Bind header+u32 to variable for clearer math

Author: CraftSpider

compiler/rustc_metadata/src/locator.rs

@@ -789,6 +789,9 @@ fn get_metadata_section<'p>(
                 loader.get_dylib_metadata(target, filename).map_err(MetadataError::LoadFailure)?;
             // The header is uncompressed
             let header_len = METADATA_HEADER.len();
+            let u32_len = core::mem::size_of::<u32>();
+            let data_start = header_len + u32_len;
+
             debug!("checking {} bytes of metadata-version stamp", header_len);
             let header = &buf[..cmp::min(header_len, buf.len())];
             if header != METADATA_HEADER {
@@ -799,14 +802,13 @@ fn get_metadata_section<'p>(
             }
 
             // Length of the compressed stream - this allows linkers to pad the section if they want
-            let u32_len = core::mem::size_of::<u32>();
-            let Ok(len_bytes) = <[u8; 4]>::try_from(&buf[header_len..cmp::min(header_len + u32_len, buf.len())]) else {
+            let Ok(len_bytes) = <[u8; 4]>::try_from(&buf[header_len..cmp::min(data_start, buf.len())]) else {
                 return Err(MetadataError::LoadFailure("invalid metadata length found".to_string()));
             };
             let compressed_len = u32::from_be_bytes(len_bytes) as usize;
 
             // Header is okay -> inflate the actual metadata
-            let compressed_bytes = &buf[(header_len + u32_len)..(compressed_len + header_len + u32_len)];
+            let compressed_bytes = &buf[data_start..(data_start + compressed_len)];
             debug!("inflating {} bytes of compressed metadata", compressed_bytes.len());
             // Assume the decompressed data will be at least the size of the compressed data, so we
             // don't have to grow the buffer as much.