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, 13 insertions, 7 deletions

diff --git a/wiretap/packetlogger.c b/wiretap/packetlogger.c
index 065ad4aaed..8526cddada 100644
--- a/wiretap/packetlogger.c
+++ b/wiretap/packetlogger.c
@@ -66,11 +66,15 @@ int packetlogger_open(wtap *wth, int *err, gchar **err_info)
 		return 0;
 	}
 
-	if (file_read(&type, 1, wth->fh) <= 0) {
-		*err = file_error(wth->fh, err_info);
-		if (*err != 0 && *err != WTAP_ERR_SHORT_READ)
-			return -1;
-		return 0;
+	if (!wtap_read_bytes(wth->fh, &type, 1, err, err_info)) {
+		if (*err == WTAP_ERR_SHORT_READ) {
+			/*
+			 * Not enough bytes for the packet, so not a
+			 * packetlogger file.
+			 */
+			return 0;
+		}
+		return -1;
 	}
 
 	/* Verify this file belongs to us */
@@ -122,8 +126,10 @@ static gboolean
 packetlogger_read_header(packetlogger_header_t *pl_hdr, FILE_T fh, int *err,
 			 gchar **err_info)
 {
-	wtap_file_read_expected_bytes(&pl_hdr->len, 4, fh, err, err_info);
-	wtap_file_read_expected_bytes(&pl_hdr->ts, 8, fh, err, err_info);
+	if (!wtap_read_bytes_or_eof(fh, &pl_hdr->len, 4, err, err_info))
+		return FALSE;
+	if (!wtap_read_bytes(fh, &pl_hdr->ts, 8, err, err_info))
+		return FALSE;
 
 	/* Convert multi-byte values from big endian to host endian */
 	pl_hdr->len = GUINT32_FROM_BE(pl_hdr->len);