wget: make -c _not_ truncate the file

function                                             old     new   delta
retrieve_file_data                                   396     436     +40
reset_beg_range_to_zero                               52      45      -7

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

1 files changed, 14 insertions, 2 deletions

diff --git a/networking/wget.c b/networking/wget.c
index 013b87801..5d5845019 100644
--- a/networking/wget.c
+++ b/networking/wget.c
@@ -352,10 +352,11 @@ static char *gethdr(FILE *fp)
 
 static void reset_beg_range_to_zero(void)
 {
-        //bb_error_msg("restart failed");
+        bb_error_msg("restart failed");
         G.beg_range = 0;
         xlseek(G.output_fd, 0, SEEK_SET);
-        ftruncate(G.output_fd, 0);
+        /* Done at the end instead: */
+        /* ftruncate(G.output_fd, 0); */
 }
 
 static FILE* prepare_ftp_session(FILE **dfpp, struct host_info *target, len_and_sockaddr *lsa)
@@ -554,6 +555,17 @@ static void NOINLINE retrieve_file_data(FILE *dfp)
                 G.got_clen = 1;
         }
 
+        /* If -c failed, we restart from the beginning,
+         * but we do not truncate file then, we do it only now, at the end.
+         * This lets user to ^C if his 99% complete 10 GB file download
+         * failed to restart *without* losing the almost complete file.
+         */
+        {
+                off_t pos = lseek(G.output_fd, 0, SEEK_CUR);
+                if (pos != (off_t)-1)
+                        ftruncate(G.output_fd, pos);
+        }
+
         /* Draw full bar and free its resources */
         G.chunked = 0;  /* makes it show 100% even for chunked download */
         G.got_clen = 1; /* makes it show 100% even for download of (formerly) unknown size */