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crates/proc_macro_api/src/version.rs

Lines changed: 22 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -64,8 +64,8 @@ pub(crate) fn read_info(dylib_path: &Path) -> io::Result<RustCInfo> {
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Ok(RustCInfo { version, channel, commit, date })
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}
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// This is used inside read_version() to locate the ".rustc" section
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// from a proc macro crate's binary file.
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/// This is used inside read_version() to locate the ".rustc" section
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/// from a proc macro crate's binary file.
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fn read_section<'a>(dylib_binary: &'a [u8], section_name: &str) -> io::Result<&'a [u8]> {
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BinaryFile::parse(dylib_binary)
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.map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?
@@ -75,25 +75,26 @@ fn read_section<'a>(dylib_binary: &'a [u8], section_name: &str) -> io::Result<&'
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.map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
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}
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// Check the version of rustc that was used to compile a proc macro crate's
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// binary file.
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// A proc macro crate binary's ".rustc" section has following byte layout:
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// * [b'r',b'u',b's',b't',0,0,0,5] is the first 8 bytes
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// * ff060000 734e6150 is followed, it's the snappy format magic bytes,
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// means bytes from here(including this sequence) are compressed in
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// snappy compression format. Version info is inside here, so decompress
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// this.
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// The bytes you get after decompressing the snappy format portion has
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// following layout:
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// * [b'r',b'u',b's',b't',0,0,0,5] is the first 8 bytes(again)
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// * [crate root bytes] next 4 bytes is to store crate root position,
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// according to rustc's source code comment
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// * [length byte] next 1 byte tells us how many bytes we should read next
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// for the version string's utf8 bytes
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// * [version string bytes encoded in utf8] <- GET THIS BOI
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// * [some more bytes that we don really care but still there] :-)
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// Check this issue for more about the bytes layout:
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// https://github.com/rust-analyzer/rust-analyzer/issues/6174
78+
/// Check the version of rustc that was used to compile a proc macro crate's
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///
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/// binary file.
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/// A proc macro crate binary's ".rustc" section has following byte layout:
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/// * [b'r',b'u',b's',b't',0,0,0,5] is the first 8 bytes
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/// * ff060000 734e6150 is followed, it's the snappy format magic bytes,
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/// means bytes from here(including this sequence) are compressed in
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/// snappy compression format. Version info is inside here, so decompress
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/// this.
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/// The bytes you get after decompressing the snappy format portion has
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/// following layout:
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/// * [b'r',b'u',b's',b't',0,0,0,5] is the first 8 bytes(again)
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/// * [crate root bytes] next 4 bytes is to store crate root position,
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/// according to rustc's source code comment
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/// * [length byte] next 1 byte tells us how many bytes we should read next
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/// for the version string's utf8 bytes
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/// * [version string bytes encoded in utf8] <- GET THIS BOI
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/// * [some more bytes that we don really care but still there] :-)
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/// Check this issue for more about the bytes layout:
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/// https://github.com/rust-analyzer/rust-analyzer/issues/6174
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fn read_version(dylib_path: &Path) -> io::Result<String> {
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let dylib_file = File::open(dylib_path)?;
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let dylib_mmaped = unsafe { Mmap::map(&dylib_file) }?;

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