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>

6 files changed, 22 insertions, 19 deletions

diff --git a/archival/libunarchive/data_align.c b/archival/libunarchive/data_align.c
index 9f2e8432f..0c8542bf5 100644
--- a/archival/libunarchive/data_align.c
+++ b/archival/libunarchive/data_align.c
@@ -10,6 +10,6 @@ void FAST_FUNC data_align(archive_handle_t *archive_handle, unsigned boundary)
 {
         unsigned skip_amount = (boundary - (archive_handle->offset % boundary)) % boundary;
 
-        archive_handle->seek(archive_handle, skip_amount);
+        archive_handle->seek(archive_handle->src_fd, skip_amount);
         archive_handle->offset += skip_amount;
 }
diff --git a/archival/libunarchive/data_skip.c b/archival/libunarchive/data_skip.c
index 438750fe5..06d3dced4 100644
--- a/archival/libunarchive/data_skip.c
+++ b/archival/libunarchive/data_skip.c
@@ -8,5 +8,5 @@
 
 void FAST_FUNC data_skip(archive_handle_t *archive_handle)
 {
-        archive_handle->seek(archive_handle, archive_handle->file_header->size);
+        archive_handle->seek(archive_handle->src_fd, archive_handle->file_header->size);
 }
diff --git a/archival/libunarchive/seek_by_jump.c b/archival/libunarchive/seek_by_jump.c
index 0a259c963..7181cb3ce 100644
--- a/archival/libunarchive/seek_by_jump.c
+++ b/archival/libunarchive/seek_by_jump.c
@@ -6,13 +6,13 @@
 #include "libbb.h"
 #include "unarchive.h"
 
-void FAST_FUNC seek_by_jump(const archive_handle_t *archive_handle, unsigned amount)
+void FAST_FUNC seek_by_jump(int fd, off_t amount)
 {
         if (amount
-         && lseek(archive_handle->src_fd, (off_t) amount, SEEK_CUR) == (off_t) -1
+         && lseek(fd, amount, SEEK_CUR) == (off_t) -1
         ) {
                 if (errno == ESPIPE)
-                        seek_by_read(archive_handle, amount);
+                        seek_by_read(fd, amount);
                 else
                         bb_perror_msg_and_die("seek failure");
         }
diff --git a/archival/libunarchive/seek_by_read.c b/archival/libunarchive/seek_by_read.c
index 2326a7512..af65e5d85 100644
--- a/archival/libunarchive/seek_by_read.c
+++ b/archival/libunarchive/seek_by_read.c
@@ -9,8 +9,8 @@
 /*  If we are reading through a pipe, or from stdin then we can't lseek,
  *  we must read and discard the data to skip over it.
  */
-void FAST_FUNC seek_by_read(const archive_handle_t *archive_handle, unsigned jump_size)
+void FAST_FUNC seek_by_read(int fd, off_t amount)
 {
-        if (jump_size)
-                bb_copyfd_exact_size(archive_handle->src_fd, -1, jump_size);
+        if (amount)
+                bb_copyfd_exact_size(fd, -1, amount);
 }
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);
diff --git a/include/unarchive.h b/include/unarchive.h
index 682e810d5..d8cb2a081 100644
--- a/include/unarchive.h
+++ b/include/unarchive.h
@@ -60,8 +60,8 @@ typedef struct archive_handle_t {
         /* Count the number of bytes processed */
         off_t offset;
 
-        /* Function that skips data: read_by_char or read_by_skip */
-        void FAST_FUNC (*seek)(const struct archive_handle_t *archive_handle, const unsigned amount);
+        /* Function that skips data */
+        void FAST_FUNC (*seek)(int fd, off_t amount);
 
         /* Temporary storage */
         char *buffer;
@@ -107,8 +107,8 @@ extern char get_header_tar_gz(archive_handle_t *archive_handle) FAST_FUNC;
 extern char get_header_tar_bz2(archive_handle_t *archive_handle) FAST_FUNC;
 extern char get_header_tar_lzma(archive_handle_t *archive_handle) FAST_FUNC;
 
-extern void seek_by_jump(const archive_handle_t *archive_handle, unsigned amount) FAST_FUNC;
-extern void seek_by_read(const archive_handle_t *archive_handle, unsigned amount) FAST_FUNC;
+extern void seek_by_jump(int fd, off_t amount) FAST_FUNC;
+extern void seek_by_read(int fd, off_t amount) FAST_FUNC;
 
 extern void data_align(archive_handle_t *archive_handle, unsigned boundary) FAST_FUNC;
 extern const llist_t *find_list_entry(const llist_t *list, const char *filename) FAST_FUNC;