cpuinfo: read data in place

Instead of reading the data to the buffer, then making a reader and a
scanner out of that buffer, let's analyze the data as we read it line by
line.

Signed-off-by: Kir Kolyshkin <[email protected]>

Author: kolyshkin

cpuinfo.go

@@ -17,13 +17,12 @@ package procfs
 
 import (
 	"bufio"
-	"bytes"
 	"errors"
+	"io"
+	"os"
 	"regexp"
 	"strconv"
 	"strings"
-
-	"github.com/prometheus/procfs/internal/util"
 )
 
 // CPUInfo contains general information about a system CPU found in /proc/cpuinfo
@@ -64,15 +63,16 @@ var (
 // CPUInfo returns information about current system CPUs.
 // See https://www.kernel.org/doc/Documentation/filesystems/proc.txt
 func (fs FS) CPUInfo() ([]CPUInfo, error) {
-	data, err := util.ReadFileNoStat(fs.proc.Path("cpuinfo"))
+	file, err := os.Open(fs.proc.Path("cpuinfo"))
 	if err != nil {
 		return nil, err
 	}
-	return parseCPUInfo(data)
+	defer file.Close()
+	return parseCPUInfo(file)
 }
 
-func parseCPUInfoX86(info []byte) ([]CPUInfo, error) {
-	scanner := bufio.NewScanner(bytes.NewReader(info))
+func parseCPUInfoX86(info io.Reader) ([]CPUInfo, error) {
+	scanner := bufio.NewScanner(info)
 
 	// find the first "processor" line
 	firstLine := firstNonEmptyLine(scanner)
@@ -186,8 +186,8 @@ func parseCPUInfoX86(info []byte) ([]CPUInfo, error) {
 	return cpuinfo, nil
 }
 
-func parseCPUInfoARM(info []byte) ([]CPUInfo, error) {
-	scanner := bufio.NewScanner(bytes.NewReader(info))
+func parseCPUInfoARM(info io.Reader) ([]CPUInfo, error) {
+	scanner := bufio.NewScanner(info)
 
 	cpuinfo := []CPUInfo{}
 	i := -1
@@ -233,8 +233,8 @@ func parseCPUInfoARM(info []byte) ([]CPUInfo, error) {
 	return cpuinfo, nil
 }
 
-func parseCPUInfoS390X(info []byte) ([]CPUInfo, error) {
-	scanner := bufio.NewScanner(bytes.NewReader(info))
+func parseCPUInfoS390X(info io.Reader) ([]CPUInfo, error) {
+	scanner := bufio.NewScanner(info)
 
 	firstLine := firstNonEmptyLine(scanner)
 	if !strings.HasPrefix(firstLine, "vendor_id") || !strings.Contains(firstLine, ":") {
@@ -301,8 +301,8 @@ func parseCPUInfoS390X(info []byte) ([]CPUInfo, error) {
 	return cpuinfo, nil
 }
 
-func parseCPUInfoPPC(info []byte) ([]CPUInfo, error) {
-	scanner := bufio.NewScanner(bytes.NewReader(info))
+func parseCPUInfoPPC(info io.Reader) ([]CPUInfo, error) {
+	scanner := bufio.NewScanner(info)
 
 	firstLine := firstNonEmptyLine(scanner)
 	if !strings.HasPrefix(firstLine, "processor") || !strings.Contains(firstLine, ":") {

cpuinfo_test.go

@@ -15,7 +15,10 @@
 
 package procfs
 
-import "testing"
+import (
+	"strings"
+	"testing"
+)
 
 const (
 	cpuinfoArm7 = `Processor : ARMv7 Processor rev 5 (v7l)
@@ -160,7 +163,7 @@ func TestCPUInfoX86(t *testing.T) {
 }
 
 func TestCPUInfoParseARM(t *testing.T) {
-	cpuinfo, err := parseCPUInfoARM([]byte(cpuinfoArm7))
+	cpuinfo, err := parseCPUInfoARM(strings.NewReader(cpuinfoArm7))
 	if err != nil || cpuinfo == nil {
 		t.Fatalf("unable to parse arm cpu info: %v", err)
 	}
@@ -176,7 +179,7 @@ func TestCPUInfoParseARM(t *testing.T) {
 }
 
 func TestCPUInfoParseARMNew(t *testing.T) {
-	cpuinfo, err := parseCPUInfoARM([]byte(cpuinfoArm7New))
+	cpuinfo, err := parseCPUInfoARM(strings.NewReader(cpuinfoArm7New))
 	if err != nil || cpuinfo == nil {
 		t.Fatalf("unable to parse arm cpu info: %v", err)
 	}
@@ -191,7 +194,7 @@ func TestCPUInfoParseARMNew(t *testing.T) {
 	}
 }
 func TestCPUInfoParseS390X(t *testing.T) {
-	cpuinfo, err := parseCPUInfoS390X([]byte(cpuinfoS390x))
+	cpuinfo, err := parseCPUInfoS390X(strings.NewReader(cpuinfoS390x))
 	if err != nil || cpuinfo == nil {
 		t.Fatalf("unable to parse s390x cpu info: %v", err)
 	}
@@ -210,7 +213,7 @@ func TestCPUInfoParseS390X(t *testing.T) {
 }
 
 func TestCPUInfoParsePPC(t *testing.T) {
-	cpuinfo, err := parseCPUInfoPPC([]byte(cpuinfoPpc64))
+	cpuinfo, err := parseCPUInfoPPC(strings.NewReader(cpuinfoPpc64))
 	if err != nil || cpuinfo == nil {
 		t.Fatalf("unable to parse ppc cpu info: %v", err)
 	}