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Update C# FlatBufferBuilder to reuse vtable array 

This commit updates the FlatBufferBuilder class to reuse the vtable
array instead of creating a new array with every StartObject() call.
This commit is contained in:
belldon 2015-12-04 10:49:03 -05:00
parent 8e6758d205
commit d5a113e5bf
1 changed files with 27 additions and 12 deletions
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39
net/FlatBuffers/FlatBufferBuilder.cs
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@ -14,9 +14,11 @@
* limitations under the License.
*/
using System;
using System.Text;
namespace FlatBuffers
{
/// <summary>
@ -29,8 +31,10 @@ namespace FlatBuffers
private ByteBuffer _bb;
private int _minAlign = 1;
// The vtable for the current table, null otherwise.
private int[] _vtable;
// The vtable for the current table (if _vtableSize >= 0)
private int[] _vtable = new int[16];
// The size of the vtable. -1 indicates no vtable
private int _vtableSize = -1;
// Starting offset of the current struct/table.
private int _objectStart;
// List of offsets of all vtables.
@ -54,9 +58,9 @@ namespace FlatBuffers
_space = _bb.Length;
_bb.Reset();
_minAlign = 1;
_vtable = null;
while (_vtableSize > 0) _vtable[--_vtableSize] = 0;
_vtableSize = -1;
_objectStart = 0;
_vtables = new int[16];
_numVtables = 0;
_vectorNumElems = 0;
}
@ -226,15 +230,22 @@ namespace FlatBuffers
{
// You should not be creating any other objects or strings/vectors
// while an object is being constructed
if (_vtable != null)
if (_vtableSize >= 0)
throw new Exception(
"FlatBuffers: object serialization must not be nested.");
}
public void StartObject(int numfields)
{
if (numfields < 0)
throw new ArgumentOutOfRangeException("Flatbuffers: invalid numfields");
NotNested();
_vtable = new int[numfields];
if (_vtable.Length < numfields)
_vtable = new int[numfields];
_vtableSize = numfields;
_objectStart = Offset;
}
@ -243,6 +254,9 @@ namespace FlatBuffers
// buffer.
public void Slot(int voffset)
{
if (voffset >= _vtableSize)
throw new IndexOutOfRangeException("Flatbuffers: invalid voffset");
_vtable[voffset] = Offset;
}
@ -284,30 +298,31 @@ namespace FlatBuffers
public int EndObject()
{
if (_vtable == null)
if (_vtableSize < 0)
throw new InvalidOperationException(
"Flatbuffers: calling endObject without a startObject");
AddInt((int)0);
var vtableloc = Offset;
// Write out the current vtable.
for (int i = _vtable.Length - 1; i >= 0 ; i--) {
for (int i = _vtableSize - 1; i >= 0 ; i--) {
// Offset relative to the start of the table.
short off = (short)(_vtable[i] != 0
? vtableloc - _vtable[i]
: 0);
AddShort(off);
// clear out written entry
_vtable[i] = 0;
}
const int standardFields = 2; // The fields below:
AddShort((short)(vtableloc - _objectStart));
AddShort((short)((_vtable.Length + standardFields) *
AddShort((short)((_vtableSize + standardFields) *
sizeof(short)));
// Search for an existing vtable that matches the current one.
int existingVtable = 0;
for (int i = 0; i < _numVtables; i++) {
int vt1 = _bb.Length - _vtables[i];
int vt2 = _space;
@ -348,7 +363,7 @@ namespace FlatBuffers
_bb.PutInt(_bb.Length - vtableloc, Offset - vtableloc);
}
_vtable = null;
_vtableSize = -1;
return vtableloc;
}