xxd -r: handle offsets

function                                             old     new   delta
xxd_main                                            1076    1439    +363
.rodata                                           105239  105251     +12
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 375/0)             Total: 375 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 50 insertions, 8 deletions

diff --git a/util-linux/hexdump_xxd.c b/util-linux/hexdump_xxd.c
index dbda34bc5..6629407de 100644
--- a/util-linux/hexdump_xxd.c
+++ b/util-linux/hexdump_xxd.c
@@ -55,6 +55,7 @@
 //usage:     "\n        -r              Reverse (with -p, assumes no offsets in input)"
 
 #include "libbb.h"
+#include "common_bufsiz.h"
 #include "dump.h"
 
 /* This is a NOEXEC applet. Be very careful! */
@@ -69,10 +70,32 @@
 #define OPT_c (1 << 7)
 #define OPT_o (1 << 8)
 
-static void reverse(unsigned opt, const char *filename)
+#define fillbuf bb_common_bufsiz1
+
+static void write_zeros(off_t count)
+{
+        errno = 0;
+        do {
+                unsigned sz = count < COMMON_BUFSIZE ? (unsigned)count : COMMON_BUFSIZE;
+                if (fwrite(fillbuf, 1, sz, stdout) != sz)
+                        bb_perror_msg_and_die("write error");
+                count -= sz;
+        } while (count != 0);
+}
+
+static void reverse(unsigned opt, const char *filename, char *opt_s)
 {
         FILE *fp;
         char *buf;
+        off_t cur, opt_s_ofs;
+
+        memset(fillbuf, 0, COMMON_BUFSIZE);
+        opt_s_ofs = cur = 0;
+        if (opt_s) {
+                opt_s_ofs = BB_STRTOOFF(opt_s, NULL, 0);
+                if (errno || opt_s_ofs < 0)
+                        bb_error_msg_and_die("invalid number '%s'", opt_s);
+        }
 
         fp = filename ? xfopen_for_read(filename) : stdin;
 
@@ -82,15 +105,31 @@ static void reverse(unsigned opt, const char *filename)
 
                 p = buf;
                 if (!(opt & OPT_p)) {
+                        char *end;
+                        off_t ofs;
  skip_address:
                         p = skip_whitespace(p);
-                        while (isxdigit(*p)) p++;
+                        ofs = BB_STRTOOFF(p, &end, 16);
+                        if ((errno && errno != EINVAL)
+                         || ofs < 0
+                        /* -s SEEK value should be added before seeking */
+                         || (ofs += opt_s_ofs) < 0
+                        ) {
+                                bb_error_msg_and_die("invalid number '%s'", p);
+                        }
+                        if (ofs != cur) {
+                                if (fseeko(stdout, ofs, SEEK_SET) != 0) {
+                                        if (ofs < cur)
+                                                bb_perror_msg_and_die("cannot seek");
+                                        write_zeros(ofs - cur);
+                                }
+                                cur = ofs;
+                        }
+                        p = end;
                         /* NB: for xxd -r, first hex portion is address even without colon */
-                        /* If it's there, skip it: */
-                        if (*p == ':') p++;
-
-//TODO: seek (or zero-pad if unseekable) to the address position
-//NOTE: -s SEEK value should be added to the address before seeking
+                        /* But if colon is there, skip it: */
+                        if (*p == ':')
+                                p++;
                 }
 
                 /* Process hex bytes optionally separated by whitespace */
@@ -168,6 +207,7 @@ static void reverse(unsigned opt, const char *filename)
                                 goto nibble2;
                         }
                         putchar(val);
+                        cur++;
                 } /* for(;;) */
                 free(buf);
         }
@@ -195,6 +235,8 @@ int xxd_main(int argc UNUSED_PARAM, char **argv)
         unsigned opt;
         int r;
 
+        setup_common_bufsiz();
+
         dumper = alloc_dumper();
 
         opt = getopt32(argv, "^" "l:s:apirg:+c:+o:" "\0" "?1" /* 1 argument max */,
@@ -222,7 +264,7 @@ int xxd_main(int argc UNUSED_PARAM, char **argv)
         }
 
         if (opt & OPT_r) {
-                reverse(opt, argv[0]);
+                reverse(opt, argv[0], opt_s);
         }
 
         if (opt & OPT_o) {