Add some higher-level file-read APIs and use them.

Add wtap_read_bytes(), which takes a FILE_T, a pointer, a byte count, an
error number pointer, and an error string pointer as arguments, and that
treats a short read of any sort, including a read that returns 0 bytes,
as a WTAP_ERR_SHORT_READ error, and that returns the error number and
string through its last two arguments.

Add wtap_read_bytes_or_eof(), which is similar, but that treats a read
that returns 0 bytes as an EOF, supplying an error number of 0 as an EOF
indication.

Use those in file readers; that simplifies the code and makes it less
likely that somebody will fail to supply the error number and error
string on a file read error.

Change-Id: Ia5dba2a6f81151e87b614461349d611cffc16210
Reviewed-on: https://code.wireshark.org/review/4512
Reviewed-by: Guy Harris <guy@alum.mit.edu>

1 files changed, 2 insertions, 5 deletions

diff --git a/wiretap/ber.c b/wiretap/ber.c
index cb1829bda3..bde6234763 100644
--- a/wiretap/ber.c
+++ b/wiretap/ber.c
@@ -107,7 +107,6 @@ int ber_open(wtap *wth, int *err, gchar **err_info)
 {
 #define BER_BYTES_TO_CHECK 8
   guint8 bytes[BER_BYTES_TO_CHECK];
-  int bytes_read;
   guint8 ber_id;
   gint8 ber_class;
   gint8 ber_tag;
@@ -117,10 +116,8 @@ int ber_open(wtap *wth, int *err, gchar **err_info)
   gint64 file_size;
   int offset = 0, i;
 
-  bytes_read = file_read(&bytes, BER_BYTES_TO_CHECK, wth->fh);
-  if (bytes_read != BER_BYTES_TO_CHECK) {
-    *err = file_error(wth->fh, err_info);
-    if (*err != 0 && *err != WTAP_ERR_SHORT_READ)
+  if (!wtap_read_bytes(wth->fh, &bytes, BER_BYTES_TO_CHECK, err, err_info)) {
+    if (*err != WTAP_ERR_SHORT_READ)
       return -1;
     return 0;
   }