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lofty_attr: Add proc macro to define EBML master elements
Signed-off-by: Serial <69764315+Serial-ATA@users.noreply.github.com>
1 parent e23eabc commit f3463d2

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3 files changed

+182
-37
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3 files changed

+182
-37
lines changed

‎lofty_attr/src/ebml.rs‎

Lines changed: 113 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,113 @@
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use proc_macro::TokenStream;
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use std::collections::HashSet;
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use syn::parse::{Parse, Parser};
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use syn::punctuated::Punctuated;
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use syn::{braced, bracketed, Ident, Token};
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pub(crate) struct EbmlMasterElement {
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pub(crate) readable_ident: Ident,
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pub(crate) info: EbmlMasterInfo,
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}
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impl Parse for EbmlMasterElement {
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fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
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let readable_ident = input.parse::<Ident>()?;
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let _: syn::Token![:] = input.parse()?;
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let info;
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braced!(info in input);
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Ok(Self {
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readable_ident,
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info: info.parse::<EbmlMasterInfo>()?,
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})
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}
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}
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pub(crate) struct EbmlMasterInfo {
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pub(crate) id: u64,
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pub(crate) children: Vec<EbmlChildElement>,
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}
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impl Parse for EbmlMasterInfo {
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fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
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let _id_field = input.parse::<Ident>()?;
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let _: syn::Token![:] = input.parse()?;
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let id = input.parse::<syn::LitInt>()?.base10_parse()?;
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let _: syn::Token![,] = input.parse()?;
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let _children_field = input.parse::<Ident>()?;
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let _: syn::Token![:] = input.parse()?;
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let children;
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bracketed!(children in input);
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let children = children
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.parse_terminated(EbmlChildElement::parse, syn::Token![,])?
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.into_iter()
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.collect();
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let _trailing_comma = input.parse::<Token![,]>().ok();
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Ok(Self { id, children })
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}
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}
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pub(crate) struct EbmlChildElement {
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pub(crate) readable_ident: Ident,
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pub(crate) info: EbmlChildInfo,
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}
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impl Parse for EbmlChildElement {
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fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
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let readable_ident = input.parse::<Ident>()?;
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let _: syn::Token![:] = input.parse()?;
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let info;
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braced!(info in input);
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Ok(Self {
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readable_ident,
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info: info.parse::<EbmlChildInfo>()?,
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})
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}
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}
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pub(crate) struct EbmlChildInfo {
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pub(crate) id: u64,
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pub(crate) data_type: Ident,
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}
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impl Parse for EbmlChildInfo {
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fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
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let id = input.parse::<syn::LitInt>()?.base10_parse()?;
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let _: syn::Token![,] = input.parse()?;
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let data_type = input.parse::<Ident>()?;
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Ok(Self { id, data_type })
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}
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}
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fn insert_element_identifiers(identifiers: &mut HashSet<Ident>, element: &EbmlMasterElement) {
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identifiers.insert(element.readable_ident.clone());
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for child in &element.info.children {
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identifiers.insert(child.readable_ident.clone());
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}
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}
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pub(crate) fn parse_ebml_master_elements(
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input: TokenStream,
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) -> syn::Result<(HashSet<Ident>, Vec<EbmlMasterElement>)> {
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let mut element_identifiers = HashSet::new();
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let parser = Punctuated::<EbmlMasterElement, Token![,]>::parse_terminated;
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let elements = parser.parse(input)?;
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for element in &elements {
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insert_element_identifiers(&mut element_identifiers, element);
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}
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Ok((element_identifiers, elements.into_iter().collect()))
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}

‎lofty_attr/src/lib.rs‎

Lines changed: 52 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -33,6 +33,7 @@
3333
clippy::needless_pass_by_value
3434
)]
3535

36+
mod ebml;
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mod internal;
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mod lofty_file;
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mod lofty_tag;
@@ -94,3 +95,54 @@ fn finish(ret: &proc_macro2::TokenStream, errors: &[syn::Error]) -> TokenStream
9495
#ret
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})
9697
}
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#[proc_macro]
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#[doc(hidden)]
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pub fn ebml_master_elements(input: TokenStream) -> TokenStream {
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let ret = ebml::parse_ebml_master_elements(input);
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if let Err(err) = ret {
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return TokenStream::from(err.to_compile_error());
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}
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let (identifiers, elements) = ret.unwrap();
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let identifiers_iter = identifiers.iter();
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let elements_map_inserts = elements.iter().map(|element| {
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let readable_ident = &element.readable_ident;
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let id = element.info.id;
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let children = element.info.children.iter().map(|child| {
114+
let readable_ident = &child.readable_ident;
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let id = child.info.id;
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let data_type = &child.info.data_type;
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quote! {
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(VInt(#id), ChildElementDescriptor {
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ident: ElementIdent::#readable_ident,
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data_type: ElementDataType::#data_type,
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})
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}
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});
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quote! {
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m.insert(
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VInt(#id),
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MasterElement {
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id: ElementIdent::#readable_ident,
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children: &[#( #children ),*][..]
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}
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);
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}
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});
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TokenStream::from(quote! {
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#[derive(Copy, Clone, Eq, PartialEq)]
138+
pub(crate) enum ElementIdent {
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#( #identifiers_iter ),*
140+
}
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static MASTER_ELEMENTS: once_cell::sync::Lazy<std::collections::HashMap<VInt, MasterElement>> = once_cell::sync::Lazy::new(|| {
143+
let mut m = std::collections::HashMap::new();
144+
#( #elements_map_inserts )*
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m
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});
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})
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}

‎src/ebml/element_reader.rs‎

Lines changed: 17 additions & 37 deletions
Original file line numberDiff line numberDiff line change
@@ -5,6 +5,7 @@ use crate::macros::decode_err;
55
use std::io::Read;
66

77
use byteorder::{BigEndian, ReadBytesExt};
8+
use lofty_attr::ebml_master_elements;
89

910
pub struct ElementHeader {
1011
pub(crate) id: VInt,
@@ -47,43 +48,7 @@ pub(crate) struct ChildElementDescriptor {
4748
pub(crate) data_type: ElementDataType,
4849
}
4950

50-
macro_rules! define_master_elements {
51-
($(
52-
$_readable_ident:ident : {
53-
id: $vint_id:literal,
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children: [
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$($_readable_child_ident:ident : { $child_id:literal, $data_ty:ident }),* $(,)?
56-
] $(,)?
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}
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),+ $(,)?) => {
59-
#[derive(Copy, Clone, Eq, PartialEq)]
60-
pub(crate) enum ElementIdent {
61-
$(
62-
$_readable_ident,
63-
$($_readable_child_ident,)*
64-
)+
65-
}
66-
67-
static MASTER_ELEMENTS: once_cell::sync::Lazy<std::collections::HashMap<VInt, MasterElement>> = once_cell::sync::Lazy::new(|| {
68-
let mut m = std::collections::HashMap::new();
69-
$(
70-
m.insert(
71-
VInt($vint_id),
72-
MasterElement {
73-
id: ElementIdent::$_readable_ident,
74-
children: &[$((VInt($child_id), ChildElementDescriptor {
75-
ident: ElementIdent::$_readable_child_ident,
76-
data_type: ElementDataType::$data_ty,
77-
})),*][..]
78-
}
79-
);
80-
)+
81-
m
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});
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}
84-
}
85-
86-
define_master_elements! {
51+
ebml_master_elements! {
8752
EBML: {
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id: 0x1A45_DFA3,
8954
children: [
@@ -103,6 +68,21 @@ define_master_elements! {
10368
DocTypeExtensionVersion: { 0x4284, UnsignedInt },
10469
],
10570
},
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// The Root Element that contains all other Top-Level Elements
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Segment: {
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id: 0x1853_8067,
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children: [
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SeekHead: { 0x114D_9B74, Master },
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Info: { 0x1549_A966, Master },
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Cluster: { 0x1F43_B675, Master },
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Tracks: { 0x1654_AE6B, Master },
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Cues: { 0x1C53_BB6B, Master },
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Tags: { 0x1254_C367, Master },
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Attachments: { 0x1941_A469, Master },
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Chapters: { 0x1043_A770, Master },
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],
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},
10686
}
10787

10888
struct ElementReaderContext {

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