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POIs there a way to mmap a stdin?
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copied!<p>I have a following problem:</p> <p>My job is to write a program that takes unsigned integer numbers that are passed to it through stdin and print out only the numbers that have more than 2 bits set to one. How should I do it efficiently? I did a version of a program where I read the numbers from a file using mmap, and it's quite quick. I read it like a very big *char buffer and using strtol I 'scrub' out each number and do my check and whatnot. </p> <p>Is there a way to operate on a string passed through stdin the same way? I though about buffering using fread, but there is a problem, where the buffer cuts off the number (meaning if i pass "1024 35" and I have a 6 byte buffer I will get "1024 3"), and I shudder to think how to get around that.</p> <p>Source:</p> <pre><code>#include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <unistd.h> #include <sys/mman.h> #include <sys/types.h> #include <sys/stat.h> #include <sys/mman.h> /* mmap() is defined in this header */ #include <fcntl.h> #include<string.h> #include"apue.h" int main (int argc, char *argv[]) { int fdin, fdout; char *src, *dst; struct stat statbuf; /* open the input file */ if ((fdin = open (argv[1], O_RDONLY)) < 0) {printf("can't open %s for reading", argv[1]);return 1;} /* find size of input file */ if (fstat (fdin,&statbuf) < 0) {printf("fstat error");return 1;} /* mmap the input file */ if ((src = mmap (0, statbuf.st_size, PROT_READ, MAP_SHARED, fdin, 0)) == (caddr_t) -1) {printf("mmap error for input");return 1;} char* beg=src; long x; char* end=&src[statbuf.st_size-1]; while(src<end) { beg=src; x = strtol (src,&src,10); if(!((x != 0) && ((x & (~x + 1)) == x))) fwrite(beg, 1, (int)(src-beg), stdout); } return 0; } </code></pre> <p><a href="http://pastebin.com/EVhG3x79" rel="nofollow">http://pastebin.com/EVhG3x79</a></p>

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