UnityのNativePluginで、Unity側のC#スクリプトからbyte配列を渡したり、プラグイン側からbyte配列を受け取る方法

Binding.cs

using UnityEngine;
using System.Runtime.InteropServices;
using System.Text;
using System.IO;
using System;

public class Binding {

	[DllImport("__Internal")]
	private static extern bool Test(byte[] ptrSrc, int srcLength, ref IntPtr ptrDest, ref int destLength);
	
	[DllImport("__Internal")]
	private static extern void Free_Memory(ref IntPtr ptrData);

	public static void Test ()
	{
		if (Application.platform == RuntimePlatform.IPhonePlayer) {
			MemoryStream ms = new MemoryStream();
			BinaryWriter bw = new BinaryWriter(ms);
			// TODO write
			bw.Flush();
			byte[] srcData = ms.ToArray();
			bw.Close();
			ms.Close();

			IntPtr ptrResult = IntPtr.Zero;
			int resultLength = 0;
			bool success = Test(srcData, srcData.Length, ref ptrResult, ref resultLength);
			byte[] result = null;
			if (success) {
				result = new byte[resultLength];
				Marshal.Copy(ptrResult, result, 0, resultLength);
				Free_Memory (ref ptrResult);
				ms = new MemoryStream(result);
				long length = ms.Length;
				BinaryReader br = new BinaryReader(ms);
				// TODO read
				br.Close();
				ms.Close();
			}
		}
	}
}

Plugin.m

bool Test (const char** ptrSrc, const int srcLength, char** ptrDest, int* destLength)
{
	NSData *src = [NSData dataWithBytes:(const void *)ptrSrc length:(sizeof(unsigned char) * srcLength)];
	// TODO read
	
	NSMutableData *result = [[[NSMutableData alloc] initWithLength:0] autorelease];
	// TODO write
	int test = 123;
	[result appendData:[NSData dataWithBytes:&test length:sizeof(test)]];
	
	NSUInteger length = [result length];
	*ptrDest = (char*)malloc(length);
	memcpy(*ptrDest, [result bytes], length);
	*destLength = length;
	return true;
}

void Free_Memory (char** ptrDest)
{
	free(*ptrDest);
}