#ifndef _NTIOAPI_H
/**
* The FILE_MAILSLOT_QUERY_INFORMATION structure contains information about a mailslot.
*
* \remarks https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntifs/ns-ntifs-_file_mailslot_query_information
*/
typedef struct _FILE_MAILSLOT_QUERY_INFORMATION
{
ULONG MaximumMessageSize; // The maximum size, in bytes, of a single message that can be written to the mailslot, or 0 for a message of any size.
ULONG MailslotQuota; // The size, in bytes, of the in-memory pool that is reserved for writes to this mailslot.
ULONG NextMessageSize; // The next message size, in bytes.
ULONG MessagesAvailable; // The total number of messages waiting to be read from the mailslot.
LARGE_INTEGER ReadTimeout; // The time, in milliseconds, that a read operation can wait for a message to be written to the mailslot before a time-out occurs.
} FILE_MAILSLOT_QUERY_INFORMATION, *PFILE_MAILSLOT_QUERY_INFORMATION;
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This structure is documented in Windows Driver Kit.