Move parsing functions to pkg/parsers and the specific kernel handling

functions to pkg/parsers/kernel, and parsing filters to
pkg/parsers/filter. Adjust imports and package references.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)

parsers/kernel/kernel.go

@@ -0,0 +1,93 @@
+package kernel
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+)
+
+type KernelVersionInfo struct {
+	Kernel int
+	Major  int
+	Minor  int
+	Flavor string
+}
+
+func (k *KernelVersionInfo) String() string {
+	return fmt.Sprintf("%d.%d.%d%s", k.Kernel, k.Major, k.Minor, k.Flavor)
+}
+
+// Compare two KernelVersionInfo struct.
+// Returns -1 if a < b, 0 if a == b, 1 it a > b
+func CompareKernelVersion(a, b *KernelVersionInfo) int {
+	if a.Kernel < b.Kernel {
+		return -1
+	} else if a.Kernel > b.Kernel {
+		return 1
+	}
+
+	if a.Major < b.Major {
+		return -1
+	} else if a.Major > b.Major {
+		return 1
+	}
+
+	if a.Minor < b.Minor {
+		return -1
+	} else if a.Minor > b.Minor {
+		return 1
+	}
+
+	return 0
+}
+
+func GetKernelVersion() (*KernelVersionInfo, error) {
+	var (
+		err error
+	)
+
+	uts, err := uname()
+	if err != nil {
+		return nil, err
+	}
+
+	release := make([]byte, len(uts.Release))
+
+	i := 0
+	for _, c := range uts.Release {
+		release[i] = byte(c)
+		i++
+	}
+
+	// Remove the \x00 from the release for Atoi to parse correctly
+	release = release[:bytes.IndexByte(release, 0)]
+
+	return ParseRelease(string(release))
+}
+
+func ParseRelease(release string) (*KernelVersionInfo, error) {
+	var (
+		kernel, major, minor, parsed int
+		flavor, partial              string
+	)
+
+	// Ignore error from Sscanf to allow an empty flavor.  Instead, just
+	// make sure we got all the version numbers.
+	parsed, _ = fmt.Sscanf(release, "%d.%d%s", &kernel, &major, &partial)
+	if parsed < 2 {
+		return nil, errors.New("Can't parse kernel version " + release)
+	}
+
+	// sometimes we have 3.12.25-gentoo, but sometimes we just have 3.12-1-amd64
+	parsed, _ = fmt.Sscanf(partial, ".%d%s", &minor, &flavor)
+	if parsed < 1 {
+		flavor = partial
+	}
+
+	return &KernelVersionInfo{
+		Kernel: kernel,
+		Major:  major,
+		Minor:  minor,
+		Flavor: flavor,
+	}, nil
+}