patterns: Add PKM pattern + add BCC checksum verification to ntag pattern (#274)

* patterns/ntag: add BCC checksum verification

* patterns: add PKM file pattern

* Add entry to README

* Added missing import

---------

Co-authored-by: Nik <werwolv98@gmail.com>

README.md

@@ -94,6 +94,7 @@ Everything will immediately show up in ImHex's Content Store and gets bundled wi
 | PP   | | [`patterns/selinuxpp.hexpat`](patterns/selinuxpp.pat) | SE Linux package |
 | PFS0 | | [`patterns/pfs0.hexpat`](patterns/pfs0.hexpat) | Nintendo Switch PFS0 archive (NSP files) |
 | PIF | `image/pif` | [`patterns/pif.hexpat`](patterns/pif.hexpat) | PIF Image Format |
+| PKM | | [`patterns/pkm.hexpat`](patterns/pkm.hexpat) | PKM texture format |
 | PNG  | `image/png` | [`patterns/png.hexpat`](patterns/png.hexpat) | PNG image files |
 | PRODINFO | | [`patterns/prodinfo.hexpat`](patterns/prodinfo.hexpat) | Nintendo Switch PRODINFO |
 | Protobuf | | [`patterns/protobuf.hexpat`](patterns/protobuf.hexpat) | Google Protobuf encoding |

patterns/ntag.hexpat

@@ -2,6 +2,7 @@
 #pragma description NTAG213/NTAG215/NTAG216, NFC Forum Type 2 Tag compliant IC
 
 import std.core;
+import std.io;
 
 using BitfieldOrder = std::core::BitfieldOrder;
 
@@ -147,6 +148,38 @@ bitfield ACCESS {
 	AUTHLIM				: 3;
 };
 
+fn validate_ntag_checksum(ManufacturerData mdata) {
+
+    /*
+    0x88 is the CT/cascade digit.
+    This is XOR'd with the first 3 bytes of the serial to calculate BCC0.
+    */
+    
+    u8 bcc0 = 0x88 ^ 
+    mdata.serial1[0] ^
+    mdata.serial1[1] ^
+    mdata.serial1[2];
+    
+    if (bcc0 == mdata.checkByte0) {
+        std::print("NTAG BCC0 checksum OK. Value: {}", bcc0);
+    } else {
+        std::warning(std::format("NTAG BCC0 checksum failed! Value: {}", bcc0));
+    }
+    
+    // BCC1 is the XOR of the last 4 serial bytes.
+    
+    u8 bcc1 = mdata.serial2[0] ^
+    mdata.serial2[1] ^
+    mdata.serial2[2] ^
+    mdata.serial2[3];
+    
+    if (bcc1 == mdata.checkByte1) {
+        std::print("NTAG BCC1 checksum OK. Value: {}", bcc1);
+    } else {
+        std::warning(std::format("NTAG BCC1 checksum failed! Value: {}", bcc1));
+    }
+};
+
 struct Config {
 	MIRROR MIRROR;
 	u8 MIRROR_PAGE;
@@ -166,3 +199,5 @@ struct NTAG {
 };
 
 NTAG ntag @ 0x00;
+
+validate_ntag_checksum(ntag.manufacturerData);

patterns/pkm.hexpat

@@ -0,0 +1,27 @@
+#pragma description PKM (PacKMan) files containing ETC (Ericsson Texture Compression)
+#pragma author applecuckoo
+#pragma endian big
+
+enum PKMFormat : u16 {
+    ETC1_RGB_NO_MIPMAPS,
+    ETC2PACKAGE_RGB_NO_MIPMAPS,
+    ETC2PACKAGE_RGBA_NO_MIPMAPS_OLD,
+    ETC2PACKAGE_RGBA_NO_MIPMAPS,
+    ETC2PACKAGE_RGBA1_NO_MIPMAPS,
+    ETC2PACKAGE_R_NO_MIPMAPS,
+    ETC2PACKAGE_RG_NO_MIPMAPS,
+    ETC2PACKAGE_R_SIGNED_NO_MIPMAPS,
+    ETC2PACKAGE_RG_SIGNED_NO_MIPMAPS
+};
+
+struct PKMHeader {
+    char id[4];
+    char version[2];
+    PKMFormat pkm_format;
+    u16 width;
+    u16 height;
+    u16 original_width;
+    u16 original_height;
+};
+
+PKMHeader pkm_header @ 0x00 [[comment("PKM file header"), name("Header")]];