;
 
+    serde_if_integer128! {
+        /// Hint that the `Deserialize` type is expecting an `u128` value.
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default behavior unconditionally returns an error.
+        fn deserialize_u128<V>(self, visitor: V) -> Result<V::Value, Self::Error>
+        where
+            V: Visitor<'de>
+        {
+            let _ = visitor;
+            Err(Error::custom("u128 is not supported"))
+        }
+    }
+
     /// Hint that the `Deserialize` type is expecting a `f32` value.
     fn deserialize_f32<V>(self, visitor: V) -> Result<V::Value, Self::Error>
     where
@@ -1250,6 +1278,20 @@ pub trait Visitor<'de>: Sized {
         Err(Error::invalid_type(Unexpected::Signed(v), &self))
     }
 
+    serde_if_integer128! {
+        /// The input contains a `i128`.
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default implementation fails with a type error.
+        fn visit_i128<E>(self, v: i128) -> Result<Self::Value, E>
+        where
+            E: Error,
+        {
+            let _ = v;
+            Err(Error::invalid_type(Unexpected::Other("i128"), &self))
+        }
+    }
+
     /// The input contains a `u8`.
     ///
     /// The default implementation forwards to [`visit_u64`].
@@ -1296,6 +1338,20 @@ pub trait Visitor<'de>: Sized {
         Err(Error::invalid_type(Unexpected::Unsigned(v), &self))
     }
 
+    serde_if_integer128! {
+        /// The input contains a `u128`.
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default implementation fails with a type error.
+        fn visit_u128<E>(self, v: u128) -> Result<Self::Value, E>
+        where
+            E: Error,
+        {
+            let _ = v;
+            Err(Error::invalid_type(Unexpected::Other("u128"), &self))
+        }
+    }
+
     /// The input contains an `f32`.
     ///
     /// The default implementation forwards to [`visit_f64`].

serde/src/de/value.rs

@@ -136,9 +136,9 @@ where
     type Error = E;
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf unit unit_struct newtype_struct seq tuple tuple_struct map
+        bytes byte_buf unit unit_struct newtype_struct seq tuple tuple_struct
-        struct enum identifier ignored_any
+        map struct enum identifier ignored_any
     }
 
     fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
@@ -189,9 +189,9 @@ macro_rules! primitive_deserializer {
             type Error = E;
 
             forward_to_deserialize_any! {
-                bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+                bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str
-                byte_buf option unit unit_struct newtype_struct seq tuple
+                string bytes byte_buf option unit unit_struct newtype_struct seq
-                tuple_struct map struct enum identifier ignored_any
+                tuple tuple_struct map struct enum identifier ignored_any
             }
 
             fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
@@ -246,9 +246,9 @@ where
     type Error = E;
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct identifier ignored_any
+        tuple_struct map struct identifier ignored_any
     }
 
     fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
@@ -339,9 +339,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct identifier ignored_any
+        tuple_struct map struct identifier ignored_any
     }
 }
 
@@ -408,9 +408,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct identifier ignored_any
+        tuple_struct map struct identifier ignored_any
     }
 }
 
@@ -483,9 +483,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct identifier ignored_any
+        tuple_struct map struct identifier ignored_any
     }
 }
 
@@ -562,9 +562,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct identifier ignored_any
+        tuple_struct map struct identifier ignored_any
     }
 }
 
@@ -618,9 +618,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct identifier ignored_any enum
+        tuple_struct map struct identifier ignored_any enum
     }
 }
 
@@ -688,9 +688,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct enum identifier ignored_any
+        tuple_struct map struct enum identifier ignored_any
     }
 }
 
@@ -803,9 +803,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct enum identifier ignored_any
+        tuple_struct map struct enum identifier ignored_any
     }
 }
 
@@ -917,9 +917,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct tuple_struct map struct
+        bytes byte_buf option unit unit_struct newtype_struct tuple_struct map
-        enum identifier ignored_any
+        struct enum identifier ignored_any
     }
 }
 
@@ -1059,9 +1059,9 @@ where
     type Error = E;
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct tuple_struct map struct
+        bytes byte_buf option unit unit_struct newtype_struct tuple_struct map
-        enum identifier ignored_any
+        struct enum identifier ignored_any
     }
 
     fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
@@ -1207,9 +1207,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct enum identifier ignored_any
+        tuple_struct map struct enum identifier ignored_any
     }
 }
 

serde/src/integer128.rs

@@ -0,0 +1,86 @@
+/// Conditional compilation depending on whether Serde is built with support for
+/// 128-bit integers.
+///
+/// Data formats that wish to support Rust compiler versions older than 1.26 may
+/// place the i128 / u128 methods of their Serializer and Deserializer behind
+/// this macro.
+///
+/// Data formats that require a minimum Rust compiler version of at least 1.26
+/// do not need to bother with this macro and may assume support for 128-bit
+/// integers.
+///
+/// ```rust
+/// #[macro_use]
+/// extern crate serde;
+///
+/// use serde::Serializer;
+/// # use serde::private::ser::Error;
+/// #
+/// # struct MySerializer;
+///
+/// impl Serializer for MySerializer {
+///     type Ok = ();
+///     type Error = Error;
+///
+///     fn serialize_i64(self, v: i64) -> Result<Self::Ok, Self::Error> {
+///         /* ... */
+/// #         unimplemented!()
+///     }
+///
+///     /* ... */
+///
+///     serde_if_integer128! {
+///         fn serialize_i128(self, v: i128) -> Result<Self::Ok, Self::Error> {
+///             /* ... */
+/// #             unimplemented!()
+///         }
+///
+///         fn serialize_u128(self, v: u128) -> Result<Self::Ok, Self::Error> {
+///             /* ... */
+/// #             unimplemented!()
+///         }
+///     }
+/// #
+/// #     __serialize_unimplemented! {
+/// #         bool i8 i16 i32 u8 u16 u32 u64 f32 f64 char str bytes none some
+/// #         unit unit_struct unit_variant newtype_struct newtype_variant seq
+/// #         tuple tuple_struct tuple_variant map struct struct_variant
+/// #     }
+/// }
+/// #
+/// # fn main() {}
+/// ```
+///
+/// When Serde is built with support for 128-bit integers, this macro expands
+/// transparently into just the input tokens.
+///
+/// ```rust
+/// macro_rules! serde_if_integer128 {
+///     ($($tt:tt)*) => {
+///         $($tt)*
+///     };
+/// }
+/// ```
+///
+/// When built without support for 128-bit integers, this macro expands to
+/// nothing.
+///
+/// ```rust
+/// macro_rules! serde_if_integer128 {
+///     ($($tt:tt)*) => {};
+/// }
+/// ```
+#[cfg(integer128)]
+#[macro_export]
+macro_rules! serde_if_integer128 {
+    ($($tt:tt)*) => {
+        $($tt)*
+    };
+}
+
+#[cfg(not(integer128))]
+#[macro_export]
+#[doc(hidden)]
+macro_rules! serde_if_integer128 {
+    ($($tt:tt)*) => {};
+}

serde/src/lib.rs

@@ -219,6 +219,9 @@ mod lib {
 #[macro_use]
 mod macros;
 
+#[macro_use]
+mod integer128;
+
 pub mod de;
 pub mod ser;
 

serde/src/macros.rs

@@ -46,8 +46,8 @@
 /// }
 /// #
 /// #     forward_to_deserialize_any! {
-/// #         i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+/// #         i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-/// #         byte_buf option unit unit_struct newtype_struct seq tuple
+/// #         bytes byte_buf option unit unit_struct newtype_struct seq tuple
 /// #         tuple_struct map struct enum identifier ignored_any
 /// #     }
 /// # }
@@ -80,8 +80,8 @@
 ///     }
 ///
 ///     forward_to_deserialize_any! {
-///         bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+///         bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-///         byte_buf option unit unit_struct newtype_struct seq tuple
+///         bytes byte_buf option unit unit_struct newtype_struct seq tuple
 ///         tuple_struct map struct enum identifier ignored_any
 ///     }
 /// }
@@ -116,9 +116,9 @@
 /// #
 /// forward_to_deserialize_any! {
 ///     <W: Visitor<'q>>
-///     bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+///     bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-///     byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+///     bytes byte_buf option unit unit_struct newtype_struct seq tuple
-///     map struct enum identifier ignored_any
+///     tuple_struct map struct enum identifier ignored_any
 /// }
 /// # }
 /// #
@@ -174,6 +174,11 @@ macro_rules! forward_to_deserialize_any_helper {
     (i64<$l:tt, $v:ident>) => {
         forward_to_deserialize_any_method!{deserialize_i64<$l, $v>()}
     };
+    (i128<$l:tt, $v:ident>) => {
+        serde_if_integer128! {
+            forward_to_deserialize_any_method!{deserialize_i128<$l, $v>()}
+        }
+    };
     (u8<$l:tt, $v:ident>) => {
         forward_to_deserialize_any_method!{deserialize_u8<$l, $v>()}
     };
@@ -186,6 +191,11 @@ macro_rules! forward_to_deserialize_any_helper {
     (u64<$l:tt, $v:ident>) => {
         forward_to_deserialize_any_method!{deserialize_u64<$l, $v>()}
     };
+    (u128<$l:tt, $v:ident>) => {
+        serde_if_integer128! {
+            forward_to_deserialize_any_method!{deserialize_u128<$l, $v>()}
+        }
+    };
     (f32<$l:tt, $v:ident>) => {
         forward_to_deserialize_any_method!{deserialize_f32<$l, $v>()}
     };

serde/src/private/de.rs

@@ -50,9 +50,9 @@ where
         }
 
         forward_to_deserialize_any! {
-            bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+            bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-            byte_buf unit unit_struct newtype_struct seq tuple tuple_struct map
+            bytes byte_buf unit unit_struct newtype_struct seq tuple
-            struct enum identifier ignored_any
+            tuple_struct map struct enum identifier ignored_any
         }
     }
 
@@ -1618,8 +1618,8 @@ mod content {
         }
 
         forward_to_deserialize_any! {
-            bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+            bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-            byte_buf option unit unit_struct newtype_struct seq tuple
+            bytes byte_buf option unit unit_struct newtype_struct seq tuple
             tuple_struct map struct enum identifier ignored_any
         }
     }
@@ -1716,8 +1716,8 @@ mod content {
         }
 
         forward_to_deserialize_any! {
-            bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+            bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-            byte_buf option unit unit_struct newtype_struct seq tuple
+            bytes byte_buf option unit unit_struct newtype_struct seq tuple
             tuple_struct map struct enum identifier ignored_any
         }
     }
@@ -2306,8 +2306,8 @@ mod content {
         }
 
         forward_to_deserialize_any! {
-            bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+            bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-            byte_buf option unit unit_struct newtype_struct seq tuple
+            bytes byte_buf option unit unit_struct newtype_struct seq tuple
             tuple_struct map struct enum identifier ignored_any
         }
     }
@@ -2406,8 +2406,8 @@ mod content {
         }
 
         forward_to_deserialize_any! {
-            bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+            bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-            byte_buf option unit unit_struct newtype_struct seq tuple
+            bytes byte_buf option unit unit_struct newtype_struct seq tuple
             tuple_struct map struct enum identifier ignored_any
         }
     }
@@ -2578,9 +2578,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct enum identifier ignored_any
+        tuple_struct map struct enum identifier ignored_any
     }
 }
 
@@ -2617,9 +2617,9 @@ where
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct enum identifier ignored_any
+        tuple_struct map struct enum identifier ignored_any
     }
 }
 

serde/src/ser/impls.rs

@@ -44,6 +44,11 @@ primitive_impl!(f32, serialize_f32);
 primitive_impl!(f64, serialize_f64);
 primitive_impl!(char, serialize_char);
 
+serde_if_integer128! {
+    primitive_impl!(i128, serialize_i128);
+    primitive_impl!(u128, serialize_u128);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 
 impl Serialize for str {

serde/src/ser/mod.rs

@@ -48,8 +48,8 @@
 //!
 //!  - **Primitive types**:
 //!    - bool
-//!    - i8, i16, i32, i64, isize
+//!    - i8, i16, i32, i64, i128, isize
-//!    - u8, u16, u32, u64, usize
+//!    - u8, u16, u32, u64, u128, usize
 //!    - f32, f64
 //!    - char
 //!    - str
@@ -245,7 +245,7 @@ pub trait Serialize {
 /// A **data format** that can serialize any data structure supported by Serde.
 ///
 /// The role of this trait is to define the serialization half of the Serde data
-/// model, which is a way to categorize every Rust data structure into one of 27
+/// model, which is a way to categorize every Rust data structure into one of 29
 /// possible types. Each method of the `Serializer` trait corresponds to one of
 /// the types of the data model.
 ///
@@ -254,10 +254,10 @@ pub trait Serialize {
 ///
 /// The types that make up the Serde data model are:
 ///
-///  - **12 primitive types**
+///  - **14 primitive types**
 ///    - bool
-///    - i8, i16, i32, i64
+///    - i8, i16, i32, i64, i128
-///    - u8, u16, u32, u64
+///    - u8, u16, u32, u64, u128
 ///    - f32, f64
 ///    - char
 ///  - **string**
@@ -492,6 +492,37 @@ pub trait Serializer: Sized {
     /// ```
     fn serialize_i64(self, v: i64) -> Result<Self::Ok, Self::Error>;
 
+    serde_if_integer128! {
+        /// Serialize an `i128` value.
+        ///
+        /// ```rust
+        /// # #[macro_use]
+        /// # extern crate serde;
+        /// #
+        /// # use serde::Serializer;
+        /// #
+        /// # __private_serialize!();
+        /// #
+        /// impl Serialize for i128 {
+        ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        ///     where
+        ///         S: Serializer,
+        ///     {
+        ///         serializer.serialize_i128(*self)
+        ///     }
+        /// }
+        /// #
+        /// # fn main() {}
+        /// ```
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default behavior unconditionally returns an error.
+        fn serialize_i128(self, v: i128) -> Result<Self::Ok, Self::Error> {
+            let _ = v;
+            Err(Error::custom("i128 is not supported"))
+        }
+    }
+
     /// Serialize a `u8` value.
     ///
     /// If the format does not differentiate between `u8` and `u64`, a
@@ -596,6 +627,37 @@ pub trait Serializer: Sized {
     /// ```
     fn serialize_u64(self, v: u64) -> Result<Self::Ok, Self::Error>;
 
+    serde_if_integer128! {
+        /// Serialize a `u128` value.
+        ///
+        /// ```rust
+        /// # #[macro_use]
+        /// # extern crate serde;
+        /// #
+        /// # use serde::Serializer;
+        /// #
+        /// # __private_serialize!();
+        /// #
+        /// impl Serialize for u128 {
+        ///     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        ///     where
+        ///         S: Serializer,
+        ///     {
+        ///         serializer.serialize_u128(*self)
+        ///     }
+        /// }
+        /// #
+        /// # fn main() {}
+        /// ```
+        ///
+        /// This method is available only on Rust compiler versions >=1.26. The
+        /// default behavior unconditionally returns an error.
+        fn serialize_u128(self, v: u128) -> Result<Self::Ok, Self::Error> {
+            let _ = v;
+            Err(Error::custom("u128 is not supported"))
+        }
+    }
+
     /// Serialize an `f32` value.
     ///
     /// If the format does not differentiate between `f32` and `f64`, a

serde_test/src/de.rs

@@ -129,8 +129,8 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
     type Error = Error;
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf unit seq map identifier ignored_any
+        bytes byte_buf unit seq map identifier ignored_any
     }
 
     fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Error>
@@ -657,8 +657,8 @@ impl<'de> de::Deserializer<'de> for BytesDeserializer {
     }
 
     forward_to_deserialize_any! {
-        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
-        byte_buf option unit unit_struct newtype_struct seq tuple tuple_struct
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
-        map struct enum identifier ignored_any
+        tuple_struct map struct enum identifier ignored_any
     }
 }

test_suite/tests/test_de.rs

@@ -259,6 +259,27 @@ declare_tests! {
         0f32 => &[Token::F32(0.)],
         0f64 => &[Token::F64(0.)],
     }
+    test_small_int_to_128 {
+        1i128 => &[Token::I8(1)],
+        1i128 => &[Token::I16(1)],
+        1i128 => &[Token::I32(1)],
+        1i128 => &[Token::I64(1)],
+
+        1i128 => &[Token::U8(1)],
+        1i128 => &[Token::U16(1)],
+        1i128 => &[Token::U32(1)],
+        1i128 => &[Token::U64(1)],
+
+        1u128 => &[Token::I8(1)],
+        1u128 => &[Token::I16(1)],
+        1u128 => &[Token::I32(1)],
+        1u128 => &[Token::I64(1)],
+
+        1u128 => &[Token::U8(1)],
+        1u128 => &[Token::U16(1)],
+        1u128 => &[Token::U32(1)],
+        1u128 => &[Token::U64(1)],
+    }
     test_char {
         'a' => &[Token::Char('a')],
         'a' => &[Token::Str("a")],

test_suite/tests/test_ser.rs

@@ -586,3 +586,10 @@ fn test_enum_skipped() {
         "the enum variant Enum::SkippedMap cannot be serialized",
     );
 }
+
+#[test]
+fn test_integer128() {
+    assert_ser_tokens_error(&1i128, &[], "i128 is not supported");
+
+    assert_ser_tokens_error(&1u128, &[], "u128 is not supported");
+}