From 88179a47fe5871f9af2eba5706fb32d036b7991c Mon Sep 17 00:00:00 2001 From: Peter Wu Date: Sat, 30 Nov 2013 19:40:55 +0100 Subject: xor-files: xor two files --- xor-files.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 xor-files.c diff --git a/xor-files.c b/xor-files.c new file mode 100644 index 0000000..762ad63 --- /dev/null +++ b/xor-files.c @@ -0,0 +1,63 @@ +/* Calculates the xor of two files. + * Copyright (C) 2013 Peter Wu + */ + +#include +#include +#include +#include + +int main(int argc, char **argv) { + int fd1, fd2; + int r1, r2; + + if (argc < 3) + errx(1, "Usage: xor-files file1 file2"); + + fd1 = open(argv[1], O_RDONLY); + if (fd1 < 0) + errx(1, "open(%s)", argv[1]); + + fd2 = open(argv[2], O_RDONLY); + if (fd2 < 0) + errx(1, "open(%s)", argv[2]); + + do { + int errno1, errno2; + char buf1[1024], buf2[1024]; + int i; + + r1 = read(fd1, buf1, sizeof(buf1)); + errno1 = errno; + r2 = read(fd2, buf2, sizeof(buf2)); + errno2 = errno; + + if (r1 == -1) { + errno = errno1; + warn("read 1 failed"); + } + if (r2 == -1) { + errno = errno2; + warn("read 2 failed"); + } + + if (r1 != r2) + warnx("read blocks do not match: %i != %i", r1, r2); + + // in case the sizes are not equal, truncate. + if (r2 < r1) + r1 = r2; + + if (r1 > 0) { + for (i = 0; i < r1; i++) + buf1[i] ^= buf2[i]; + + write(STDOUT_FILENO, buf1, r1); + } + } while (r1 > 0 && r1 == r2); + + close(fd1); + close(fd2); + + return 0; +} -- cgit v1.2.1