logger: Refactor fread() error check in logger_read()

ktrzcinx · jajanusz · commit 18fabd3d6eb4 · 2020-09-25T15:04:57.000+02:00
fread() returns number of readed blocks, 0 when nothing read.
Comparison fread return value with "!ret" is quite misleading -
may suggests that negative value is returrned after fail.

Swapping if content makes flow easier, then first is error check,
and eventyally return statement, next try to reopen file.
It allows to check error condition only in one place, so there
won't be possibility to use different error checks in subsequent
stages (like ferror() and errno).

in_file alignment with trace entry size check has been added,
to warn about corrupted file.

Signed-off-by: Karol Trzcinski &lt;karolx.trzcinski@linux.intel.com&gt;
diff --git a/tools/logger/convert.c b/tools/logger/convert.c
@@ -638,8 +638,20 @@ static int logger_read(void)
 	while (!ferror(global_config->in_fd)) {
 		/* getting entry parameters from dma dump */
 		ret = fread(&dma_log, sizeof(dma_log), 1, global_config->in_fd);
-		if (!ret) {
-			if (global_config->trace && !ferror(global_config->in_fd)) {
+		if (ret != 1) {
+			/*
+			 * use ferror (not errno) to check fread fail -
+			 * see https://www.gnu.org/software/gnulib/manual/html_node/fread.html
+			 */
+			ret = -ferror(global_config->in_fd);
+			if (ret) {
+				log_err("in %s(), fread(..., %s) failed: %s(%d)\n",
+					__func__, global_config->in_file,
+					strerror(-ret), ret);
+				return ret;
+			}
+			/* for trace mode, try to reopen */
+			if (global_config->trace) {
 				if (freopen(NULL, "rb", global_config->in_fd)) {
 					continue;
 				} else {
@@ -648,13 +660,13 @@ static int logger_read(void)
 						strerror(errno), errno);
 					return -errno;
 				}
+			} else {
+				/* EOF */
+				if (!feof(global_config->in_fd))
+					log_err("file '%s' is unaligned with trace entry size (%ld)\n",
+						global_config->in_file, sizeof(dma_log));
+				break;
 			}
-			ret = -ferror(global_config->in_fd);
-			if (ret)
-				log_err("in %s(), fread(..., %s) failed: %s(%d)\n",
-					__func__, global_config->in_file,
-					strerror(-ret), ret);
-			return ret;
 		}
 
 		/* checking if received trace address is located in
