diff --git a/dlls/ntdll/locale.c b/dlls/ntdll/locale.c
index 508de48a0f9..d1b7ec83809 100644
--- a/dlls/ntdll/locale.c
+++ b/dlls/ntdll/locale.c
@@ -687,7 +687,8 @@ static NTSTATUS open_nls_data_file( ULONG type, ULONG id, HANDLE *file )
 
 void init_unix_codepage(void)
 {
-    unix_funcs->get_unix_codepage( &unix_table );
+    USHORT *data = unix_funcs->get_unix_codepage_data();
+    if (data) RtlInitCodePageTable( data, &unix_table );
 }
 
 
diff --git a/dlls/ntdll/unix/env.c b/dlls/ntdll/unix/env.c
index e57b6256890..e285bbbef0d 100644
--- a/dlls/ntdll/unix/env.c
+++ b/dlls/ntdll/unix/env.c
@@ -73,10 +73,17 @@ char **main_argv = NULL;
 char **main_envp = NULL;
 static WCHAR **main_wargv;
 
-static CPTABLEINFO unix_table;
 static char system_locale[LOCALE_NAME_MAX_LENGTH];
 static char user_locale[LOCALE_NAME_MAX_LENGTH];
 
+static struct
+{
+    USHORT *data;
+    USHORT *dbcs;
+    USHORT *mbtable;
+    void   *wctable;
+} unix_cp;
+
 static void *read_nls_file( const char *name )
 {
     const char *dir = build_dir ? build_dir : data_dir;
@@ -108,6 +115,21 @@ static void *read_nls_file( const char *name )
 }
 
 
+static int get_utf16( const WCHAR *src, unsigned int srclen, unsigned int *ch )
+{
+    if (IS_HIGH_SURROGATE( src[0] ))
+    {
+        if (srclen <= 1) return 0;
+        if (!IS_LOW_SURROGATE( src[1] )) return 0;
+        *ch = 0x10000 + ((src[0] & 0x3ff) << 10) + (src[1] & 0x3ff);
+        return 2;
+    }
+    if (IS_LOW_SURROGATE( src[0] )) return 0;
+    *ch = src[0];
+    return 1;
+}
+
+
 #ifdef __APPLE__
 
 /* The Apple filesystem enforces NFD so we need the compose tables to put it back into NFC */
@@ -148,20 +170,6 @@ static void init_unix_codepage(void)
     nfc_table = read_nls_file( "normnfc" );
 }
 
-static int get_utf16( const WCHAR *src, unsigned int srclen, unsigned int *ch )
-{
-    if (IS_HIGH_SURROGATE( src[0] ))
-    {
-        if (srclen <= 1) return 0;
-        if (!IS_LOW_SURROGATE( src[1] )) return 0;
-        *ch = 0x10000 + ((src[0] & 0x3ff) << 10) + (src[1] & 0x3ff);
-        return 2;
-    }
-    if (IS_LOW_SURROGATE( src[0] )) return 0;
-    *ch = src[0];
-    return 1;
-}
-
 static void put_utf16( WCHAR *dst, unsigned int ch )
 {
     if (ch >= 0x10000)
@@ -352,6 +360,17 @@ static const struct { const char *name; UINT cp; } charset_names[] =
     { "UTF8", CP_UTF8 }
 };
 
+static void init_unix_cptable( USHORT *ptr )
+{
+    unix_cp.data = ptr;
+    ptr += ptr[0];
+    unix_cp.wctable = ptr + ptr[0] + 1;
+    unix_cp.mbtable = ++ptr;
+    ptr += 256;
+    if (*ptr++) ptr += 256;  /* glyph table */
+    if (*ptr) unix_cp.dbcs = ptr + 1; /* dbcs ranges */
+}
+
 static void init_unix_codepage(void)
 {
     char charset_name[16];
@@ -383,7 +402,7 @@ static void init_unix_codepage(void)
                 void *data;
 
                 sprintf( name, "c_%03u", charset_names[pos].cp );
-                if ((data = read_nls_file( name ))) RtlInitCodePageTable( data, &unix_table );
+                if ((data = read_nls_file( name ))) init_unix_cptable( data );
             }
             return;
         }
@@ -422,6 +441,58 @@ static inline BOOL is_special_env_var( const char *var )
 }
 
 
+static unsigned int decode_utf8_char( unsigned char ch, const char **str, const char *strend )
+{
+    /* number of following bytes in sequence based on first byte value (for bytes above 0x7f) */
+    static const char utf8_length[128] =
+    {
+        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 0x80-0x8f */
+        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 0x90-0x9f */
+        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 0xa0-0xaf */
+        0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, /* 0xb0-0xbf */
+        0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1, /* 0xc0-0xcf */
+        1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, /* 0xd0-0xdf */
+        2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, /* 0xe0-0xef */
+        3,3,3,3,3,0,0,0,0,0,0,0,0,0,0,0  /* 0xf0-0xff */
+    };
+
+    /* first byte mask depending on UTF-8 sequence length */
+    static const unsigned char utf8_mask[4] = { 0x7f, 0x1f, 0x0f, 0x07 };
+
+    unsigned int len = utf8_length[ch - 0x80];
+    unsigned int res = ch & utf8_mask[len];
+    const char *end = *str + len;
+
+    if (end > strend)
+    {
+        *str = end;
+        return ~0;
+    }
+    switch (len)
+    {
+    case 3:
+        if ((ch = end[-3] ^ 0x80) >= 0x40) break;
+        res = (res << 6) | ch;
+        (*str)++;
+        if (res < 0x10) break;
+    case 2:
+        if ((ch = end[-2] ^ 0x80) >= 0x40) break;
+        res = (res << 6) | ch;
+        if (res >= 0x110000 >> 6) break;
+        (*str)++;
+        if (res < 0x20) break;
+        if (res >= 0xd800 >> 6 && res <= 0xdfff >> 6) break;
+    case 1:
+        if ((ch = end[-1] ^ 0x80) >= 0x40) break;
+        res = (res << 6) | ch;
+        (*str)++;
+        if (res < 0x80) break;
+        return res;
+    }
+    return ~0;
+}
+
+
 /******************************************************************
  *      ntdll_umbstowcs
  */
@@ -429,15 +500,66 @@ DWORD ntdll_umbstowcs( const char *src, DWORD srclen, WCHAR *dst, DWORD dstlen )
 {
     DWORD reslen;
 
-    if (unix_table.CodePage)
-        RtlCustomCPToUnicodeN( &unix_table, dst, dstlen * sizeof(WCHAR), &reslen, src, srclen );
-    else
-        RtlUTF8ToUnicodeN( dst, dstlen * sizeof(WCHAR), &reslen, src, srclen );
+    if (unix_cp.data)
+    {
+        DWORD i;
 
-    reslen /= sizeof(WCHAR);
+        if (unix_cp.dbcs)
+        {
+            for (i = dstlen; srclen && i; i--, srclen--, src++, dst++)
+            {
+                USHORT off = unix_cp.dbcs[(unsigned char)*src];
+                if (off && srclen > 1)
+                {
+                    src++;
+                    srclen--;
+                    *dst = unix_cp.dbcs[off + (unsigned char)*src];
+                }
+                else *dst = unix_cp.mbtable[(unsigned char)*src];
+            }
+            reslen = dstlen - i;
+        }
+        else
+        {
+            reslen = min( srclen, dstlen );
+            for (i = 0; i < reslen; i++) dst[i] = unix_cp.mbtable[(unsigned char)src[i]];
+        }
+    }
+    else  /* utf-8 */
+    {
+        unsigned int res;
+        const char *srcend = src + srclen;
+        WCHAR *dstend = dst + dstlen;
+
+        while ((dst < dstend) && (src < srcend))
+        {
+            unsigned char ch = *src++;
+            if (ch < 0x80)  /* special fast case for 7-bit ASCII */
+            {
+                *dst++ = ch;
+                continue;
+            }
+            if ((res = decode_utf8_char( ch, &src, srcend )) <= 0xffff)
+            {
+                *dst++ = res;
+            }
+            else if (res <= 0x10ffff)  /* we need surrogates */
+            {
+                res -= 0x10000;
+                *dst++ = 0xd800 | (res >> 10);
+                if (dst == dstend) break;
+                *dst++ = 0xdc00 | (res & 0x3ff);
+            }
+            else
+            {
+                *dst++ = 0xfffd;
+            }
+        }
+        reslen = dstlen - (dstend - dst);
 #ifdef __APPLE__  /* work around broken Mac OS X filesystem that enforces NFD */
-    if (reslen && nfc_table) reslen = compose_string( nfc_table, dst, reslen );
+        if (reslen && nfc_table) reslen = compose_string( nfc_table, dst, reslen );
 #endif
+    }
     return reslen;
 }
 
@@ -449,25 +571,24 @@ int ntdll_wcstoumbs( const WCHAR *src, DWORD srclen, char *dst, DWORD dstlen, BO
 {
     DWORD i, reslen;
 
-    if (unix_table.CodePage)
+    if (unix_cp.data)
     {
-        if (unix_table.DBCSOffsets)
+        if (unix_cp.dbcs)
         {
-            const unsigned short *uni2cp = unix_table.WideCharTable;
+            const unsigned short *uni2cp = unix_cp.wctable;
             for (i = dstlen; srclen && i; i--, srclen--, src++)
             {
                 unsigned short ch = uni2cp[*src];
                 if (ch >> 8)
                 {
-                    if (strict && unix_table.DBCSOffsets[unix_table.DBCSOffsets[ch >> 8] + (ch & 0xff)] != *src)
-                        return -1;
+                    if (strict && unix_cp.dbcs[unix_cp.dbcs[ch >> 8] + (ch & 0xff)] != *src) return -1;
                     if (i == 1) break;  /* do not output a partial char */
                     i--;
                     *dst++ = ch >> 8;
                 }
                 else
                 {
-                    if (unix_table.MultiByteTable[ch] != *src) return -1;
+                    if (unix_cp.mbtable[ch] != *src) return -1;
                     *dst++ = (char)ch;
                 }
             }
@@ -475,18 +596,72 @@ int ntdll_wcstoumbs( const WCHAR *src, DWORD srclen, char *dst, DWORD dstlen, BO
         }
         else
         {
-            const unsigned char *uni2cp = unix_table.WideCharTable;
+            const unsigned char *uni2cp = unix_cp.wctable;
             reslen = min( srclen, dstlen );
             for (i = 0; i < reslen; i++)
             {
                 unsigned char ch = uni2cp[src[i]];
-                if (strict && unix_table.MultiByteTable[ch] != src[i]) return -1;
+                if (strict && unix_cp.mbtable[ch] != src[i]) return -1;
                 dst[i] = ch;
             }
         }
     }
-    else RtlUnicodeToUTF8N( dst, dstlen, &reslen, src, srclen * sizeof(WCHAR) );
+    else  /* utf-8 */
+    {
+        char *end;
+        unsigned int val;
 
+        for (end = dst + dstlen; srclen; srclen--, src++)
+        {
+            WCHAR ch = *src;
+
+            if (ch < 0x80)  /* 0x00-0x7f: 1 byte */
+            {
+                if (dst > end - 1) break;
+                *dst++ = ch;
+                continue;
+            }
+            if (ch < 0x800)  /* 0x80-0x7ff: 2 bytes */
+            {
+                if (dst > end - 2) break;
+                dst[1] = 0x80 | (ch & 0x3f);
+                ch >>= 6;
+                dst[0] = 0xc0 | ch;
+                dst += 2;
+                continue;
+            }
+            if (!get_utf16( src, srclen, &val ))
+            {
+                if (strict) return -1;
+                val = 0xfffd;
+            }
+            if (val < 0x10000)  /* 0x800-0xffff: 3 bytes */
+            {
+                if (dst > end - 3) break;
+                dst[2] = 0x80 | (val & 0x3f);
+                val >>= 6;
+                dst[1] = 0x80 | (val & 0x3f);
+                val >>= 6;
+                dst[0] = 0xe0 | val;
+                dst += 3;
+            }
+            else   /* 0x10000-0x10ffff: 4 bytes */
+            {
+                if (dst > end - 4) break;
+                dst[3] = 0x80 | (val & 0x3f);
+                val >>= 6;
+                dst[2] = 0x80 | (val & 0x3f);
+                val >>= 6;
+                dst[1] = 0x80 | (val & 0x3f);
+                val >>= 6;
+                dst[0] = 0xf0 | val;
+                dst += 4;
+                src++;
+                srclen--;
+            }
+        }
+        reslen = dstlen - (end - dst);
+    }
     return reslen;
 }
 
@@ -1055,13 +1230,13 @@ void CDECL get_initial_directory( UNICODE_STRING *dir )
 
 
 /*************************************************************************
- *		get_unix_codepage
+ *		get_unix_codepage_data
  *
  * Return the Unix codepage data.
  */
-void CDECL get_unix_codepage( CPTABLEINFO *table )
+USHORT * CDECL get_unix_codepage_data(void)
 {
-    *table = unix_table;
+    return unix_cp.data;
 }
 
 
diff --git a/dlls/ntdll/unix/loader.c b/dlls/ntdll/unix/loader.c
index 3ea7adf9f0a..a8af46e2dfd 100644
--- a/dlls/ntdll/unix/loader.c
+++ b/dlls/ntdll/unix/loader.c
@@ -1509,7 +1509,7 @@ static struct unix_funcs unix_funcs =
     get_dynamic_environment,
     get_initial_console,
     get_initial_directory,
-    get_unix_codepage,
+    get_unix_codepage_data,
     get_locales,
     get_version,
     get_build_id,
diff --git a/dlls/ntdll/unix/unix_private.h b/dlls/ntdll/unix/unix_private.h
index 71d6ee7d4f2..4f93aa2c54b 100644
--- a/dlls/ntdll/unix/unix_private.h
+++ b/dlls/ntdll/unix/unix_private.h
@@ -100,7 +100,7 @@ extern NTSTATUS CDECL get_startup_info( startup_info_t *info, SIZE_T *total_size
 extern NTSTATUS CDECL get_dynamic_environment( WCHAR *env, SIZE_T *size ) DECLSPEC_HIDDEN;
 extern void CDECL get_initial_directory( UNICODE_STRING *dir ) DECLSPEC_HIDDEN;
 extern void CDECL get_initial_console( HANDLE *handle, HANDLE *std_in, HANDLE *std_out, HANDLE *std_err ) DECLSPEC_HIDDEN;
-extern void CDECL get_unix_codepage( CPTABLEINFO *table ) DECLSPEC_HIDDEN;
+extern USHORT * CDECL get_unix_codepage_data(void) DECLSPEC_HIDDEN;
 extern void CDECL get_locales( WCHAR *sys, WCHAR *user ) DECLSPEC_HIDDEN;
 extern NTSTATUS CDECL virtual_map_section( HANDLE handle, PVOID *addr_ptr, unsigned short zero_bits_64, SIZE_T commit_size,
                                            const LARGE_INTEGER *offset_ptr, SIZE_T *size_ptr, ULONG alloc_type,
diff --git a/dlls/ntdll/unixlib.h b/dlls/ntdll/unixlib.h
index 7e73400dae2..89ca0e960ce 100644
--- a/dlls/ntdll/unixlib.h
+++ b/dlls/ntdll/unixlib.h
@@ -28,7 +28,7 @@ struct msghdr;
 struct _DISPATCHER_CONTEXT;
 
 /* increment this when you change the function table */
-#define NTDLL_UNIXLIB_VERSION 69
+#define NTDLL_UNIXLIB_VERSION 70
 
 struct unix_funcs
 {
@@ -303,7 +303,7 @@ struct unix_funcs
     void          (CDECL *get_initial_console)( HANDLE *handle, HANDLE *std_in,
                                                 HANDLE *std_out, HANDLE *std_err );
     void          (CDECL *get_initial_directory)( UNICODE_STRING *dir );
-    void          (CDECL *get_unix_codepage)( CPTABLEINFO *table );
+    USHORT *      (CDECL *get_unix_codepage_data)(void);
     void          (CDECL *get_locales)( WCHAR *sys, WCHAR *user );
     const char *  (CDECL *get_version)(void);
     const char *  (CDECL *get_build_id)(void);