examples/util.c: cope with msvc read/write

examples/util.c

@@ -28,6 +28,94 @@
 #include "fido/rs256.h"
 #include "extern.h"
 
+#ifdef _MSC_VER
+int
+write_blob(const char *path, const unsigned char *ptr, size_t len)
+{
+	int fd, ok = -1;
+	int n;
+
+	if ((fd = open(path, O_WRONLY | O_CREAT, 0644)) < 0) {
+		warn("open %s", path);
+		goto fail;
+	}
+
+	if (len > UINT_MAX) {
+		warn("len %zu", len);
+		goto fail;
+	}
+	if ((n = write(fd, ptr, (unsigned int)len)) < 0) {
+		warn("write");
+		goto fail;
+	}
+	if ((size_t)n != len) {
+		warnx("write");
+		goto fail;
+	}
+
+	ok = 0;
+fail:
+	if (fd != -1) {
+		close(fd);
+	}
+
+	return (ok);
+}
+
+int
+read_blob(const char *path, unsigned char **ptr, size_t *len)
+{
+	int fd, ok = -1;
+	struct stat st;
+	int n;
+
+	*ptr = NULL;
+	*len = 0;
+
+	if ((fd = open(path, O_RDONLY)) < 0) {
+		warn("open %s", path);
+		goto fail;
+	}
+	if (fstat(fd, &st) < 0) {
+		warn("stat %s", path);
+		goto fail;
+	}
+	if (st.st_size < 0) {
+		warnx("stat %s: invalid size", path);
+		goto fail;
+	}
+	*len = (size_t)st.st_size;
+	if (*len > UINT_MAX) {
+		warn("len %zu", *len);
+		goto fail;
+	}
+	if ((*ptr = malloc(*len)) == NULL) {
+		warn("malloc");
+		goto fail;
+	}
+	if ((n = read(fd, *ptr, (unsigned int)*len)) < 0) {
+		warn("read");
+		goto fail;
+	}
+	if ((size_t)n != *len) {
+		warnx("read");
+		goto fail;
+	}
+
+	ok = 0;
+fail:
+	if (fd != -1) {
+		close(fd);
+	}
+	if (ok < 0) {
+		free(*ptr);
+		*ptr = NULL;
+		*len = 0;
+	}
+
+	return (ok);
+}
+#else
 int
 write_blob(const char *path, const unsigned char *ptr, size_t len)
 {
@@ -106,6 +194,7 @@ read_blob(const char *path, unsigned char **ptr, size_t *len)
 
 	return (ok);
 }
+#endif /* _MSC_VER */
 
 EC_KEY *
 read_ec_pubkey(const char *path)