Add Mii selector applet (appletEd) (#372)

libctru/include/3ds.h

@@ -77,6 +77,7 @@ extern "C" {
 
 #include <3ds/applets/swkbd.h>
 #include <3ds/applets/error.h>
+#include <3ds/applets/miiselector.h>
   
 #include <3ds/sdmc.h>
 #include <3ds/romfs.h>

libctru/include/3ds/applets/miiselector.h

@@ -0,0 +1,90 @@
+/**
+ * @file miiselector.h
+ * @brief Mii Selector Applet (appletEd).
+ */
+
+#pragma once
+
+/// Magic value needed to launch the applet.
+#define MIISELECTOR_MAGIC 0x13DE28CF
+
+/// Maximum length of title to be displayed at the top of the Mii selector applet
+#define MIISELECTOR_TITLE_LEN 64
+
+/// Number of Guest Miis available for selection
+#define MIISELECTOR_GUESTMII_SLOTS 6
+
+/// Maximum number of user Miis available for selection
+#define MIISELECTOR_USERMII_SLOTS 100
+
+/// Parameter structure passed to AppletEd
+typedef struct
+{
+	char enable_cancel_button;        ///< Enables canceling of selection if nonzero.
+	char enable_selecting_guests;     ///< Makes Guets Miis selectable if nonzero.
+	char show_on_top_screen;          ///< Shows applet on top screen if nonzero,
+	                                  ///< otherwise show it on the bottom screen.
+	char _unk0x3[5];                  ///< @private
+	u16 title[MIISELECTOR_TITLE_LEN]; ///< UTF16-LE string displayed at the top of the applet. If
+	                                  ///< set to the empty string, a default title is displayed.
+	char _unk0x88[4];                 ///< @private
+	char show_guest_page;             ///< If nonzero, the applet shows a page with Guest
+	                                  ///< Miis on launch.
+	char _unk0x8D[3];                 ///< @private
+	u32 initial_index;                ///< Index of the initially selected Mii. If
+	                                  ///< @ref MiiSelectorConf.show_guest_page is
+	                                  ///< set, this is the index of a Guest Mii,
+	                                  ///< otherwise that of a user Mii.
+	char mii_guest_whitelist[MIISELECTOR_GUESTMII_SLOTS]; ///< Each byte set to a nonzero value
+	                                                      ///< enables its corresponding Guest
+	                                                      ///< Mii to be enabled for selection.
+	char mii_whitelist[MIISELECTOR_USERMII_SLOTS]; ///< Each byte set to a nonzero value enables
+	                                               ///< its corresponding user Mii to be enabled
+	                                               ///< for selection.
+	u16 _unk0xFE;                                  ///< @private
+	u32 magic; ///< Will be set to @ref MIISELECTOR_MAGIC before launching the
+	           ///< applet.
+} MiiSelectorConf;
+
+/// Size of the data describing a single Mii
+#define MIISELECTOR_MIIDATA_SIZE 0x5c
+
+/// Maximum length of the localized name of a Guest Mii
+#define MIISELECTOR_GUESTMII_NAME_LEN 12
+
+/// Structure written by AppletEd
+typedef struct
+{
+	u32 no_mii_selected;                ///< 0 if a Mii was selected, 1 if the selection was
+	                                    ///< canceled.
+	u32 guest_mii_was_selected;         ///< 1 if a Guest Mii was selected, 0 otherwise.
+	u32 guest_mii_index;                ///< Index of the selected Guest Mii,
+	                                    ///< 0xFFFFFFFF if no guest was selected.
+	char mii[MIISELECTOR_MIIDATA_SIZE]; ///< Data of selected Mii.
+	u16 _pad0x68;                       ///< @private
+	u16 checksum;                       ///< Checksum of the returned Mii data.
+	                                    ///< Stored as a big-endian value; use
+	                                    ///< @ref miiSelectorChecksumIsValid to
+	                                    ///< verify.
+	u16 guest_mii_name[MIISELECTOR_GUESTMII_NAME_LEN]; ///< Localized name of a Guest Mii,
+	                                                   ///< if one was selected (UTF16-LE
+	                                                   ///< string). Zeroed otherwise.
+} MiiSelectorReturn;
+
+/**
+ * @brief Launch the Mii selector library applet
+ *
+ * @param conf Configuration determining how the applet should behave
+ * @param returnbuf Data returned by the applet
+ */
+Result miiSelectorLaunch(const MiiSelectorConf *conf, MiiSelectorReturn* returnbuf);
+
+/**
+ * @brief Verifies that the Mii data returned from the applet matches its
+ * checksum
+ *
+ * @param returnbuffer Buffer filled by Mii selector applet
+ *
+ * @return `true` if `returnbuf->checksum` is the same as the one computed from `returnbuf`
+ */
+bool miiSelectorChecksumIsValid(const MiiSelectorReturn *returnbuf);

libctru/source/applets/miiselector.c

@@ -0,0 +1,57 @@
+#include <3ds/types.h>
+#include <3ds/result.h>
+#include <3ds/services/apt.h>
+
+#include <3ds/applets/miiselector.h>
+
+#include <string.h> // for memcpy
+
+Result miiSelectorLaunch(const MiiSelectorConf *conf, MiiSelectorReturn *returnbuf)
+{
+	union {
+		MiiSelectorConf config;
+		MiiSelectorReturn ret;
+	} ctx;
+
+	memcpy(&ctx.config, conf, sizeof(MiiSelectorConf));
+	ctx.config.magic = MIISELECTOR_MAGIC;
+
+	Result ret = aptLaunchLibraryApplet(APPID_APPLETED, &ctx.config, sizeof(MiiSelectorConf), 0);
+	if(R_SUCCEEDED(ret) && returnbuf) {
+		memcpy(returnbuf, &ctx.ret, sizeof(MiiSelectorReturn));
+	}
+
+	return ret;
+}
+
+static u16 crc16_ccitt(void const *buf, size_t len, uint32_t starting_val)
+{
+	if(buf == NULL) {
+		return -1;
+	}
+
+	u8 const *cbuf = buf;
+	u32 crc        = starting_val;
+
+	static const u16 POLY = 0x1021;
+
+	for(size_t i = 0; i < len; i++) {
+		for(int bit = 7; bit >= 0; bit--) {
+			crc = ((crc << 1) | ((cbuf[i] >> bit) & 0x1)) ^ (crc & 0x8000 ? POLY : 0);
+		}
+	}
+
+	for(int _ = 0; _ < 16; _++) {
+		crc = (crc << 1) ^ (crc & 0x8000 ? POLY : 0);
+	}
+
+	return (u16)(crc & 0xffff);
+}
+
+bool miiSelectorChecksumIsValid(const MiiSelectorReturn *returnbuf)
+{
+	u16 computed =
+	    crc16_ccitt(&returnbuf->mii, sizeof(returnbuf->mii) + sizeof(returnbuf->_pad0x68), 0x0000);
+	u16 chk_little_endian = __builtin_bswap16(returnbuf->checksum);
+	return computed == chk_little_endian;
+}