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// --------------------------------------------------
// local
// --------------------------------------------------
use super::{constants, key_match_gen};
use crate::ast::{attr::MainContainer, types};
// --------------------------------------------------
// external
// --------------------------------------------------
use quote::quote;
pub(super) fn gen_decode_partial_impl(
name: &syn::Ident,
partial_name: &syn::Ident,
stream: &syn::Type,
generics: &syn::Generics,
) -> proc_macro2::TokenStream {
// --------------------------------------------------
// split generics
// --------------------------------------------------
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
// --------------------------------------------------
// fresh-start dispatch: build a default partial struct
// and hand off to resume entry
// --------------------------------------------------
quote! {
#[doc(hidden)]
#[automatically_derived]
#[doc = concat!(" [`", stringify!(#name), "`] implementation of [`tinyklv::prelude::DecodePartial`] for [`", stringify!(#stream), "`]")]
impl #impl_generics ::tinyklv::traits::DecodePartial<#stream> for #name #ty_generics #where_clause {
type Partial = #partial_name #ty_generics;
#[inline(always)]
fn decode_partial(
input: &mut #stream,
) -> ::core::result::Result<
::tinyklv::decoder::Packet<Self, Self::Partial>,
&'static str,
> {
<Self as ::tinyklv::traits::ResumePartial<#stream>>::resume_partial(
input,
<#partial_name #ty_generics as ::core::default::Default>::default(),
)
}
}
}
}
pub(super) fn gen_resume_partial_impl(
input: &MainContainer,
name: &syn::Ident,
partial_name: &syn::Ident,
stream: &syn::Type,
key_decoder: &types::XcoderType,
len_decoder: &types::XcoderType,
) -> proc_macro2::TokenStream {
// --------------------------------------------------
// split generics
// --------------------------------------------------
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
// --------------------------------------------------
// container attributes
// --------------------------------------------------
let debug_on = input.attrs.debug.is_some();
let deny_unknown_keys = input.attrs.deny_unknown_keys.is_some();
// --------------------------------------------------
// * field assignment during decode
// * known-keys precheck - only if deny_unknown_keys is enabled
// --------------------------------------------------
let items_match = key_match_gen::gen_items_match(&input.data, stream, debug_on);
let (pre_check_gate, pre_check_clippy_allow) = if deny_unknown_keys {
(
key_match_gen::gen_known_keys_check(name, &input.data),
quote! {
#[allow(
clippy::manual_range_patterns,
reason = "the matches!(key, K1 | K2 | ...) pattern is generated by the macro and cannot be avoided. this lint appears when keys are consecutive",
)]
},
)
} else {
(quote! {}, quote! {})
};
// --------------------------------------------------
// debug statement after key/len parse
// --------------------------------------------------
let debug_key_val = match debug_on {
true => {
let logger = constants::logger();
quote! {
#logger ("key: {}, len: {}", key, len);
}
}
false => quote! {},
};
// --------------------------------------------------
// return impl - this is main decoding logic
// --------------------------------------------------
quote! {
#[doc(hidden)]
#[automatically_derived]
#[doc = concat!(" [`", stringify!(#name), "`] implementation of [`tinyklv::traits::ResumePartial`] for [`", stringify!(#stream), "`].")]
impl #impl_generics ::tinyklv::traits::ResumePartial<#stream> for #name #ty_generics #where_clause {
#pre_check_clippy_allow
fn resume_partial(
input: &mut #stream,
mut __acc: #partial_name #ty_generics,
) -> ::core::result::Result<
::tinyklv::decoder::Packet<Self, #partial_name #ty_generics>,
&'static str,
> {
let checkpoint = input.checkpoint();
let _ = checkpoint;
loop {
// --------------------------------------------------
// EOF: "the buffer just ran out", NOT "the packet
// is done". surface the in-flight partial via
// NeedMore so the caller can `feed` more bytes
// and resume. an entity does not know the stream
// is complete unless the user implements a `Done`
// break condition; without one, the caller owns
// the finalise call (typically via
// [`tinyklv::Decoder::finish`]).
// --------------------------------------------------
if input.eof_offset() == 0 {
return ::core::result::Result::Ok(
::tinyklv::decoder::Packet::NeedMore(__acc)
);
}
let checkpoint_inner = input.checkpoint();
// --------------------------------------------------
// parse key then len sequentially. splitting the
// prefix lets us distinguish truncation from
// malformation:
//
// * key parse fails with zero bytes consumed ->
// we ran out of input before the prefix could
// start. surface as NeedMore so the caller can
// `feed` more.
// * key parses but len parse fails -> we have a
// partial prefix; len bytes are short, so this
// is also truncation (NeedMore).
// * key parse fails with bytes consumed -> the
// key decoder rejected the bytes it saw; this
// is actual malformation (Malformed).
//
// a single `(key, len).parse_next` cannot tell
// these apart because the tuple's error path
// doesn't expose "which sub-parser" failed or how
// many bytes it consumed.
// --------------------------------------------------
let __key_offset_before = input.eof_offset();
let key = match #key_decoder.parse_next(input) {
Ok(k) => k,
Err(_) => {
let __consumed = __key_offset_before - input.eof_offset();
input.reset(&checkpoint_inner);
if __consumed == 0 {
// recoverable: ran out of input before
// a single key byte was consumed.
return ::core::result::Result::Ok(
::tinyklv::decoder::Packet::NeedMore(__acc)
);
}
// --------------------------------------------------
// unrecoverable: key bytes existed but could not be decoded. attempt finalize
// on whatever the partial holds; success surfaces as Ready, failure propagates
// the label outward to the Decoder (which owns input/checkpoint context)
// --------------------------------------------------
return match <#partial_name #ty_generics as ::tinyklv::traits::Partial>::finalize(__acc) {
Ok(v) => ::core::result::Result::Ok(
::tinyklv::decoder::Packet::Ready(v)
),
Err(label) => ::core::result::Result::Err(label),
};
}
};
let len = match #len_decoder.parse_next(input) {
Ok(l) => l,
Err(_) => {
// --------------------------------------------------
// key parsed but len short: always
// truncation. rewind to iteration start so
// both key and len will be re-read once
// more bytes arrive.
// --------------------------------------------------
input.reset(&checkpoint_inner);
return ::core::result::Result::Ok(
::tinyklv::decoder::Packet::NeedMore(__acc)
);
}
};
match Self::break_condition(key, len) {
::tinyklv::BreakConditionType::Proceed => (),
::tinyklv::BreakConditionType::Skip => {
// --------------------------------------------------
// not enough bytes for the value being
// skipped: rewind so the next iteration
// re-reads the same key/len once more
// bytes arrive, then surface the in-flight
// partial via NeedMore.
// --------------------------------------------------
if input.eof_offset() < len {
input.reset(&checkpoint_inner);
return ::core::result::Result::Ok(
::tinyklv::decoder::Packet::NeedMore(__acc)
);
}
// --------------------------------------------------
// pre-checked above; `take` should never fail here
// --------------------------------------------------
let _ = ::tinyklv::__export::winnow::token::take::<
usize,
#stream,
::tinyklv::__export::winnow::error::ContextError,
>(len).parse_next(input);
continue;
}
::tinyklv::BreakConditionType::Done => break,
::tinyklv::BreakConditionType::Abort(_) => {
// --------------------------------------------------
// user-signalled abort. the abort's own
// ContextError is not preserved here - the
// codegen returns a static label and the
// Decoder wraps it with real input
// context. carrying the user's
// ContextError through the &'static str
// boundary is left as a follow-up.
// --------------------------------------------------
return match <#partial_name #ty_generics as ::tinyklv::traits::Partial>::finalize(__acc) {
Ok(v) => ::core::result::Result::Ok(
::tinyklv::decoder::Packet::Ready(v)
),
Err(_) => ::core::result::Result::Err(
"break_condition::abort"
),
};
}
}
#debug_key_val
#pre_check_gate
if input.eof_offset() < len {
// --------------------------------------------------
// value bytes incomplete for the current key.
// rewind, surface partial via NeedMore.
// --------------------------------------------------
input.reset(&checkpoint_inner);
return ::core::result::Result::Ok(
::tinyklv::decoder::Packet::NeedMore(__acc)
);
}
// --------------------------------------------------
// extract the value subinput. pre-checked above, so
// the take cannot fail in practice; on the unlikely
// parser-internal error attempt finalize on the
// partial and surface its outcome.
// --------------------------------------------------
let mut subinput: <#stream as ::tinyklv::__export::winnow::stream::Stream>::Slice = match ::tinyklv::__export::winnow::token::take::<
usize,
#stream,
::tinyklv::__export::winnow::error::ContextError,
>(len).parse_next(input) {
Ok(s) => s,
Err(_) => return match <#partial_name #ty_generics as ::tinyklv::traits::Partial>::finalize(__acc) {
Ok(v) => ::core::result::Result::Ok(
::tinyklv::decoder::Packet::Ready(v)
),
Err(label) => ::core::result::Result::Err(label),
},
};
// --------------------------------------------------
// field dispatch into the partial accumulator.
// unknown keys (when allowed) hit the `_ => ()` arm
// and are silently ignored after their bytes have
// already been consumed by the take above.
// --------------------------------------------------
match key {
#items_match
_ => (),
}
}
// --------------------------------------------------
// BreakConditionType::Done dropped us out of the loop.
// attempt finalize on whatever the partial holds.
// success -> Ready; required-field failure -> propagate
// the &'static str label outward (the Decoder will
// wrap it with input/checkpoint context).
// --------------------------------------------------
match <#partial_name #ty_generics as ::tinyklv::traits::Partial>::finalize(__acc) {
Ok(v) => ::core::result::Result::Ok(
::tinyklv::decoder::Packet::Ready(v)
),
Err(label) => ::core::result::Result::Err(label),
}
}
}
}
}