cartel-pg 0.29.0

Async PostgreSQL driver for the dope runtime
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use crate::{
    protocol::{Wire, value::decode},
    schema,
};
use std::marker;

mod cursor;
mod sealed;
pub use cursor::Cursor;
pub(crate) use sealed::Sealed;

/// The closed field descriptions supported by retained, validated projection.
pub trait Fields: schema::Row + Sealed {
    fn read<'row>(cursor: &mut Cursor<'row>) -> Self::View<'row>;
}

/// A complete immutable row validated against this exact field description.
pub(crate) struct Row<'row, T: Fields> {
    bytes: &'row [u8],
    fields: marker::PhantomData<T>,
}

impl<'row, T: Fields> Row<'row, T> {
    pub(crate) fn validate(bytes: Wire<'row>, columns: u16) -> Result<(), crate::Error> {
        let mut reader = decode::RowReader::new(bytes, columns)?;
        T::decode(&mut reader)?;
        reader.finish()
    }

    /// # Safety
    /// The immutable retained owner validated these same bytes as T.
    pub(crate) unsafe fn new(bytes: &'row [u8]) -> Self {
        Self {
            bytes,
            fields: marker::PhantomData,
        }
    }

    pub(crate) fn read(self) -> T::View<'row> {
        // SAFETY: validation consumed the complete two-byte row header.
        let bytes = unsafe { self.bytes.get_unchecked(2..) };
        T::read(&mut Cursor { bytes })
    }
}

const _: () = {
    assert!(size_of::<Row<'static, (i64, (String, ()))>>() == size_of::<&[u8]>());
    assert!(size_of::<Cursor<'static>>() == size_of::<&[u8]>());
};

impl<A: Fields> Fields for (A, ()) {
    fn read<'row>(cursor: &mut Cursor<'row>) -> Self::View<'row> {
        (A::read(cursor), ())
    }
}

impl<A: Fields, B: Fields> Fields for (A, B) {
    fn read<'row>(cursor: &mut Cursor<'row>) -> Self::View<'row> {
        (A::read(cursor), B::read(cursor))
    }
}

impl Fields for bool {
    fn read<'row>(cursor: &mut Cursor<'row>) -> bool {
        // SAFETY: the closed field sequence validated a nonnull byte equal to zero or one.
        let [value] = unsafe { cursor.fixed() };
        value != 0
    }
}

impl Fields for i32 {
    fn read<'row>(cursor: &mut Cursor<'row>) -> i32 {
        // SAFETY: the closed field sequence validated this nonnull four-byte scalar.
        i32::from_be_bytes(unsafe { cursor.fixed() })
    }
}

impl Fields for i64 {
    fn read<'row>(cursor: &mut Cursor<'row>) -> i64 {
        // SAFETY: the closed field sequence validated this nonnull eight-byte scalar.
        i64::from_be_bytes(unsafe { cursor.fixed() })
    }
}

impl Fields for String {
    fn read<'row>(cursor: &mut Cursor<'row>) -> &'row str {
        // SAFETY: validation proved the length prefix, complete nonnull payload and UTF-8.
        unsafe { cursor.text::<0>() }
    }
}

impl Fields for crate::Jsonb {
    fn read<'row>(cursor: &mut Cursor<'row>) -> &'row str {
        // SAFETY: validation also proved the version byte and UTF-8 after that byte.
        unsafe { cursor.text::<1>() }
    }
}