1 files changed, 101 insertions, 0 deletions
diff --git a/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Helpers.swift b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Helpers.swift
new file mode 100644
index 0000000000..a34b128e23
--- /dev/null
+++ b/third_party/rust/uniffi_bindgen/src/bindings/swift/templates/Helpers.swift
@@ -0,0 +1,101 @@
+// An error type for FFI errors. These errors occur at the UniFFI level, not
+// the library level.
+fileprivate enum UniffiInternalError: LocalizedError {
+    case bufferOverflow
+    case incompleteData
+    case unexpectedOptionalTag
+    case unexpectedEnumCase
+    case unexpectedNullPointer
+    case unexpectedRustCallStatusCode
+    case unexpectedRustCallError
+    case unexpectedStaleHandle
+    case rustPanic(_ message: String)
+
+    public var errorDescription: String? {
+        switch self {
+        case .bufferOverflow: return "Reading the requested value would read past the end of the buffer"
+        case .incompleteData: return "The buffer still has data after lifting its containing value"
+        case .unexpectedOptionalTag: return "Unexpected optional tag; should be 0 or 1"
+        case .unexpectedEnumCase: return "Raw enum value doesn't match any cases"
+        case .unexpectedNullPointer: return "Raw pointer value was null"
+        case .unexpectedRustCallStatusCode: return "Unexpected RustCallStatus code"
+        case .unexpectedRustCallError: return "CALL_ERROR but no errorClass specified"
+        case .unexpectedStaleHandle: return "The object in the handle map has been dropped already"
+        case let .rustPanic(message): return message
+        }
+    }
+}
+
+fileprivate let CALL_SUCCESS: Int8 = 0
+fileprivate let CALL_ERROR: Int8 = 1
+fileprivate let CALL_PANIC: Int8 = 2
+fileprivate let CALL_CANCELLED: Int8 = 3
+
+fileprivate extension RustCallStatus {
+    init() {
+        self.init(
+            code: CALL_SUCCESS,
+            errorBuf: RustBuffer.init(
+                capacity: 0,
+                len: 0,
+                data: nil
+            )
+        )
+    }
+}
+
+private func rustCall<T>(_ callback: (UnsafeMutablePointer<RustCallStatus>) -> T) throws -> T {
+    try makeRustCall(callback, errorHandler: nil)
+}
+
+private func rustCallWithError<T>(
+    _ errorHandler: @escaping (RustBuffer) throws -> Error,
+    _ callback: (UnsafeMutablePointer<RustCallStatus>) -> T) throws -> T {
+    try makeRustCall(callback, errorHandler: errorHandler)
+}
+
+private func makeRustCall<T>(
+    _ callback: (UnsafeMutablePointer<RustCallStatus>) -> T,
+    errorHandler: ((RustBuffer) throws -> Error)?
+) throws -> T {
+    uniffiEnsureInitialized()
+    var callStatus = RustCallStatus.init()
+    let returnedVal = callback(&callStatus)
+    try uniffiCheckCallStatus(callStatus: callStatus, errorHandler: errorHandler)
+    return returnedVal
+}
+
+private func uniffiCheckCallStatus(
+    callStatus: RustCallStatus,
+    errorHandler: ((RustBuffer) throws -> Error)?
+) throws {
+    switch callStatus.code {
+        case CALL_SUCCESS:
+            return
+
+        case CALL_ERROR:
+            if let errorHandler = errorHandler {
+                throw try errorHandler(callStatus.errorBuf)
+            } else {
+                callStatus.errorBuf.deallocate()
+                throw UniffiInternalError.unexpectedRustCallError
+            }
+
+        case CALL_PANIC:
+            // When the rust code sees a panic, it tries to construct a RustBuffer
+            // with the message.  But if that code panics, then it just sends back
+            // an empty buffer.
+            if callStatus.errorBuf.len > 0 {
+                throw UniffiInternalError.rustPanic(try {{ Type::String.borrow()|lift_fn }}(callStatus.errorBuf))
+            } else {
+                callStatus.errorBuf.deallocate()
+                throw UniffiInternalError.rustPanic("Rust panic")
+            }
+
+        case CALL_CANCELLED:
+                throw CancellationError()
+
+        default:
+            throw UniffiInternalError.unexpectedRustCallStatusCode
+    }
+}