xxd is a utility, bundled with vim, that has been used to encode answers to code golf problems on this site. It converts a binary file into a hex dump and back again.
Implement the xxd and xxd -r commands in the programming language(s) of your choice. Scoring is based on the character/byte lengths of a) your program(s) and b) any command line argument(s) necessary to switch a combined program between modes (they need not be -r). As in golf, lower scores are better.
- For two separate programs: forward code + reverse code
- For a combined program: combined code + sum(forward arguments) + sum(reverse arguments) - 2
Specification of the chosen xxd subset
The forward command (e.g. xxd) accepts 0 ≤ n ≤ 216 bytes from standard input and generates ceil(n / 16) lines of standard output in the following format (all hex digits lowercase):
- Offset of the first encoded byte (format string
"%07x:"); ends in"0" - At most 16 hex-encoded bytes, grouped into pairs (format string
" %02x"for even bytes,"%02x"for odd bytes) and right-padded with spaces to 42 characters - The encoded bytes interpreted as ASCII characters, values not between 0x20 and 0x7e (
'\40'and'\176') inclusive becoming"." - A newline (
"\n";"\r\n"allowed when standard output is in binary mode)
Minimal ungolfed C implementation:
#include <stdio.h> int main() { unsigned char L[16]; int t = 0, n, i, s; for (; (n = fread(L, 1, 16, stdin)); t += n) { printf("%07x:", t); s = 42; for (i = 0; i < n; i++) s -= printf(i & 1 ? "%02x" : " %02x", L[i]); printf("%*s", s, ""); for (i = 0; i < n; i++) putchar(L[i] > '\37' && L[i] < '\177' ? L[i] : '.'); printf("\n"); } return 0; } The reverse command (e.g. xxd -r) accepts any unmodified output of the forward command (given a valid input to that command) and produces that original input.
Example usage
$ xxd < /dev/null | wc -c 0 $ php -r 'echo join(range("\0",~"\0"));' | xxd 0000000: 0001 0203 0405 0607 0809 0a0b 0c0d 0e0f ................ 0000010: 1011 1213 1415 1617 1819 1a1b 1c1d 1e1f ................ 0000020: 2021 2223 2425 2627 2829 2a2b 2c2d 2e2f !"#$%&'()*+,-./ 0000030: 3031 3233 3435 3637 3839 3a3b 3c3d 3e3f 0123456789:;<=>? 0000040: 4041 4243 4445 4647 4849 4a4b 4c4d 4e4f @ABCDEFGHIJKLMNO 0000050: 5051 5253 5455 5657 5859 5a5b 5c5d 5e5f PQRSTUVWXYZ[\]^_ 0000060: 6061 6263 6465 6667 6869 6a6b 6c6d 6e6f `abcdefghijklmno 0000070: 7071 7273 7475 7677 7879 7a7b 7c7d 7e7f pqrstuvwxyz{|}~. 0000080: 8081 8283 8485 8687 8889 8a8b 8c8d 8e8f ................ 0000090: 9091 9293 9495 9697 9899 9a9b 9c9d 9e9f ................ 00000a0: a0a1 a2a3 a4a5 a6a7 a8a9 aaab acad aeaf ................ 00000b0: b0b1 b2b3 b4b5 b6b7 b8b9 babb bcbd bebf ................ 00000c0: c0c1 c2c3 c4c5 c6c7 c8c9 cacb cccd cecf ................ 00000d0: d0d1 d2d3 d4d5 d6d7 d8d9 dadb dcdd dedf ................ 00000e0: e0e1 e2e3 e4e5 e6e7 e8e9 eaeb eced eeef ................ 00000f0: f0f1 f2f3 f4f5 f6f7 f8f9 fafb fcfd feff ................ $ xxd <<< 'The quick brown fox jumps over the lazy dog.' 0000000: 5468 6520 7175 6963 6b20 6272 6f77 6e20 The quick brown 0000010: 666f 7820 6a75 6d70 7320 6f76 6572 2074 fox jumps over t 0000020: 6865 206c 617a 7920 646f 672e 0a he lazy dog.. $ xxd <<< 'The quick brown fox jumps over the lazy dog.' | xxd -r The quick brown fox jumps over the lazy dog. 
