imbue builders and readers with cap tables

Author: vaci

runtime/src/main/java/org/capnproto/AnyPointer.java

@@ -26,30 +26,30 @@ public static final class Factory
             implements PointerFactory<Builder, Reader>,
                        SetPointerBuilder<Builder, Reader>
     {
-        public final Reader fromPointerReader(SegmentReader segment, int pointer, int nestingLimit) {
-            return new Reader(segment, pointer, nestingLimit);
+        public final Reader fromPointerReader(SegmentReader segment, CapTableReader capTable, int pointer, int nestingLimit) {
+            return new Reader(segment, capTable, pointer, nestingLimit);
         }
-        public final Builder fromPointerBuilder(SegmentBuilder segment, int pointer) {
-            return new Builder(segment, pointer);
+        public final Builder fromPointerBuilder(SegmentBuilder segment, CapTableBuilder capTable, int pointer) {
+            return new Builder(segment, capTable, pointer);
         }
-        public final Builder initFromPointerBuilder(SegmentBuilder segment, int pointer, int elementCount) {
-            Builder result = new Builder(segment, pointer);
+        public final Builder initFromPointerBuilder(SegmentBuilder segment, CapTableBuilder capTable, int pointer, int elementCount) {
+            Builder result = new Builder(segment, capTable, pointer);
             result.clear();
             return result;
         }
-        public void setPointerBuilder(SegmentBuilder segment, int pointer, Reader value) {
+        public void setPointerBuilder(SegmentBuilder segment, CapTableBuilder capTable, int pointer, Reader value) {
             if (value.isNull()) {
-                WireHelpers.zeroObject(segment, pointer);
+                WireHelpers.zeroObject(segment, capTable, pointer);
                 WireHelpers.zeroPointerAndFars(segment, pointer);
             }
             else {
-                WireHelpers.copyPointer(segment, pointer, value.segment, value.pointer, value.nestingLimit);
+                WireHelpers.copyPointer(segment, capTable, pointer, value.segment, value.capTable, value.pointer, value.nestingLimit);
             }
         }
     }
     public static final Factory factory = new Factory();
 
-    public final static class Reader {
+    public final static class Reader extends CapTableReader.ReaderContext {
         final SegmentReader segment;
         final int pointer; // offset in words
         final int nestingLimit;
@@ -60,16 +60,29 @@ public Reader(SegmentReader segment, int pointer, int nestingLimit) {
             this.nestingLimit = nestingLimit;
         }
 
+        public Reader(SegmentReader segment, CapTableReader capTable, int pointer, int nestingLimit) {
+            this.segment = segment;
+            this.pointer = pointer;
+            this.nestingLimit = nestingLimit;
+            this.capTable = capTable;
+        }
+
+        final Reader imbue(CapTableReader capTable) {
+            Reader result = new Reader(segment, pointer, nestingLimit);
+            result.capTable = capTable;
+            return result;
+        }
+
         public final boolean isNull() {
             return WirePointer.isNull(this.segment.buffer.getLong(this.pointer * Constants.BYTES_PER_WORD));
         }
 
         public final <T> T getAs(FromPointerReader<T> factory) {
-            return factory.fromPointerReader(this.segment, this.pointer, this.nestingLimit);
+            return factory.fromPointerReader(this.segment, this.capTable, this.pointer, this.nestingLimit);
         }
     }
 
-    public static final class Builder {
+    public static final class Builder extends CapTableBuilder.BuilderContext {
         final SegmentBuilder segment;
         final int pointer;
 
@@ -78,34 +91,43 @@ public Builder(SegmentBuilder segment, int pointer) {
             this.pointer = pointer;
         }
 
+        Builder(SegmentBuilder segment, CapTableBuilder capTable, int pointer) {
+            this.segment = segment;
+            this.pointer = pointer;
+            this.capTable = capTable;
+        }
+
+        final Builder imbue(CapTableBuilder capTable) {
+            return new Builder(segment, capTable, pointer);
+        }
+
         public final boolean isNull() {
             return WirePointer.isNull(this.segment.buffer.getLong(this.pointer * Constants.BYTES_PER_WORD));
         }
 
         public final <T> T getAs(FromPointerBuilder<T> factory) {
-            return factory.fromPointerBuilder(this.segment, this.pointer);
+            return factory.fromPointerBuilder(this.segment, this.capTable, this.pointer);
         }
 
         public final <T> T initAs(FromPointerBuilder<T> factory) {
-            return factory.initFromPointerBuilder(this.segment, this.pointer, 0);
+            return factory.initFromPointerBuilder(this.segment, this.capTable, this.pointer, 0);
         }
 
         public final <T> T initAs(FromPointerBuilder<T> factory, int elementCount) {
-            return factory.initFromPointerBuilder(this.segment, this.pointer, elementCount);
+            return factory.initFromPointerBuilder(this.segment, this.capTable, this.pointer, elementCount);
         }
 
         public final <T, U> void setAs(SetPointerBuilder<T, U> factory, U reader) {
-            factory.setPointerBuilder(this.segment, this.pointer, reader);
+            factory.setPointerBuilder(this.segment, this.capTable, this.pointer, reader);
         }
 
         public final Reader asReader() {
-            return new Reader(segment, pointer, java.lang.Integer.MAX_VALUE);
+            return new Reader(segment, this.capTable, pointer, java.lang.Integer.MAX_VALUE);
         }
 
         public final void clear() {
-            WireHelpers.zeroObject(this.segment, this.pointer);
+            WireHelpers.zeroObject(this.segment, this.capTable, this.pointer);
             this.segment.buffer.putLong(this.pointer * 8, 0L);
         }
     }
-
 }

runtime/src/main/java/org/capnproto/BuilderArena.java

@@ -24,6 +24,7 @@
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
 import java.util.ArrayList;
+import java.util.List;
 
 public final class BuilderArena implements Arena {
     public enum AllocationStrategy {
@@ -38,6 +39,34 @@ public enum AllocationStrategy {
     public final ArrayList<SegmentBuilder> segments;
     private final Allocator allocator;
 
+    private final CapTableBuilder localCapTable = new CapTableBuilder() {
+
+        private final List<ClientHook> capTable = new ArrayList<>();
+
+        @Override
+        public int injectCap(ClientHook cap) {
+            int result = this.capTable.size();
+            this.capTable.add(cap);
+            return result;
+        }
+
+        @Override
+        public void dropCap(int index) {
+            if (index < this.capTable.size()) {
+                assert false : "Invalid capability descriptor in message.";
+                return;
+            }
+            this.capTable.set(index, null);
+        }
+
+        @Override
+        public ClientHook extractCap(int index) {
+            return index < this.capTable.size()
+                    ? this.capTable.get(index)
+                    : null;
+        }
+    };
+
     public BuilderArena(int firstSegmentSizeWords, AllocationStrategy allocationStrategy) {
         this.segments = new ArrayList<SegmentBuilder>();
         {
@@ -64,7 +93,17 @@ public BuilderArena(Allocator allocator, ByteBuffer firstSegment) {
         this.allocator = allocator;
     }
 
-     /**
+    /**
+     * Return a CapTableBuilder that merely implements local loopback. That is, you can set
+     * capabilities, then read the same capabilities back, but there is no intent ever to transmit
+     * these capabilities. A MessageBuilder that isn't imbued with some other CapTable uses this
+     * by default.
+     */
+    public CapTableBuilder getLocalCapTable() {
+        return this.localCapTable;
+    }
+
+    /**
      * Constructs a BuilderArena from a ReaderArena and uses the size of the largest segment
      * as the next allocation size.
      */

runtime/src/main/java/org/capnproto/CapTableBuilder.java

@@ -0,0 +1,16 @@
+package org.capnproto;
+
+public interface CapTableBuilder extends CapTableReader {
+
+    class BuilderContext {
+        public CapTableBuilder capTable;
+    }
+
+    int injectCap(ClientHook cap);
+
+    void dropCap(int index);
+
+    default ClientHook[] getTable() {
+        return new ClientHook[0];
+    }
+}

runtime/src/main/java/org/capnproto/CapTableReader.java

@@ -0,0 +1,10 @@
+package org.capnproto;
+
+public interface CapTableReader {
+
+    class ReaderContext {
+        public CapTableReader capTable;
+    }
+
+    ClientHook extractCap(int index);
+}

runtime/src/main/java/org/capnproto/Capability.java

@@ -0,0 +1,32 @@
+package org.capnproto;
+
+import static org.capnproto.ClientHook.BROKEN_CAPABILITY_BRAND;
+import static org.capnproto.ClientHook.NULL_CAPABILITY_BRAND;
+
+public final class Capability {
+
+    public static ClientHook newBrokenCap(String reason) {
+        return newBrokenClient(reason, false, BROKEN_CAPABILITY_BRAND);
+    }
+
+    public static ClientHook newBrokenCap(Throwable exc) {
+        return newBrokenClient(exc, false, BROKEN_CAPABILITY_BRAND);
+    }
+
+    public static ClientHook newNullCap() {
+        return newBrokenClient(RpcException.failed("Called null capability"), true, NULL_CAPABILITY_BRAND);
+    }
+
+    private static ClientHook newBrokenClient(String reason, boolean resolved, Object brand) {
+        return newBrokenClient(RpcException.failed(reason), resolved, brand);
+    }
+
+    private static ClientHook newBrokenClient(Throwable exc, boolean resolved, Object brand) {
+        return new ClientHook() {
+            @Override
+            public Object getBrand() {
+                return brand;
+            }
+        };
+    }
+}

runtime/src/main/java/org/capnproto/ClientHook.java

@@ -0,0 +1,29 @@
+package org.capnproto;
+
+public interface ClientHook {
+
+    static final Object NULL_CAPABILITY_BRAND = new Object();
+    static final Object BROKEN_CAPABILITY_BRAND = new Object();
+
+    /**
+     Returns an opaque object that identifies who made this client. This can be used by an RPC adapter to
+     discover when a capability it needs to marshal is one that it created in the first place, and
+     therefore it can transfer the capability without proxying.
+    */
+    Object getBrand();
+
+    /**
+     * Returns true if the capability was created as a result of assigning a Client to null or by
+     * reading a null pointer out of a Cap'n Proto message.
+     */
+    default boolean isNull() {
+        return getBrand() == NULL_CAPABILITY_BRAND;
+    }
+
+    /**
+     * Returns true if the capability was created by newBrokenCap().
+     */
+    default boolean isError() {
+        return getBrand() == BROKEN_CAPABILITY_BRAND;
+    }
+}

runtime/src/main/java/org/capnproto/Data.java

@@ -39,35 +39,42 @@ public final Reader fromPointerReader(SegmentReader segment, int pointer, int ne
             return WireHelpers.readDataPointer(segment, pointer, null, 0, 0);
         }
 
+        @Override
+        public final Reader fromPointerReader(SegmentReader segment, CapTableReader capTable, int pointer, int nestingLimit) {
+            return WireHelpers.readDataPointer(segment, pointer, null, 0, 0);
+        }
+
         @Override
         public final Builder fromPointerBuilderBlobDefault(
             SegmentBuilder segment,
+            CapTableBuilder capTable,
             int pointer,
             java.nio.ByteBuffer defaultBuffer,
             int defaultOffset,
             int defaultSize) {
             return WireHelpers.getWritableDataPointer(pointer,
                                                       segment,
+                                                      capTable,
                                                       defaultBuffer,
                                                       defaultOffset,
                                                       defaultSize);
         }
-
         @Override
-        public final Builder fromPointerBuilder(SegmentBuilder segment, int pointer) {
+        public final Builder fromPointerBuilder(SegmentBuilder segment, CapTableBuilder capTable, int pointer) {
             return WireHelpers.getWritableDataPointer(pointer,
                                                       segment,
+                                                      capTable,
                                                       null, 0, 0);
         }
 
         @Override
-        public final Builder initFromPointerBuilder(SegmentBuilder segment, int pointer, int size) {
-            return WireHelpers.initDataPointer(pointer, segment, size);
+        public final Builder initFromPointerBuilder(SegmentBuilder segment, CapTableBuilder capTable, int pointer, int size) {
+            return WireHelpers.initDataPointer(pointer, segment, capTable, size);
         }
 
         @Override
-        public final void setPointerBuilder(SegmentBuilder segment, int pointer, Reader value) {
-            WireHelpers.setDataPointer(pointer, segment, value);
+        public final void setPointerBuilder(SegmentBuilder segment, CapTableBuilder capTable, int pointer, Reader value) {
+            WireHelpers.setDataPointer(pointer, segment, capTable, value);
         }
     }
     public static final Factory factory = new Factory();

runtime/src/main/java/org/capnproto/FromPointerBuilder.java

@@ -22,6 +22,15 @@
 package org.capnproto;
 
 public interface FromPointerBuilder<T> {
-    T fromPointerBuilder(SegmentBuilder segment, int pointer);
-    T initFromPointerBuilder(SegmentBuilder segment, int pointer, int elementCount);
+    default T fromPointerBuilder(SegmentBuilder segment, int pointer) {
+        return fromPointerBuilder(segment, null, pointer);
+    }
+
+    T fromPointerBuilder(SegmentBuilder segment, CapTableBuilder capTable, int pointer);
+
+    default T initFromPointerBuilder(SegmentBuilder segment, int pointer, int elementCount) {
+        return initFromPointerBuilder(segment, null, pointer, elementCount);
+    }
+
+    T initFromPointerBuilder(SegmentBuilder segment, CapTableBuilder capTable, int pointer, int elementCount);
 }

runtime/src/main/java/org/capnproto/FromPointerBuilderBlobDefault.java

@@ -22,6 +22,11 @@
 package org.capnproto;
 
 public interface FromPointerBuilderBlobDefault<T> {
-    T fromPointerBuilderBlobDefault(SegmentBuilder segment, int pointer,
+    default T fromPointerBuilderBlobDefault(SegmentBuilder segment, int pointer,
+                                    java.nio.ByteBuffer defaultBuffer, int defaultOffset, int defaultSize) {
+        return fromPointerBuilderBlobDefault(segment, null, pointer, defaultBuffer, defaultOffset, defaultSize);
+    }
+
+    T fromPointerBuilderBlobDefault(SegmentBuilder segment, CapTableBuilder capTable, int pointer,
                                     java.nio.ByteBuffer defaultBuffer, int defaultOffset, int defaultSize);
 }

runtime/src/main/java/org/capnproto/FromPointerBuilderRefDefault.java

@@ -22,5 +22,10 @@
 package org.capnproto;
 
 public interface FromPointerBuilderRefDefault<T> {
-    T fromPointerBuilderRefDefault(SegmentBuilder segment, int pointer, SegmentReader defaultSegment, int defaultOffset);
+
+    default T fromPointerBuilderRefDefault(SegmentBuilder segment, int pointer, SegmentReader defaultSegment, int defaultOffset) {
+        return fromPointerBuilderRefDefault(segment, null, pointer, defaultSegment, defaultOffset);
+    }
+
+    T fromPointerBuilderRefDefault(SegmentBuilder segment, CapTableBuilder capTable, int pointer, SegmentReader defaultSegment, int defaultOffset);
 }