Commit ace9a74

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Auto merge of #145848 - Kobzol:optimize-file-read, r=the8472

Slightly optimize reading of source files Discussed on Zulip (https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/rustc.20uses.20silly.20amount.20of.20syscalls.20for.20file.20IO/with/536015625. Do not open/close each source file twice when reading it. We still stat it twice though.

2 parents d327d65 + 3145c06 commit ace9a74Copy full SHA for ace9a74

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Lines changed: 8 additions & 2 deletions

Original file line number	Diff line number	Diff line change
`@@ -9,6 +9,7 @@`
`9`	`9`	//! within the `SourceMap`, which upon request can be converted to line and column
`10`	`10`	`//! information, source code snippets, etc.`
`11`	`11`
	`12`	`+use std::fs::File;`
`12`	`13`	`use std::io::{self, BorrowedBuf, Read};`
`13`	`14`	`use std::{fs, path};`
`14`	`15`
`@@ -115,13 +116,18 @@ impl FileLoader for RealFileLoader {`
`115`	`116`	`}`
`116`	`117`
`117`	`118`	`fn read_file(&self, path: &Path) -> io::Result<String> {`
`118`		`- if path.metadata().is_ok_and(\|metadata\| metadata.len() > SourceFile::MAX_FILE_SIZE.into()) {`
	`119`	`+ let mut file = File::open(path)?;`
	`120`	`+ let size = file.metadata().map(\|metadata\| metadata.len()).ok().unwrap_or(0);`
	`121`	`+`
	`122`	`+ if size > SourceFile::MAX_FILE_SIZE.into() {`
`119`	`123`	`return Err(io::Error::other(format!(`
`120`	`124`	`"text files larger than {} bytes are unsupported",`
`121`	`125`	`SourceFile::MAX_FILE_SIZE`
`122`	`126`	`)));`
`123`	`127`	`}`
`124`		`- fs::read_to_string(path)`
	`128`	`+ let mut contents = String::new();`
	`129`	`+ file.read_to_string(&mut contents)?;`
	`130`	`+ Ok(contents)`
`125`	`131`	`}`
`126`	`132`
`127`	`133`	`fn read_binary_file(&self, path: &Path) -> io::Result<Arc<[u8]>> {`

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