>>I need to convert binary strings to ascii by changing nonprintable non-ascii
>>charaters to a \\nnn strings where nnn is octal representation.
>>
>>I created the following routine. For 381 KB byte strings, the conversion takes 5 (!) minutes and task manager shows that my application takes a lot of MBs memory.
>>
>>Any way to speed up this conversion ?
>>
>>

FUNCTION toBYTEA( cStr )
>>
>>LOCAL i, j, cRes, nChr, cDig
>>
>>cRes = ''
>>FOR i=1 TO LEN(m.cStr)
>>  nChr = ASC( SUBSTR( m.cStr, m.i,1))
>>  * The following four lines cna be removed if this can speed the conversion.
>>  IF BETWEEN( nChr, 32,126 ) AND !INLIST( nChr,39,92)
>>    cRes = m.cRes + SUBSTR( m.cStr, m.i,1)
>>    LOOP
>>    ENDIF
>>
>>  cDig = ''
>>  FOR j=1 TO 3
>>    cDig= CHR(ASC('0')+ m.nChr%8) + m.cDig
>>    nChr = INT(m.nChr/8)
>>    ENDFOR
>>  cRes = m.cRes + '\\'+ m.cDig
>>  ENDFOR
>>RETURN m.cRes
>>ENDFUNC

>
>Andrus,
>
>VFP's code optimization is near to zero.
>
>With your code VFP copy the 381KB string
>1+381KB*(1+x+0.5+)=381000 ..780000 times
>Then VFP move more of 150..304GB !
>
>Until a VFPM (Calvin Hsia ? ) implement a @m.string reference for VFP commands
>all VFP programs with large string suffer of this problem.
>
>This can reduce the time ( put m. everywhere )
>

>FUNCTION toBYTEA( cStr )
>
>	PRIVATE i,  cRes, cChr, nChr
>
>	cRes = ''
>	FOR i=1 TO LEN(m.cStr)
>		STORE SUBSTR( m.cStr, m.i,1)	TO cChr
>		STORE ASC( m.cChr)				TO nChr
>		cRes = m.cRes + IIF(BETWEEN( m.nChr, 32,126 ) AND !INLIST( m.nChr,39,92);
>	  			,	m.cChr	;
>	  			,	'\\'+ CHR(48+ BITAND(m.nChr/64,7))+CHR(48+ BITAND(m.nChr/8,7))+CHR(48+ BITAND(m.nChr,7)))
>	ENDFOR
>	RETURN m.cRes
>ENDFUNC
>

>
>your Vfp VERSION ?

hi Fabio,

I agree for the m. prefix

Still, I'd say that appending a byte to a string 381 k times, is really slowing it down

The string has to be reallocated/expanded 381k times
Bytes moved totally = (381*1024) * (381*1024+1) / 2 is about (381*1024)^2/2 or over 72 Gb (if the string is not expanded at the same place in memory)


The StrTran() approach works faster imo

I get for a worst case (repl(chr(0), 381*1024)) less than 13 sec with strtran() where the string is reallocated 163 times