From 6065678e627643cc3275c677408d11f48802595e Mon Sep 17 00:00:00 2001 From: Barosl Lee Date: Wed, 26 Aug 2015 21:27:32 +0900 Subject: [PATCH] Use a different buffer doubling logic for `std::sys::os::getcwd` Make `std::sys::os::getcwd` call `Vec::reserve(1)` followed by `Vec::set_len` to double the buffer. This is to align with other similar functions, such as: - `std::sys_common::io::read_to_end_uninitialized` - `std::sys::fs::readlink` Also, reduce the initial buffer size from 2048 to 512. The previous size was introduced with 4bc26ce in 2013, but it seems a bit excessive. This is probably because buffer doubling was not implemented back then. --- src/libstd/sys/unix/os.rs | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs index 2b6b50a1a56..fa31ac682d4 100644 --- a/src/libstd/sys/unix/os.rs +++ b/src/libstd/sys/unix/os.rs @@ -30,7 +30,6 @@ use sys::c; use sys::fd; use vec; -const GETCWD_BUF_BYTES: usize = 2048; const TMPBUF_SZ: usize = 128; /// Returns the platform-specific value of errno @@ -94,11 +93,9 @@ pub fn error_string(errno: i32) -> String { } pub fn getcwd() -> io::Result { - let mut buf = Vec::new(); - let mut n = GETCWD_BUF_BYTES; + let mut buf = Vec::with_capacity(512); loop { unsafe { - buf.reserve(n); let ptr = buf.as_mut_ptr() as *mut libc::c_char; if !libc::getcwd(ptr, buf.capacity() as libc::size_t).is_null() { let len = CStr::from_ptr(buf.as_ptr() as *const libc::c_char).to_bytes().len(); @@ -111,7 +108,12 @@ pub fn getcwd() -> io::Result { return Err(error); } } - n *= 2; + + // Trigger the internal buffer resizing logic of `Vec` by requiring + // more space than the current capacity. + let cap = buf.capacity(); + buf.set_len(cap); + buf.reserve(1); } } }