Function CopyBuffer

engine/gamesys/src/gamesys/scripts/script_buffer.cpp:596–681

copies one buffer to another * * Copy all data streams from one buffer to another, element wise. * * [icon:attention] Each of the source streams must have a matching stream in the * destination buffer. The streams must match in both type and size. * The source and destination buffer can be the same. * * @name buffer.copy_buffer * @param dst [type:buffer

     * ```
    */
    static int CopyBuffer(lua_State* L)
    {
        DM_LUA_STACK_CHECK(L, 0);

        dmBuffer::HBuffer dst_hbuffer = dmScript::CheckBufferUnpack(L, 1);
        dmBuffer::HBuffer src_hbuffer = dmScript::CheckBufferUnpack(L, 3);
        dmBuffer::HBuffer dstbuffer = dst_hbuffer;
        dmBuffer::HBuffer srcbuffer = src_hbuffer;
        int dstoffset = luaL_checkint(L, 2);
        int srcoffset = luaL_checkint(L, 4);
        int count = luaL_checkint(L, 5);

        // Validate first
        if( count <= 0 )
        {
            return DM_LUA_ERROR("Invalid elements to copy: %u", count);
        }

        dmBuffer::Result r;
        uint32_t dstcount;
        uint32_t srccount;
        dmBuffer::GetCount(dstbuffer, &dstcount);
        dmBuffer::GetCount(srcbuffer, &srccount);
        if( (dstoffset + count) > (int)dstcount )
        {
            return DM_LUA_ERROR("Trying to write too many elements: Destination buffer length: %u, Offset: %u, Values to copy: %u", dstcount, dstoffset, count);
        }
        if( (srcoffset + count) > (int)srccount )
        {
            return DM_LUA_ERROR("Trying to read too many elements: Destination buffer length: %u, Offset: %u, Values to copy: %u", dstcount, dstoffset, count);
        }

        // Validate that target buffer has those stream names
        uint32_t num_streams;
        dmBuffer::GetNumStreams(srcbuffer, &num_streams);

        // Simple optimisation: Reusing this struct to hold some data between the validation step and the actual copy step
        BufferStream* stream_info = (BufferStream*)alloca( num_streams * 2 * sizeof(BufferStream) );

        for( uint32_t i = 0; i < num_streams; ++i )
        {
            BufferStream* dststream = &stream_info[i*2 + 0];
            BufferStream* srcstream = &stream_info[i*2 + 1];

            dmBuffer::GetStreamName(srcbuffer, i, &srcstream->m_Name);
            dmhash_t stream_name = srcstream->m_Name;

            r = dmBuffer::GetStream(dstbuffer, stream_name, (void**)&dststream->m_Data, &dststream->m_Count, &dststream->m_TypeCount, &dststream->m_Stride);
            if( r == dmBuffer::RESULT_STREAM_MISSING )
            {
                return DM_LUA_ERROR("buffer.copy_buffer: Destination buffer has no stream named: %s", dmHashReverseSafe64(stream_name));
            }
            else if( r != dmBuffer::RESULT_OK )
            {
                return DM_LUA_ERROR("buffer.copy_buffer: Failed getting destination byte array: %s", dmBuffer::GetResultString(r));
            }

            dmBuffer::GetStream(srcbuffer,  stream_name, (void**)&srcstream->m_Data, &srcstream->m_Count, &srcstream->m_TypeCount, &srcstream->m_Stride);