# ILockBytes::WriteAt

Writes the specified number of bytes starting at a specified offset from the beginning of the byte array.

HRESULT WriteAt(

ULARGE_INTEGER ulOffset, | //Specifies the starting point for writing data
void const *pv, | //Points to the buffer containing the data to be written
ULONG cb, | //Specifies the number of bytes to write
ULONG *pcbWritten | //Pointer to location that contains actual number of bytes written
); |

Parameters

ulOffset
  [in]Specifies the starting point from the beginning of the byte array for the data to be written.
pv
  [in]Points to the buffer containing the data to be written.
cb
  [in]Specifies the number of bytes of data to attempt to write into the byte array.
pcbRead
  [out]Pointer to a location where this method specifies the actual number of bytes written to the byte array. You can set this pointer to NULL to indicate that you are not interested in this value. In this case, this method does not provide the actual number of bytes written.

Return Values

S_OK
  Indicates that the specified number of bytes were written.
E_FAIL
  A general failure occurred during the write.
E_PENDING
  Asynchronous Storage only: Part or all of the data to be written is currently unavailable. For more information see IFillLockBytes and [insert jump to asynchronous storage overview, which is to come].
STG_E_ACCESSDENIED
  The caller does not have sufficient permissions for writing this byte array.
STG_E_WRITEFAULT
  The number of bytes to be written does not equal the number of bytes that were acutally written.
STG_E_MEDIUMFULL
  The write operation was not completed because there is no space left on the storage device. The actual number of bytes written is still returned in pcbWritten.

Remarks

ILockBytes::WriteAt writes the specified data at the specified location in the byte array. The number of bytes actually written must always be returned in pcbWritten, even if an error is returned. If the byte count is zero bytes, the write operation has no effect.

If ulOffset is past the end of the byte array and cb is greater than zero, ILockBytes::WriteAt increases the size of the byte array. The fill bytes written to the byte array are not initialized to any particular value.

See Also

ILockBytes::ReadAt, ILockBytes::SetSize, ILockBytes&emdash;File-Based Implementation, ILockBytes&emdash;Global Memory Implementation