src/types/from_sql.rs

use super::{Value, ValueRef};
use std::convert::TryInto;
use std::error::Error;
use std::fmt;

/// Enum listing possible errors from [`FromSql`] trait.
#[derive(Debug)]
#[non_exhaustive]
pub enum FromSqlError {
    /// Error when an SQLite value is requested, but the type of the result
    /// cannot be converted to the requested Rust type.
    InvalidType,

    /// Error when the i64 value returned by SQLite cannot be stored into the
    /// requested type.
    OutOfRange(i64),

    /// Error when the blob result returned by SQLite cannot be stored into the
    /// requested type due to a size mismatch.
    InvalidBlobSize {
        /// The expected size of the blob.
        expected_size: usize,
        /// The actual size of the blob that was returned.
        blob_size: usize,
    },

    /// An error case available for implementors of the [`FromSql`] trait.
    Other(Box<dyn Error + Send + Sync + 'static>),
}

impl PartialEq for FromSqlError {
    fn eq(&self, other: &FromSqlError) -> bool {
        match (self, other) {
            (FromSqlError::InvalidType, FromSqlError::InvalidType) => true,
            (FromSqlError::OutOfRange(n1), FromSqlError::OutOfRange(n2)) => n1 == n2,
            (
                FromSqlError::InvalidBlobSize {
                    expected_size: es1,
                    blob_size: bs1,
                },
                FromSqlError::InvalidBlobSize {
                    expected_size: es2,
                    blob_size: bs2,
                },
            ) => es1 == es2 && bs1 == bs2,
            (..) => false,
        }
    }
}

impl fmt::Display for FromSqlError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match *self {
            FromSqlError::InvalidType => write!(f, "Invalid type"),
            FromSqlError::OutOfRange(i) => write!(f, "Value {} out of range", i),
            FromSqlError::InvalidBlobSize {
                expected_size,
                blob_size,
            } => {
                write!(
                    f,
                    "Cannot read {} byte value out of {} byte blob",
                    expected_size, blob_size
                )
            }
            FromSqlError::Other(ref err) => err.fmt(f),
        }
    }
}

impl Error for FromSqlError {
    fn source(&self) -> Option<&(dyn Error + 'static)> {
        if let FromSqlError::Other(ref err) = self {
            Some(&**err)
        } else {
            None
        }
    }
}

/// Result type for implementors of the [`FromSql`] trait.
pub type FromSqlResult<T> = Result<T, FromSqlError>;

/// A trait for types that can be created from a SQLite value.
pub trait FromSql: Sized {
    /// Converts SQLite value into Rust value.
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self>;
}

macro_rules! from_sql_integral(
    ($t:ident) => (
        impl FromSql for $t {
            #[inline]
            fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
                let i = i64::column_result(value)?;
                i.try_into().map_err(|_| FromSqlError::OutOfRange(i))
            }
        }
    )
);

from_sql_integral!(i8);
from_sql_integral!(i16);
from_sql_integral!(i32);
// from_sql_integral!(i64); // Not needed because the native type is i64.
from_sql_integral!(isize);
from_sql_integral!(u8);
from_sql_integral!(u16);
from_sql_integral!(u32);
from_sql_integral!(u64);
from_sql_integral!(usize);

impl FromSql for i64 {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        value.as_i64()
    }
}

impl FromSql for f32 {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        match value {
            ValueRef::Integer(i) => Ok(i as f32),
            ValueRef::Real(f) => Ok(f as f32),
            _ => Err(FromSqlError::InvalidType),
        }
    }
}

impl FromSql for f64 {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        match value {
            ValueRef::Integer(i) => Ok(i as f64),
            ValueRef::Real(f) => Ok(f),
            _ => Err(FromSqlError::InvalidType),
        }
    }
}

impl FromSql for bool {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        i64::column_result(value).map(|i| i != 0)
    }
}

impl FromSql for String {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        value.as_str().map(ToString::to_string)
    }
}

impl FromSql for Box<str> {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        value.as_str().map(Into::into)
    }
}

impl FromSql for std::rc::Rc<str> {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        value.as_str().map(Into::into)
    }
}

impl FromSql for std::sync::Arc<str> {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        value.as_str().map(Into::into)
    }
}

impl FromSql for Vec<u8> {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        value.as_blob().map(<[u8]>::to_vec)
    }
}

impl<const N: usize> FromSql for [u8; N] {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        let slice = value.as_blob()?;
        slice.try_into().map_err(|_| FromSqlError::InvalidBlobSize {
            expected_size: N,
            blob_size: slice.len(),
        })
    }
}

#[cfg(feature = "i128_blob")]
#[cfg_attr(docsrs, doc(cfg(feature = "i128_blob")))]
impl FromSql for i128 {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        let bytes = <[u8; 16]>::column_result(value)?;
        Ok(i128::from_be_bytes(bytes) ^ (1_i128 << 127))
    }
}

#[cfg(feature = "uuid")]
#[cfg_attr(docsrs, doc(cfg(feature = "uuid")))]
impl FromSql for uuid::Uuid {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        let bytes = <[u8; 16]>::column_result(value)?;
        Ok(uuid::Uuid::from_u128(u128::from_be_bytes(bytes)))
    }
}

impl<T: FromSql> FromSql for Option<T> {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        match value {
            ValueRef::Null => Ok(None),
            _ => FromSql::column_result(value).map(Some),
        }
    }
}

impl FromSql for Value {
    #[inline]
    fn column_result(value: ValueRef<'_>) -> FromSqlResult<Self> {
        Ok(value.into())
    }
}

#[cfg(test)]
mod test {
    use super::FromSql;
    use crate::{Connection, Error, Result};

    #[test]
    fn test_integral_ranges() -> Result<()> {
        let db = Connection::open_in_memory()?;

        fn check_ranges<T>(db: &Connection, out_of_range: &[i64], in_range: &[i64])
        where
            T: Into<i64> + FromSql + ::std::fmt::Debug,
        {
            for n in out_of_range {
                let err = db
                    .query_row("SELECT ?", &[n], |r| r.get::<_, T>(0))
                    .unwrap_err();
                match err {
                    Error::IntegralValueOutOfRange(_, value) => assert_eq!(*n, value),
                    _ => panic!("unexpected error: {}", err),
                }
            }
            for n in in_range {
                assert_eq!(
                    *n,
                    db.query_row("SELECT ?", &[n], |r| r.get::<_, T>(0))
                        .unwrap()
                        .into()
                );
            }
        }

        check_ranges::<i8>(&db, &[-129, 128], &[-128, 0, 1, 127]);
        check_ranges::<i16>(&db, &[-32769, 32768], &[-32768, -1, 0, 1, 32767]);
        check_ranges::<i32>(
            &db,
            &[-2_147_483_649, 2_147_483_648],
            &[-2_147_483_648, -1, 0, 1, 2_147_483_647],
        );
        check_ranges::<u8>(&db, &[-2, -1, 256], &[0, 1, 255]);
        check_ranges::<u16>(&db, &[-2, -1, 65536], &[0, 1, 65535]);
        check_ranges::<u32>(&db, &[-2, -1, 4_294_967_296], &[0, 1, 4_294_967_295]);
        Ok(())
    }
}