From 5eacd3abee879ad62dc8abdca6ad54f17d403658 Mon Sep 17 00:00:00 2001
From: Gautham Warrier <gautham.r.w@gmail.com>
Date: Sat, 23 Jan 2021 15:55:41 +0530
Subject: perf: use built-in EPOCHREALTIME env-var to compute cmd_duration for
 ZSH5+ (#1751)

We currently invoke `starship time` in a sub-shell to compute time, which is non-performant. By using $EPOCHREALTIME,
which is an inbuilt env-var in ZSH5, we can get better performance. This commit only targets ZSH5+ and maintains the
old behaviour.
---
 src/init/starship.zsh | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/init/starship.zsh b/src/init/starship.zsh
index 07afe7cc1..f0140fa04 100644
--- a/src/init/starship.zsh
+++ b/src/init/starship.zsh
@@ -16,6 +16,20 @@ starship_render() {
     PROMPT="$(::STARSHIP:: prompt --keymap="${KEYMAP-}" --status=$STARSHIP_CMD_STATUS --cmd-duration=${STARSHIP_DURATION-} --jobs="$NUM_JOBS")"
 }
 
+# Defines a function `__starship_get_time` that sets the time since epoch in millis in STARSHIP_CAPTURED_TIME.
+if [[ $ZSH_VERSION == ([1-4]*) ]]; then
+    # ZSH <= 5; Does not have a built-in variable so we will rely on Starship's inbuilt time function.
+    __starship_get_time() {
+        STARSHIP_CAPTURED_TIME=$(::STARSHIP:: time)
+    }
+else
+    zmodload zsh/datetime
+    zmodload zsh/mathfunc
+    __starship_get_time() {
+        ((STARSHIP_CAPTURED_TIME = int(rint($EPOCHREALTIME * 1000))))
+    }
+fi
+
 # Will be run before every prompt draw
 starship_precmd() {
     # Save the status, because commands in this pipeline will change $?
@@ -24,8 +38,8 @@ starship_precmd() {
     # Compute cmd_duration, if we have a time to consume, otherwise clear the
     # previous duration
     if [[ -n "${STARSHIP_START_TIME+1}" ]]; then
-        STARSHIP_END_TIME=$(::STARSHIP:: time)
-        STARSHIP_DURATION=$((STARSHIP_END_TIME - STARSHIP_START_TIME))
+        __starship_get_time && STARSHIP_END_TIME=$STARSHIP_CAPTURED_TIME
+        ((STARSHIP_DURATION = STARSHIP_END_TIME - STARSHIP_START_TIME))
         unset STARSHIP_START_TIME
     else
         unset STARSHIP_DURATION
@@ -35,7 +49,7 @@ starship_precmd() {
     starship_render
 }
 starship_preexec() {
-    STARSHIP_START_TIME=$(::STARSHIP:: time)
+    __starship_get_time && STARSHIP_START_TIME=$STARSHIP_CAPTURED_TIME
 }
 
 # If precmd/preexec arrays are not already set, set them. If we don't do this,
@@ -74,7 +88,8 @@ else
     zle -N zle-keymap-select starship_zle-keymap-select-wrapped;
 fi
 
-STARSHIP_START_TIME=$(::STARSHIP:: time)
+__starship_get_time && STARSHIP_START_TIME=$STARSHIP_CAPTURED_TIME
+
 export STARSHIP_SHELL="zsh"
 
 # Set up the session key that will be used to store logs
-- 
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