zcat: if seamless uncompressors are defined, autodetect file's format

function                                             old     new   delta
bbunpack                                             526     622     +96
packed_usage                                       29335   29341      +6
gunzip_main                                           64      67      +3

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

1 files changed, 40 insertions, 14 deletions

diff --git a/archival/bbunzip.c b/archival/bbunzip.c
index 46f99cf78..54dc2f5f1 100644
--- a/archival/bbunzip.c
+++ b/archival/bbunzip.c
@@ -14,6 +14,7 @@ enum {
         OPT_VERBOSE    = 1 << 2,
         OPT_DECOMPRESS = 1 << 3,
         OPT_TEST       = 1 << 4,
+        SEAMLESS_MAGIC = (1 << 31) * SEAMLESS_COMPRESSION,
 };
 
 static
@@ -39,7 +40,7 @@ int FAST_FUNC bbunpack(char **argv,
 )
 {
         struct stat stat_buf;
-        IF_DESKTOP(long long) int status;
+        IF_DESKTOP(long long) int status = 0;
         char *filename, *new_name;
         smallint exitcode = 0;
         transformer_aux_data_t aux;
@@ -54,14 +55,23 @@ int FAST_FUNC bbunpack(char **argv,
 
                 /* Open src */
                 if (filename) {
-                        if (stat(filename, &stat_buf) != 0) {
-                                bb_simple_perror_msg(filename);
+                        if (!(option_mask32 & SEAMLESS_MAGIC)) {
+                                if (stat(filename, &stat_buf) != 0) {
+ err_name:
+                                        bb_simple_perror_msg(filename);
  err:
-                                exitcode = 1;
-                                goto free_name;
+                                        exitcode = 1;
+                                        goto free_name;
+                                }
+                                if (open_to_or_warn(STDIN_FILENO, filename, O_RDONLY, 0))
+                                        goto err;
+                        } else {
+                                /* "clever zcat" */
+                                int fd = open_zipped(filename);
+                                if (fd < 0)
+                                        goto err_name;
+                                xmove_fd(fd, STDIN_FILENO);
                         }
-                        if (open_to_or_warn(STDIN_FILENO, filename, O_RDONLY, 0))
-                                goto err;
                 }
 
                 /* Special cases: test, stdout */
@@ -98,11 +108,23 @@ int FAST_FUNC bbunpack(char **argv,
                                         "use -f to force it");
                 }
 
-                init_transformer_aux_data(&aux);
-                aux.check_signature = 1;
-                status = unpacker(&aux);
-                if (status < 0)
-                        exitcode = 1;
+                if (!(option_mask32 & SEAMLESS_MAGIC)) {
+                        init_transformer_aux_data(&aux);
+                        aux.check_signature = 1;
+                        status = unpacker(&aux);
+                        if (status < 0)
+                                exitcode = 1;
+                } else {
+                        /* "clever zcat" */
+                        if (!filename) {
+                                if (setup_unzip_on_fd(STDIN_FILENO, /*fail_if_not_detected*/ 0))
+                                        goto err;
+                        }
+                        if (bb_copyfd_eof(STDIN_FILENO, STDOUT_FILENO) < 0) {
+                                /* Disk full, tty closed, etc. No point in continuing */
+                                xfunc_die();
+                        }
+                }
 
                 if (!(option_mask32 & OPT_STDOUT))
                         xclose(STDOUT_FILENO); /* with error check! */
@@ -294,9 +316,13 @@ int gunzip_main(int argc UNUSED_PARAM, char **argv)
 {
         getopt32(argv, "cfvdtn");
         argv += optind;
-        /* if called as zcat */
+
+        /* If called as zcat...
+         * Normally, "zcat" is just "gunzip -c".
+         * But if seamless magic is enabled, then we are much more clever.
+         */
         if (applet_name[1] == 'c')
-                option_mask32 |= OPT_STDOUT;
+                option_mask32 |= OPT_STDOUT | SEAMLESS_MAGIC;
 
         return bbunpack(argv, unpack_gunzip, make_new_name_gunzip, /*unused:*/ NULL);
 }