Uemis downloader: don't ignore return values from fs operations

In most cases the existing code might have done the right thing, but some
of the hard to reproduce errors might actually stem from the fact that we
have intermittend fs errors. Maybe this addresses things?

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 31 insertions, 11 deletions

diff --git a/uemis-downloader.c b/uemis-downloader.c
index c9d57acfb..b7d877823 100644
--- a/uemis-downloader.c
+++ b/uemis-downloader.c
@@ -134,6 +134,8 @@ static long bytes_available(int file)
 	long now = lseek(file, 0, SEEK_CUR);
 	result = lseek(file, 0, SEEK_END);
 	lseek(file, now, SEEK_SET);
+	if (now == -1 || result == -1)
+		return 0;
 	return result;
 }
 
@@ -249,13 +251,18 @@ static void trigger_response(int file, char *command, int nr, long tailpos)
 #if UEMIS_DEBUG & 4
 	fprintf(debugfile, ":tr %s (after seeks)\n", fl);
 #endif
-	lseek(file, 0, SEEK_SET);
-	write(file, fl, strlen(fl));
-	lseek(file, tailpos, SEEK_SET);
-	write(file, fl + 1, strlen(fl + 1));
+	if (lseek(file, 0, SEEK_SET) == -1)
+		goto fs_error;
+	if (write(file, fl, strlen(fl)) == -1)
+		goto fs_error;
+	if (lseek(file, tailpos, SEEK_SET) == -1)
+		goto fs_error;
+	if (write(file, fl + 1, strlen(fl + 1)) == -1)
+		goto fs_error;
 #ifndef WIN32
 	fsync(file);
 #endif
+fs_error:
 	close(file);
 }
 
@@ -491,10 +498,16 @@ static bool uemis_get_answer(const char *path, char *request, int n_param_in,
 			ans_file = subsurface_open(ans_path, O_RDONLY, 0666);
 			size = bytes_available(ans_file);
 			if (size > 3) {
-				char *buf = malloc(size - 2);
-				lseek(ans_file, 3, SEEK_CUR);
-				read(ans_file, buf, size - 3);
-				buf[size - 3] = '\0';
+				char *buf;
+				int r;
+				if (lseek(ans_file, 3, SEEK_CUR) == -1)
+					goto fs_error;
+				buf = malloc(size - 2);
+				if ((r = read(ans_file, buf, size - 3) != size - 3)) {
+					free(buf);
+					goto fs_error;
+				}
+				buf[r] = '\0';
 				buffer_add(&mbuf, &mbuf_size, buf);
 				show_progress(buf, what);
 				free(buf);
@@ -515,10 +528,15 @@ static bool uemis_get_answer(const char *path, char *request, int n_param_in,
 			ans_file = subsurface_open(ans_path, O_RDONLY, 0666);
 			size = bytes_available(ans_file);
 			if (size > 3) {
+				int r;
+				if (lseek(ans_file, 3, SEEK_CUR) == -1)
+					goto fs_error;
 				buf = malloc(size - 2);
-				lseek(ans_file, 3, SEEK_CUR);
-				read(ans_file, buf, size - 3);
-				buf[size - 3] = '\0';
+				if ((r = read(ans_file, buf, size - 3)) != size - 3) {
+					free(buf);
+					goto fs_error;
+				}
+				buf[r] = '\0';
 				buffer_add(&mbuf, &mbuf_size, buf);
 				show_progress(buf, what);
 #if UEMIS_DEBUG & 8
@@ -545,6 +563,8 @@ static bool uemis_get_answer(const char *path, char *request, int n_param_in,
 		fprintf(debugfile, "::: %d: %s\n", i, param_buff[i]);
 #endif
 	return found_answer;
+fs_error:
+	return false;
 }
 
 static void parse_divespot(char *buf)