Date: Mon, 16 May 2005 22:56:47 +0200 From: alexander <arundel@h3c.de> To: freebsd-hackers@freebsd.org Subject: Re: Console ASCII interpretation Message-ID: <20050516205647.GA21498@skatecity> In-Reply-To: <200505162032.j4GKWFqe072034@realtime.exit.com> References: <20050516202029.GA21139@skatecity> <200505162032.j4GKWFqe072034@realtime.exit.com>
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On Mon May 16 05, Frank Mayhar wrote: > > Not "much easier." "Correct." > > The fact that your code wrote three NULs to the console in the first > place meant that your code, not the console, was broken. > -- > Frank Mayhar frank@exit.com http://www.exit.com/ > Exit Consulting http://www.gpsclock.com/ > http://www.exit.com/blog/frank/ OK. Got it. I was just a bit surprised, because the code I'm using is taken from a site called 'The assembly gems page'. The author claims that he tested this code very throroughly. It seems not thoroughly enough. Thx for all the help. ***************************************************************************** Here's the code if anybody is interested. %eax=ulong, %edi=mem_pointer ulong2ascii: ; Credits go to Norbert Juffa and ; John Eckerdal's 'Assembly Gems page' ; at http://www.df.lth.se/~john_e/ mov ecx,eax ; save original argument mov esi,89705f41h ; 1e-9*2^61 rounded mul esi ; divide by 1e9 by mult. with recip. add eax,80000000h ; round division result mov esi,0abcc7712h ; 2^28/1e8 * 2^30 rounded up adc edx,0 ; EDX<31:29> = argument / 1e9 mov eax,ecx ; restore original argument shr edx,29 ; leading decimal digit, 0...4 mov ecx,8 ; produce eight more digits mov ebx,edx ; flags whether non-zero digit seen yet or edx,'0' ; convert digit to ASCII mov [edi],dl ; store out to memory cmp ebx,1 ; first digit nonzero ? CY=0 : CY=1 sbb edi,-1 ; incr. pointer if first digit non-zero imul ebx,1000000000 ; multiply quotient digit by divisor sub eax,ebx ; remainder after first digit mul esi ; convert number < 1e9 shld edx,eax, 2 ; into fraction such inc edx ; that 1.0 = 2^28 mov eax,edx ; save result shr eax,28 ; next digit and edx,0fffffffh ; fraction part or ebx,eax ; any non-zero yet ? or eax,'0' ; convert digit to ASCII cvt_loop: mov [edi],al ; store digit out to memory add edx,edx ; 2*fraction cmp ebx,1 ; any non-zero digit seen ? CY=0 : CY=1 lea edx,[edx*4+edx] ; 10*fraction, new digit EAX<31:28>, ; new fraction EAX<27:0> sbb edi,-1 ; incr. ptr if any non-zero digit seen mov eax,edx ; save result shr eax,28 ; next digit = integer part and edx,0fffffffh ; fraction part or ebx,eax ; any non-zero digit yet ? or eax,'0' ; convert digit to ASCII dec ecx ; one more digit jnz cvt_loop ; until all nine digits done mov [edi],al ; store last digit out to memory mov [edi+1],ah ; place string end marker ret *****************************************************************************
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