vvfat: correctly create base short names for non-ASCII filenames

More specifically, create short name from filename and change blacklist of
invalid chars to whitelist of valid chars.

Windows 9x also now correctly see long file names of filenames containing a space,
but Scandisk still complains about mismatch between SFN and LFN.

[kwolf: Build fix for this intermediate patch (it included declarations
 for variables that are only used in the next patch) ]

Specification: "FAT: General overview of on-disk format" v1.03, pages 30-31
Signed-off-by: NHervé Poussineau <hpoussin@reactos.org>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/vvfat.c

@@ -515,6 +515,80 @@ static void set_begin_of_direntry(direntry_t* direntry, uint32_t begin)
     direntry->begin_hi = cpu_to_le16((begin >> 16) & 0xffff);
 }
 
+static uint8_t to_valid_short_char(gunichar c)
+{
+    c = g_unichar_toupper(c);
+    if ((c >= '0' && c <= '9') ||
+        (c >= 'A' && c <= 'Z') ||
+        strchr("$%'-_@~`!(){}^#&", c) != 0) {
+        return c;
+    } else {
+        return 0;
+    }
+}
+
+static direntry_t *create_short_filename(BDRVVVFATState *s,
+                                         const char *filename)
+{
+    int j = 0;
+    direntry_t *entry = array_get_next(&(s->directory));
+    const gchar *p, *last_dot = NULL;
+    gunichar c;
+    bool lossy_conversion = false;
+
+    if (!entry) {
+        return NULL;
+    }
+    memset(entry->name, 0x20, sizeof(entry->name));
+
+    /* copy filename and search last dot */
+    for (p = filename; ; p = g_utf8_next_char(p)) {
+        c = g_utf8_get_char(p);
+        if (c == '\0') {
+            break;
+        } else if (c == '.') {
+            if (j == 0) {
+                /* '.' at start of filename */
+                lossy_conversion = true;
+            } else {
+                if (last_dot) {
+                    lossy_conversion = true;
+                }
+                last_dot = p;
+            }
+        } else if (!last_dot) {
+            /* first part of the name; copy it */
+            uint8_t v = to_valid_short_char(c);
+            if (j < 8 && v) {
+                entry->name[j++] = v;
+            } else {
+                lossy_conversion = true;
+            }
+        }
+    }
+
+    /* copy extension (if any) */
+    if (last_dot) {
+        j = 0;
+        for (p = g_utf8_next_char(last_dot); ; p = g_utf8_next_char(p)) {
+            c = g_utf8_get_char(p);
+            if (c == '\0') {
+                break;
+            } else {
+                /* extension; copy it */
+                uint8_t v = to_valid_short_char(c);
+                if (j < 3 && v) {
+                    entry->name[8 + (j++)] = v;
+                } else {
+                    lossy_conversion = true;
+                }
+            }
+        }
+    }
+    (void)lossy_conversion;
+    return entry;
+}
+
 /* fat functions */
 
 static inline uint8_t fat_chksum(const direntry_t* entry)
@@ -613,7 +687,7 @@ static inline void init_fat(BDRVVVFATState* s)
 static inline direntry_t* create_short_and_long_name(BDRVVVFATState* s,
         unsigned int directory_start, const char* filename, int is_dot)
 {
-    int i,j,long_index=s->directory.next;
+    int long_index = s->directory.next;
     direntry_t* entry = NULL;
     direntry_t* entry_long = NULL;
 
@@ -625,33 +699,7 @@ static inline direntry_t* create_short_and_long_name(BDRVVVFATState* s,
     }
 
     entry_long=create_long_filename(s,filename);
-
-    i = strlen(filename);
-    for(j = i - 1; j>0  && filename[j]!='.';j--);
-    if (j > 0)
-        i = (j > 8 ? 8 : j);
-    else if (i > 8)
-        i = 8;
-
-    entry=array_get_next(&(s->directory));
-    memset(entry->name, 0x20, sizeof(entry->name));
-    memcpy(entry->name, filename, i);
-
-    if (j > 0) {
-        for (i = 0; i < 3 && filename[j + 1 + i]; i++) {
-            entry->name[8 + i] = filename[j + 1 + i];
-        }
-    }
-
-    /* upcase & remove unwanted characters */
-    for(i=10;i>=0;i--) {
-        if(i==10 || i==7) for(;i>0 && entry->name[i]==' ';i--);
-        if(entry->name[i]<=' ' || entry->name[i]>0x7f
-                || strchr(".*?<>|\":/\\[];,+='",entry->name[i]))
-            entry->name[i]='_';
-        else if(entry->name[i]>='a' && entry->name[i]<='z')
-            entry->name[i]+='A'-'a';
-    }
+    entry = create_short_filename(s, filename);
 
     /* mangle duplicates */
     while(1) {