I know this is one of the most trivial things to implement in a high level language. In C it goes like this:<\/p>\n
void print_integer(unsigned int x)
\n{
\nif ((x \/ 10) != 0) pi(x \/ 10);
\nputch((x % 10) + ‘0’);
\n}<\/p>\n
The annoying thing is that you have to div twice and do a modulo once. Which in reality can be merged into a single X86 instruction. Another thing is that if you want to be able to print a normal result for an input of 0 you will have to test the result of the division instead of checking simply x itself. The conversion is done from the least significant digit to the most. But when we display the result (or put it in a buffer) we have to reverse it. Therefore the recursion is so handy here. This is my go in 16bit, it’s a code that I wrote a few years ago, and I just decided I should put it here for a reference. I have to admit that I happened to use this same code for also 32bits or even different processors and since it’s so elegant it works so well and easy to port. But I leave it for you to judge ;)<\/p>\n
bits 16
\nmov ax, 12345
\ncall print_integer
\nxor ax, ax
\ncall print_integer
\nret<\/p>\n
print_integer:
\n; base 10
\npush byte 10
\npop bx
\n.next:; make a 32 bits division, remainder in dx, quotient in ax
\nxor dx, dx
\ndiv bx
\npush dx ; push remainder
\nor ax, ax ; if the result if 0, we will stop recursing
\njz .stop
\ncall .next ; now this is the coolest twist ever, the IP that is pushed onto the stack…
\n.stop:
\npop ax ; get the remainder (in reversed order)
\nadd al, 0x30 ; convert it to a character
\nint 0x29 ; use (what used to be an undocumented) interrupt to print al
\nret ; go back to ‘stop’ and read the next digit…<\/p>\n
I urge you to compile the C code with full optimization and compare the codes for yourself.<\/p>\n","protected":false},"excerpt":{"rendered":"
I know this is one of the most trivial things to implement in a high level language. In C it goes like this: void print_integer(unsigned int x) { if ((x \/ 10) != 0) pi(x \/ 10); putch((x % 10) + ‘0’); } The annoying thing is that you have to div twice and do […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":"","jetpack_publicize_message":""},"categories":[21,5],"tags":[],"jetpack_featured_media_url":"","jetpack_publicize_connections":[],"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/pbWKd-Q","_links":{"self":[{"href":"https:\/\/www.ragestorm.net\/blogs\/index.php?rest_route=\/wp\/v2\/posts\/52"}],"collection":[{"href":"https:\/\/www.ragestorm.net\/blogs\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ragestorm.net\/blogs\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ragestorm.net\/blogs\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ragestorm.net\/blogs\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=52"}],"version-history":[{"count":0,"href":"https:\/\/www.ragestorm.net\/blogs\/index.php?rest_route=\/wp\/v2\/posts\/52\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.ragestorm.net\/blogs\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=52"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ragestorm.net\/blogs\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=52"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ragestorm.net\/blogs\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=52"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}