[Qemu-devel] [PATCH 09/13] vvfat: correctly create base short names for non-ASCII filenames

From: "Hervé Poussineau" <hpoussin@reactos.org>
To: qemu-devel@nongnu.org
Cc: "Kevin Wolf" <kwolf@redhat.com>, "Max Reitz" <mreitz@redhat.com>,
	qemu-block@nongnu.org, "Hervé Poussineau" <hpoussin@reactos.org>
Subject: [Qemu-devel] [PATCH 09/13] vvfat: correctly create base short names for non-ASCII filenames
Date: Mon, 15 May 2017 22:31:09 +0200	[thread overview]
Message-ID: <20170515203114.9477-10-hpoussin@reactos.org> (raw)
In-Reply-To: <20170515203114.9477-1-hpoussin@reactos.org>

More specifically, create short name from long name 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.

Specification: "FAT: General overview of on-disk format" v1.03, pages 30/31
Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
---
 block/vvfat.c | 84 +++++++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 56 insertions(+), 28 deletions(-)

diff --git a/block/vvfat.c b/block/vvfat.c
index 5f6356c834..37cfaa85fc 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -589,6 +589,60 @@ 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(uint8_t c)
+{
+    if ((c >= '0' && c <= '9') ||
+        (c >= 'A' && c <= 'Z') ||
+        strchr("$%'-_@~`!(){}^#&", c) != 0) {
+        return c;
+    } else if (c >= 'a' && c <= 'z') {
+        return c - 'a' + 'A';
+    } else {
+        return 0;
+    }
+}
+
+static direntry_t *create_short_filename(BDRVVVFATState *s, long_file_name *lfn)
+{
+    int i, j = 0;
+    direntry_t *entry = array_get_next(&(s->directory));
+    uint8_t c;
+
+    if (!entry) {
+        return NULL;
+    }
+    memset(entry->name, 0x20, sizeof(entry->name));
+
+    /* create short name (keep only valid chars and upcase letters) */
+    for (i = 0; i < lfn->len && j < 8; i += 2) {
+        c = to_valid_short_char(lfn->name[i]);
+        if (lfn->name[i + 1] == 0 && c != 0) {
+            entry->name[j++] = c;
+        } else if (lfn->name[i + 1] == 0 &&
+                   (lfn->name[i] == '.' || lfn->name[i] == 0)) {
+            break;
+        }
+    }
+    /* search last extension */
+    for (i = lfn->len - 2; i > 0; i -= 2) {
+        if (lfn->name[i] == '.' && lfn->name[i + 1] == 0) {
+            break;
+        }
+    }
+    if (i != 0) {
+        /* create short extension */
+        for (; i < lfn->len && j < 11; i += 2) {
+            c = to_valid_short_char(lfn->name[i]);
+            if (lfn->name[i + 1] == 0 && c != 0) {
+                entry->name[j++] = c;
+            } else if (lfn->name[i + 1] == 0 && lfn->name[i] == 0) {
+                break;
+            }
+        }
+    }
+    return entry;
+}
+
 /* fat functions */
 
 static inline uint8_t fat_chksum(const direntry_t* entry)
@@ -687,7 +741,7 @@ 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;
     long_file_name lfn;
@@ -700,33 +754,7 @@ static inline direntry_t* create_short_and_long_name(BDRVVVFATState* s,
     }
 
     entry_long = create_long_filename(s, filename, &lfn);
-
-    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, &lfn);
 
     /* mangle duplicates */
     while(1) {
-- 
2.11.0
