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Small optimizations around parsing on linux #138

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Merged
tklauser merged 2 commits into from
Nov 12, 2025
Merged

Small optimizations around parsing on linux #138

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c4488ff
Use strings.SplitSeq
tklauser Nov 12, 2025
cf0bda3
Trim cpu string in countCPURange/listCPURange
tklauser Nov 12, 2025
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10 changes: 7 additions & 3 deletions numcpus_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -47,18 +47,20 @@ func readCPURangeWith[T any](file string, f func(cpus string) (T, error)) (T, er
if err != nil {
return zero, err
}
return f(strings.Trim(string(buf), "\n "))
return f(string(buf))
}

func countCPURange(cpus string) (int, error) {
cpus = strings.Trim(cpus, "\n ")

// Treat empty file as valid. This might be the case if there are no offline CPUs in which
// case /sys/devices/system/cpu/offline is empty.
if cpus == "" {
return 0, nil
}

n := int(0)
for _, cpuRange := range strings.Split(cpus, ",") {
for cpuRange := range strings.SplitSeq(cpus, ",") {
if cpuRange == "" {
return 0, fmt.Errorf("empty CPU range in CPU string %q", cpus)
}
Expand All @@ -84,13 +86,15 @@ func countCPURange(cpus string) (int, error) {
}

func listCPURange(cpus string) ([]int, error) {
cpus = strings.Trim(cpus, "\n ")

// See comment in countCPURange.
if cpus == "" {
return []int{}, nil
}

list := []int{}
for _, cpuRange := range strings.Split(cpus, ",") {
for cpuRange := range strings.SplitSeq(cpus, ",") {
if cpuRange == "" {
return nil, fmt.Errorf("empty CPU range in CPU string %q", cpus)
}
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14 changes: 14 additions & 0 deletions numcpus_linux_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,11 @@ func TestCPURange(t *testing.T) {
wantCount: 0,
wantList: []int{},
},
{
str: "\n",
wantCount: 0,
wantList: []int{},
},
{
str: "0",
wantCount: 1,
Expand Down Expand Up @@ -86,6 +91,11 @@ func TestCPURange(t *testing.T) {
wantCount: 9,
wantList: []int{0, 2, 3, 4, 6, 8, 9, 10, 31},
},
{
str: " 0,2-7\n",
wantCount: 7,
wantList: []int{0, 2, 3, 4, 5, 6, 7},
},
{
str: "invalid",
wantErr: true,
Expand Down Expand Up @@ -130,6 +140,10 @@ func TestCPURange(t *testing.T) {
str: "0,5-3",
wantErr: true,
},
{
str: "0, 5 - 3",
wantErr: true,
},
}

for _, tc := range testCases {
Expand Down