tar: optional support for --to-command

function                                             old     new   delta
data_extract_to_command                                -     430    +430
dec2env                                                -      44     +44
tar_main                                             778     819     +41
str2env                                                -      37     +37
tar_var                                                -      32     +32
xputenv                                                -      22     +22
tar_longopts                                         257     270     +13
------------------------------------------------------------------------------
(add/remove: 6/0 grow/shrink: 2/0 up/down: 619/0)             Total: 619 bytes

Signed-off-by: Ladislav Michl <Ladislav.Michl@seznam.cz>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 138 insertions, 0 deletions

diff --git a/archival/libunarchive/Kbuild.src b/archival/libunarchive/Kbuild.src
index 81854558b..6ad1d7a65 100644
--- a/archival/libunarchive/Kbuild.src
+++ b/archival/libunarchive/Kbuild.src
@@ -53,6 +53,7 @@ lib-$(CONFIG_FEATURE_SEAMLESS_BZ2)      += open_transformer.o decompress_bunzip2
 lib-$(CONFIG_FEATURE_SEAMLESS_LZMA)     += open_transformer.o decompress_unlzma.o get_header_tar_lzma.o
 lib-$(CONFIG_FEATURE_SEAMLESS_XZ)       += open_transformer.o decompress_unxz.o
 lib-$(CONFIG_FEATURE_COMPRESS_USAGE)    += decompress_bunzip2.o
+lib-$(CONFIG_FEATURE_TAR_TO_COMMAND)    += data_extract_to_command.o
 
 ifneq ($(lib-y),)
 lib-y += $(COMMON_FILES)
diff --git a/archival/libunarchive/data_extract_to_command.c b/archival/libunarchive/data_extract_to_command.c
new file mode 100644
index 000000000..983c5301d
--- /dev/null
+++ b/archival/libunarchive/data_extract_to_command.c
@@ -0,0 +1,137 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+#include "libbb.h"
+#include "unarchive.h"
+
+enum {
+        //TAR_FILETYPE,
+        TAR_MODE,
+        TAR_FILENAME,
+        TAR_REALNAME,
+#if ENABLE_FEATURE_TAR_UNAME_GNAME
+        TAR_UNAME,
+        TAR_GNAME,
+#endif
+        TAR_SIZE,
+        TAR_UID,
+        TAR_GID,
+        TAR_MAX,
+};
+
+static const char *const tar_var[] = {
+        // "FILETYPE",
+        "MODE",
+        "FILENAME",
+        "REALNAME",
+#if ENABLE_FEATURE_TAR_UNAME_GNAME
+        "UNAME",
+        "GNAME",
+#endif
+        "SIZE",
+        "UID",
+        "GID",
+};
+
+static void xputenv(char *str)
+{
+        if (putenv(str))
+                bb_error_msg_and_die(bb_msg_memory_exhausted);
+}
+
+static void str2env(char *env[], int idx, const char *str)
+{
+        env[idx] = xasprintf("TAR_%s=%s", tar_var[idx], str);
+        xputenv(env[idx]);
+}
+
+static void dec2env(char *env[], int idx, unsigned long long val)
+{
+        env[idx] = xasprintf("TAR_%s=%llu", tar_var[idx], val);
+        xputenv(env[idx]);
+}
+
+static void oct2env(char *env[], int idx, unsigned long val)
+{
+        env[idx] = xasprintf("TAR_%s=%lo", tar_var[idx], val);
+        xputenv(env[idx]);
+}
+
+void FAST_FUNC data_extract_to_command(archive_handle_t *archive_handle)
+{
+        file_header_t *file_header = archive_handle->file_header;
+
+#if 0 /* do we need this? ENABLE_FEATURE_TAR_SELINUX */
+        char *sctx = archive_handle->tar__next_file_sctx;
+        if (!sctx)
+                sctx = archive_handle->tar__global_sctx;
+        if (sctx) { /* setfscreatecon is 4 syscalls, avoid if possible */
+                setfscreatecon(sctx);
+                free(archive_handle->tar__next_file_sctx);
+                archive_handle->tar__next_file_sctx = NULL;
+        }
+#endif
+
+        if ((file_header->mode & S_IFMT) == S_IFREG) {
+                pid_t pid;
+                int p[2], status;
+                char *tar_env[TAR_MAX];
+
+                memset(tar_env, 0, sizeof(tar_env));
+
+                xpipe(p);
+                pid = BB_MMU ? fork() : vfork();
+                switch (pid) {
+                case -1:
+                        bb_perror_msg_and_die(BB_MMU ? "fork" : "vfork");
+                case 0:
+                        /* Child */
+                        /* str2env(tar_env, TAR_FILETYPE, "f"); - parent should do it once */
+                        oct2env(tar_env, TAR_MODE, file_header->mode);
+                        str2env(tar_env, TAR_FILENAME, file_header->name);
+                        str2env(tar_env, TAR_REALNAME, file_header->name);
+#if ENABLE_FEATURE_TAR_UNAME_GNAME
+                        str2env(tar_env, TAR_UNAME, file_header->tar__uname);
+                        str2env(tar_env, TAR_GNAME, file_header->tar__gname);
+#endif
+                        dec2env(tar_env, TAR_SIZE, file_header->size);
+                        dec2env(tar_env, TAR_UID, file_header->uid);
+                        dec2env(tar_env, TAR_GID, file_header->gid);
+                        close(p[1]);
+                        xdup2(p[0], STDIN_FILENO);
+                        signal(SIGPIPE, SIG_DFL);
+                        execl("/bin/sh", "/bin/sh" + 5, "-c", archive_handle->tar__to_command, NULL);
+                        bb_perror_msg_and_die("can't execute '%s'", "/bin/sh");
+                }
+                close(p[0]);
+                /* Our caller is expected to do signal(SIGPIPE, SIG_IGN)
+                 * so that we don't die if child don't read all the input: */
+                bb_copyfd_exact_size(archive_handle->src_fd, p[1], file_header->size);
+                close(p[1]);
+
+                if (safe_waitpid(pid, &status, 0) == -1)
+                        bb_perror_msg_and_die("waitpid");
+                if (WIFEXITED(status) && WEXITSTATUS(status))
+                        bb_error_msg_and_die("'%s' returned status %d",
+                                archive_handle->tar__to_command, WEXITSTATUS(status));
+                if (WIFSIGNALED(status))
+                        bb_error_msg_and_die("'%s' terminated on signal %d",
+                                archive_handle->tar__to_command, WTERMSIG(status));
+
+                if (!BB_MMU) {
+                        int i;
+                        for (i = 0; i < TAR_MAX; i++) {
+                                if (tar_env[i])
+                                        bb_unsetenv_and_free(tar_env[i]);
+                        }
+                }
+        }
+
+#if 0 /* ENABLE_FEATURE_TAR_SELINUX */
+        if (sctx)
+                /* reset the context after creating an entry */
+                setfscreatecon(NULL);
+#endif
+}