Add a Swift backend for LibertyXDR

CMakeLists.txt

@@ -72,7 +72,7 @@ add_test (test-cmake-parser
 # Test protocol code generation
 set (lxdrgen_outputs)
 set (lxdrgen_base "${PROJECT_BINARY_DIR}/lxdrgen.lxdr")
-foreach (backend c go mjs)
+foreach (backend c go mjs swift)
 	list (APPEND lxdrgen_outputs ${lxdrgen_base}.${backend})
 	add_custom_command (OUTPUT ${lxdrgen_base}.${backend}
 		COMMAND env LC_ALL=C awk
@@ -108,3 +108,11 @@ if (NODE_EXECUTABLE)
 else ()
 	message (WARNING "Cannot test generated protocol code for Javascript")
 endif ()
+
+find_program (SWIFTC_EXECUTABLE swiftc)
+if (SWIFTC_EXECUTABLE)
+	add_test (test-lxdrgen-swift
+		${SWIFTC_EXECUTABLE} -typecheck ${lxdrgen_base}.swift)
+else ()
+	message (WARNING "Cannot test generated protocol code for Swift")
+endif ()

README.adoc

@@ -54,6 +54,9 @@ lxdrgen-mjs.awk::
 	LibertyXDR backend for Javascript, currently for decoding only.
 	It cuts a corner by not using BigInts, on par with `JSON.parse()`.
 
+lxdrgen-swift.awk::
+	LibertyXDR backend for the Swift programming language.
+
 Contributing and Support
 ------------------------
 Use https://git.janouch.name/p/liberty to report any bugs, request features,

tools/lxdrgen-go.awk

@@ -441,7 +441,7 @@ function codegen_struct(name, cg,    gotype) {
 
 function codegen_union_tag(d, cg) {
 	cg["tagtype"] = d["type"]
-	cg["tagname"] = d["name"]
+	cg["tagname"] = snaketocamel(d["name"])
 	# The tag is implied from the type of struct stored in the interface.
 }
 
@@ -450,8 +450,8 @@ function codegen_union_struct(name, casename, cg, scg,     structname, init) {
 	structname = name snaketocamel(casename)
 	codegen_struct(structname, scg)
 
-	init = CodegenGoType[structname] "{" snaketocamel(cg["tagname"]) \
+	init = CodegenGoType[structname] "{" cg["tagname"] \
-		": " decapitalize(snaketocamel(cg["tagname"])) "}"
+		": " decapitalize(cg["tagname"]) "}"
 	append(cg, "unmarshal",
 		"\tcase " CodegenGoType[cg["tagtype"]] snaketocamel(casename) ":\n" \
 		"\t\ts := " init "\n" \
@@ -467,7 +467,7 @@ function codegen_union_struct(name, casename, cg, scg,     structname, init) {
 		"\t\tu.Interface = &s\n")
 }
 
-function codegen_union(name, cg,    gotype, tagfield, tagvar) {
+function codegen_union(name, cg,    gotype, tagvar) {
 	gotype = PrefixCamel name
 	print "type " gotype " struct {"
 	print "\tInterface any"
@@ -481,18 +481,17 @@ function codegen_union(name, cg,    gotype, tagfield, tagvar) {
 	print "}"
 	print ""
 
-	tagfield = snaketocamel(cg["tagname"])
+	tagvar = decapitalize(cg["tagname"])
-	tagvar = decapitalize(tagfield)
 	print "func (u *" gotype ") UnmarshalJSON(data []byte) (err error) {"
 	print "\tvar t struct {"
-	print "\t\t" tagfield " " CodegenGoType[cg["tagtype"]] \
+	print "\t\t" cg["tagname"] " " CodegenGoType[cg["tagtype"]] \
 		" `json:\"" tagvar "\"`"
 	print "\t}"
 	print "\tif err := json.Unmarshal(data, &t); err != nil {"
 	print "\t\treturn err"
 	print "\t}"
 	print ""
-	print "\tswitch " tagvar " := t." tagfield "; " tagvar " {"
+	print "\tswitch " tagvar " := t." cg["tagname"] "; " tagvar " {"
 	print cg["unmarshal"] "\tdefault:"
 	print "\t\terr = errors.New(`unsupported value: ` + " tagvar ".String())"
 	print "\t}"

tools/lxdrgen-mjs.awk

@@ -185,14 +185,14 @@ function codegen_struct(name, cg) {
 
 function codegen_union_tag(d, cg) {
 	cg["tagtype"] = d["type"]
-	cg["tagname"] = d["name"]
+	cg["tagname"] = decapitalize(snaketocamel(d["name"]))
 }
 
 function codegen_union_struct(name, casename, cg, scg,     structname) {
 	append(scg, "methods",
 		"\n" \
 		"\tconstructor() {\n" \
-		"\t\tthis." decapitalize(snaketocamel(cg["tagname"])) \
+		"\t\tthis." cg["tagname"] \
 			" = " cg["tagtype"] "." snaketocamel(casename) "\n" \
 		"\t}\n")
 
@@ -209,7 +209,7 @@ function codegen_union_struct(name, casename, cg, scg,     structname) {
 }
 
 function codegen_union(name, cg,    tagvar) {
-	tagvar = decapitalize(snaketocamel(cg["tagname"]))
+	tagvar = cg["tagname"]
 
 	print ""
 	print "export function deserialize" name "(r) {"

tools/lxdrgen-swift.awk

@@ -0,0 +1,276 @@
+# lxdrgen-swift.awk: Swift backend for lxdrgen.awk.
+#
+# Copyright (c) 2023, Přemysl Eric Janouch <p@janouch.name>
+# SPDX-License-Identifier: 0BSD
+
+function define_internal(name, swifttype) {
+	Types[name] = "internal"
+	CodegenSwiftType[name] = swifttype
+	CodegenDeserialize[name] = "%s.read()"
+}
+
+function define_sint(size,    shortname, swifttype) {
+	shortname = "i" size
+	swifttype = "Int" size
+	define_internal(shortname, swifttype)
+}
+
+function define_uint(size,    shortname, swifttype) {
+	shortname = "u" size
+	swifttype = "UInt" size
+	define_internal(shortname, swifttype)
+}
+
+function codegen_begin() {
+	define_sint("8")
+	define_sint("16")
+	define_sint("32")
+	define_sint("64")
+	define_uint("8")
+	define_uint("16")
+	define_uint("32")
+	define_uint("64")
+	define_internal("bool", "Bool")
+	define_internal("string", "String")
+
+	print "// Code generated from " FILENAME ". DO NOT EDIT."
+	print "import Foundation"
+	print ""
+	print "public struct RelayReader {"
+	print "\tpublic var data: Data"
+	print ""
+	print "\tpublic enum ReadError: Error {"
+	print "\t\tcase unexpectedEOF"
+	print "\t\tcase invalidEncoding"
+	print "\t\tcase overflow"
+	print "\t\tcase unexpectedValue"
+	print "\t}"
+	print ""
+	print "\tpublic mutating func read<T: FixedWidthInteger>() throws -> T {"
+	print "\t\tlet size = MemoryLayout<T>.size"
+	print "\t\tguard data.count >= size else {"
+	print "\t\t\tthrow ReadError.unexpectedEOF"
+	print "\t\t}"
+	print "\t\tvar acc: T = 0"
+	print "\t\tdata.prefix(size).forEach { acc = acc << 8 | T($0) }"
+	print "\t\tdata = data.dropFirst(size)"
+	print "\t\treturn acc"
+	print "\t}"
+	print ""
+	print "\tpublic mutating func read() throws -> Bool {"
+	print "\t\ttry read() != UInt8(0)"
+	print "\t}"
+	print ""
+	print "\tpublic mutating func read() throws -> String {"
+	print "\t\tlet size: UInt32 = try self.read()"
+	print "\t\tguard let count = Int(exactly: size) else {"
+	print "\t\t\tthrow ReadError.overflow"
+	print "\t\t}"
+	print "\t\tguard data.count >= count else {"
+	print "\t\t\tthrow ReadError.unexpectedEOF"
+	print "\t\t}"
+	print "\t\tdefer {"
+	print "\t\t\tdata = data.dropFirst(count)"
+	print "\t\t}"
+	print "\t\tif let s = String(data: data.prefix(count), encoding: .utf8) {"
+	print "\t\t\treturn s"
+	print "\t\t} else {"
+	print "\t\t\tthrow ReadError.invalidEncoding"
+	print "\t\t}"
+	print "\t}"
+	print ""
+	print "\tpublic mutating func read<" \
+		"T: RawRepresentable<Int8>>() throws -> T {"
+	print "\t\tguard let value = T(rawValue: try read()) else {"
+	print "\t\t\tthrow ReadError.unexpectedValue"
+	print "\t\t}"
+	print "\t\treturn value"
+	print "\t}"
+	print ""
+	print "\tpublic mutating func read<T>("
+	print "\t\t\t_ read: (inout Self) throws -> T) throws -> [T] {"
+	print "\t\tlet size: UInt32 = try self.read()"
+	print "\t\tguard let count = Int(exactly: size) else {"
+	print "\t\t\tthrow ReadError.overflow"
+	print "\t\t}"
+	print "\t\tvar array = [T]()"
+	print "\t\tarray.reserveCapacity(count)"
+	print "\t\tfor _ in 0..<count {"
+	print "\t\t\tarray.append(try read(&self))"
+	print "\t\t}"
+	print "\t\treturn array"
+	print "\t}"
+	print "}"
+	print ""
+	print "public struct RelayWriter {"
+	print "\tpublic var data = Data()"
+	print ""
+	print "\tpublic mutating func append<T: FixedWidthInteger>(_ number: T) {"
+	print "\t\tvar n = number.byteSwapped"
+	print "\t\tfor _ in 0..<MemoryLayout<T>.size {"
+	print "\t\t\tdata.append(UInt8(truncatingIfNeeded: n))"
+	print "\t\t\tn >>= 8"
+	print "\t\t}"
+	print "\t}"
+	print ""
+	print "\tpublic mutating func append(_ bool: Bool) {"
+	print "\t\tappend(UInt8(bool ? 1 : 0))"
+	print "\t}"
+	print ""
+	print "\tpublic mutating func append(_ string: String) {"
+	print "\t\tlet bytes = string.data(using: .utf8)!"
+	print "\t\tappend(UInt32(bytes.count))"
+	print "\t\tdata.append(bytes)"
+	print "\t}"
+	print ""
+	print "\tpublic mutating func append<" \
+		"T: RawRepresentable<Int8>>(_ value: T) {"
+	print "\t\tappend(value.rawValue)"
+	print "\t}"
+	print ""
+	print "\tpublic mutating func append<T>("
+	print "\t\t\t_ array: Array<T>, _ write: (inout Self, T) -> ()) {"
+	print "\t\tappend(UInt32(array.count))"
+	print "\t\tfor i in 0..<array.count {"
+	print "\t\t\twrite(&self, array[i])"
+	print "\t\t}"
+	print "\t}"
+	print ""
+	print "\tpublic mutating func append<T: RelayEncodable>(_ value: T) {"
+	print "\t\tvalue.encode(to: &self)"
+	print "\t}"
+	print "}"
+	print ""
+	print "public protocol RelayEncodable { " \
+		"func encode(to: inout RelayWriter) }"
+}
+
+function codegen_constant(name, value) {
+	print ""
+	print "public let " decapitalize(PrefixCamel snaketocamel(name)) " = " value
+}
+
+function codegen_enum_value(name, subname, value, cg) {
+	append(cg, "fields",
+		"\tcase " decapitalize(snaketocamel(subname)) " = " value "\n")
+}
+
+function codegen_enum(name, cg,    swifttype) {
+	swifttype = PrefixCamel name
+	print ""
+	print "public enum " swifttype ": Int8 {"
+	print cg["fields"] "}"
+
+	CodegenSwiftType[name] = swifttype
+	CodegenDeserialize[name] = "%s.read()"
+	for (i in cg)
+		delete cg[i]
+}
+
+function codegen_struct_field(d, cg,    camel) {
+	camel = decapitalize(snaketocamel(d["name"]))
+	if (!d["isarray"]) {
+		append(cg, "fields",
+			"\tpublic var " camel ": " CodegenSwiftType[d["type"]] "\n")
+		append(cg, "deserialize",
+			"\t\tself." camel " = try " \
+				sprintf(CodegenDeserialize[d["type"]], "from") "\n")
+		append(cg, "serialize",
+			"\t\tto.append(self." camel ")\n")
+		return
+	}
+
+	append(cg, "fields",
+		"\tpublic var " camel ": [" CodegenSwiftType[d["type"]] "]\n")
+	append(cg, "deserialize",
+		"\t\tself." camel " = try from.read() { r in try " \
+			sprintf(CodegenDeserialize[d["type"]], "r") " }\n")
+	append(cg, "serialize",
+		"\t\tto.append(self." camel ") { (w, value) in w.append(value) }\n")
+}
+
+function codegen_struct_tag(d, cg,    camel) {
+	camel = decapitalize(snaketocamel(d["name"]))
+	append(cg, "serialize",
+		"\t\tto.append(self." camel ")\n")
+}
+
+function codegen_struct(name, cg,    swifttype) {
+	swifttype = PrefixCamel name
+	print ""
+	print "public struct " swifttype " {\n" cg["fields"] "}"
+	print ""
+	print "extension " swifttype ": " PrefixCamel "Encodable {"
+	print "\tpublic init(from: inout RelayReader) throws {"
+	print cg["deserialize"] "\t}"
+	print ""
+	print "\tpublic func encode(to: inout RelayWriter) {"
+	print cg["serialize"] "\t}"
+	print "}"
+
+	CodegenSwiftType[name] = swifttype
+	CodegenDeserialize[name] = "%s.read()"
+	for (i in cg)
+		delete cg[i]
+}
+
+function codegen_union_tag(d, cg) {
+	cg["tagtype"] = d["type"]
+	cg["tagname"] = decapitalize(snaketocamel(d["name"]))
+}
+
+function codegen_union_struct(name, casename, cg, scg,     swifttype) {
+	# And thus not all generated structs are present in Types.
+	swifttype = PrefixCamel name snaketocamel(casename)
+	casename = decapitalize(snaketocamel(casename))
+	print ""
+	print "public struct " swifttype ": " PrefixCamel name " {"
+	print "\tpublic var " cg["tagname"] \
+		": " CodegenSwiftType[cg["tagtype"]] " { ." casename " }"
+	print scg["fields"] "}"
+	print ""
+	print "extension " swifttype ": " PrefixCamel "Encodable {"
+	print "\tfileprivate init(from: inout RelayReader) throws {"
+	print scg["deserialize"] "\t}"
+	print ""
+	print "\tpublic func encode(to: inout RelayWriter) {"
+	print scg["serialize"] "\t}"
+	print "}"
+
+	append(cg, "cases", "\tcase ." casename ":\n" \
+		"\t\treturn try " swifttype "(from: &from)\n")
+
+	CodegenSwiftType[name] = swifttype
+	CodegenDeserialize[name] = "%s.read()"
+	for (i in scg)
+		delete scg[i]
+}
+
+function codegen_union(name, cg,    swifttype, init) {
+	# Classes don't have automatic member-wise initializers,
+	# thus using structs and protocols.
+	swifttype = PrefixCamel name
+	print ""
+	print "public protocol " swifttype ": " PrefixCamel "Encodable {"
+	print "\tvar " cg["tagname"] ": " CodegenSwiftType[cg["tagtype"]] " { get }"
+	print "}"
+
+	init = decapitalize(swifttype)
+	print ""
+	print "public func " init \
+		"(from: inout RelayReader) throws -> " swifttype " {"
+	print "\tlet " cg["tagname"] ": " CodegenSwiftType[cg["tagtype"]] \
+		" = try from.read()"
+	print "\tswitch " cg["tagname"] " {"
+	# TODO: Only generate the default if there are remaining values,
+	# so that swiftc doesn't produce warnings.
+	print cg["cases"] "\tdefault:"
+	print "\t\tthrow RelayReader.ReadError.unexpectedValue"
+	print"\t}"
+	print "}"
+
+	CodegenSwiftType[name] = swifttype
+	CodegenDeserialize[name] = init "(from: &%s)"
+	for (i in cg)
+		delete cg[i]
+}