[hackers] [sbase] tar: Allow extracting only a given list of files || sin

[git]

commit 258d0793ac830d247f8c7b54c7749f04f583faa4
Author: sin <s...@2f30.org>
Date:   Tue Apr 21 15:29:22 2015 +0100

    tar: Allow extracting only a given list of files
    
    tar -xf foo.tar a b c

diff --git a/tar.c b/tar.c
index 44523ff..bb4677b 100644
--- a/tar.c
+++ b/tar.c
@@ -313,26 +313,34 @@ sanitize(struct header *h)
 }
 
 static void
-xt(int (*fn)(char *, ssize_t, char[BLKSIZ]))
+xt(int argc, char *argv[], int (*fn)(char *, ssize_t, char[BLKSIZ]))
 {
        char b[BLKSIZ], fname[256 + 1], *p;
-       struct header *h;
+       struct header *h = (struct header *)b;
        long size;
-       int n;
+       int i, n;
 
-       h = (void *)b;
+       while (fread(b, BLKSIZ, 1, tarfile) == 1 && *h->name) {
+               sanitize(h), n = 0;
 
-       while (fread(b, BLKSIZ, 1, tarfile) == 1 && *(h->name)) {
-               sanitize(h);
-               n = 0;
+               /* small dance around non-null terminated fields */
                if (h->prefix[0])
                        n = snprintf(fname, sizeof(fname), "%.*s/",
                                     (int)sizeof(h->prefix), h->prefix);
                snprintf(fname + n, sizeof(fname) - n, "%.*s",
                         (int)sizeof(h->name), h->name);
+
+               if (argc) {
+                       /* only extract the given files */
+                       for (i = 0; i < argc; i++)
+                               if (!strcmp(argv[i], fname))
+                                       break;
+                       if (i == argc)
+                               continue;
+               }
+
                if ((size = strtol(h->size, &p, 8)) < 0 || *p != '\0')
                        eprintf("strtol %s: invalid number\n", h->size);
-
                fn(fname, size, b);
        }
        if (ferror(tarfile))
@@ -430,7 +438,7 @@ main(int argc, char *argv[])
 
                if (chdir(dir) < 0)
                        eprintf("chdir %s:", dir);
-               xt((mode == 'x') ? unarchive : print);
+               xt(argc, argv, (mode == 'x') ? unarchive : print);
                break;
        }