fileprivate extension RustBuffer {
// Allocate a new buffer, copying the contents of a `UInt8` array.
init(bytes: [UInt8]) {
let rbuf = bytes.withUnsafeBufferPointer { ptr in
RustBuffer.from(ptr)
}
self.init(capacity: rbuf.capacity, len: rbuf.len, data: rbuf.data)
}
static func empty() -> RustBuffer {
RustBuffer(capacity: 0, len:0, data: nil)
}
static func from(_ ptr: UnsafeBufferPointer<UInt8>) -> RustBuffer {
try! rustCall { {{ ci.ffi_rustbuffer_from_bytes().name() }}(ForeignBytes(bufferPointer: ptr), $0) }
}
// Frees the buffer in place.
// The buffer must not be used after this is called.
func deallocate() {
try! rustCall { {{ ci.ffi_rustbuffer_free().name() }}(self, $0) }
}
}
fileprivate extension ForeignBytes {
init(bufferPointer: UnsafeBufferPointer<UInt8>) {
self.init(len: Int32(bufferPointer.count), data: bufferPointer.baseAddress)
}
init(rawBufferPointer: UnsafeRawBufferPointer) {
self.init(
len: Int32(rawBufferPointer.count),
data: rawBufferPointer.baseAddress?.assumingMemoryBound(to: UInt8.self)
)
}
}
// Converter for `&[u8]` / `[ByRef] bytes` arguments.
//
// Conforms to `FfiConverter` so the compiler enforces the full converter
// method set. Only the scope-bound `lower(_:_body:)` overload is sound —
// zero-copy byte buffers only flow foreign -> Rust, and only in argument
// position. The four protocol-witness methods (`lift`, `lower`, `read`,
// `write`) `fatalError` at runtime if anyone reaches them.
//
// The scope-bound `lower` takes a closure because the `ForeignBytes`
// pointer is only guaranteed valid for the duration of
// `Data.withUnsafeBytes`. Callers must run the full FFI call inside
// the closure body.
fileprivate enum FfiConverterByRefBytes: FfiConverter {
typealias SwiftType = Data
typealias FfiType = ForeignBytes
static func lower<R>(_ value: Data, _ body: (ForeignBytes) throws -> R) rethrows -> R {
return try value.withUnsafeBytes { rawBuf in
try body(ForeignBytes(rawBufferPointer: rawBuf))
}
}
static func lower(_ value: Data) -> ForeignBytes {
fatalError("ByRef bytes cannot use the plain lower: returning ForeignBytes escapes the Data.withUnsafeBytes scope. Use the scope-bound lower(_:_body:) overload instead.")
}
static func lift(_ value: ForeignBytes) throws -> Data {
fatalError("ByRef bytes cannot be lifted: zero-copy &[u8] only flows foreign->Rust")
}
static func read(from buf: inout (data: Data, offset: Data.Index)) throws -> Data {
fatalError("ByRef bytes cannot be read from a buffer: zero-copy &[u8] is only supported in argument position, not nested in records/options/etc.")
}
static func write(_ value: Data, into buf: inout [UInt8]) {
fatalError("ByRef bytes cannot be written to a buffer: zero-copy &[u8] is only supported in argument position, not nested in records/options/etc.")
}
}
// For every type used in the interface, we provide helper methods for conveniently
// lifting and lowering that type from C-compatible data, and for reading and writing
// values of that type in a buffer.
// Helper classes/extensions that don't change.
// Someday, this will be in a library of its own.
fileprivate extension Data {
init(rustBuffer: RustBuffer) {
self.init(
bytesNoCopy: rustBuffer.data!,
count: Int(rustBuffer.len),
deallocator: .none
)
}
}
// Define reader functionality. Normally this would be defined in a class or
// struct, but we use standalone functions instead in order to make external
// types work.
//
// With external types, one swift source file needs to be able to call the read
// method on another source file's FfiConverter, but then what visibility
// should Reader have?
// - If Reader is fileprivate, then this means the read() must also
// be fileprivate, which doesn't work with external types.
// - If Reader is internal/public, we'll get compile errors since both source
// files will try define the same type.
//
// Instead, the read() method and these helper functions input a tuple of data
fileprivate func createReader(data: Data) -> (data: Data, offset: Data.Index) {
(data: data, offset: 0)
}
// Reads an integer at the current offset, in big-endian order, and advances
// the offset on success. Throws if reading the integer would move the
// offset past the end of the buffer.
fileprivate func readInt<T: FixedWidthInteger>(_ reader: inout (data: Data, offset: Data.Index)) throws -> T {
let range = reader.offset..<reader.offset + MemoryLayout<T>.size
guard reader.data.count >= range.upperBound else {
throw UniffiInternalError.bufferOverflow
}
if T.self == UInt8.self {
let value = reader.data[reader.offset]
reader.offset += 1
return value as! T
}
var value: T = 0
let _ = withUnsafeMutableBytes(of: &value, { reader.data.copyBytes(to: $0, from: range)})
reader.offset = range.upperBound
return value.bigEndian
}
// Reads an arbitrary number of bytes, to be used to read
// raw bytes, this is useful when lifting strings
fileprivate func readBytes(_ reader: inout (data: Data, offset: Data.Index), count: Int) throws -> Array<UInt8> {
let range = reader.offset..<(reader.offset+count)
guard reader.data.count >= range.upperBound else {
throw UniffiInternalError.bufferOverflow
}
var value = [UInt8](repeating: 0, count: count)
value.withUnsafeMutableBufferPointer({ buffer in
reader.data.copyBytes(to: buffer, from: range)
})
reader.offset = range.upperBound
return value
}
// Reads a float at the current offset.
fileprivate func readFloat(_ reader: inout (data: Data, offset: Data.Index)) throws -> Float {
return Float(bitPattern: try readInt(&reader))
}
// Reads a float at the current offset.
fileprivate func readDouble(_ reader: inout (data: Data, offset: Data.Index)) throws -> Double {
return Double(bitPattern: try readInt(&reader))
}
// Indicates if the offset has reached the end of the buffer.
fileprivate func hasRemaining(_ reader: (data: Data, offset: Data.Index)) -> Bool {
return reader.offset < reader.data.count
}
// Define writer functionality. Normally this would be defined in a class or
// struct, but we use standalone functions instead in order to make external
// types work. See the above discussion on Readers for details.
fileprivate func createWriter() -> [UInt8] {
return []
}
fileprivate func writeBytes<S>(_ writer: inout [UInt8], _ byteArr: S) where S: Sequence, S.Element == UInt8 {
writer.append(contentsOf: byteArr)
}
// Writes an integer in big-endian order.
//
// Warning: make sure what you are trying to write
// is in the correct type!
fileprivate func writeInt<T: FixedWidthInteger>(_ writer: inout [UInt8], _ value: T) {
var value = value.bigEndian
withUnsafeBytes(of: &value) { writer.append(contentsOf: $0) }
}
fileprivate func writeFloat(_ writer: inout [UInt8], _ value: Float) {
writeInt(&writer, value.bitPattern)
}
fileprivate func writeDouble(_ writer: inout [UInt8], _ value: Double) {
writeInt(&writer, value.bitPattern)
}
// Protocol for types that transfer other types across the FFI. This is
// analogous to the Rust trait of the same name.
fileprivate protocol FfiConverter {
associatedtype FfiType
associatedtype SwiftType
static func lift(_ value: FfiType) throws -> SwiftType
static func lower(_ value: SwiftType) -> FfiType
static func read(from buf: inout (data: Data, offset: Data.Index)) throws -> SwiftType
static func write(_ value: SwiftType, into buf: inout [UInt8])
}
// Types conforming to `Primitive` pass themselves directly over the FFI.
fileprivate protocol FfiConverterPrimitive: FfiConverter where FfiType == SwiftType { }
extension FfiConverterPrimitive {
#if swift(>=5.8)
@_documentation(visibility: private)
#endif
public static func lift(_ value: FfiType) throws -> SwiftType {
return value
}
#if swift(>=5.8)
@_documentation(visibility: private)
#endif
public static func lower(_ value: SwiftType) -> FfiType {
return value
}
}
// Types conforming to `FfiConverterRustBuffer` lift and lower into a `RustBuffer`.
// Used for complex types where it's hard to write a custom lift/lower.
fileprivate protocol FfiConverterRustBuffer: FfiConverter where FfiType == RustBuffer {}
extension FfiConverterRustBuffer {
#if swift(>=5.8)
@_documentation(visibility: private)
#endif
public static func lift(_ buf: RustBuffer) throws -> SwiftType {
var reader = createReader(data: Data(rustBuffer: buf))
let value = try read(from: &reader)
if hasRemaining(reader) {
throw UniffiInternalError.incompleteData
}
buf.deallocate()
return value
}
#if swift(>=5.8)
@_documentation(visibility: private)
#endif
public static func lower(_ value: SwiftType) -> RustBuffer {
var writer = createWriter()
write(value, into: &writer)
return RustBuffer(bytes: writer)
}
}