get root

Makefile

@@ -1,6 +1,7 @@
 CXX=g++ -std=c++11
 
 CAPNP_SOURCES=\
+	src/capnp/AnyPointer.java\
 	src/capnp/FieldSize.java\
 	src/capnp/FromStructReader.java\
 	src/capnp/InputStreamMessageReader.java\

src/capnp/AnyPointer.java

@@ -0,0 +1,17 @@
+package capnp;
+
+public class AnyPointer {
+
+    public static class Reader {
+        public PointerReader reader;
+
+        public Reader(PointerReader reader) {
+            this.reader = reader;
+        }
+
+        public <T> T getAsStruct(FromStructReader<T> factory) {
+            return factory.fromStructReader(this.reader.getStruct());
+        }
+    }
+
+}

src/capnp/InputStreamMessageReader.java

@@ -3,24 +3,75 @@ package capnp;
 import java.io.InputStream;
 import java.io.IOException;
 import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.Vector;
+
 
 public class InputStreamMessageReader {
-    static MessageReader create(InputStream is) throws IOException {
-        byte[] firstWord = new byte[8];
+
+    static byte[] readExact(InputStream is, int length) throws IOException {
+        byte[] bytes = new byte[length];
 
         int bytesRead = 0;
-        while (bytesRead < 8) {
-            int n = is.read(firstWord, bytesRead, 8 - bytesRead);
-            if (n < 0) {
+        while (bytesRead < length) {
+            int r = is.read(bytes, bytesRead, length - bytesRead);
+            if (r < 0) {
                 throw new IOException("premature EOF");
             }
-            bytesRead += n;
+            bytesRead += r;
         }
 
-        ByteBuffer.wrap(firstWord);
+        return bytes;
+    }
 
+    static ByteBuffer makeByteBuffer(byte[] bytes) {
+        ByteBuffer result = ByteBuffer.wrap(bytes);
+        result.order(ByteOrder.LITTLE_ENDIAN);
+        return result;
+    }
 
-        throw new Error();
+    public static MessageReader create(InputStream is) throws IOException {
+        ByteBuffer firstWord = makeByteBuffer(readExact(is, 8));
+
+        int segmentCount = 1 + firstWord.getInt();
+
+        int segment0Size = 0;
+        if (segmentCount > 0) {
+            segment0Size = firstWord.getInt(1);
+        }
+
+        int totalWords = segment0Size;
+
+        if (segmentCount > 512) {
+            throw new IOException("too many segments");
+        }
+
+        Vector<Integer> moreSizes = new Vector<Integer>();
+
+        if (segmentCount > 1) {
+            ByteBuffer moreSizesRaw = makeByteBuffer(readExact(is, 4 * (segmentCount & ~1)));
+            for(int ii = 0; ii < segmentCount - 1; ++ii) {
+                int size = moreSizesRaw.getInt(ii);
+                moreSizes.add(size);
+                totalWords += size;
+            }
+        }
+
+        // TODO check that totalWords is reasonable
+
+        byte[] allSegments = readExact(is, totalWords * 8);
+
+        ByteBuffer[] segmentSlices = new ByteBuffer[segmentCount];
+
+        segmentSlices[0] = ByteBuffer.wrap(allSegments, 0, segment0Size);
+        int offset = segment0Size;
+
+        for (int ii = 1; ii < segmentCount; ++ii) {
+            segmentSlices[ii] = ByteBuffer.wrap(allSegments, offset, moreSizes.get(ii - 1));
+            offset += moreSizes.get(ii - 1);
+        }
+
+        return new MessageReader(segmentSlices);
     }
 
 }

src/capnp/MessageReader.java

@@ -1,5 +1,20 @@
 package capnp;
 
-public class MessageReader {
+import java.nio.ByteBuffer;
 
+public class MessageReader {
+    ByteBuffer[] segmentSlices;
+
+    public MessageReader(ByteBuffer[] segmentSlices) {
+        this.segmentSlices = segmentSlices;
+    }
+
+    public <T> T getRoot(FromStructReader<T> factory) {
+        SegmentReader segment = new SegmentReader(this.segmentSlices[0]);
+        PointerReader pointerReader = PointerReader.getRoot(segment,
+                                                            new WordPointer(this.segmentSlices[0], 0),
+                                                            0x7fffffff /* XXX */);
+        AnyPointer.Reader any = new AnyPointer.Reader(pointerReader);
+        return any.getAsStruct(factory);
+    }
 }

src/capnp/PointerReader.java

@@ -17,12 +17,27 @@ public class PointerReader {
         this.nestingLimit = nestingLimit;
     }
 
+    public static PointerReader getRoot(SegmentReader segment,
+                                        WordPointer location,
+                                        int nestingLimit) {
+        // TODO bounds check
+        return new PointerReader(segment, location.offset, nestingLimit);
+    }
+
+    public StructReader getStruct() {
+        WirePointer ref = new WirePointer(this.segment.ptr, this.pointer);
+        return WireHelpers.readStructPointer(this.segment,
+                                             ref,
+                                             this.nestingLimit);
+    }
+
     public ListReader getList(byte expectedElementSize) {
         // TODO check nullness
         WirePointer ref = new WirePointer(this.segment.ptr, this.pointer);
         return WireHelpers.readListPointer(this.segment,
                                            ref,
-                                           expectedElementSize);
+                                           expectedElementSize,
+                                           this.nestingLimit);
     }
 
     public Text.Reader getText() {

src/capnp/SegmentReader.java

@@ -4,4 +4,8 @@ import java.nio.ByteBuffer;
 
 public class SegmentReader {
     ByteBuffer ptr;
+
+    public SegmentReader(ByteBuffer ptr) {
+        this.ptr = ptr;
+    }
 }

src/capnp/WireHelpers.java

@@ -2,8 +2,30 @@ package capnp;
 
 class WireHelpers {
 
+    public static StructReader readStructPointer(SegmentReader segment,
+                                                 WirePointer ref,
+                                                 int nestingLimit) {
+
+        // TODO error handling
+
+        WordPointer ptr = ref.target();
+        StructPointer structPtr = (StructPointer)ref;
+        int dataSizeWords = structPtr.dataSize();
+
+        return new StructReader(segment,
+                                ptr.offset * 8,
+                                (ptr.offset + dataSizeWords) * 8,
+                                dataSizeWords * 64,
+                                structPtr.ptrCount(),
+                                (byte)0,
+                                nestingLimit - 1);
+
+    }
+
+
     public static ListReader readListPointer(SegmentReader segment,
                                              WirePointer ref,
+                                             byte expectedElementSize,
                                              int nestingLimit) {
 
         // TODO check for null, follow fars, nestingLimit
@@ -30,7 +52,7 @@ class WireHelpers {
             // TODO check whether the size is compatible
 
             return new ListReader(segment,    // TODO follow fars
-                                  ptr.offset, //
+                                  ptr.offset * 8, //
                                   size,
                                   wordsPerElement * 64,
                                   structPtr.dataSize() * 64,