Source code of Windows XP (NT5)
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BREAK <Disk I/O Buffer Header>
;** BUFFER.INC ; ; Field definition for I/O buffer information
BUFFINFO STRUC buf_next DW ? ; Pointer to next buffer in list buf_prev DW ? ; Pointer to prev buffer in list buf_ID DB ? ; Drive of buffer (bit 7 = 0) ; SFT table index (bit 7 = 1) ; = FFH if buffer free buf_flags DB ? ; Bit 7 = 1 if Remote file buffer ; = 0 if Local device buffer ; Bit 6 = 1 if buffer dirty ; Bit 5 = Reserved ; Bit 4 = Search bit (bit 7 = 1) ; Bit 3 = 1 if buffer is DATA ; Bit 2 = 1 if buffer is DIR ; Bit 1 = 1 if buffer is FAT ; Bit 0 = Reserved buf_sector DD ? ; Sector number of buffer (bit 7 = 0) ; The next two items are often refed as a word (bit 7 = 0) buf_wrtcnt DB ? ; For FAT sectors, # times sector written out buf_wrtcntinc DW ? ; " " " , # sectors between each write buf_DPB DD ? ; Pointer to drive parameters buf_fill DW ? ; How full buffer is (bit 7 = 1) buf_reserved DB ? ; make DWORD boundary for 386 BUFFINFO ENDS
buf_offset EQU DWORD PTR buf_sector ;For bit 7 = 1, this is the byte ;offset of the start of the buffer in ;the file pointed to by buf_ID. Thus ;the buffer starts at location ;buf_offset in the file and contains ;buf_fill bytes.
BUFINSIZ EQU SIZE BUFFINFO ; Size of structure in bytes
buf_Free EQU 0FFh ; buf_id of free buffer
;Flag byte masks buf_isnet EQU 10000000B buf_dirty EQU 01000000B ;*** buf_visit EQU 00100000B ;*** buf_snbuf EQU 00010000B
buf_isDATA EQU 00001000B buf_isDIR EQU 00000100B buf_isFAT EQU 00000010B buf_type_0 EQU 11110001B ; AND sets type to "none"
buf_NetID EQU BUFINSIZ
; ; Buffer Hash Entry Structure ; ;BUFFER_HASH_ENTRY STRUC ; DOS 4.00 ;EMS_PAGE_NUM DW -1 ; logical page number for EMS handle ;BUFFER_BUCKET DD ? ; pointer to buffers ;DIRTY_COUNT DB 0 ; number of dirty buffers ;BUFFER_RESERVED DB 0 ; reserved ;BUFFER_HASH_ENTRY ENDS ; ;MaxBuffinBucket EQU 15 ; Max number of buffers per bucket ;MaxBucketinPage EQU 2 ; Max number of buckets per 16kb page ; ; ; ; ; C A V E A T P R O G R A M M E R ; ;----+----+----+----+----+----+----+----+----+----+----+----+----+----+----;
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