1 files changed, 53 insertions, 0 deletions
diff --git a/src/fastsum.c b/src/fastsum.c
new file mode 100644
index 0000000..4578ff2
--- /dev/null
+++ b/src/fastsum.c
@@ -0,0 +1,53 @@
+#include <errno.h>    /* for errno */
+#include <error.h>    /* for error(3gnu) */
+#include <fcntl.h>    /* for O_RDONLY */
+#include <inttypes.h> /* for PRI*, uint*_t, int*_t */
+#include <stdbool.h>  /* for bool */
+#include <stdio.h>    /* for printf */
+#include <sys/stat.h> /* for open(2), fstat(2) and struct stat */
+#include <unistd.h>   /* for close(2), read(2), lseek(2), SEEK_SET */
+
+int main(int argc, char *argv[]) {
+	bool err = false;
+	for (int i = 1; i < argc; i++) {
+		const char *filename = argv[i];
+
+		int fd = open(filename, O_RDONLY);
+		if (fd < 0) {
+			err = true;
+			error(0, errno, "open %s", filename);
+			continue;
+		}
+
+		struct stat st;
+		if (fstat(fd, &st) < 0) {
+			err = true;
+			error(0, errno, "fstat %s", filename);
+			close(fd);
+			continue;
+		}
+
+		if (lseek(fd, st.st_size/2, SEEK_SET) < 0) {
+			err = true;
+			error(0, errno, "lseek %s", filename);
+			close(fd);
+			continue;
+		}
+
+		uint8_t b;
+		int n = read(fd, &b, sizeof(b));
+		if (n <= 0) {
+			if (n == 0)
+				error(0, 0, "read %s: unexpected end of file", filename);
+			else
+				error(0, errno, "read %s", filename);
+			err = true;
+			close(fd);
+			continue;
+		}
+
+		printf("%"PRId64":%"PRIx8"  %s\n", (int64_t)st.st_size, b, filename);
+		close(fd);
+	}
+	return err ? 1 : 0;
+}