solana_borsh/

macros.rs

//! Macros for implementing functions across multiple versions of Borsh

macro_rules! impl_get_packed_len_v1 {
    ($borsh:ident $(,#[$meta:meta])?) => {
        /// Get the worst-case packed length for the given BorshSchema
        ///
        /// Note: due to the serializer currently used by Borsh, this function cannot
        /// be used on-chain in the Solana SBF execution environment.
        $(#[$meta])?
        pub fn get_packed_len<S: $borsh::BorshSchema>() -> usize {
            let container = $borsh::schema_container_of::<S>();
            get_declaration_packed_len(container.declaration(), &container)
        }

        /// Get packed length for the given BorshSchema Declaration
        fn get_declaration_packed_len(
            declaration: &str,
            container: &$borsh::schema::BorshSchemaContainer,
        ) -> usize {
            match container.get_definition(declaration) {
                Some($borsh::schema::Definition::Sequence { length_width, length_range, elements }) if *length_width == 0 => {
                    *length_range.end() as usize * get_declaration_packed_len(elements, container)
                }
                Some($borsh::schema::Definition::Enum { tag_width, variants }) => {
                    (*tag_width as usize) + variants
                        .iter()
                        .map(|(_, _, declaration)| get_declaration_packed_len(declaration, container))
                        .max()
                        .unwrap_or(0)
                }
                Some($borsh::schema::Definition::Struct { fields }) => match fields {
                    $borsh::schema::Fields::NamedFields(named_fields) => named_fields
                        .iter()
                        .map(|(_, declaration)| get_declaration_packed_len(declaration, container))
                        .sum(),
                    $borsh::schema::Fields::UnnamedFields(declarations) => declarations
                        .iter()
                        .map(|declaration| get_declaration_packed_len(declaration, container))
                        .sum(),
                    $borsh::schema::Fields::Empty => 0,
                },
                Some($borsh::schema::Definition::Sequence {
                    ..
                }) => panic!("Missing support for Definition::Sequence"),
                Some($borsh::schema::Definition::Tuple { elements }) => elements
                    .iter()
                    .map(|element| get_declaration_packed_len(element, container))
                    .sum(),
                Some($borsh::schema::Definition::Primitive(size)) => *size as usize,
                None => match declaration {
                    "bool" | "u8" | "i8" => 1,
                    "u16" | "i16" => 2,
                    "u32" | "i32" => 4,
                    "u64" | "i64" => 8,
                    "u128" | "i128" => 16,
                    "nil" => 0,
                    _ => panic!("Missing primitive type: {declaration}"),
                },
            }
        }
    }
}
pub(crate) use impl_get_packed_len_v1;

macro_rules! impl_try_from_slice_unchecked {
    ($borsh:ident, $borsh_io:ident $(,#[$meta:meta])?) => {
        /// Deserializes without checking that the entire slice has been consumed
        ///
        /// Normally, `try_from_slice` checks the length of the final slice to ensure
        /// that the deserialization uses up all of the bytes in the slice.
        ///
        /// Note that there is a potential issue with this function. Any buffer greater than
        /// or equal to the expected size will properly deserialize. For example, if the
        /// user passes a buffer destined for a different type, the error won't get caught
        /// as easily.
        $(#[$meta])?
        pub fn try_from_slice_unchecked<T: $borsh::BorshDeserialize>(data: &[u8]) -> Result<T, $borsh_io::Error> {
            let mut data_mut = data;
            let result = T::deserialize(&mut data_mut)?;
            Ok(result)
        }
    }
}
pub(crate) use impl_try_from_slice_unchecked;

macro_rules! impl_get_instance_packed_len {
    ($borsh:ident, $borsh_io:ident $(,#[$meta:meta])?) => {
        /// Helper struct which to count how much data would be written during serialization
        #[derive(Default)]
        struct WriteCounter {
            count: usize,
        }

        impl $borsh_io::Write for WriteCounter {
            fn write(&mut self, data: &[u8]) -> Result<usize, $borsh_io::Error> {
                let amount = data.len();
                self.count += amount;
                Ok(amount)
            }

            fn flush(&mut self) -> Result<(), $borsh_io::Error> {
                Ok(())
            }
        }

        /// Get the packed length for the serialized form of this object instance.
        ///
        /// Useful when working with instances of types that contain a variable-length
        /// sequence, such as a Vec or HashMap.  Since it is impossible to know the packed
        /// length only from the type's schema, this can be used when an instance already
        /// exists, to figure out how much space to allocate in an account.
        $(#[$meta])?
        pub fn get_instance_packed_len<T: $borsh::BorshSerialize>(instance: &T) -> Result<usize, $borsh_io::Error> {
            let mut counter = WriteCounter::default();
            instance.serialize(&mut counter)?;
            Ok(counter.count)
        }
    }
}
pub(crate) use impl_get_instance_packed_len;

#[cfg(test)]
macro_rules! impl_tests {
    ($borsh:ident, $borsh_io:ident) => {
        extern crate alloc;
        use {
            super::*,
            std::{collections::HashMap, mem::size_of},
            $borsh::{BorshDeserialize, BorshSerialize},
            $borsh_io::ErrorKind,
        };

        type Child = [u8; 64];
        type Parent = Vec<Child>;

        #[test]
        fn unchecked_deserialization() {
            let parent = vec![[0u8; 64], [1u8; 64], [2u8; 64]];

            // exact size, both work
            let mut byte_vec = vec![0u8; 4 + get_packed_len::<Child>() * 3];
            let mut bytes = byte_vec.as_mut_slice();
            parent.serialize(&mut bytes).unwrap();
            let deserialized = Parent::try_from_slice(&byte_vec).unwrap();
            assert_eq!(deserialized, parent);
            let deserialized = try_from_slice_unchecked::<Parent>(&byte_vec).unwrap();
            assert_eq!(deserialized, parent);

            // too big, only unchecked works
            let mut byte_vec = vec![0u8; 4 + get_packed_len::<Child>() * 10];
            let mut bytes = byte_vec.as_mut_slice();
            parent.serialize(&mut bytes).unwrap();
            let err = Parent::try_from_slice(&byte_vec).unwrap_err();
            assert_eq!(err.kind(), ErrorKind::InvalidData);
            let deserialized = try_from_slice_unchecked::<Parent>(&byte_vec).unwrap();
            assert_eq!(deserialized, parent);
        }

        #[test]
        fn packed_len() {
            assert_eq!(get_packed_len::<u64>(), size_of::<u64>());
            assert_eq!(get_packed_len::<Child>(), size_of::<u8>() * 64);
        }

        #[test]
        fn instance_packed_len_matches_packed_len() {
            let child = [0u8; 64];
            assert_eq!(
                get_packed_len::<Child>(),
                get_instance_packed_len(&child).unwrap(),
            );
            assert_eq!(
                get_packed_len::<u8>(),
                get_instance_packed_len(&0u8).unwrap(),
            );
            assert_eq!(
                get_packed_len::<u16>(),
                get_instance_packed_len(&0u16).unwrap(),
            );
            assert_eq!(
                get_packed_len::<u32>(),
                get_instance_packed_len(&0u32).unwrap(),
            );
            assert_eq!(
                get_packed_len::<u64>(),
                get_instance_packed_len(&0u64).unwrap(),
            );
            assert_eq!(
                get_packed_len::<u128>(),
                get_instance_packed_len(&0u128).unwrap(),
            );
            assert_eq!(
                get_packed_len::<[u8; 10]>(),
                get_instance_packed_len(&[0u8; 10]).unwrap(),
            );
            assert_eq!(
                get_packed_len::<(i8, i16, i32, i64, i128)>(),
                get_instance_packed_len(&(i8::MAX, i16::MAX, i32::MAX, i64::MAX, i128::MAX))
                    .unwrap(),
            );
        }

        #[test]
        fn instance_packed_len_with_vec() {
            let parent = vec![
                [0u8; 64], [1u8; 64], [2u8; 64], [3u8; 64], [4u8; 64], [5u8; 64],
            ];
            assert_eq!(
                get_instance_packed_len(&parent).unwrap(),
                4 + parent.len() * get_packed_len::<Child>()
            );
        }

        #[test]
        fn instance_packed_len_with_varying_sizes_in_hashmap() {
            let mut data = HashMap::new();
            let key1 = "the first string, it's actually really really long".to_string();
            let value1 = "".to_string();
            let key2 = "second string, shorter".to_string();
            let value2 = "a real value".to_string();
            let key3 = "third".to_string();
            let value3 = "an even longer value".to_string();
            data.insert(key1.clone(), value1.clone());
            data.insert(key2.clone(), value2.clone());
            data.insert(key3.clone(), value3.clone());
            assert_eq!(
                get_instance_packed_len(&data).unwrap(),
                4 + get_instance_packed_len(&key1).unwrap()
                    + get_instance_packed_len(&value1).unwrap()
                    + get_instance_packed_len(&key2).unwrap()
                    + get_instance_packed_len(&value2).unwrap()
                    + get_instance_packed_len(&key3).unwrap()
                    + get_instance_packed_len(&value3).unwrap()
            );
        }
    };
}
#[cfg(test)]
pub(crate) use impl_tests;