[Toybox] [PATCH 1/2] pending/file: add cpio, tar, zip formats.

[Isaac Dunham]

int magic needs to be declared at the top level, so the cpio branch
can use it. It would be possible to rename it and use the same variable
for this, chunk_length (png), and ver (zip).
---
 toys/pending/file.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/toys/pending/file.c b/toys/pending/file.c
index 1d09471..83e8c8e 100644
--- a/toys/pending/file.c
+++ b/toys/pending/file.c
@@ -126,6 +126,7 @@ static void do_regular_file(int fd, char *name)
 {
   char *s;
   int len = read(fd, s = toybuf, sizeof(toybuf)-256);
+  int magic;
 
   if (len<0) perror_msg("%s", name);
 
@@ -166,9 +167,32 @@ static void do_regular_file(int fd, char *name)
     xprintf("Java class file, version %d.%d\n",
       (int)peek_be(s+6, 2), (int)peek_be(s, 2));
 
-    // TODO: cpio archive.
-    // TODO: tar archive.
-    // TODO: zip/jar/apk archive.
+  // https://people.freebsd.org/~kientzle/libarchive/man/cpio.5.txt
+  // the lengths for cpio are size of header + 9 bytes, since any valid
+  // cpio archive ends with a record for "TARGET!!!"
+  else if (len>85 && strstart(&s, "07070")) {
+    char *cpioformat = "unknown type";
+    if (toybuf[5] == '7') cpioformat = "pre-SVR4 or odc";
+    else if (toybuf[5] == '1') cpioformat = "SVR4 with no CRC";
+    else if (toybuf[5] == '2') cpioformat = "SVR4 with CRC";
+    xprintf("ASCII cpio archive (%s)\n", cpioformat);
+  }
+  else if (len>33 && (magic=peek(&s,2), magic==0143561 || magic==070707)) {
+    if (magic == 0143561) printf("byte-swapped ");
+    xprintf("cpio archive\n");
+  }
+  // tar archive (ustar/pax or gnu)
+  else if (len>500 && !strncmp(s+257, "ustar", 5)) {
+    xprintf("POSIX tar archive%s\n", strncmp(s+262,"  ",2)?"":" (GNU)");
+  }
+  // zip/jar/apk archive, ODF/OOXML document, or such
+  else if (len>5 && strstart(&s, "PK\03\04")) {
+    int ver = (int)(char)(toybuf[4]);
+    xprintf("Zip archive data");
+    if (ver)
+      xprintf(", requires at least v%d.%d to extract", ver/10, ver%10);
+    xputc('\n');
+  }
   else {
     char *what = 0;
     int i, bytes;
-- 
2.7.2


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