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Merged
li-feng-sc merged 11 commits into from
Dec 9, 2025
Merged

C++ wrapper classes for generated C API #214

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51f8cad
Generate interace cpp wrapper
kthornberrysc Dec 1, 2025
b36ba69
Generate record cpp wrapper
kthornberrysc Dec 1, 2025
4d45cc8
WIP
kthornberrysc Dec 1, 2025
8a05159
cli arg
kthornberrysc Dec 1, 2025
a0db587
WIP
kthornberrysc Dec 1, 2025
c757fbf
tidy
kthornberrysc Dec 1, 2025
a2e2ceb
tidy
kthornberrysc Dec 1, 2025
bff6f2a
Remove Ref template param
kthornberrysc Dec 3, 2025
da7ef9b
const ref return
kthornberrysc Dec 3, 2025
36fec0e
Ref::get() should return const ref
kthornberrysc Dec 3, 2025
9904962
record make() function
kthornberrysc Dec 3, 2025
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255 changes: 186 additions & 69 deletions src/source/CGenerator.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -44,16 +44,20 @@ class CGenerator(spec: Spec) extends Generator(spec) {

def privateHeader(t: TypeDecl): String = q(spec.cppIncludePrefix + spec.cppFileIdentStyle(t.ident.name) + "." + spec.cppHeaderExt)

private def writeExternCBegin(w: IndentWriter): Unit = {
private def wrapIfCpp(w: IndentWriter, f: IndentWriter => Unit) = {
w.wl("#ifdef __cplusplus")
w.wl("extern \"C\" {")
f(w)
w.wl("#endif // __cplusplus")
}

private def writeExternCEnd(w: IndentWriter): Unit = {
w.wl("#ifdef __cplusplus")
w.wl("} // extern \"C\"")
w.wl("#endif // __cplusplus")
private def wrapExternC(w: IndentWriter, f: IndentWriter => Unit) = {
wrapIfCpp(w, (w: IndentWriter) => {
w.wl("extern \"C\" {")
})
w.wl
f(w)
wrapIfCpp(w, (w: IndentWriter) => {
w.wl("} // extern \"C\"")
})
}

private def writeCFile(origin: String, ident: Ident, ext: String, f: IndentWriter => Unit): Unit = {
Expand All @@ -76,13 +80,7 @@ class CGenerator(spec: Spec) extends Generator(spec) {
publicIncludes.foreach(w.wl)

w.wl

writeExternCBegin(w)
w.wl

header(w)

writeExternCEnd(w)
})

writeCFile(origin, ident, "cpp", (w: IndentWriter) => {
Expand All @@ -99,14 +97,15 @@ class CGenerator(spec: Spec) extends Generator(spec) {
writeCFilePair(origin, ident, List.empty[String], List.empty[String])((w: IndentWriter) => {
val symbolName = resolveSymbolName(ident.name)
val enumCasePrefix = symbolName + "_"
writeDoc(w, doc)
w.w("typedef enum")
w.bracedEnd(s" ${symbolName};") {
writeEnumOptionNone(w, e, idCpp.enum, "=", enumCasePrefix)
writeEnumOptions(w, e, idCpp.enum, "=", enumCasePrefix)
writeEnumOptionAll(w, e, idCpp.enum, "=", enumCasePrefix)
}

wrapExternC(w, (w: IndentWriter) => {
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@kevinthornberry kevinthornberry Dec 1, 2025

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This file is better to review with whitespace ignored as there are some block indentation changes

writeDoc(w, doc)
w.w("typedef enum")
w.bracedEnd(s" ${symbolName};") {
writeEnumOptionNone(w, e, idCpp.enum, "=", enumCasePrefix)
writeEnumOptions(w, e, idCpp.enum, "=", enumCasePrefix)
writeEnumOptionAll(w, e, idCpp.enum, "=", enumCasePrefix)
}
})
}, (w: IndentWriter) => {
})
}
Expand Down Expand Up @@ -151,6 +150,69 @@ class CGenerator(spec: Spec) extends Generator(spec) {
}
}

private def writeCppWrapperClass(ident: Ident, w: IndentWriter, methods: IndentWriter => Unit): Unit = {
val typeName = resolveRefSymbolTypeName(ident)
val cppClassName = ident.name
val cppNamespace = spec.cWrapperCppNamespace.getOrElse(spec.cppNamespace + "::c_wrappers")
wrapIfCpp(w, (w: IndentWriter) => {
w.wl("#include <utility>")
wrapNamespace(w, cppNamespace, (w: IndentWriter) => {
w.w(s"class ${cppClassName}").bracedSemi {
w.wlOutdent("public:")
w.wl
w.wl(s"${cppClassName}(const ${typeName}& ref) : _ref(ref) { djinni_ref_retain(_ref); }")
w.wl(s"${cppClassName}(${typeName}&& ref) noexcept : _ref(std::move(ref)) {}")
w.wl(s"${cppClassName}(const ${cppClassName}& other) : _ref(other._ref) { djinni_ref_retain(_ref); }")
w.wl(s"${cppClassName}(${cppClassName}&& other) : _ref(std::move(other._ref)) { other._ref = nullptr; }")
w.wl(s"~${cppClassName}() { djinni_ref_release(_ref); }")

val assignOps =
s"""${cppClassName}& operator=(const ${cppClassName}& other) {
| if (&other != this) {
| auto old = _ref;
| _ref = other._ref;
| djinni_ref_retain(_ref);
| djinni_ref_release(old);
| }
| return *this;
|}
|${cppClassName}& operator=(${cppClassName}&& other) noexcept {
| if (&other != this) {
| auto old = _ref;
| _ref = other._ref;
| other._ref = nullptr;
|
| djinni_ref_release(old);
| }
| return *this;
|}
|${cppClassName}& operator=(${typeName}&& ref) {
| auto old = _ref;
| _ref = ref;
| djinni_ref_release(old);
| return *this;
|}
|${cppClassName}& operator=(const ${typeName}& ref) {
| auto old = _ref;
| _ref = ref;
| djinni_ref_retain(ref);
| djinni_ref_release(old);
| return *this;
|}""".stripMargin
assignOps.split("\n").toSeq.foreach(line => w.wl(line))

w.wl
w.wl(s"operator const ${typeName}&() const { return _ref; }")
w.wl(s"const ${typeName}& _djinni_ref() const { return _ref; }")
w.wl
methods(w)
w.wlOutdent("private:")
w.wl(s"${typeName} _ref;")
}
})
})
}

override def generateRecord(origin: String, ident: Ident, doc: Doc, params: Seq[TypeParam], r: ast.Record): Unit = {
val selfCpp = cppMarshal.fqTypename(ident, r)

Expand All @@ -162,24 +224,56 @@ class CGenerator(spec: Spec) extends Generator(spec) {
val resolvedConsts = r.consts.map(r => new ResolvedConst(r, typeResolver.resolve(r.ty.resolved)))

writeCFilePair(origin, ident, typeResolver.publicImports.toSeq, typeResolver.privateImports.toSeq)((w: IndentWriter) => {
writeDoc(w, doc)
w.wl(s"""typedef djinni_record_ref ${typeName};""")
w.wl
wrapExternC(w, (w: IndentWriter) => {
writeDoc(w, doc)
w.wl(s"""typedef djinni_record_ref ${typeName};""")
w.wl

w.w(s"""${typeName} ${prefix}_new(""")
writeParamListWithResolvedFields(w, resolvedFields)
w.wl(");")
w.wl
w.w(s"""${typeName} ${prefix}_new(""")
writeParamListWithResolvedFields(w, resolvedFields)
w.wl(");")
w.wl

generateConstsHeader(prefix, resolvedConsts, w)
generateConstsHeader(prefix, resolvedConsts, w)

for (resolvedField <- resolvedFields) {
val fieldName = resolvedField.field.ident.name
val fieldTypename = resolvedField.translator.typename
writeDoc(w, resolvedField.field.doc)
w.wl(s"""${fieldTypename} ${prefix}_get_${fieldName}(${typeName} instance);""")
w.wl(s"""void ${prefix}_set_${fieldName}(${typeName} instance, ${fieldTypename} value);""")
for (resolvedField <- resolvedFields) {
val fieldName = resolvedField.field.ident.name
val fieldTypename = resolvedField.translator.typename
writeDoc(w, resolvedField.field.doc)
w.wl(s"""${fieldTypename} ${prefix}_get_${fieldName}(${typeName} instance);""")
w.wl(s"""void ${prefix}_set_${fieldName}(${typeName} instance, ${fieldTypename} value);""")
w.wl
}
})

if (spec.cWrapperCppNamespace.isDefined) {
w.wl
writeCppWrapperClass(ident, w, (w: IndentWriter) => {
w.w(s"static ${ident.name} make(")
writeParamListWithResolvedFields(w, resolvedFields)
w.w(")")
w.braced {
w.w(s"return ${prefix}_new(")
w.w(resolvedFields.map(p => p.field.ident.name).mkString(", "))
w.wl(");")
}
w.wl
for (resolvedField <- resolvedFields) {
val fieldName = resolvedField.field.ident.name
val fieldTypename = resolvedField.translator.typename
w.w(s"${fieldTypename} ${fieldName}() const")
w.braced {
w.wl(s"return ${prefix}_get_${fieldName}(_ref);")
}
w.wl
w.w(s"${ident.name}& ${fieldName}(${fieldTypename} value)")
w.braced {
w.wl(s"${prefix}_set_${fieldName}(_ref, value);")
w.wl("return *this;")
}
w.wl
}
})
}
}, (w: IndentWriter) => {
w.w(s"""${typeName} ${prefix}_new(""")
Expand Down Expand Up @@ -217,7 +311,6 @@ class CGenerator(spec: Spec) extends Generator(spec) {
}
w.wl
}

})
}

Expand Down Expand Up @@ -327,53 +420,77 @@ class CGenerator(spec: Spec) extends Generator(spec) {
val proxyClassName = s"${resolveSymbolName(ident)}_proxy_class_ref"
val methodDefsStructName = s"${resolveSymbolName(ident)}_method_defs"
writeCFilePair(origin, ident, typeResolver.publicImports.toSeq, typeResolver.privateImports.toSeq)((w: IndentWriter) => {
writeDoc(w, doc)
w.wl(s"""typedef djinni_interface_ref ${typeName};""")
wrapExternC(w, (w: IndentWriter) => {
writeDoc(w, doc)
w.wl(s"""typedef djinni_interface_ref ${typeName};""")

if (i.ext.cc) {
w.wl(s"""typedef djinni_proxy_class_ref ${proxyClassName};""")
w.wl
if (i.ext.cc) {
w.wl(s"""typedef djinni_proxy_class_ref ${proxyClassName};""")
w.wl

w.wl(s"""typedef struct """)
w.bracedEnd(s" ${methodDefsStructName};") {
w.wl(s"""typedef struct """)
w.bracedEnd(s" ${methodDefsStructName};") {

if (resolvedMethods.isEmpty) {
w.wl("void *reserved[1];")
} else {
for (resolvedMethod <- resolvedMethods) {
w.w(s"""${resolvedMethod.retTypename} (*${resolvedMethod.method.ident.name})(""")
writeDelimited(w, "void *" +: resolvedMethod.parameters.map(p => p.translator.typename), ", ")(s => w.w(s))
w.wl(");")
if (resolvedMethods.isEmpty) {
w.wl("void *reserved[1];")
} else {
for (resolvedMethod <- resolvedMethods) {
w.w(s"""${resolvedMethod.retTypename} (*${resolvedMethod.method.ident.name})(""")
writeDelimited(w, "void *" +: resolvedMethod.parameters.map(p => p.translator.typename), ", ")(s => w.w(s))
w.wl(");")
}
}
}
w.wl

w.wl(s"${proxyClassName} ${prefix}_proxy_class_new(const ${methodDefsStructName} *method_defs, djinni_opaque_deallocator opaque_deallocator);")
w.wl
w.wl(s"${typeName} ${prefix}_new(${proxyClassName} proxy_class, void *opaque);")
w.wl("")
} else {
w.wl
}
w.wl

w.wl(s"${proxyClassName} ${prefix}_proxy_class_new(const ${methodDefsStructName} *method_defs, djinni_opaque_deallocator opaque_deallocator);")
w.wl
w.wl(s"${typeName} ${prefix}_new(${proxyClassName} proxy_class, void *opaque);")
w.wl("")
} else {
w.wl
}
generateConstsHeader(prefix, resolvedConsts, w)

generateConstsHeader(prefix, resolvedConsts, w)
for (resolvedMethod <- resolvedMethods) {
writeDoc(w, resolvedMethod.method.doc)
w.w(s"${resolvedMethod.retTypename} ${prefix}_${resolvedMethod.resolvedName}(")

for (resolvedMethod <- resolvedMethods) {
writeDoc(w, resolvedMethod.method.doc)
w.w(s"${resolvedMethod.retTypename} ${prefix}_${resolvedMethod.resolvedName}(")
if (resolvedMethod.method.static) {
writeParamList(w, resolvedMethod.parameters.map(p => (p.translator.typename, p.field.ident.name)))
} else {
writeParamList(w, (typeName, "instance") +: resolvedMethod.parameters.map(p => (p.translator.typename, p.field.ident.name)))
}

if (resolvedMethod.method.static) {
writeParamList(w, resolvedMethod.parameters.map(p => (p.translator.typename, p.field.ident.name)))
} else {
writeParamList(w, (typeName, "instance") +: resolvedMethod.parameters.map(p => (p.translator.typename, p.field.ident.name)))
}
w.wl(");")

w.wl(");")
w.wl
}
})

if (i.ext.cpp && spec.cWrapperCppNamespace.isDefined) {
w.wl
writeCppWrapperClass(ident, w, (w: IndentWriter) => {
for (resolvedMethod <- resolvedMethods) {
if (resolvedMethod.method.static) {
w.w("static ")
}
w.w(s"${resolvedMethod.retTypename} ${resolvedMethod.resolvedName}(")
writeParamList(w, resolvedMethod.parameters.map(p => (p.translator.typename, p.field.ident.name)))
w.w(") ")
w.braced {
val argsList = resolvedMethod.parameters.map(p => (p.field.ident.name))
val fullArgsList = if (resolvedMethod.method.static) argsList else "_ref" +: argsList
if (resolvedMethod.retTypename != "void") {
w.w("return ")
}
w.wl(s"${prefix}_${resolvedMethod.resolvedName}(${fullArgsList.mkString(", ")});")
}
w.wl
}
})
}

}, (w: IndentWriter) => {
if (i.ext.cc) {
val proxyClassNameCpp = writeProxyClass(w, ident, methodDefsStructName, resolvedMethods)
Expand Down
4 changes: 4 additions & 0 deletions src/source/Main.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -116,6 +116,7 @@ object Main {
var cNamespace: String = ""
var cBaseLibIncludePrefix: String = ""
var cIncludePrefix: String = ""
var cWrapperCppNamespace: Option[String] = None
var swiftOutFolder: Option[File] = None
var swiftModule: String = "Module"
var swiftIdentStyle = IdentStyle.swiftDefault
Expand Down Expand Up @@ -316,6 +317,8 @@ object Main {
.text("The C base library's include path, relative to the C files.")
opt[String]("c-include-prefix").valueName("...").foreach(x => cIncludePrefix = x)
.text("The prefix for #includes of header files from C++ files.")
opt[String]("c-wrapper-cpp-namespace").valueName("...").foreach(x => cWrapperCppNamespace = Some(x))
.text("The C++ namespace to use for C API wrapper convenience classes.")
opt[File]("swift-out").valueName("<out-folder>").foreach(x => swiftOutFolder = Some(x))
.text("The output folder for Swift files (Generator disabled if unspecified).")
opt[String]("swift-module").valueName("<name>").foreach(swiftModule = _)
Expand Down Expand Up @@ -541,6 +544,7 @@ object Main {
cNamespace,
cBaseLibIncludePrefix,
cIncludePrefix,
cWrapperCppNamespace,
swiftOutFolder,
swiftIdentStyle,
swiftModule,
Expand Down
1 change: 1 addition & 0 deletions src/source/generator.scala
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Expand Up @@ -118,6 +118,7 @@ package object generatorTools {
cNamespace: String,
cBaseLibIncludePrefix: String,
cIncludePrefix: String,
cWrapperCppNamespace: Option[String],
swiftOutFolder: Option[File],
swiftIdentStyle: SwiftIdentStyle,
swiftModule: String,
Expand Down
2 changes: 1 addition & 1 deletion support-lib/cpp/djinni_c_ref.hpp
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Expand Up @@ -41,7 +41,7 @@ template <typename T> class Ref {
return *this;
}

T get() const { return _ref; }
const T& get() const { return _ref; }
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@kevinthornberry kevinthornberry Dec 8, 2025

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Made this const ref to ensure correct constructor overload is called when doing things like

Ref<djinni_ref> myRef = ....
WrapperClass myWrapper(myRef.get());

The lvalue constructor should be used to ensure the ref count is appropriately incremented


private:
T _ref;
Expand Down