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mod fixed_text;
mod impls;
mod scalar;
use std::io;
use crate::{Config, Context, ContextUnit, Preamble};
pub use fixed_text::FixedText;
pub use scalar::Scalar;
/// Describe a CDF element
pub trait Element: Sized {
/// Configuration for the serialization and deserialization
type Config: for<'a> From<&'a Config>;
/// A zeroed/default instance of the type.
fn zeroed() -> Self;
/// Serializable length
///
/// Every element is a function of the config so seek/lookups will be constant-time.
///
/// The serialized type must not contain more bytes than specified here. However, it might,
/// optionally, use less bytes. Regardless, it will consume this defined amount of bytes during
/// serialization.
fn len(config: &Self::Config) -> usize;
/// Write the type into the buffer.
///
/// # Panics
///
/// The buffer must, provided a correct definition of [`Element::len`], contain enough bytes to
/// fully serialize the type. This can be checkedvia [`Element::validate_buffer_len`].
fn to_buffer(&self, config: &Self::Config, context: &mut ContextUnit, buf: &mut [u8]);
/// Deserialize the type from a given buffer
///
/// As in [`Self::to_buffer`] the implementor of this function can assume the buffer is big
/// enough to contain all the required bytes.
fn try_from_buffer_in_place<S>(
&mut self,
config: &Self::Config,
context: &mut Context<S>,
buf: &[u8],
) -> io::Result<()>
where
S: io::Read + io::Seek;
/// Perform the internal validations of the associated element
fn validate(&self, preamble: &Preamble) -> io::Result<()>;
/// Assert the buffer is big enough to store the type
fn validate_buffer_len(config: &Self::Config, len: usize) -> io::Result<()> {
if len < Self::len(config) {
return Err(io::Error::new(
io::ErrorKind::InvalidData,
"the provided buffer isn't big enough",
));
}
Ok(())
}
/// Serialize the object into a bytes array.
fn to_vec(&self, config: &Self::Config, context: &mut ContextUnit) -> Vec<u8> {
let mut bytes = vec![0u8; Self::len(config)];
self.to_buffer(config, context, &mut bytes);
bytes
}
/// Create a new instance of the type from the provided buffer
fn try_from_buffer<S>(
config: &Self::Config,
context: &mut Context<S>,
buf: &[u8],
) -> io::Result<Self>
where
S: io::Read + io::Seek,
{
let mut slf = Self::zeroed();
slf.try_from_buffer_in_place(config, context, buf)?;
Ok(slf)
}
/// Write an element from the buffer, and return the remainder bytes
///
/// Assume its inside a validate buffer context
fn try_decode_in_place<'a, S>(
&mut self,
config: &Self::Config,
context: &mut Context<S>,
buf: &'a [u8],
) -> io::Result<&'a [u8]>
where
S: io::Read + io::Seek,
{
self.try_from_buffer_in_place(config, context, buf)
.map(|_| &buf[Self::len(config)..])
}
/// Write an element from the buffer, and return the remainder bytes
///
/// Assume its inside a validate buffer context
fn try_decode<'a, S>(
config: &Self::Config,
context: &mut Context<S>,
buf: &'a [u8],
) -> io::Result<(Self, &'a [u8])>
where
S: io::Read + io::Seek,
{
let mut slf = Self::zeroed();
let buf = slf.try_decode_in_place(config, context, buf)?;
Ok((slf, buf))
}
/// Read an element into the buffer, returning the remainder bytes
///
/// Assume its inside a validate buffer context
fn encode<'a>(
&self,
config: &Self::Config,
context: &mut ContextUnit,
buf: &'a mut [u8],
) -> &'a mut [u8] {
self.to_buffer(config, context, buf);
&mut buf[Self::len(config)..]
}
/// Send the bytes representation of an element to a writer
fn try_to_writer<W>(
&self,
mut writer: W,
config: &Self::Config,
context: &mut ContextUnit,
) -> io::Result<usize>
where
W: io::Write,
{
writer.write(&self.to_vec(config, context))
}
/// Fetch a new element from a context
fn try_from_context<S>(config: &Self::Config, context: &mut Context<S>) -> io::Result<Self>
where
S: io::Read + io::Seek,
{
let mut slf = vec![0u8; Self::len(config)];
context
.source()
.ok_or_else(|| {
io::Error::new(io::ErrorKind::Other, "no reader available in the context")
})
.and_then(|r| r.read(&mut slf))?;
Self::try_from_buffer(config, context, &slf)
}
}