WASM ABI: implement row_iter_bsatn_advance & row_iter_bsatn_close (…

…#1622)

crates/bindings-csharp/Runtime/Exceptions.cs

@@ -27,6 +27,11 @@ public class BufferTooSmallException : StdbException
     public override string Message => "The provided buffer is not large enough to store the data";
 }
 
+public class NoSuchIterException : StdbException
+{
+    public override string Message => "The provided row iterator does not exist";
+}
+
 public class NoSuchBytesException : StdbException
 {
     public override string Message => "The provided bytes source or sink does not exist";
@@ -39,9 +44,9 @@ public class NoSpaceException : StdbException
 
 public class UnknownException : StdbException
 {
-    private readonly FFI.Errno code;
+    private readonly Errno code;
 
-    internal UnknownException(FFI.Errno code) => this.code = code;
+    internal UnknownException(Errno code) => this.code = code;
 
     public override string Message => $"SpacetimeDB error code {code}";
 }

crates/bindings-csharp/Runtime/Internal/FFI.cs

@@ -18,6 +18,20 @@ public readonly record struct BytesSource(uint Handle)
 [StructLayout(LayoutKind.Sequential)]
 public readonly record struct BytesSink(uint Handle) { }
 
+public enum Errno : short
+{
+    EXHAUSTED = -1,
+    OK = 0,
+    HOST_CALL_FAILURE = 1,
+    NO_SUCH_TABLE = 4,
+    LOOKUP_NOT_FOUND = 2,
+    NO_SUCH_ITER = 6,
+    NO_SUCH_BYTES = 8,
+    NO_SPACE = 9,
+    BUFFER_TOO_SMALL = 11,
+    UNIQUE_ALREADY_EXISTS = 12,
+}
+
 #pragma warning disable IDE1006 // Naming Styles - Not applicable to FFI stuff.
 internal static partial class FFI
 {
@@ -32,18 +46,6 @@ internal static partial class FFI
 #endif
     ;
 
-    public enum Errno : ushort
-    {
-        OK = 0,
-        HOST_CALL_FAILURE = 1,
-        NO_SUCH_TABLE = 4,
-        LOOKUP_NOT_FOUND = 2,
-        NO_SUCH_BYTES = 8,
-        NO_SPACE = 9,
-        BUFFER_TOO_SMALL = 11,
-        UNIQUE_ALREADY_EXISTS = 12,
-    }
-
     [NativeMarshalling(typeof(Marshaller))]
     public struct CheckedStatus
     {
@@ -108,7 +110,7 @@ public readonly struct LogLevel(byte log_level)
     [StructLayout(LayoutKind.Sequential)]
     public readonly record struct RowIter(uint Handle)
     {
-        public static readonly RowIter INVALID = new(uint.MaxValue);
+        public static readonly RowIter INVALID = new(0);
     }
 
     [LibraryImport(StdbNamespace)]
@@ -159,14 +161,14 @@ out RowIter out_
     );
 
     [LibraryImport(StdbNamespace)]
-    public static partial CheckedStatus _iter_advance(
+    public static partial Errno _row_iter_bsatn_advance(
         RowIter iter_handle,
         [MarshalUsing(CountElementName = nameof(buffer_len))] [Out] byte[] buffer,
         ref uint buffer_len
     );
 
     [LibraryImport(StdbNamespace)]
-    public static partial void _iter_drop(RowIter iter_handle);
+    public static partial CheckedStatus _row_iter_bsatn_close(RowIter iter_handle);
 
     [LibraryImport(StdbNamespace)]
     public static partial void _volatile_nonatomic_schedule_immediate(
@@ -189,7 +191,7 @@ uint message_len
     );
 
     [LibraryImport(StdbNamespace)]
-    public static partial short _bytes_source_read(
+    public static partial Errno _bytes_source_read(
         BytesSource source,
         Span<byte> buffer,
         ref uint buffer_len

crates/bindings-csharp/Runtime/Internal/ITable.cs

@@ -22,31 +22,53 @@ public class Enumerator(FFI.RowIter handle) : IDisposable
 
             public bool MoveNext()
             {
+                if (handle == FFI.RowIter.INVALID)
+                {
+                    return false;
+                }
+
                 uint buffer_len;
                 while (true)
                 {
                     buffer_len = (uint)buffer.Length;
-                    try
+                    var ret = FFI._row_iter_bsatn_advance(handle, buffer, ref buffer_len);
+                    if (ret == Errno.EXHAUSTED)
                     {
-                        FFI._iter_advance(handle, buffer, ref buffer_len);
+                        handle = FFI.RowIter.INVALID;
                     }
-                    catch (BufferTooSmallException)
+                    // On success, the only way `buffer_len == 0` is for the iterator to be exhausted.
+                    // This happens when the host iterator was empty from the start.
+                    System.Diagnostics.Debug.Assert(!(ret == Errno.OK && buffer_len == 0));
+                    switch (ret)
                     {
-                        buffer = new byte[buffer_len];
-                        continue;
+                        // Iterator advanced and may also be `EXHAUSTED`.
+                        // When `OK`, we'll need to advance the iterator in the next call to `MoveNext`.
+                        // In both cases, copy over the row data to `Current` from the scratch `buffer`.
+                        case Errno.EXHAUSTED
+                        or Errno.OK:
+                            Current = new byte[buffer_len];
+                            Array.Copy(buffer, 0, Current, 0, buffer_len);
+                            return buffer_len != 0;
+                        // Couldn't find the iterator, error!
+                        case Errno.NO_SUCH_ITER:
+                            throw new NoSuchIterException();
+                        // The scratch `buffer` is too small to fit a row / chunk.
+                        // Grow `buffer` and try again.
+                        // The `buffer_len` will have been updated with the necessary size.
+                        case Errno.BUFFER_TOO_SMALL:
+                            buffer = new byte[buffer_len];
+                            continue;
+                        default:
+                            throw new UnknownException(ret);
                     }
-                    break;
                 }
-                Current = new byte[buffer_len];
-                Array.Copy(buffer, 0, Current, 0, buffer_len);
-                return buffer_len != 0;
             }
 
             public void Dispose()
             {
-                if (!handle.Equals(FFI.RowIter.INVALID))
+                if (handle != FFI.RowIter.INVALID)
                 {
-                    FFI._iter_drop(handle);
+                    FFI._row_iter_bsatn_close(handle);
                     handle = FFI.RowIter.INVALID;
                     // Avoid running ~RowIter if Dispose was executed successfully.
                     GC.SuppressFinalize(this);

crates/bindings-csharp/Runtime/Internal/Module.cs

@@ -238,24 +238,24 @@ private static byte[] Consume(this BytesSource source)
             switch (ret)
             {
                 // Host side source exhausted, we're done.
-                case -1:
+                case Errno.EXHAUSTED:
                     Array.Resize(ref buffer, (int)written);
                     return buffer;
                 // Wrote the entire spare capacity.
                 // Need to reserve more space in the buffer.
-                case 0 when written == buffer.Length:
+                case Errno.OK when written == buffer.Length:
                     Array.Resize(ref buffer, buffer.Length + 1024);
                     break;
                 // Host didn't write as much as possible.
                 // Try to read some more.
                 // The host will likely not trigger this branch (current host doesn't),
                 // but a module should be prepared for it.
-                case 0:
+                case Errno.OK:
                     break;
-                case (short)(ushort)FFI.Errno.NO_SUCH_BYTES:
+                case Errno.NO_SUCH_BYTES:
                     throw new NoSuchBytesException();
                 default:
-                    throw new UnknownException((FFI.Errno)(ushort)ret);
+                    throw new UnknownException(ret);
             }
         }
     }
@@ -291,7 +291,7 @@ public static void __describe_module__(BytesSink description)
         }
     }
 
-    public static short __call_reducer__(
+    public static Errno __call_reducer__(
         uint id,
         ulong sender_0,
         ulong sender_1,
@@ -323,14 +323,14 @@ BytesSink error
             {
                 throw new Exception("Unrecognised extra bytes in the reducer arguments");
             }
-            return 0; /* no exception */
+            return Errno.OK; /* no exception */
         }
         catch (Exception e)
         {
             var error_str = e.ToString();
             var error_bytes = System.Text.Encoding.UTF8.GetBytes(error_str);
             error.Write(error_bytes);
-            return (short)(ushort)FFI.Errno.HOST_CALL_FAILURE;
+            return Errno.HOST_CALL_FAILURE;
         }
     }
 }

crates/bindings-csharp/Runtime/bindings.c

@@ -65,10 +65,10 @@ IMPORT(Status, _iter_start_filtered,
        (TableId table_id, const uint8_t* filter, uint32_t filter_len,
         RowIter* iter),
        (table_id, filter, filter_len, iter));
-IMPORT(Status, _iter_advance,
-       (RowIter iter, uint8_t* buffer, size_t* buffer_len),
-       (iter, buffer, buffer_len));
-IMPORT(void, _iter_drop, (RowIter iter), (iter));
+IMPORT(int16_t, _row_iter_bsatn_advance,
+       (RowIter iter, uint8_t* buffer_ptr, size_t* buffer_len_ptr),
+       (iter, buffer_ptr, buffer_len_ptr));
+IMPORT(uint16_t, _row_iter_bsatn_close, (RowIter iter), (iter));
 IMPORT(void, _volatile_nonatomic_schedule_immediate,
        (const uint8_t* name, size_t name_len, const uint8_t* args, size_t args_len),
        (name, name_len, args, args_len));

crates/bindings-csharp/Runtime/build/SpacetimeDB.Runtime.targets

@@ -5,15 +5,14 @@
     <UnmanagedEntryPointsAssembly Include="SpacetimeDB.Runtime" />
     <WasmImport Include="$(SpacetimeNamespace)!_console_log" />
     <WasmImport Include="$(SpacetimeNamespace)!_get_table_id" />
-    <WasmImport Include="$(SpacetimeNamespace)!_create_index" />
     <WasmImport Include="$(SpacetimeNamespace)!_iter_by_col_eq" />
     <WasmImport Include="$(SpacetimeNamespace)!_insert" />
     <WasmImport Include="$(SpacetimeNamespace)!_delete_by_col_eq" />
     <WasmImport Include="$(SpacetimeNamespace)!_delete_by_rel" />
     <WasmImport Include="$(SpacetimeNamespace)!_iter_start" />
     <WasmImport Include="$(SpacetimeNamespace)!_iter_start_filtered" />
-    <WasmImport Include="$(SpacetimeNamespace)!_iter_next" />
-    <WasmImport Include="$(SpacetimeNamespace)!_iter_drop" />
+    <WasmImport Include="$(SpacetimeNamespace)!_row_iter_bsatn_advance" />
+    <WasmImport Include="$(SpacetimeNamespace)!_row_iter_bsatn_close" />
     <WasmImport Include="$(SpacetimeNamespace)!_bytes_source_read" />
     <WasmImport Include="$(SpacetimeNamespace)!_bytes_sink_write" />