1e41f4b71Sopenharmony_ci# UsbDeviceMemMap 2e41f4b71Sopenharmony_ci 3e41f4b71Sopenharmony_ci 4e41f4b71Sopenharmony_ci## Overview 5e41f4b71Sopenharmony_ci 6e41f4b71Sopenharmony_ciDevice memory map created by calling [OH_Usb_CreateDeviceMemMap()](_usb_ddk.md#oh_usb_createdevicememmap). A buffer using the device memory map can provide better performance. 7e41f4b71Sopenharmony_ci 8e41f4b71Sopenharmony_ci**Since** 9e41f4b71Sopenharmony_ci 10e41f4b71Sopenharmony_ci10 11e41f4b71Sopenharmony_ci 12e41f4b71Sopenharmony_ci**Related Modules** 13e41f4b71Sopenharmony_ci 14e41f4b71Sopenharmony_ci[USB DDK](_usb_ddk.md) 15e41f4b71Sopenharmony_ci 16e41f4b71Sopenharmony_ci 17e41f4b71Sopenharmony_ci## Summary 18e41f4b71Sopenharmony_ci 19e41f4b71Sopenharmony_ci 20e41f4b71Sopenharmony_ci### Member Variables 21e41f4b71Sopenharmony_ci 22e41f4b71Sopenharmony_ci| Name| Description| 23e41f4b71Sopenharmony_ci| -------- | -------- | 24e41f4b71Sopenharmony_ci| [address](#address) | Buffer address.| 25e41f4b71Sopenharmony_ci| [size](#size) | Buffer size.| 26e41f4b71Sopenharmony_ci| [offset](#offset) | Offset of the used buffer. The default value is 0, indicating that there is no offset and the buffer starts from the specified address.| 27e41f4b71Sopenharmony_ci| [bufferLength](#bufferlength) | Length of the used buffer. By default, the value is equal to the size, indicating that the entire buffer is used.| 28e41f4b71Sopenharmony_ci| [transferedLength](#transferedlength) | Length of the transferred data.| 29e41f4b71Sopenharmony_ci 30e41f4b71Sopenharmony_ci 31e41f4b71Sopenharmony_ci## Member Variable Description 32e41f4b71Sopenharmony_ci 33e41f4b71Sopenharmony_ci 34e41f4b71Sopenharmony_ci### address 35e41f4b71Sopenharmony_ci 36e41f4b71Sopenharmony_ci 37e41f4b71Sopenharmony_ci``` 38e41f4b71Sopenharmony_ciuint8_t* const UsbDeviceMemMap::address 39e41f4b71Sopenharmony_ci``` 40e41f4b71Sopenharmony_ci 41e41f4b71Sopenharmony_ci**Description** 42e41f4b71Sopenharmony_ci 43e41f4b71Sopenharmony_ci Buffer address. 44e41f4b71Sopenharmony_ci 45e41f4b71Sopenharmony_ci 46e41f4b71Sopenharmony_ci### bufferLength 47e41f4b71Sopenharmony_ci 48e41f4b71Sopenharmony_ci 49e41f4b71Sopenharmony_ci``` 50e41f4b71Sopenharmony_ciuint32_t UsbDeviceMemMap::bufferLength 51e41f4b71Sopenharmony_ci``` 52e41f4b71Sopenharmony_ci 53e41f4b71Sopenharmony_ci**Description** 54e41f4b71Sopenharmony_ci 55e41f4b71Sopenharmony_ciLength of the used buffer. By default, the value is equal to the size, indicating that the entire buffer is used. 56e41f4b71Sopenharmony_ci 57e41f4b71Sopenharmony_ci 58e41f4b71Sopenharmony_ci### offset 59e41f4b71Sopenharmony_ci 60e41f4b71Sopenharmony_ci 61e41f4b71Sopenharmony_ci``` 62e41f4b71Sopenharmony_ciuint32_t UsbDeviceMemMap::offset 63e41f4b71Sopenharmony_ci``` 64e41f4b71Sopenharmony_ci 65e41f4b71Sopenharmony_ci**Description** 66e41f4b71Sopenharmony_ci 67e41f4b71Sopenharmony_ciOffset of the used buffer. The default value is 0, indicating that there is no offset and the buffer starts from the specified address. 68e41f4b71Sopenharmony_ci 69e41f4b71Sopenharmony_ci 70e41f4b71Sopenharmony_ci### size 71e41f4b71Sopenharmony_ci 72e41f4b71Sopenharmony_ci 73e41f4b71Sopenharmony_ci``` 74e41f4b71Sopenharmony_ciconst size_t UsbDeviceMemMap::size 75e41f4b71Sopenharmony_ci``` 76e41f4b71Sopenharmony_ci 77e41f4b71Sopenharmony_ci**Description** 78e41f4b71Sopenharmony_ci 79e41f4b71Sopenharmony_ciBuffer size. 80e41f4b71Sopenharmony_ci 81e41f4b71Sopenharmony_ci 82e41f4b71Sopenharmony_ci### transferedLength 83e41f4b71Sopenharmony_ci 84e41f4b71Sopenharmony_ci 85e41f4b71Sopenharmony_ci``` 86e41f4b71Sopenharmony_ciuint32_t UsbDeviceMemMap::transferedLength 87e41f4b71Sopenharmony_ci``` 88e41f4b71Sopenharmony_ci 89e41f4b71Sopenharmony_ci**Description** 90e41f4b71Sopenharmony_ci 91e41f4b71Sopenharmony_ciLength of the transferred data. 92