Int 1A/AX=B001h/CX=4D52h

Microsoft Real-Time Compression Interface (MRCI) - ROM-BASED SERVER

AX = B001h
CX = 4D52h ("MR")
DX = 4349h ("CI")

Return:
CX = 4943h ("IC") if installed
DX = 524Dh ("RM") if installed
ES:DI -> MRCINFO structure (see #00725)

Note: This call is functionally identical to INT 2F/AX=4A12h, which should be called first, as this call is used for the first, ROM-based MRCI server, while the other call is used for RAM-based servers which may be partially or entirely replacing a prior server

See Also: INT 2F/AX=4A12h

Format of MRCINFO structure: Offset Size Description (Table 00725) 00h 4 BYTEs vendor signature "MSFT" Microsoft 04h WORD server version (high=major) 06h WORD MRCI specification version 08h DWORD address of server entry point (see #00727)

0Ch WORD bit flags:
Server capabilities (see #00726)

0Eh WORD bit flags:
Hardware assisted capabilities (see #00726) 10h WORD maximum block size supported by server (at least 8192 bytes)

Bitfields for MRCI capabilities: Bit(s) Description (Table 00726) 0 standard compress 1 standard decompress 2 update compress 3 MaxCompress (not present in initial public release) 4 reserved 5 incremental decompress 6 MRCI 2.0 standard compress 7 MRCI 2.0 standard decompress 8-14 reserved 15 this structure is in ROM and can't be modified. (server capabilities only)

(Table 00727) Call MRCI entry point with:. DS:SI -> MRCREQUEST structure (see #00728). CX = type of client (0000h application, 0001h file system). AX = operation 0001h perform standard compression 0002h perform standard decompression 0004h perform update compression 0008h perform MaxCompress 0020h perform incremental decompression 0040h perform MRCI 2.0 standard compression 0080h perform MRCI 2.0 standard decompression. AX = FFFFh clear flags BX = bitmask of flags to clear (set bits in BX are flags to clear)

Return:
AX = status 0000h successful 0001h invalid function 0002h server busy, try again 0003h destination buffer too small 0004h incompressible data 0005h bad compressed data format BP destroyed (MS-DOS 6.2)

Note: MRCI driver may chain to a previous driver

Format of MRCREQUEST structure: Offset Size Description (Table 00728) 00h DWORD pointer to source buffer 04h WORD size of source buffer (0000h = 64K) 06h WORD (UpdateCompress only) (call) offset in source buffer of beginning of changed data (ret) offset in destination buffer of beginning of changed compressed data 08h DWORD pointer to destination buffer must contain original compressed data for UpdateCompress 0Ch WORD size of destination buffer (0000h = 64K)

any compression:
Size of buffer for compressed data

standard decompression:
Number of bytes to be decompressed

incremental decompression:
Number of byte to decompress now (ret) actual size of resulting data 0Eh WORD client compressed data storage allocation size 10h DWORD incremental decompression state data set to 00000000h before first incremental decompression call

Notes: The source and destination buffers may not overlap. The source and destination buffer sizes should normally be the same. Application should not update the contents of the MRCREQUEST structure between incremental decompression calls

Category: Disk I/O Enhancements - Int 1Ah - M

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