rpm2cpio: handle unseekable input correctly

function                                             old     new   delta
data_skip                                             14      20      +6
seek_by_jump                                          67      72      +5
data_align                                            81      84      +3
seek_by_read                                          20      19      -1
skip_header                                           99      94      -5
rpm2cpio_main                                        183     177      -6
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/3 up/down: 14/-12)              Total: 2 bytes

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

1 files changed, 10 insertions, 7 deletions

diff --git a/archival/rpm2cpio.c b/archival/rpm2cpio.c
index 566a9f213..30ec80e22 100644
--- a/archival/rpm2cpio.c
+++ b/archival/rpm2cpio.c
@@ -33,9 +33,10 @@ struct rpm_header {
         uint32_t size; /* Size of store (4 bytes) */
 };
 
-static off_t skip_header(int rpm_fd)
+static unsigned skip_header(int rpm_fd)
 {
         struct rpm_header header;
+        unsigned len;
 
         xread(rpm_fd, &header, sizeof(header));
 //      if (strncmp((char *) &header.magic, RPM_HEADER_MAGIC_STR, 3) != 0) {
@@ -48,10 +49,12 @@ static off_t skip_header(int rpm_fd)
                 bb_error_msg_and_die("invalid RPM header magic or unsupported version");
                 // ": %x != %x", header.magic_and_ver, htonl(RPM_HEADER_VERnMAGIC));
         }
-        /* Seek past index entries */
-        lseek(rpm_fd, 16 * ntohl(header.entries), SEEK_CUR);
-        /* Seek past store */
-        return lseek(rpm_fd, ntohl(header.size), SEEK_CUR);
+
+        /* Seek past index entries, and past store */
+        len = 16 * ntohl(header.entries) + ntohl(header.size);
+        seek_by_jump(rpm_fd, len);
+
+        return sizeof(header) + len;
 }
 
 /* No getopt required */
@@ -60,7 +63,7 @@ int rpm2cpio_main(int argc UNUSED_PARAM, char **argv)
 {
         struct rpm_lead lead;
         int rpm_fd;
-        off_t pos;
+        unsigned pos;
         unsigned char magic[2];
         IF_DESKTOP(long long) int FAST_FUNC (*unpack)(int src_fd, int dst_fd);
 
@@ -78,7 +81,7 @@ int rpm2cpio_main(int argc UNUSED_PARAM, char **argv)
 
         /* Skip the signature header, align to 8 bytes */
         pos = skip_header(rpm_fd);
-        lseek(rpm_fd, (8 - (unsigned)pos) & 7, SEEK_CUR);
+        seek_by_jump(rpm_fd, (8 - pos) & 7);
 
         /* Skip the main header */
         skip_header(rpm_fd);