libfdisk: add firstsector utils

Signed-off-by: Karel Zak <kzak@redhat.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/libfdisk/src/utils.c b/libfdisk/src/utils.c
new file mode 100644
index 000000000..6668e23e3
--- /dev/null
+++ b/libfdisk/src/utils.c
@@ -0,0 +1,42 @@
+
+#include "fdiskP.h"
+
+/*
+ * Zeros in-memory first sector buffer
+ */
+void fdisk_zeroize_firstsector(struct fdisk_context *cxt)
+{
+	if (!cxt || !cxt->firstsector)
+		return;
+
+	DBG(CONTEXT, dbgprint("zeroize in-memory first sector buffer"));
+	memset(cxt->firstsector, 0, cxt->sector_size);
+}
+
+int fdisk_read_firstsector(struct fdisk_context *cxt)
+{
+	ssize_t r;
+
+	assert(cxt);
+	assert(cxt->sector_size);
+
+	DBG(TOPOLOGY, dbgprint("initialize first sector "
+				"buffer [sector_size=%lu]", cxt->sector_size));
+
+	if (!cxt->firstsector) {
+		cxt->firstsector = calloc(1, cxt->sector_size);
+		if (!cxt->firstsector)
+			return -ENOMEM;
+	} else
+		fdisk_zeroize_firstsector(cxt);
+
+	r = read(cxt->dev_fd, cxt->firstsector, cxt->sector_size);
+
+	if (r != cxt->sector_size) {
+		if (!errno)
+			errno = EINVAL;	/* probably too small file/device */
+		return -errno;
+	}
+
+	return 0;
+}