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Remove unnecessary lseek syscall when using std::fs::read #106664

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Merged
merged 2 commits into from
Jan 11, 2023
Merged

Remove unnecessary lseek syscall when using std::fs::read #106664

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eae615d
Remove unnecessary lseek syscall when using std::fs::read
chenyukang Jan 7, 2023
f7bc68b
use with_capacity in read read_to_string
chenyukang Jan 10, 2023
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10 changes: 6 additions & 4 deletions library/std/src/fs.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -249,8 +249,9 @@ pub struct DirBuilder {
pub fn read<P: AsRef<Path>>(path: P) -> io::Result<Vec<u8>> {
fn inner(path: &Path) -> io::Result<Vec<u8>> {
let mut file = File::open(path)?;
let mut bytes = Vec::new();
file.read_to_end(&mut bytes)?;
let size = file.metadata().map(|m| m.len()).unwrap_or(0);
let mut bytes = Vec::with_capacity(size as usize);
io::default_read_to_end(&mut file, &mut bytes)?;
Ok(bytes)
}
inner(path.as_ref())
Expand Down Expand Up @@ -288,8 +289,9 @@ pub fn read<P: AsRef<Path>>(path: P) -> io::Result<Vec<u8>> {
pub fn read_to_string<P: AsRef<Path>>(path: P) -> io::Result<String> {
fn inner(path: &Path) -> io::Result<String> {
let mut file = File::open(path)?;
let mut string = String::new();
file.read_to_string(&mut string)?;
let size = file.metadata().map(|m| m.len()).unwrap_or(0);
let mut string = String::with_capacity(size as usize);
io::default_read_to_string(&mut file, &mut string)?;
Ok(string)
}
inner(path.as_ref())
Expand Down