libgo/go/runtime/ffi.go - gofrontend - Git at Google

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // Only build this file if libffi is supported.

 // +build libffi

 package runtime

 import "unsafe"

 // This file contains the code that converts a Go type to an FFI type.
 // This has to be written in Go because it allocates memory in the Go heap.

 // C functions to return pointers to libffi variables.

 func ffi_type_pointer() *__ffi_type
 func ffi_type_sint8() *__ffi_type
 func ffi_type_sint16() *__ffi_type
 func ffi_type_sint32() *__ffi_type
 func ffi_type_sint64() *__ffi_type
 func ffi_type_uint8() *__ffi_type
 func ffi_type_uint16() *__ffi_type
 func ffi_type_uint32() *__ffi_type
 func ffi_type_uint64() *__ffi_type
 func ffi_type_float() *__ffi_type
 func ffi_type_double() *__ffi_type
 func ffi_supports_complex() bool
 func ffi_type_complex_float() *__ffi_type
 func ffi_type_complex_double() *__ffi_type
 func ffi_type_void() *__ffi_type

 // C functions defined in libffi.

 //extern ffi_prep_cif
 func ffi_prep_cif(*_ffi_cif, _ffi_abi, uint32, *__ffi_type, **__ffi_type) _ffi_status

 // ffiFuncToCIF is called from C code.
 //go:linkname ffiFuncToCIF runtime.ffiFuncToCIF

 // ffiFuncToCIF builds an _ffi_cif struct for function described by ft.
 func ffiFuncToCIF(ft *functype, isInterface bool, isMethod bool, cif *_ffi_cif) {
 	nparams := len(ft.in)
 	nargs := nparams
 	if isInterface {
 		nargs++
 	}
 	args := make([]*__ffi_type, nargs)
 	i := 0
 	off := 0
 	if isInterface {
 		args[0] = ffi_type_pointer()
 		off = 1
 	} else if isMethod {
 		args[0] = ffi_type_pointer()
 		i = 1
 	}
 	for ; i < nparams; i++ {
 		args[i+off] = typeToFFI(ft.in[i])
 	}

 	rettype := funcReturnFFI(ft)

 	var pargs **__ffi_type
 	if len(args) > 0 {
 		pargs = &args[0]
 	}
 	status := ffi_prep_cif(cif, _FFI_DEFAULT_ABI, uint32(nargs), rettype, pargs)
 	if status != _FFI_OK {
 		throw("ffi_prep_cif failed")
 	}
 }

 // funcReturnFFI returns the FFI definition of the return type of ft.
 func funcReturnFFI(ft *functype) *__ffi_type {
 	c := len(ft.out)
 	if c == 0 {
 		return ffi_type_void()
 	}

 	// Compile a function that returns a zero-sized value as
 	// though it returns void. This works around a problem in
 	// libffi: it can't represent a zero-sized value.
 	var size uintptr
 	for _, v := range ft.out {
 		size += v.size
 	}
 	if size == 0 {
 		return ffi_type_void()
 	}

 	if c == 1 {
 		return typeToFFI(ft.out[0])
 	}

 	elements := make([]*__ffi_type, c+1)
 	for i, v := range ft.out {
 		elements[i] = typeToFFI(v)
 	}
 	elements[c] = nil

 	return &__ffi_type{
 		_type:    _FFI_TYPE_STRUCT,
 		elements: &elements[0],
 	}
 }

 // typeToFFI returns the __ffi_type for a Go type.
 func typeToFFI(typ *_type) *__ffi_type {
 	switch typ.kind & kindMask {
 	case kindBool:
 		switch unsafe.Sizeof(false) {
 		case 1:
 			return ffi_type_uint8()
 		case 4:
 			return ffi_type_uint32()
 		default:
 			throw("bad bool size")
 			return nil
 		}
 	case kindInt:
 		return intToFFI()
 	case kindInt8:
 		return ffi_type_sint8()
 	case kindInt16:
 		return ffi_type_sint16()
 	case kindInt32:
 		return ffi_type_sint32()
 	case kindInt64:
 		return ffi_type_sint64()
 	case kindUint:
 		switch unsafe.Sizeof(uint(0)) {
 		case 4:
 			return ffi_type_uint32()
 		case 8:
 			return ffi_type_uint64()
 		default:
 			throw("bad uint size")
 			return nil
 		}
 	case kindUint8:
 		return ffi_type_uint8()
 	case kindUint16:
 		return ffi_type_uint16()
 	case kindUint32:
 		return ffi_type_uint32()
 	case kindUint64:
 		return ffi_type_uint64()
 	case kindUintptr:
 		switch unsafe.Sizeof(uintptr(0)) {
 		case 4:
 			return ffi_type_uint32()
 		case 8:
 			return ffi_type_uint64()
 		default:
 			throw("bad uinptr size")
 			return nil
 		}
 	case kindFloat32:
 		return ffi_type_float()
 	case kindFloat64:
 		return ffi_type_double()
 	case kindComplex64:
 		if ffi_supports_complex() {
 			return ffi_type_complex_float()
 		} else {
 			return complexToFFI(ffi_type_float())
 		}
 	case kindComplex128:
 		if ffi_supports_complex() {
 			return ffi_type_complex_double()
 		} else {
 			return complexToFFI(ffi_type_double())
 		}
 	case kindArray:
 		return arrayToFFI((*arraytype)(unsafe.Pointer(typ)))
 	case kindChan, kindFunc, kindMap, kindPtr, kindUnsafePointer:
 		// These types are always simple pointers, and for FFI
 		// purposes nothing else matters.
 		return ffi_type_pointer()
 	case kindInterface:
 		return interfaceToFFI()
 	case kindSlice:
 		return sliceToFFI((*slicetype)(unsafe.Pointer(typ)))
 	case kindString:
 		return stringToFFI()
 	case kindStruct:
 		return structToFFI((*structtype)(unsafe.Pointer(typ)))
 	default:
 		throw("unknown type kind")
 		return nil
 	}
 }

 // interfaceToFFI returns an ffi_type for a Go interface type.
 // This is used for both empty and non-empty interface types.
 func interfaceToFFI() *__ffi_type {
 	elements := make([]*__ffi_type, 3)
 	elements[0] = ffi_type_pointer()
 	elements[1] = elements[0]
 	elements[2] = nil
 	return &__ffi_type{
 		_type:    _FFI_TYPE_STRUCT,
 		elements: &elements[0],
 	}
 }

 // stringToFFI returns an ffi_type for a Go string type.
 func stringToFFI() *__ffi_type {
 	elements := make([]*__ffi_type, 3)
 	elements[0] = ffi_type_pointer()
 	elements[1] = intToFFI()
 	elements[2] = nil
 	return &__ffi_type{
 		_type:    _FFI_TYPE_STRUCT,
 		elements: &elements[0],
 	}
 }

 // structToFFI returns an ffi_type for a Go struct type.
 func structToFFI(typ *structtype) *__ffi_type {
 	c := len(typ.fields)
 	if c == 0 {
 		return emptyStructToFFI()
 	}

 	fields := make([]*__ffi_type, 0, c+1)
 	checkPad := false
 	for i, v := range typ.fields {
 		// Skip zero-sized fields; they confuse libffi,
 		// and there is no value to pass in any case.
 		// We do have to check whether the alignment of the
 		// zero-sized field introduces any padding for the
 		// next field.
 		if v.typ.size == 0 {
 			checkPad = true
 			continue
 		}

 		if checkPad {
 			off := uintptr(0)
 			for j := i - 1; j >= 0; j-- {
 				if typ.fields[j].typ.size > 0 {
 					off = typ.fields[j].offset() + typ.fields[j].typ.size
 					break
 				}
 			}
 			off += uintptr(v.typ.align) - 1
 			off &^= uintptr(v.typ.align) - 1
 			if off != v.offset() {
 				fields = append(fields, padFFI(v.offset()-off))
 			}
 			checkPad = false
 		}

 		fields = append(fields, typeToFFI(v.typ))
 	}

 	fields = append(fields, nil)

 	return &__ffi_type{
 		_type:    _FFI_TYPE_STRUCT,
 		elements: &fields[0],
 	}
 }

 // sliceToFFI returns an ffi_type for a Go slice type.
 func sliceToFFI(typ *slicetype) *__ffi_type {
 	elements := make([]*__ffi_type, 4)
 	elements[0] = ffi_type_pointer()
 	elements[1] = intToFFI()
 	elements[2] = elements[1]
 	elements[3] = nil
 	return &__ffi_type{
 		_type:    _FFI_TYPE_STRUCT,
 		elements: &elements[0],
 	}
 }

 // complexToFFI returns an ffi_type for a Go complex type.
 // This is only used if libffi does not support complex types internally
 // for this target.
 func complexToFFI(ffiFloatType *__ffi_type) *__ffi_type {
 	elements := make([]*__ffi_type, 3)
 	elements[0] = ffiFloatType
 	elements[1] = ffiFloatType
 	elements[2] = nil
 	return &__ffi_type{
 		_type:    _FFI_TYPE_STRUCT,
 		elements: &elements[0],
 	}
 }

 // arrayToFFI returns an ffi_type for a Go array type.
 func arrayToFFI(typ *arraytype) *__ffi_type {
 	if typ.len == 0 {
 		return emptyStructToFFI()
 	}
 	elements := make([]*__ffi_type, typ.len+1)
 	et := typeToFFI(typ.elem)
 	for i := uintptr(0); i < typ.len; i++ {
 		elements[i] = et
 	}
 	elements[typ.len] = nil
 	return &__ffi_type{
 		_type:    _FFI_TYPE_STRUCT,
 		elements: &elements[0],
 	}
 }

 // intToFFI returns an ffi_type for the Go int type.
 func intToFFI() *__ffi_type {
 	switch unsafe.Sizeof(0) {
 	case 4:
 		return ffi_type_sint32()
 	case 8:
 		return ffi_type_sint64()
 	default:
 		throw("bad int size")
 		return nil
 	}
 }

 // emptyStructToFFI returns an ffi_type for an empty struct.
 // The libffi library won't accept a struct with no fields.
 func emptyStructToFFI() *__ffi_type {
 	elements := make([]*__ffi_type, 2)
 	elements[0] = ffi_type_void()
 	elements[1] = nil
 	return &__ffi_type{
 		_type:    _FFI_TYPE_STRUCT,
 		elements: &elements[0],
 	}
 }

 // padFFI returns a padding field of the given size
 func padFFI(size uintptr) *__ffi_type {
 	elements := make([]*__ffi_type, size+1)
 	for i := uintptr(0); i < size; i++ {
 		elements[i] = ffi_type_uint8()
 	}
 	elements[size] = nil
 	return &__ffi_type{
 		_type:    _FFI_TYPE_STRUCT,
 		elements: &elements[0],
 	}
 }

 //go:linkname makeCIF reflect.makeCIF

 // makeCIF is used by the reflect package to allocate a CIF.
 func makeCIF(ft *functype) *_ffi_cif {
 	cif := new(_ffi_cif)
 	ffiFuncToCIF(ft, false, false, cif)
 	return cif
 }
	// Copyright 2009 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// Only build this file if libffi is supported.

	// +build libffi

	package runtime

	import "unsafe"

	// This file contains the code that converts a Go type to an FFI type.
	// This has to be written in Go because it allocates memory in the Go heap.

	// C functions to return pointers to libffi variables.

	func ffi_type_pointer() *__ffi_type
	func ffi_type_sint8() *__ffi_type
	func ffi_type_sint16() *__ffi_type
	func ffi_type_sint32() *__ffi_type
	func ffi_type_sint64() *__ffi_type
	func ffi_type_uint8() *__ffi_type
	func ffi_type_uint16() *__ffi_type
	func ffi_type_uint32() *__ffi_type
	func ffi_type_uint64() *__ffi_type
	func ffi_type_float() *__ffi_type
	func ffi_type_double() *__ffi_type
	func ffi_supports_complex() bool
	func ffi_type_complex_float() *__ffi_type
	func ffi_type_complex_double() *__ffi_type
	func ffi_type_void() *__ffi_type

	// C functions defined in libffi.

	//extern ffi_prep_cif
	func ffi_prep_cif(_ffi_cif, _ffi_abi, uint32, __ffi_type, **__ffi_type) _ffi_status

	// ffiFuncToCIF is called from C code.
	//go:linkname ffiFuncToCIF runtime.ffiFuncToCIF

	// ffiFuncToCIF builds an _ffi_cif struct for function described by ft.
	func ffiFuncToCIF(ft functype, isInterface bool, isMethod bool, cif _ffi_cif) {
	nparams := len(ft.in)
	nargs := nparams
	if isInterface {
	nargs++
	}
	args := make([]*__ffi_type, nargs)
	i := 0
	off := 0
	if isInterface {
	args[0] = ffi_type_pointer()
	off = 1
	} else if isMethod {
	args[0] = ffi_type_pointer()
	i = 1
	}
	for ; i < nparams; i++ {
	args[i+off] = typeToFFI(ft.in[i])
	}

	rettype := funcReturnFFI(ft)

	var pargs **__ffi_type
	if len(args) > 0 {
	pargs = &args[0]
	}
	status := ffi_prep_cif(cif, _FFI_DEFAULT_ABI, uint32(nargs), rettype, pargs)
	if status != _FFI_OK {
	throw("ffi_prep_cif failed")
	}
	}

	// funcReturnFFI returns the FFI definition of the return type of ft.
	func funcReturnFFI(ft functype) __ffi_type {
	c := len(ft.out)
	if c == 0 {
	return ffi_type_void()
	}

	// Compile a function that returns a zero-sized value as
	// though it returns void. This works around a problem in
	// libffi: it can't represent a zero-sized value.
	var size uintptr
	for _, v := range ft.out {
	size += v.size
	}
	if size == 0 {
	return ffi_type_void()
	}

	if c == 1 {
	return typeToFFI(ft.out[0])
	}

	elements := make([]*__ffi_type, c+1)
	for i, v := range ft.out {
	elements[i] = typeToFFI(v)
	}
	elements[c] = nil

	return &__ffi_type{
	_type: _FFI_TYPE_STRUCT,
	elements: &elements[0],
	}
	}

	// typeToFFI returns the __ffi_type for a Go type.
	func typeToFFI(typ _type) __ffi_type {
	switch typ.kind & kindMask {
	case kindBool:
	switch unsafe.Sizeof(false) {
	case 1:
	return ffi_type_uint8()
	case 4:
	return ffi_type_uint32()
	default:
	throw("bad bool size")
	return nil
	}
	case kindInt:
	return intToFFI()
	case kindInt8:
	return ffi_type_sint8()
	case kindInt16:
	return ffi_type_sint16()
	case kindInt32:
	return ffi_type_sint32()
	case kindInt64:
	return ffi_type_sint64()
	case kindUint:
	switch unsafe.Sizeof(uint(0)) {
	case 4:
	return ffi_type_uint32()
	case 8:
	return ffi_type_uint64()
	default:
	throw("bad uint size")
	return nil
	}
	case kindUint8:
	return ffi_type_uint8()
	case kindUint16:
	return ffi_type_uint16()
	case kindUint32:
	return ffi_type_uint32()
	case kindUint64:
	return ffi_type_uint64()
	case kindUintptr:
	switch unsafe.Sizeof(uintptr(0)) {
	case 4:
	return ffi_type_uint32()
	case 8:
	return ffi_type_uint64()
	default:
	throw("bad uinptr size")
	return nil
	}
	case kindFloat32:
	return ffi_type_float()
	case kindFloat64:
	return ffi_type_double()
	case kindComplex64:
	if ffi_supports_complex() {
	return ffi_type_complex_float()
	} else {
	return complexToFFI(ffi_type_float())
	}
	case kindComplex128:
	if ffi_supports_complex() {
	return ffi_type_complex_double()
	} else {
	return complexToFFI(ffi_type_double())
	}
	case kindArray:
	return arrayToFFI((*arraytype)(unsafe.Pointer(typ)))
	case kindChan, kindFunc, kindMap, kindPtr, kindUnsafePointer:
	// These types are always simple pointers, and for FFI
	// purposes nothing else matters.
	return ffi_type_pointer()
	case kindInterface:
	return interfaceToFFI()
	case kindSlice:
	return sliceToFFI((*slicetype)(unsafe.Pointer(typ)))
	case kindString:
	return stringToFFI()
	case kindStruct:
	return structToFFI((*structtype)(unsafe.Pointer(typ)))
	default:
	throw("unknown type kind")
	return nil
	}
	}

	// interfaceToFFI returns an ffi_type for a Go interface type.
	// This is used for both empty and non-empty interface types.
	func interfaceToFFI() *__ffi_type {
	elements := make([]*__ffi_type, 3)
	elements[0] = ffi_type_pointer()
	elements[1] = elements[0]
	elements[2] = nil
	return &__ffi_type{
	_type: _FFI_TYPE_STRUCT,
	elements: &elements[0],
	}
	}

	// stringToFFI returns an ffi_type for a Go string type.
	func stringToFFI() *__ffi_type {
	elements := make([]*__ffi_type, 3)
	elements[0] = ffi_type_pointer()
	elements[1] = intToFFI()
	elements[2] = nil
	return &__ffi_type{
	_type: _FFI_TYPE_STRUCT,
	elements: &elements[0],
	}
	}

	// structToFFI returns an ffi_type for a Go struct type.
	func structToFFI(typ structtype) __ffi_type {
	c := len(typ.fields)
	if c == 0 {
	return emptyStructToFFI()
	}

	fields := make([]*__ffi_type, 0, c+1)
	checkPad := false
	for i, v := range typ.fields {
	// Skip zero-sized fields; they confuse libffi,
	// and there is no value to pass in any case.
	// We do have to check whether the alignment of the
	// zero-sized field introduces any padding for the
	// next field.
	if v.typ.size == 0 {
	checkPad = true
	continue
	}

	if checkPad {
	off := uintptr(0)
	for j := i - 1; j >= 0; j-- {
	if typ.fields[j].typ.size > 0 {
	off = typ.fields[j].offset() + typ.fields[j].typ.size
	break
	}
	}
	off += uintptr(v.typ.align) - 1
	off &^= uintptr(v.typ.align) - 1
	if off != v.offset() {
	fields = append(fields, padFFI(v.offset()-off))
	}
	checkPad = false
	}

	fields = append(fields, typeToFFI(v.typ))
	}

	fields = append(fields, nil)

	return &__ffi_type{
	_type: _FFI_TYPE_STRUCT,
	elements: &fields[0],
	}
	}

	// sliceToFFI returns an ffi_type for a Go slice type.
	func sliceToFFI(typ slicetype) __ffi_type {
	elements := make([]*__ffi_type, 4)
	elements[0] = ffi_type_pointer()
	elements[1] = intToFFI()
	elements[2] = elements[1]
	elements[3] = nil
	return &__ffi_type{
	_type: _FFI_TYPE_STRUCT,
	elements: &elements[0],
	}
	}

	// complexToFFI returns an ffi_type for a Go complex type.
	// This is only used if libffi does not support complex types internally
	// for this target.
	func complexToFFI(ffiFloatType __ffi_type) __ffi_type {
	elements := make([]*__ffi_type, 3)
	elements[0] = ffiFloatType
	elements[1] = ffiFloatType
	elements[2] = nil
	return &__ffi_type{
	_type: _FFI_TYPE_STRUCT,
	elements: &elements[0],
	}
	}

	// arrayToFFI returns an ffi_type for a Go array type.
	func arrayToFFI(typ arraytype) __ffi_type {
	if typ.len == 0 {
	return emptyStructToFFI()
	}
	elements := make([]*__ffi_type, typ.len+1)
	et := typeToFFI(typ.elem)
	for i := uintptr(0); i < typ.len; i++ {
	elements[i] = et
	}
	elements[typ.len] = nil
	return &__ffi_type{
	_type: _FFI_TYPE_STRUCT,
	elements: &elements[0],
	}
	}

	// intToFFI returns an ffi_type for the Go int type.
	func intToFFI() *__ffi_type {
	switch unsafe.Sizeof(0) {
	case 4:
	return ffi_type_sint32()
	case 8:
	return ffi_type_sint64()
	default:
	throw("bad int size")
	return nil
	}
	}

	// emptyStructToFFI returns an ffi_type for an empty struct.
	// The libffi library won't accept a struct with no fields.
	func emptyStructToFFI() *__ffi_type {
	elements := make([]*__ffi_type, 2)
	elements[0] = ffi_type_void()
	elements[1] = nil
	return &__ffi_type{
	_type: _FFI_TYPE_STRUCT,
	elements: &elements[0],
	}
	}

	// padFFI returns a padding field of the given size
	func padFFI(size uintptr) *__ffi_type {
	elements := make([]*__ffi_type, size+1)
	for i := uintptr(0); i < size; i++ {
	elements[i] = ffi_type_uint8()
	}
	elements[size] = nil
	return &__ffi_type{
	_type: _FFI_TYPE_STRUCT,
	elements: &elements[0],
	}
	}

	//go:linkname makeCIF reflect.makeCIF

	// makeCIF is used by the reflect package to allocate a CIF.
	func makeCIF(ft functype) _ffi_cif {
	cif := new(_ffi_cif)
	ffiFuncToCIF(ft, false, false, cif)
	return cif
	}