-speed: print cpu model

When somebody posts "gocryptfs -speed" results, they are
most helpful together with the CPU model. Add the cpu model
to the output.

Example:

$ ./gocryptfs -speed
gocryptfs v2.2.0-beta1-5-g52b0444-dirty; go-fuse v2.1.1-0.20210825171523-3ab5d95a30ae; 2021-09-14 go1.17.1 linux/amd64
cpu: Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz; with AES acceleration
AES-GCM-256-OpenSSL       	 862.79 MB/s
AES-GCM-256-Go            	 997.71 MB/s	(selected in auto mode)
AES-SIV-512-Go            	 159.58 MB/s
XChaCha20-Poly1305-OpenSSL	 729.65 MB/s
XChaCha20-Poly1305-Go     	 843.97 MB/s	(selected in auto mode)

1 files changed, 54 insertions, 0 deletions

diff --git a/internal/speed/cpuinfo.go b/internal/speed/cpuinfo.go
new file mode 100644
index 0000000..09e7a89
--- /dev/null
+++ b/internal/speed/cpuinfo.go
@@ -0,0 +1,54 @@
+package speed
+
+import (
+	"io/ioutil"
+	"os"
+	"runtime"
+	"strings"
+)
+
+// cpuModelName returns the "model name" acc. to /proc/cpuinfo, or ""
+// on error.
+//
+// Examples: On my desktop PC:
+//
+//   $ grep "model name" /proc/cpuinfo
+//   model name	: Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz
+//
+// --> Returns "Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz".
+//
+// On a Raspberry Pi 4:
+//
+//   $ grep "model name" /proc/cpuinfo
+//   (empty)
+//   $ grep Hardware /proc/cpuinfo
+//   Hardware	: BCM2835
+//
+// --> Returns "BCM2835"
+func cpuModelName() string {
+	if runtime.GOOS != "linux" {
+		return ""
+	}
+	f, err := os.Open("/proc/cpuinfo")
+	if err != nil {
+		return ""
+	}
+	content, err := ioutil.ReadAll(f)
+	if err != nil {
+		return ""
+	}
+	lines := strings.Split(string(content), "\n")
+	// Look for "model name", then for "Hardware" (arm devices don't have "model name")
+	for _, want := range []string{"model name", "Hardware"} {
+		for _, line := range lines {
+			if strings.HasPrefix(line, want) {
+				parts := strings.SplitN(line, ":", 2)
+				if len(parts) != 2 {
+					continue
+				}
+				return strings.TrimSpace(parts[1])
+			}
+		}
+	}
+	return ""
+}