From 576182b49181cdf4a3196f0134d3294202b40e12 Mon Sep 17 00:00:00 2001
From: Michael Aaron Murphy <mmstickman@gmail.com>
Date: Mon, 6 Nov 2017 15:49:26 -0500
Subject: [PATCH] Eliminate Heap Allocation w/ !* Designator
---
src/shell/binary/designators.rs | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/src/shell/binary/designators.rs b/src/shell/binary/designators.rs
index 82319fb4..7ef640d6 100644
--- a/src/shell/binary/designators.rs
+++ b/src/shell/binary/designators.rs
@@ -106,9 +106,19 @@ pub(crate) fn expand_designators<'a>(shell: &Shell, cmd: &'a str) -> Cow<'a, str
fn command<'a>(text: &'a str) -> &'a str { ArgumentSplitter::new(text).next().unwrap_or(text) }
-// TODO: do this without allocating a string.
-fn args(text: &str) -> String {
- ArgumentSplitter::new(text).skip(1).collect::<Vec<&str>>().join(" ")
+fn args(text: &str) -> &str {
+ let bytes = text.as_bytes();
+ bytes.iter()
+ // Obtain position of the first space character,
+ .position(|&x| x == b' ')
+ // and then obtain the arguments to the command.
+ .and_then(|fp| bytes[fp+1..].iter()
+ // Find the position of the first character in the first argument.
+ .position(|&x| x != b' ')
+ // Then slice the argument string from the original command.
+ .map(|sp| &text[fp+sp+1..]))
+ // Unwrap the arguments string if it exists, else return the original string.
+ .unwrap_or(text)
}
fn first_arg<'a>(text: &'a str) -> &'a str { ArgumentSplitter::new(text).nth(1).unwrap_or(text) }
--
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