file_seek() used to be a wrapper around fseek() or gzseek(), both of

which could use lseek() and were thus expensive due to system call
overhead.  To avoid making a system call for every packet on a
sequential read, we maintained a data_offset field in the wtap structure
for sequential reads.

It's now a routine that just returns information from the FILE_T data
structure, so it's cheap.  Use it, rather than maintaining the data_offset
field.

Readers for some file formats need to maintain file offset themselves;
have them do so in their private data structures.

svn path=/trunk/; revision=42423

1 files changed, 1 insertions, 8 deletions

diff --git a/wiretap/visual.c b/wiretap/visual.c
index de10c33f43..0b0e0aebb5 100644
--- a/wiretap/visual.c
+++ b/wiretap/visual.c
@@ -266,10 +266,6 @@ int visual_open(wtap *wth, int *err, gchar **err_info)
     wth->file_encap = encap;
     wth->snapshot_length = pletohs(&vfile_hdr.max_length);
 
-    /* Save the pointer to the beginning of the packet data so
-       that the later seek_reads work correctly. */
-    wth->data_offset = CAPTUREFILE_HEADER_SIZE;
-
     /* Set up the pointers to the handlers for this file type */
     wth->subtype_read = visual_read;
     wth->subtype_seek_read = visual_seek_read;
@@ -326,7 +322,6 @@ static gboolean visual_read(wtap *wth, int *err, gchar **err_info,
         }
         return FALSE;
     }
-    wth->data_offset += phdr_size;
 
     /* Get the included length of data. This includes extra headers + payload */
     packet_size = pletohs(&vpkt_hdr.incl_len);
@@ -346,7 +341,6 @@ static gboolean visual_read(wtap *wth, int *err, gchar **err_info,
            }
            return FALSE;
        }
-       wth->data_offset += ahdr_size;
        
        /* Remove ATM header from length of included bytes in capture, as 
           this header was appended by the processor doing the packet reassembly,
@@ -365,7 +359,7 @@ static gboolean visual_read(wtap *wth, int *err, gchar **err_info,
         return FALSE;
     }
     buffer_assure_space(wth->frame_buffer, packet_size);
-    *data_offset = wth->data_offset;
+    *data_offset = file_tell(wth->fh);
     errno = WTAP_ERR_CANT_READ;
     bytes_read = file_read(buffer_start_ptr(wth->frame_buffer),
             packet_size, wth->fh);
@@ -377,7 +371,6 @@ static gboolean visual_read(wtap *wth, int *err, gchar **err_info,
             *err = WTAP_ERR_SHORT_READ;
         return FALSE;
     }
-    wth->data_offset += packet_size;
 
     wth->phdr.presence_flags = WTAP_HAS_TS|WTAP_HAS_CAP_LEN;