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, 5 insertions, 19 deletions

diff --git a/wiretap/libpcap.c b/wiretap/libpcap.c
index 431c899516..1b0e2b4571 100644
--- a/wiretap/libpcap.c
+++ b/wiretap/libpcap.c
@@ -73,7 +73,6 @@ static int libpcap_read_header(wtap *wth, FILE_T fh, int *err, gchar **err_info,
 
 int libpcap_open(wtap *wth, int *err, gchar **err_info)
 {
-	int bytes_read;
 	guint32 magic;
 	struct pcap_hdr hdr;
 	gboolean byte_swapped;
@@ -107,10 +106,8 @@ int libpcap_open(wtap *wth, int *err, gchar **err_info)
 
 	/* Read in the number that should be at the start of a "libpcap" file */
 	errno = WTAP_ERR_CANT_READ;
-	bytes_read = file_read(&magic, sizeof magic, wth->fh);
-	if (bytes_read != sizeof magic) {
-		*err = file_error(wth->fh, err_info);
-		if (*err != 0 && *err != WTAP_ERR_SHORT_READ)
+	if (!wtap_read_bytes(wth->fh, &magic, sizeof magic, err, err_info)) {
+		if (*err != WTAP_ERR_SHORT_READ)
 			return -1;
 		return 0;
 	}
@@ -177,13 +174,8 @@ int libpcap_open(wtap *wth, int *err, gchar **err_info)
 
 	/* Read the rest of the header. */
 	errno = WTAP_ERR_CANT_READ;
-	bytes_read = file_read(&hdr, sizeof hdr, wth->fh);
-	if (bytes_read != sizeof hdr) {
-		*err = file_error(wth->fh, err_info);
-		if (*err == 0)
-			*err = WTAP_ERR_SHORT_READ;
+	if (!wtap_read_bytes(wth->fh, &hdr, sizeof hdr, err, err_info))
 		return -1;
-	}
 
 	if (byte_swapped) {
 		/* Byte-swap the header fields about which we care. */
@@ -745,7 +737,7 @@ libpcap_read_packet(wtap *wth, FILE_T fh, struct wtap_pkthdr *phdr,
 static int libpcap_read_header(wtap *wth, FILE_T fh, int *err, gchar **err_info,
     struct pcaprec_ss990915_hdr *hdr)
 {
-	int bytes_to_read, bytes_read;
+	int bytes_to_read;
 	guint32 temp;
 	libpcap_t *libpcap;
 
@@ -775,14 +767,8 @@ static int libpcap_read_header(wtap *wth, FILE_T fh, int *err, gchar **err_info,
 		g_assert_not_reached();
 		bytes_to_read = 0;
 	}
-	bytes_read = file_read(hdr, bytes_to_read, fh);
-	if (bytes_read != bytes_to_read) {
-		*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, bytes_to_read, err, err_info))
 		return FALSE;
-	}
 
 	libpcap = (libpcap_t *)wth->priv;
 	if (libpcap->byte_swapped) {