golang/xenlight: begin Go to C type marshaling

Implement conversions for basic types such as strings and integer
types in toC functions.

Modify function signatures of toC implementations for builtin
types to be consistent with the signature of the generated toC
functions.

Signed-off-by: Nick Rosbrook <rosbrookn@ainfosec.com>
Reviewed-by: George Dunlap <george.dunlap@citrix.com>

tools/golang/xenlight/gengotypes.py

@@ -234,6 +234,9 @@ def xenlight_golang_generate_helpers(path = None, types = None, comment = None):
                 f.write(extra)
                 f.write('\n')
 
+            f.write(xenlight_golang_define_to_C(ty))
+            f.write('\n')
+
     go_fmt(path)
 
 def xenlight_golang_define_from_C(ty = None):
@@ -434,6 +437,84 @@ def xenlight_golang_array_from_C(ty = None):
 
     return s
 
+def xenlight_golang_define_to_C(ty = None, typename = None, nested = False):
+    """
+    Define the toC marshaling function for the type
+    represented by ty.
+    """
+    func = 'func (x *{}) toC(xc *C.{}) (err error){{{}\n return nil \n }}\n'
+    body = ''
+
+    if ty.dispose_fn is not None:
+        body += 'defer func(){{\nif err != nil{{\nC.{}(xc)}}\n}}()\n\n'.format(ty.dispose_fn)
+
+    goname = xenlight_golang_fmt_name(ty.typename)
+    cname  = ty.typename
+
+    for f in ty.fields:
+        if f.type.typename is not None:
+            if isinstance(f.type, idl.Array):
+                # TODO
+                continue
+
+            body += xenlight_golang_convert_to_C(f)
+
+        elif isinstance(f.type, idl.Struct):
+            for nf in f.type.fields:
+                body += xenlight_golang_convert_to_C(nf, outer_name=f.name)
+
+        elif isinstance(f.type, idl.KeyedUnion):
+            # TODO
+            pass
+
+        else:
+            raise Exception('type {} not supported'.format(f.type))
+
+    return func.format(goname, cname, body)
+
+def xenlight_golang_convert_to_C(ty = None, outer_name = None):
+    """
+    Returns a line of Go code that converts the Go type represented
+    by ty to its corresponding Go type.
+
+    If outer_name is set, the type is treated as nested within another field
+    named outer_name.
+    """
+    s = ''
+
+    gotypename = xenlight_golang_fmt_name(ty.type.typename)
+    ctypename  = ty.type.typename
+    goname     = xenlight_golang_fmt_name(ty.name)
+    cname      = ty.name
+
+    # In cgo, C names that conflict with Go keywords can be
+    # accessed by prepending an underscore to the name.
+    if cname in go_keywords:
+        cname = '_' + cname
+
+    # If outer_name is set, treat this as nested.
+    if outer_name is not None:
+        goname = '{}.{}'.format(xenlight_golang_fmt_name(outer_name), goname)
+        cname  = '{}.{}'.format(outer_name, cname)
+
+    is_castable = (ty.type.json_parse_type == 'JSON_INTEGER' or
+                   isinstance(ty.type, idl.Enumeration) or
+                   gotypename in go_builtin_types)
+
+    if not is_castable:
+        s += 'if err := x.{}.toC(&xc.{}); err != nil {{\n'.format(goname,cname)
+        s += 'return err\n}\n'
+
+    elif gotypename == 'string':
+        # Use the cgo helper for converting C strings.
+        s += 'if x.{} != "" {{\n'.format(goname)
+        s += 'xc.{} = C.CString(x.{})}}\n'.format(cname,goname)
+
+    else:
+        s += 'xc.{} = C.{}(x.{})\n'.format(cname,ctypename,goname)
+
+    return s
+
 def xenlight_golang_fmt_name(name, exported = True):
     """
     Take a given type name and return an

tools/golang/xenlight/xenlight.go

@@ -140,14 +140,12 @@ func (u *Uuid) fromC(c *C.libxl_uuid) error {
 	return nil
 }
 
-func (u *Uuid) toC() (C.libxl_uuid, error) {
-	var c C.libxl_uuid
-
+func (u *Uuid) toC(cu *C.libxl_uuid) error {
 	for i, v := range u {
-		c.uuid[i] = C.uint8_t(v)
+		cu.uuid[i] = C.uint8_t(v)
 	}
 
-	return c, nil
+	return nil
 }
 
 // defboolVal represents a defbool value.
@@ -232,15 +230,13 @@ func (d *Defbool) fromC(c *C.libxl_defbool) error {
 	return nil
 }
 
-func (d *Defbool) toC() (C.libxl_defbool, error) {
-	var c C.libxl_defbool
-
+func (d *Defbool) toC(cd *C.libxl_defbool) error {
 	if !d.IsDefault() {
 		val, _ := d.Val()
-		C.libxl_defbool_set(&c, C.bool(val))
+		C.libxl_defbool_set(cd, C.bool(val))
 	}
 
-	return c, nil
+	return nil
 }
 
 // Mac represents a libxl_mac, or simply a MAC address.
@@ -266,14 +262,12 @@ func (mac *Mac) fromC(cmac *C.libxl_mac) error {
 	return nil
 }
 
-func (mac Mac) toC() (C.libxl_mac, error) {
-	var cmac C.libxl_mac
-
+func (mac Mac) toC(cm *C.libxl_mac) error {
 	for i, v := range mac {
-		cmac[i] = C.uint8_t(v)
+		(*cm)[i] = C.uint8_t(v)
 	}
 
-	return cmac, nil
+	return nil
 }
 
 // MsVmGenid represents a libxl_ms_vm_genid.
@@ -287,14 +281,12 @@ func (mvg *MsVmGenid) fromC(cmvg *C.libxl_ms_vm_genid) error {
 	return nil
 }
 
-func (mvg *MsVmGenid) toC() (C.libxl_ms_vm_genid, error) {
-	var cmvg C.libxl_ms_vm_genid
-
+func (mvg *MsVmGenid) toC(cmvg *C.libxl_ms_vm_genid) error {
 	for i, v := range mvg {
 		cmvg.bytes[i] = C.uint8_t(v)
 	}
 
-	return cmvg, nil
+	return nil
 }
 
 // EvLink represents a libxl_ev_link.
@@ -304,8 +296,8 @@ func (mvg *MsVmGenid) toC() (C.libxl_ms_vm_genid, error) {
 // through the Go package.
 type EvLink struct{}
 
-func (el *EvLink) fromC(cel *C.libxl_ev_link) error      { return nil }
-func (el *EvLink) toC() (cel C.libxl_ev_link, err error) { return }
+func (el *EvLink) fromC(cel *C.libxl_ev_link) error     { return nil }
+func (el *EvLink) toC(cel *C.libxl_ev_link) (err error) { return }
 
 // CpuidPolicyList represents a libxl_cpuid_policy_list.
 //
@@ -316,20 +308,18 @@ type CpuidPolicyList string
 
 func (cpl CpuidPolicyList) fromC(ccpl *C.libxl_cpuid_policy_list) error { return nil }
 
-func (cpl CpuidPolicyList) toC() (C.libxl_cpuid_policy_list, error) {
-	var ccpl C.libxl_cpuid_policy_list
-
+func (cpl CpuidPolicyList) toC(ccpl *C.libxl_cpuid_policy_list) error {
 	s := C.CString(string(cpl))
 	defer C.free(unsafe.Pointer(s))
 
-	ret := C.libxl_cpuid_parse_config(&ccpl, s)
+	ret := C.libxl_cpuid_parse_config(ccpl, s)
 	if ret != 0 {
-		C.libxl_cpuid_dispose(&ccpl)
+		C.libxl_cpuid_dispose(ccpl)
 
-		return ccpl, Error(-ret)
+		return Error(-ret)
 	}
 
-	return ccpl, nil
+	return nil
 }
 
 // Hwcap represents a libxl_hwcap.
@@ -343,14 +333,12 @@ func (hwcap *Hwcap) fromC(chwcap *C.libxl_hwcap) error {
 	return nil
 }
 
-func (hwcap *Hwcap) toC() (C.libxl_hwcap, error) {
-	var chwcap C.libxl_hwcap
-
+func (hwcap *Hwcap) toC(chwcap *C.libxl_hwcap) error {
 	for i, v := range hwcap {
-		chwcap[i] = C.uint32_t(v)
+		(*chwcap)[i] = C.uint32_t(v)
 	}
 
-	return chwcap, nil
+	return nil
 }
 
 // KeyValueList represents a libxl_key_value_list.
@@ -360,8 +348,8 @@ func (hwcap *Hwcap) toC() (C.libxl_hwcap, error) {
 // Go package.
 type KeyValueList struct{}
 
-func (kvl KeyValueList) fromC(ckvl *C.libxl_key_value_list) error      { return nil }
-func (kvl KeyValueList) toC() (ckvl C.libxl_key_value_list, err error) { return }
+func (kvl KeyValueList) fromC(ckvl *C.libxl_key_value_list) error     { return nil }
+func (kvl KeyValueList) toC(ckvl *C.libxl_key_value_list) (err error) { return }
 
 // StringList represents a libxl_string_list.
 type StringList []string
@@ -379,17 +367,17 @@ func (sl *StringList) fromC(csl *C.libxl_string_list) error {
 	return nil
 }
 
-func (sl StringList) toC() (C.libxl_string_list, error) {
+func (sl StringList) toC(csl *C.libxl_string_list) error {
 	var char *C.char
 	size := len(sl)
-	csl := (C.libxl_string_list)(C.malloc(C.ulong(size) * C.ulong(unsafe.Sizeof(char))))
+	*csl = (C.libxl_string_list)(C.malloc(C.ulong(size) * C.ulong(unsafe.Sizeof(char))))
 	clist := (*[1 << 30]*C.char)(unsafe.Pointer(csl))[:size:size]
 
 	for i, v := range sl {
 		clist[i] = C.CString(v)
 	}
 
-	return csl, nil
+	return nil
 }
 
 // Bitmap represents a libxl_bitmap.
@@ -421,9 +409,7 @@ func (bm *Bitmap) fromC(cbm *C.libxl_bitmap) error {
 	return nil
 }
 
-func (bm *Bitmap) toC() (C.libxl_bitmap, error) {
-	var cbm C.libxl_bitmap
-
+func (bm *Bitmap) toC(cbm *C.libxl_bitmap) error {
 	size := len(bm.bitmap)
 	cbm.size = C.uint32_t(size)
 	cbm._map = (*C.uint8_t)(C.malloc(C.ulong(cbm.size) * C.sizeof_uint8_t))
@@ -431,7 +417,7 @@ func (bm *Bitmap) toC() (C.libxl_bitmap, error) {
 
 	copy(cs, bm.bitmap)
 
-	return cbm, nil
+	return nil
 }
 
 func (sr ShutdownReason) String() (str string) {
@@ -534,8 +520,8 @@ func (Ctx *Context) CpupoolCreate(Name string, Scheduler Scheduler, Cpumap Bitma
 	var uuid C.libxl_uuid
 	C.libxl_uuid_generate(&uuid)
 
-	cbm, err := Cpumap.toC()
-	if err != nil {
+	var cbm C.libxl_bitmap
+	if err = Cpumap.toC(&cbm); err != nil {
 		return
 	}
 	defer C.libxl_bitmap_dispose(&cbm)
@@ -577,8 +563,8 @@ func (Ctx *Context) CpupoolCpuadd(Poolid uint32, Cpu int) (err error) {
 // int libxl_cpupool_cpuadd_cpumap(libxl_ctx *ctx, uint32_t poolid,
 //                                 const libxl_bitmap *cpumap);
 func (Ctx *Context) CpupoolCpuaddCpumap(Poolid uint32, Cpumap Bitmap) (err error) {
-	cbm, err := Cpumap.toC()
-	if err != nil {
+	var cbm C.libxl_bitmap
+	if err = Cpumap.toC(&cbm); err != nil {
 		return
 	}
 	defer C.libxl_bitmap_dispose(&cbm)
@@ -606,8 +592,8 @@ func (Ctx *Context) CpupoolCpuremove(Poolid uint32, Cpu int) (err error) {
 // int libxl_cpupool_cpuremove_cpumap(libxl_ctx *ctx, uint32_t poolid,
 //                                    const libxl_bitmap *cpumap);
 func (Ctx *Context) CpupoolCpuremoveCpumap(Poolid uint32, Cpumap Bitmap) (err error) {
-	cbm, err := Cpumap.toC()
-	if err != nil {
+	var cbm C.libxl_bitmap
+	if err = Cpumap.toC(&cbm); err != nil {
 		return
 	}
 	defer C.libxl_bitmap_dispose(&cbm)