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/// A trait to be implemented by types that encode [`Item`] values into a
/// buffer of type [`B`].
pub trait Encoder<B, Item = Self> {
/// The type of error that can occur if encoding fails.
type Error;
/// Encodes the given input into the output buffer.
///
/// This method does not return a result because calls to
/// [`Encoder::encode`] never do.
///
/// # Arguments
/// * `item` - The input to encode.
/// * `buf` - The output buffer to write the encoded input to.
fn encode(item: &Item, buf: &mut B) -> Result<(), Self::Error>;
/// Returns the number of bytes required to encode the given input.
///
/// This method is useful for pre-allocating buffers that will be used for encoding.
///
/// # Arguments
/// * `item` - The input to encode.
/// * `buf` - The output buffer used for encoding.
///
/// # Returns
/// The number of bytes required to encode the given input.
fn size_of(item: &Item, buf: &B) -> usize;
}
#[cfg(test)]
mod tests {
use crate as recode;
use crate::util::EncoderExt;
use crate::Encoder;
#[test]
fn basic_test() {
#[derive(Encoder)]
#[recode(encoder(buffer_name = "buf", error = "crate::Error"))]
struct TestType {
age: u32,
salary: u64,
first_name: crate::codec::Ascii<u8>,
last_name: crate::codec::Utf8<u16>,
image: crate::codec::Buffer<u32>,
}
const IMAGE_BUF: [u8; 32] = [
0xBA, 0x3E, 0x9D, 0x6B, 0xAE, 0xF5, 0x91, 0xCC, 0xE2, 0xF0, 0xCB,
0x4F, 0xBB, 0x5B, 0x2B, 0xBE, 0xA7, 0xF4, 0x9D, 0xFB, 0x87, 0x43,
0x0E, 0xDF, 0x30, 0x6F, 0x7D, 0x6E, 0x22, 0xAB, 0xCC, 0x47,
];
let test_item = TestType {
age: 0x01234567,
salary: 0x1122334455667788,
first_name: "ayman".into(),
last_name: "القاضي".into(),
image: IMAGE_BUF.as_ref().into(),
};
let mut buf = bytes::BytesMut::new();
assert_eq!(test_item.age.size(&buf), 4);
assert_eq!(test_item.salary.size(&buf), 8);
assert_eq!(test_item.first_name.size(&buf), 1 + 5);
assert_eq!(test_item.last_name.size(&buf), 2 + 12);
assert_eq!(test_item.image.size(&buf), 4 + 32);
assert_eq!(test_item.size(&buf), 4 + 8 + (1 + 5) + (2 + 12) + (4 + 32));
TestType::encode(&test_item, &mut buf).unwrap();
const BUF: [u8; 68] = [
// age (4 bytes)
0x01, 0x23, 0x45, 0x67, // salary (8 bytes)
0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88,
// first name (1 bytes prefixed ascii; 6 bytes)
0x05, b'a', b'y', b'm', b'a', b'n',
// last name (2 bytes prefixed utf8; 6 bytes)
0x00, 0x0C, 0xD8, 0xA7, 0xD9, 0x84, 0xD9, 0x82, 0xD8, 0xA7, 0xD8,
0xB6, 0xD9, 0x8A,
// image (4 bytes prefixed buffer; 36 bytes)
0x00, 0x00, 0x00, 0x20, 0xBA, 0x3E, 0x9D, 0x6B, 0xAE, 0xF5, 0x91,
0xCC, 0xE2, 0xF0, 0xCB, 0x4F, 0xBB, 0x5B, 0x2B, 0xBE, 0xA7, 0xF4,
0x9D, 0xFB, 0x87, 0x43, 0x0E, 0xDF, 0x30, 0x6F, 0x7D, 0x6E, 0x22,
0xAB, 0xCC, 0x47,
];
assert_eq!(buf, BUF.as_ref());
}
}