[gnome-boxes] Add utility function to compare CPU architectures

[Zeeshan Ali Khattak <zeeshanak src gnome org>]

commit fb018a674e7a30a891a65a6c92234d10d1723bc2
Author: Zeeshan Ali (Khattak) <zeeshanak gnome org>
Date:   Wed Jan 16 17:03:03 2013 +0200

    Add utility function to compare CPU architectures
    
    https://bugzilla.gnome.org/show_bug.cgi?id=692246

 src/installer-media.vala |   11 ++++---
 src/util-app.vala        |   69 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+), 5 deletions(-)
---
diff --git a/src/installer-media.vala b/src/installer-media.vala
index 7351505..278d4da 100644
--- a/src/installer-media.vala
+++ b/src/installer-media.vala
@@ -94,11 +94,12 @@ private class Boxes.InstallerMedia : GLib.Object {
     }
 
     public bool is_architecture_compatible (string architecture) {
-        return os_media == null || // Unknown media
-               os_media.architecture == architecture ||
-               (os_media.architecture == "i386" && architecture == "i686") ||
-               (os_media.architecture == "i386" && architecture == "x86_64") ||
-               (os_media.architecture == "i686" && architecture == "x86_64");
+        if (os_media == null) // Unknown media
+            return true;
+
+        var compatibility = compare_cpu_architectures (architecture, os_media.architecture);
+
+        return compatibility != CPUArchCompatibity.INCOMPATIBLE;
     }
 
     protected void add_cd_config (Domain         domain,
diff --git a/src/util-app.vala b/src/util-app.vala
index 674a137..d98f259 100644
--- a/src/util-app.vala
+++ b/src/util-app.vala
@@ -394,6 +394,75 @@ namespace Boxes {
         } catch (IOError.EXISTS error) {}
     }
 
+    // Warning: architecture compability is not computative. e.g "i386" is compatible with "i686" but "i686" is
+    // incompatible with "i386".
+    public enum CPUArchCompatibity {
+        INCOMPATIBLE             = -1, // First architecture is incompatible to second one
+        IDENTICAL                = 0,  // First architecture is identical to second one
+        COMPATIBLE               = 1,  // First architecture is compatible with second one
+        COMPATIBLE_DIFF_WORDSIZE = 2,  // First architecture is more modern than but compatible
+                                      // with second one but has different word-size
+    }
+
+    public CPUArchCompatibity compare_cpu_architectures (string arch1, string arch2) {
+        switch (arch2) {
+        case "i386":
+            switch (arch1) {
+            case "i386":
+                return CPUArchCompatibity.IDENTICAL;
+            case "i486":
+            case "i586":
+            case "i686":
+                return CPUArchCompatibity.COMPATIBLE;
+            case "x86_64":
+                return CPUArchCompatibity.COMPATIBLE_DIFF_WORDSIZE;
+            default:
+                return CPUArchCompatibity.INCOMPATIBLE;
+            }
+        case "i486":
+            switch (arch1) {
+            case "i486":
+                return CPUArchCompatibity.IDENTICAL;
+            case "i586":
+            case "i686":
+                return CPUArchCompatibity.COMPATIBLE;
+            case "x86_64":
+                return CPUArchCompatibity.COMPATIBLE_DIFF_WORDSIZE;
+            default:
+                return CPUArchCompatibity.INCOMPATIBLE;
+            }
+        case "i586":
+            switch (arch1) {
+            case "i586":
+                return CPUArchCompatibity.IDENTICAL;
+            case "i686":
+                return CPUArchCompatibity.COMPATIBLE;
+            case "x86_64":
+                return CPUArchCompatibity.COMPATIBLE_DIFF_WORDSIZE;
+            default:
+                return CPUArchCompatibity.INCOMPATIBLE;
+            }
+        case "i686":
+            switch (arch1) {
+            case "i686":
+                return CPUArchCompatibity.IDENTICAL;
+            case "x86_64":
+                return CPUArchCompatibity.COMPATIBLE_DIFF_WORDSIZE;
+            default:
+                return CPUArchCompatibity.INCOMPATIBLE;
+            }
+        case "x86_64":
+            switch (arch1) {
+            case "x86_64":
+                return CPUArchCompatibity.IDENTICAL;
+            default:
+                return CPUArchCompatibity.INCOMPATIBLE;
+            }
+        default:
+            return CPUArchCompatibity.INCOMPATIBLE;
+        }
+    }
+
     namespace UUID {
         [CCode (cname = "uuid_generate", cheader_filename = "uuid/uuid.h")]
         internal extern static void generate ([CCode (array_length = false)] uchar[] uuid);