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, 6 insertions, 19 deletions

diff --git a/wiretap/aethra.c b/wiretap/aethra.c
index 6eb37202b9..87e5515037 100644
--- a/wiretap/aethra.c
+++ b/wiretap/aethra.c
@@ -121,17 +121,15 @@ static gboolean aethra_read_rec_header(wtap *wth, FILE_T fh, struct aethrarec_hd
 
 int aethra_open(wtap *wth, int *err, gchar **err_info)
 {
-	int bytes_read;
 	struct aethra_hdr hdr;
 	struct tm tm;
 	aethra_t *aethra;
 
 	/* Read in the string that should be at the start of a "aethra" file */
 	errno = WTAP_ERR_CANT_READ;
-	bytes_read = file_read(hdr.magic, sizeof hdr.magic, wth->fh);
-	if (bytes_read != sizeof hdr.magic) {
-		*err = file_error(wth->fh, err_info);
-		if (*err != 0 && *err != WTAP_ERR_SHORT_READ)
+	if (!wtap_read_bytes(wth->fh, hdr.magic, sizeof hdr.magic, err,
+	    err_info)) {
+		if (*err != WTAP_ERR_SHORT_READ)
 			return -1;
 		return 0;
 	}
@@ -141,14 +139,9 @@ int aethra_open(wtap *wth, int *err, gchar **err_info)
 
 	/* Read the rest of the header. */
 	errno = WTAP_ERR_CANT_READ;
-	bytes_read = file_read((char *)&hdr + sizeof hdr.magic,
-	    sizeof hdr - sizeof hdr.magic, wth->fh);
-	if (bytes_read != sizeof hdr - sizeof hdr.magic) {
-		*err = file_error(wth->fh, err_info);
-		if (*err == 0)
-			*err = WTAP_ERR_SHORT_READ;
+	if (!wtap_read_bytes(wth->fh, (char *)&hdr + sizeof hdr.magic,
+	    sizeof hdr - sizeof hdr.magic, err, err_info))
 		return -1;
-	}
 	wth->file_type_subtype = WTAP_FILE_TYPE_SUBTYPE_AETHRA;
 	aethra = (aethra_t *)g_malloc(sizeof(aethra_t));
 	wth->priv = (void *)aethra;
@@ -303,20 +296,14 @@ aethra_read_rec_header(wtap *wth, FILE_T fh, struct aethrarec_hdr *hdr,
     struct wtap_pkthdr *phdr, int *err, gchar **err_info)
 {
 	aethra_t *aethra = (aethra_t *)wth->priv;
-	int	bytes_read;
 	guint32 rec_size;
 	guint32	packet_size;
 	guint32	msecs;
 
 	/* Read record header. */
 	errno = WTAP_ERR_CANT_READ;
-	bytes_read = file_read(hdr, sizeof *hdr, fh);
-	if (bytes_read != sizeof *hdr) {
-		*err = file_error(fh, err_info);
-		if (*err == 0 && bytes_read != 0)
-			*err = WTAP_ERR_SHORT_READ;
+	if (!wtap_read_bytes_or_eof(fh, hdr, sizeof *hdr, err, err_info))
 		return FALSE;
-	}
 
 	rec_size = pletoh16(hdr->rec_size);
 	if (rec_size < (sizeof *hdr - sizeof hdr->rec_size)) {