🐛 Fix M23 long filename support (#25540)

Marlin/src/sd/SdBaseFile.cpp

@@ -703,7 +703,10 @@ bool SdBaseFile::open(SdBaseFile *dirFile, const uint8_t dname[11]
               // Get VFat dir entry
               pvFat = (vfat_t *) p;
               // Get checksum from the last entry of the sequence
-              if (pvFat->sequenceNumber & 0x40) lfnChecksum = pvFat->checksum;
+              if (pvFat->sequenceNumber & 0x40) {
+                lfnChecksum = pvFat->checksum;
+                ZERO(lfnName);
+              }
               // Get LFN sequence number
               lfnSequenceNumber = pvFat->sequenceNumber & 0x1F;
               if WITHIN(lfnSequenceNumber, 1, reqEntriesNum) {
@@ -711,6 +714,7 @@ bool SdBaseFile::open(SdBaseFile *dirFile, const uint8_t dname[11]
                 if (lfnChecksum == pvFat->checksum) {
                   // Set chunk of LFN from VFAT entry into lfnName
                   getLFNName(pvFat, (char *)lfnName, lfnSequenceNumber);
+                  TERN_(UTF_FILENAME_SUPPORT, convertUtf16ToUtf8((char *)lfnName));
                   // LFN found?
                   if (!strncasecmp((char*)dlname, (char*)lfnName, lfnNameLength)) lfnFileFound = true;
                 }
@@ -1132,13 +1136,13 @@ bool SdBaseFile::openNext(SdBaseFile *dirFile, uint8_t oflag) {
    * Get the LFN filename block from a dir. Get the block in lname at startOffset
    */
   void SdBaseFile::getLFNName(vfat_t *pFatDir, char *lname, uint8_t sequenceNumber) {
-    uint8_t startOffset = (sequenceNumber - 1) * FILENAME_LENGTH;
+    const uint8_t startOffset = (sequenceNumber - 1) * FILENAME_LENGTH;
     LOOP_L_N(i, FILENAME_LENGTH) {
       const uint16_t utf16_ch = (i >= 11) ? pFatDir->name3[i - 11] : (i >= 5) ? pFatDir->name2[i - 5] : pFatDir->name1[i];
       #if ENABLED(UTF_FILENAME_SUPPORT)
         // We can't reconvert to UTF-8 here as UTF-8 is variable-size encoding, but joining LFN blocks
         // needs static bytes addressing. So here just store full UTF-16LE words to re-convert later.
-        uint16_t idx = (startOffset + i) * 2; // This is fixed as FAT LFN always contain UTF-16LE encoding
+        const uint16_t idx = (startOffset + i) * 2; // This is fixed as FAT LFN always contain UTF-16LE encoding
         lname[idx] = utf16_ch & 0xFF;
         lname[idx + 1] = (utf16_ch >> 8) & 0xFF;
       #else
@@ -1152,8 +1156,8 @@ bool SdBaseFile::openNext(SdBaseFile *dirFile, uint8_t oflag) {
    * Set the LFN filename block lname to a dir. Put the block based on sequence number
    */
   void SdBaseFile::setLFNName(vfat_t *pFatDir, char *lname, uint8_t sequenceNumber) {
-    uint8_t startOffset = (sequenceNumber - 1) * FILENAME_LENGTH;
+    const uint8_t startOffset = (sequenceNumber - 1) * FILENAME_LENGTH,
-    uint8_t nameLength = strlen(lname);
+                  nameLength = strlen(lname);
     LOOP_L_N(i, FILENAME_LENGTH) {
       uint16_t ch = 0;
       if ((startOffset + i) < nameLength)
@@ -1424,7 +1428,7 @@ int16_t SdBaseFile::read(void *buf, uint16_t nbyte) {
  * readDir() called before a directory has been opened, this is not
  * a directory file or an I/O error occurred.
  */
-int8_t SdBaseFile::readDir(dir_t *dir, char *longFilename) {
+int8_t SdBaseFile::readDir(dir_t *dir, char * const longFilename) {
   int16_t n;
   // if not a directory file or miss-positioned return an error
   if (!isDir() || (0x1F & curPosition_)) return -1;
@@ -1506,44 +1510,55 @@ int8_t SdBaseFile::readDir(dir_t *dir, char *longFilename) {
     // Post-process normal file or subdirectory longname, if any
     if (DIR_IS_FILE_OR_SUBDIR(dir)) {
       #if ENABLED(UTF_FILENAME_SUPPORT)
-        #if LONG_FILENAME_CHARSIZE > 2
-          // Add warning for developers for unsupported 3-byte cases.
-          // (Converting 2-byte codepoints to 3-byte in-place would break the rest of filename.)
-          #error "Currently filename re-encoding is done in-place. It may break the remaining chars to use 3-byte codepoints."
-        #endif
-
         // Is there a long filename to decode?
         if (longFilename) {
-          // Reset n to the start of the long name
+          n = convertUtf16ToUtf8(longFilename);
-          n = 0;
+        }
-          for (uint16_t idx = 0; idx < (LONG_FILENAME_LENGTH); idx += 2) {  // idx is fixed since FAT LFN always contains UTF-16LE encoding
-            const uint16_t utf16_ch = longFilename[idx] | (longFilename[idx + 1] << 8);
-            if (0xD800 == (utf16_ch & 0xF800))                              // Surrogate pair - encode as '_'
-              longFilename[n++] = '_';
-            else if (0 == (utf16_ch & 0xFF80))                              // Encode as 1-byte UTF-8 char
-              longFilename[n++] = utf16_ch & 0x007F;
-            else if (0 == (utf16_ch & 0xF800)) {                            // Encode as 2-byte UTF-8 char
-              longFilename[n++] = 0xC0 | ((utf16_ch >> 6) & 0x1F);
-              longFilename[n++] = 0x80 | ( utf16_ch       & 0x3F);
-            }
-            else {
-              #if LONG_FILENAME_CHARSIZE > 2                                // Encode as 3-byte UTF-8 char
-                longFilename[n++] = 0xE0 | ((utf16_ch >> 12) & 0x0F);
-                longFilename[n++] = 0xC0 | ((utf16_ch >>  6) & 0x3F);
-                longFilename[n++] = 0xC0 | ( utf16_ch        & 0x3F);
-              #else                                                         // Encode as '_'
-                longFilename[n++] = '_';
-              #endif
-            }
-            if (0 == utf16_ch) break; // End of filename
-          } // idx
-        } // longFilename
       #endif
       return n;
     } // DIR_IS_FILE_OR_SUBDIR
   }
 }
 
+#if ENABLED(UTF_FILENAME_SUPPORT)
+
+  uint8_t SdBaseFile::convertUtf16ToUtf8(char * const longFilename) {
+    #if LONG_FILENAME_CHARSIZE > 2
+      // Add warning for developers for unsupported 3-byte cases.
+      // (Converting 2-byte codepoints to 3-byte in-place would break the rest of filename.)
+      #error "Currently filename re-encoding is done in-place. It may break the remaining chars to use 3-byte codepoints."
+    #endif
+
+    int16_t n;
+    // Reset n to the start of the long name
+    n = 0;
+    for (uint16_t idx = 0; idx < (LONG_FILENAME_LENGTH); idx += 2) {  // idx is fixed since FAT LFN always contains UTF-16LE encoding
+      const uint16_t utf16_ch = longFilename[idx] | (longFilename[idx + 1] << 8);
+      if (0xD800 == (utf16_ch & 0xF800))                              // Surrogate pair - encode as '_'
+        longFilename[n++] = '_';
+      else if (0 == (utf16_ch & 0xFF80))                              // Encode as 1-byte UTF-8 char
+        longFilename[n++] = utf16_ch & 0x007F;
+      else if (0 == (utf16_ch & 0xF800)) {                            // Encode as 2-byte UTF-8 char
+        longFilename[n++] = 0xC0 | ((utf16_ch >> 6) & 0x1F);
+        longFilename[n++] = 0x80 | ( utf16_ch       & 0x3F);
+      }
+      else {
+        #if LONG_FILENAME_CHARSIZE > 2                                // Encode as 3-byte UTF-8 char
+          longFilename[n++] = 0xE0 | ((utf16_ch >> 12) & 0x0F);
+          longFilename[n++] = 0xC0 | ((utf16_ch >>  6) & 0x3F);
+          longFilename[n++] = 0xC0 | ( utf16_ch        & 0x3F);
+        #else                                                         // Encode as '_'
+          longFilename[n++] = '_';
+        #endif
+      }
+      if (0 == utf16_ch) break; // End of filename
+    } // idx
+
+    return n;
+  }
+
+#endif // UTF_FILENAME_SUPPORT
+
 // Read next directory entry into the cache
 // Assumes file is correctly positioned
 dir_t* SdBaseFile::readDirCache() {

Marlin/src/sd/SdBaseFile.h

@@ -298,7 +298,7 @@ class SdBaseFile {
   bool printName();
   int16_t read();
   int16_t read(void *buf, uint16_t nbyte);
-  int8_t readDir(dir_t *dir, char *longFilename);
+  int8_t readDir(dir_t *dir, char * const longFilename);
   static bool remove(SdBaseFile *dirFile, const char *path);
   bool remove();
 
@@ -392,14 +392,16 @@ class SdBaseFile {
   bool openCachedEntry(uint8_t cacheIndex, uint8_t oflags);
   dir_t* readDirCache();
 
+  #if ENABLED(UTF_FILENAME_SUPPORT)
+    uint8_t convertUtf16ToUtf8(char * const longFilename);
+  #endif
+
   // Long Filename create/write support
   #if ENABLED(LONG_FILENAME_WRITE_SUPPORT)
     static bool isDirLFN(const dir_t* dir);
     static bool isDirNameLFN(const char *dirname);
     static bool parsePath(const char *str, uint8_t *name, uint8_t *lname, const char **ptr);
-    /**
+    // Return the number of entries needed in the FAT for this LFN
-     * Return the number of entries needed in the FAT for this LFN
-     */
     static inline uint8_t getLFNEntriesNum(const char *lname) { return (strlen(lname) + 12) / 13; }
     static void getLFNName(vfat_t *vFatDir, char *lname, uint8_t startOffset);
     static void setLFNName(vfat_t *vFatDir, char *lname, uint8_t lfnSequenceNumber);