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Here is a sample RPG program which takes into consideration the EBCDIC to ASCII conversion, the hash generation, and the creation of a
suitable text string. The program assumes that EBCDIC means CCSID 37 and ASCII CCSID 819. These assumptions may not hold true for all languages.
Bruce
H DFTACTGRP(*NO) ACTGRP('QILE') BNDDIR('QC2LE')
DCipher PR EXTPROC('_CIPHER')
D * VALUE
D * VALUE
D * VALUE
DConvert PR EXTPROC('_XLATEB')
D * VALUE
D * VALUE
D 10u 0 VALUE
Dcvthc PR EXTPROC('cvthc')
D 1
D 1
D 10i 0 VALUE
DControls DS
D Function 5i 0 inz(5)
D HashAlg 1 inz(x'00')
D Sequence 1 inz(x'00')
D DataLngth 10i 0 inz(15)
D Unused 8 inz(*LOVAL)
D HashCtxPtr * inz(%addr(HashWorkArea))
DHashWorkArea S 96 inz(*LOVAL)
DMsg S 50
DReceiverHex S 16
DReceiverPtr S * inz(%addr(ReceiverHex))
DReceiverChr S 32
DSourcePtr S * inz(%addr(Msg))
DStartMap s 256
DTo819 s 256
DCCSID1 s 10i 0 inz(37)
DST1 s 10i 0 inz(0)
DL1 s 10i 0 inz(%size(StartMap))
DCCSID2 s 10i 0 inz(819)
DST2 s 10i 0 inz(0)
DGCCASN s 10i 0 inz(0)
DL2 s 10i 0 inz(%size(To819))
DL3 s 10i 0
DL4 s 10i 0
DFB s 12
D ds
D x 5i 0
D LowX 2 2
D* Get all single byte ebcdic hex values
C 0 do 255 x
C eval %subst(StartMap:x+1:1) = LowX
C enddo
C* Get conversion table for 819 from 37
C call 'QTQCVRT'
C parm CCSID1
C parm ST1
C parm StartMap
C parm L1
C parm CCSID2
C parm ST2
C parm GCCASN
C parm L2
C parm To819
C parm L3
C parm L4
C parm FB
C* Set message text
C eval Msg = 'message digest'
C eval DataLngth = %len(%trimr(Msg))
C* Now Change Msg to 819 from 37 using MI
C callp Convert( %addr(Msg)
C :%addr(To819)
C :%size(Msg))
C* Get MD5 for Msg
C callp Cipher( %addr(ReceiverPtr)
C :%addr(Controls)
C :%addr(SourcePtr))
C* Convert nibbles to characters
C callp cvthc( ReceiverChr
C :ReceiverHex
C :%size(ReceiverChr))
C* Display the "proof"
C ReceiverChr dsply
C eval *INLR = '1'
C return
P*--------------------------------------------------
P* Procedure name: calculateMD5Checksum
P* Purpose:
P* Returns: MD5 checksum value
P* Parameter: ifsobj => IFS object
P*--------------------------------------------------
P calculateMD5Checksum...
P B
D calculateMD5Checksum...
D PI 32A
D streamfile 5000A CONST
D OPTIONS(*VARSIZE)
D* Local fields
D md5value S 32A
*
* _CIPHER MI builtin. Allows access to cryptographic
* functions in the licensed internal code.
*
D cipher PR extproc('_CIPHER')
D receiver * value
D control * value
D source * value
D HASH C const(5)
D MD5 C const(x'00')
D SHA1 C const(x'01')
D ONLY C const(x'00')
D FIRST C const(x'01')
D MIDDLE C const(x'02')
D FINAL C const(x'03')
*
* These control how the system creates a hash
*
D HashCtrl DS qualified
D Function 5I 0 inz(HASH)
D HashAlg 1A inz(x'00')
D Sequence 1A inz(x'00')
D Length 10I 0 inz
D Output 1A inz(x'00')
D Reserved 7A inz(x'00000000000000')
D CtxPtr * inz(%addr(WorkArea))
D WorkArea S 160A inz(*loval)
*
* MI builtin to create a hex dump of a spot in memory
*
D hexdump PR EXTPROC('cvthc')
D output 40A
D input 20A
D output_len 10I 0 value
D fsstats ds likeds(ds_statvfs)
D ReadBuf S *
D BufSize s 10I 0
D Len s 10I 0
D fd s 10I 0
D BinHash S 20A inz(*loval)
D hexHash S 40A inz(*loval)
D p_BinHash s * inz(%addr(BinHash))
/FREE
if (statvfs( %trimr(StreamFile): fsstats ) = -1);
ReportError();
endif;
BufSize = fsstats.f_bsize * 8;
ReadBuf = %alloc(BufSize);
//
// Open the stream file for reading
//
fd = open( %trimr(StreamFile) : O_RDONLY+O_LARGEFILE );
if (fd < 0);
dealloc readbuf;
ReportError();
endif;
// Read stream file, calculate hash on each chunk
// of data.
len = read(fd: readBuf: bufSize);
hashCtrl.Sequence = FIRST;
dow (len > 0);
hashCtrl.Length = len;
cipher( %addr(p_BinHash)
: %addr(HashCtrl)
: %addr(ReadBuf) );
len = read(fd: readBuf: bufSize);
hashCtrl.Sequence = MIDDLE;
enddo;
// At the very end, call cipher with Sequence=FINAL
// to get back the MD5 hash
hashCtrl.Sequence = FINAL;
hashCtrl.Length = 0;
cipher( %addr(p_BinHash)
: %addr(HashCtrl)
: %addr(ReadBuf) );
dealloc readbuf;
callp close(fd);
// Apps that use MD5 hashes usually want them to be
// hexidecimal and lowercase. Here, that is done...
hexdump( HexHash : BinHash : %size(HexHash) );
HexHash = %xlate('ABCDEF': 'abcdef': HexHash);
md5value= %subst(hexhash : 1: 32);
RETURN md5value;
/END-FREE
P calculateMD5Checksum...
P E
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