fat: add ioctl to get current sector/cluster

include/fat.h

@@ -24,6 +24,7 @@
 #define LIBDRAGON_FAT_H
 
 #include <stdint.h>
+#include "ioctl.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -97,6 +98,33 @@ typedef struct {
 } fat_disk_t;
 
 
+/**
+ * @brief Return the current cluster number
+ * 
+ * The cluster number is a 32-bit integer value.
+ * 
+ * \code{.c}
+ *    FILE *f = fopen("sd:/myfile.dat", "rb");
+ *    int32_t cluster = 0;
+ *    ioctl(fileno(f), IOFAT_GET_CLUSTER, &cluster);
+ * \endcode
+ */
+#define IOFAT_GET_CLUSTER       _IO('F', 1)
+
+/**
+ * @brief Return the current sector number
+ * 
+ * The sector number is a 64-bit integer value.
+ * 
+ * \code{.c}
+ *   FILE *f = fopen("sd:/myfile.dat", "rb");
+ *   int64_t sector = 0;
+ *   ioctl(fileno(f), IOFAT_GET_SECTOR, &sector);
+ * \endcode
+ */
+#define IOFAT_GET_SECTOR        _IO('F', 2)
+
+
 /** 
  * @brief Mount the volume only when it is accessed for the first time.
  * 

src/fat.c

@@ -253,6 +253,27 @@ static int __fat_lseek(void *file, int offset, int whence)
 	return f_tell(f);
 }
 
+static int __fat_ioctl(void *file, unsigned long request, void *arg)
+{
+	FIL *f = file;
+	switch (request) {
+		case IOFAT_GET_CLUSTER: {
+			int32_t *cluster = arg;
+			*cluster = f->clust;
+			return 0;
+		}
+		case IOFAT_GET_SECTOR: {
+			int64_t *sector = arg;
+			*sector = f->sect;
+			return 0;
+		}
+		default: {
+			errno = ENOTTY;
+			return -1;
+		}
+	}
+}
+
 static int __fat_unlink(char *name, int volid)
 {
 	FRESULT res = f_unlink(MAKE_FAT_NAME(volid, name));
@@ -325,6 +346,7 @@ static const filesystem_t fat_newlib_fs = {
 	.read = __fat_read,
 	.write = __fat_write,
 	.close = __fat_close,
+	.ioctl = __fat_ioctl,
 	.unlink = NULL, 		// per-volume function
 	.findfirst = NULL, 		// per-volume function
 	.findnext = __fat_findnext,