From 2902b6c753930d0c5805bb2d98483aa5afdb24f2 Mon Sep 17 00:00:00 2001
From: David Renshaw <dwrenshaw@gmail.com>
Date: Tue, 4 Nov 2014 21:53:34 -0500
Subject: [PATCH] working on WireHelpers.zeroObject

---
 .../java/org/capnproto/SegmentBuilder.java    |  5 ++
 .../main/java/org/capnproto/WireHelpers.java  | 54 ++++++++++++++++++-
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/runtime/src/main/java/org/capnproto/SegmentBuilder.java b/runtime/src/main/java/org/capnproto/SegmentBuilder.java
index 216a50c..5ac34ff 100644
--- a/runtime/src/main/java/org/capnproto/SegmentBuilder.java
+++ b/runtime/src/main/java/org/capnproto/SegmentBuilder.java
@@ -63,4 +63,9 @@ public final class SegmentBuilder extends SegmentReader {
     public final BuilderArena getArena() {
         return (BuilderArena)this.arena;
     }
+
+    public final boolean isWritable() {
+        // TODO support external non-writable segments
+        return true;
+    }
 }
diff --git a/runtime/src/main/java/org/capnproto/WireHelpers.java b/runtime/src/main/java/org/capnproto/WireHelpers.java
index 446b9d1..f46334d 100644
--- a/runtime/src/main/java/org/capnproto/WireHelpers.java
+++ b/runtime/src/main/java/org/capnproto/WireHelpers.java
@@ -166,9 +166,54 @@ final class WireHelpers {
         //# about to be overwritten making the target object no longer
         //# reachable.
 
-        // TODO
+        //# We shouldn't zero out external data linked into the message.
+        if (!segment.isWritable()) return;
+
+        long ref = segment.get(refOffset);
+
+        switch (WirePointer.kind(ref)) {
+        case WirePointer.STRUCT:
+        case WirePointer.LIST:
+            zeroObject(segment, ref, WirePointer.target(refOffset, ref));
+            break;
+        case WirePointer.FAR: {
+            segment = segment.getArena().getSegment(FarPointer.getSegmentId(ref));
+            if (!segment.isWritable()) { //# Don't zero external data.
+                // TODO
+
+            }
+            break;
+        }
+        case WirePointer.OTHER: {
+        }
+        }
     }
 
+    static void zeroObject(SegmentBuilder segment, long tag, int ptr) {
+        //# We shouldn't zero out external data linked into the message.
+        if (!segment.isWritable()) return;
+
+        switch (WirePointer.kind(tag)) {
+        case WirePointer.STRUCT: {
+            int pointerSection = ptr + StructPointer.dataSize(tag);
+            int count = StructPointer.ptrCount(tag);
+            for (int ii = 0; ii < count; ++ii) {
+                zeroObject(segment, pointerSection + ii);
+            }
+            memset(segment.buffer, ptr * Constants.BYTES_PER_WORD, (byte)0,
+                   StructPointer.wordSize(tag) * Constants.BYTES_PER_WORD);
+            break;
+        }
+        case WirePointer.LIST: {
+            // TODO
+            break;
+        }
+        case WirePointer.FAR:
+            throw new Error("Unexpected FAR pointer.");
+        case WirePointer.OTHER:
+            throw new Error("Unexpected OTHER pointer.");
+        }
+    }
 
     static <T> T initStructPointer(StructBuilder.Factory<T> factory,
                                    int refOffset,
@@ -625,6 +670,13 @@ final class WireHelpers {
         }
     }
 
+    static void memset(ByteBuffer dstBuffer, int dstByteOffset, byte value, int length) {
+        // TODO we can probably do this faster
+        for (int ii = dstByteOffset; ii < dstByteOffset + length; ++ii) {
+            dstBuffer.put(ii, value);
+        }
+    }
+
     static void memcpy(ByteBuffer dstBuffer, int dstByteOffset, ByteBuffer srcBuffer, int srcByteOffset, int length) {
         ByteBuffer dstDup = dstBuffer.duplicate();
         dstDup.position(dstByteOffset);