[lxc-devel] [lxd/master] shared: Switch ParseNumberFromFile to simple read

[stgraber on Github]

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From 5796954f6b6a132036714c67d84e0320133bb6d5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Graber?= <stgraber at ubuntu.com>
Date: Wed, 13 Mar 2019 15:59:02 -0400
Subject: [PATCH] shared: Switch ParseNumberFromFile to simple read
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This should avoid some issues with polling /proc

Signed-off-by: Stéphane Graber <stgraber at ubuntu.com>
---
 shared/util.go | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/shared/util.go b/shared/util.go
index 6ff230361e..060b576563 100644
--- a/shared/util.go
+++ b/shared/util.go
@@ -1100,12 +1100,19 @@ func DownloadFileHash(httpClient *http.Client, useragent string, progress func(p
 }
 
 func ParseNumberFromFile(file string) (int64, error) {
-	buf, err := ioutil.ReadFile(file)
+	f, err := os.Open(file)
+	if err != nil {
+		return int64(0), err
+	}
+	defer f.Close()
+
+	buf := make ([]byte, 4096)
+	n, err := f.Read(buf)
 	if err != nil {
 		return int64(0), err
 	}
 
-	str := strings.TrimSpace(string(buf))
+	str := strings.TrimSpace(string(buf[0:n]))
 	nr, err := strconv.Atoi(str)
 	if err != nil {
 		return int64(0), err