r2599: avoid free()ing our static unalloceted memory that ends up in memory corruption.
[tprouty/samba.git] / source / lib / iconv.c
index e54a74864e1eedb2b533ea1d12c7e6f27353650b..66a6e6cd8bc91adb6d455421d8d26130605d847f 100644 (file)
@@ -2,7 +2,7 @@
    Unix SMB/CIFS implementation.
    minimal iconv implementation
    Copyright (C) Andrew Tridgell 2001
-   Copyright (C) Jelmer Vernooij 2002
+   Copyright (C) Jelmer Vernooij 2002,2003
    
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
 
 #include "includes.h"
 
-static size_t ascii_pull(void *,char **, size_t *, char **, size_t *);
-static size_t ascii_push(void *,char **, size_t *, char **, size_t *);
-static size_t  utf8_pull(void *,char **, size_t *, char **, size_t *);
-static size_t  utf8_push(void *,char **, size_t *, char **, size_t *);
-static size_t ucs2hex_pull(void *,char **, size_t *, char **, size_t *);
-static size_t ucs2hex_push(void *,char **, size_t *, char **, size_t *);
-static size_t iconv_copy(void *,char **, size_t *, char **, size_t *);
-
-struct charset_functions builtin_functions[] = {
-               {"UCS-2LE",  iconv_copy, iconv_copy},
-               {"UTF8",   utf8_pull,  utf8_push},
-               {"ASCII", ascii_pull, ascii_push},
-               {"UCS2-HEX", ucs2hex_pull, ucs2hex_push},
-               {NULL, NULL, NULL}
+/*
+ * We have to use strcasecmp here as the character conversions
+ * haven't been initialised yet. JRA.
+ */
+
+#undef strcasecmp
+
+/**
+ * @file
+ *
+ * @brief Samba wrapper/stub for iconv character set conversion.
+ *
+ * iconv is the XPG2 interface for converting between character
+ * encodings.  This file provides a Samba wrapper around it, and also
+ * a simple reimplementation that is used if the system does not
+ * implement iconv.
+ *
+ * Samba only works with encodings that are supersets of ASCII: ascii
+ * characters like whitespace can be tested for directly, multibyte
+ * sequences start with a byte with the high bit set, and strings are
+ * terminated by a nul byte.
+ *
+ * Note that the only function provided by iconv is conversion between
+ * characters.  It doesn't directly support operations like
+ * uppercasing or comparison.  We have to convert to UCS-2 and compare
+ * there.
+ *
+ * @sa Samba Developers Guide
+ **/
+
+static size_t ascii_pull(void *,const char **, size_t *, char **, size_t *);
+static size_t ascii_push(void *,const char **, size_t *, char **, size_t *);
+static size_t latin1_push(void *,const char **, size_t *, char **, size_t *);
+static size_t  utf8_pull(void *,const char **, size_t *, char **, size_t *);
+static size_t  utf8_push(void *,const char **, size_t *, char **, size_t *);
+static size_t ucs2hex_pull(void *,const char **, size_t *, char **, size_t *);
+static size_t ucs2hex_push(void *,const char **, size_t *, char **, size_t *);
+static size_t iconv_copy(void *,const char **, size_t *, char **, size_t *);
+static size_t iconv_swab  (void *,const char **, size_t *, char **, size_t *);
+
+static struct charset_functions builtin_functions[] = {
+       /* windows is really neither UCS-2 not UTF-16 */
+       {"UCS-2LE",  iconv_copy, iconv_copy},
+       {"UTF-16LE",  iconv_copy, iconv_copy},
+       {"UCS-2BE",  iconv_swab, iconv_swab},
+       {"UTF-16BE",  iconv_swab, iconv_swab},
+
+       /* we include the UTF-8 alias to cope with differing locale settings */
+       {"UTF8",   utf8_pull,  utf8_push},
+       {"UTF-8",   utf8_pull,  utf8_push},
+       {"ASCII", ascii_pull, ascii_push},
+       {"646", ascii_pull, ascii_push},
+       {"ISO-8859-1", ascii_pull, latin1_push},
+       {"UCS2-HEX", ucs2hex_pull, ucs2hex_push},
+       {NULL, NULL, NULL}
 };
 
 static struct charset_functions *charsets = NULL;
 
-BOOL smb_register_charset(struct charset_functions *funcs
+static struct charset_functions *find_charset_functions(const char *name
 {
        struct charset_functions *c = charsets;
 
-       DEBUG(5, ("Attempting to register new charset %s\n", funcs->name));
-       /* Check whether we already have this charset... */
        while(c) {
-               if(!strcasecmp(c->name, funcs->name)){ 
-                       DEBUG(2, ("Duplicate charset %s, not registering\n", funcs->name));
-                       return False;
+               if (strcasecmp(name, c->name) == 0) {
+                       return c;
                }
                c = c->next;
        }
 
+       return NULL;
+}
+
+NTSTATUS smb_register_charset(struct charset_functions *funcs) 
+{
+       if (!funcs) {
+               return NT_STATUS_INVALID_PARAMETER;
+       }
+
+       DEBUG(5, ("Attempting to register new charset %s\n", funcs->name));
+       /* Check whether we already have this charset... */
+       if (find_charset_functions(funcs->name)) {
+               DEBUG(0, ("Duplicate charset %s, not registering\n", funcs->name));
+               return NT_STATUS_OBJECT_NAME_COLLISION;
+       }
+
        funcs->next = funcs->prev = NULL;
        DEBUG(5, ("Registered charset %s\n", funcs->name));
        DLIST_ADD(charsets, funcs);
-       return True;
+       return NT_STATUS_OK;
 }
 
-void lazy_initialize_iconv(void)
+static void lazy_initialize_iconv(void)
 {
-       static BOOL initialized = False;
+       static BOOL initialized;
        int i;
 
        if (!initialized) {
                initialized = True;
                for(i = 0; builtin_functions[i].name; i++) 
                        smb_register_charset(&builtin_functions[i]);
+               static_init_charset;
        }
 }
 
@@ -75,14 +130,18 @@ void lazy_initialize_iconv(void)
    this ensures that we don't have a shift state remaining for
    character sets like SJIS */
 static size_t sys_iconv(void *cd, 
-                       char **inbuf, size_t *inbytesleft,
+                       const char **inbuf, size_t *inbytesleft,
                        char **outbuf, size_t *outbytesleft)
 {
 #ifdef HAVE_NATIVE_ICONV
        size_t ret = iconv((iconv_t)cd, 
-                          inbuf, inbytesleft, 
+                          (char **)inbuf, inbytesleft, 
                           outbuf, outbytesleft);
-       if (ret == (size_t)-1) iconv(cd, NULL, NULL, NULL, NULL);
+       if (ret == (size_t)-1) {
+               int saved_errno = errno;
+               iconv(cd, NULL, NULL, NULL, NULL);
+               errno = saved_errno;
+       }
        return ret;
 #else
        errno = EINVAL;
@@ -90,11 +149,12 @@ static size_t sys_iconv(void *cd,
 #endif
 }
 
-/*
-  this is a simple portable iconv() implementaion. It only knows about
-  a very small number of character sets - just enough that Samba works
-  on systems that don't have iconv
- */
+/**
+ * This is a simple portable iconv() implementaion.
+ *
+ * It only knows about a very small number of character sets - just
+ * enough that Samba works on systems that don't have iconv.
+ **/
 size_t smb_iconv(smb_iconv_t cd, 
                 const char **inbuf, size_t *inbytesleft,
                 char **outbuf, size_t *outbytesleft)
@@ -106,7 +166,7 @@ size_t smb_iconv(smb_iconv_t cd,
        /* in many cases we can go direct */
        if (cd->direct) {
                return cd->direct(cd->cd_direct, 
-                                 (char **)inbuf, inbytesleft, outbuf, outbytesleft);
+                                 inbuf, inbytesleft, outbuf, outbytesleft);
        }
 
 
@@ -116,20 +176,27 @@ size_t smb_iconv(smb_iconv_t cd,
                bufsize = sizeof(cvtbuf);
                
                if (cd->pull(cd->cd_pull, 
-                            (char **)inbuf, inbytesleft, &bufp, &bufsize) == -1
+                            inbuf, inbytesleft, &bufp, &bufsize) == -1
                    && errno != E2BIG) return -1;
 
                bufp = cvtbuf;
                bufsize = sizeof(cvtbuf) - bufsize;
 
                if (cd->push(cd->cd_push, 
-                            &bufp, &bufsize, 
+                            (const char **)&bufp, &bufsize, 
                             outbuf, outbytesleft) == -1) return -1;
        }
 
        return 0;
 }
 
+
+static BOOL is_utf16(const char *name)
+{
+       return strcasecmp(name, "UCS-2LE") == 0 ||
+               strcasecmp(name, "UTF-16LE") == 0;
+}
+
 /*
   simple iconv_open() wrapper
  */
@@ -153,57 +220,82 @@ smb_iconv_t smb_iconv_open(const char *tocode, const char *fromcode)
        ret->to_name = strdup(tocode);
 
        /* check for the simplest null conversion */
-       if (strcmp(fromcode, tocode) == 0) {
+       if (strcasecmp(fromcode, tocode) == 0) {
                ret->direct = iconv_copy;
                return ret;
        }
 
-       while (from) {
-               if (strcasecmp(from->name, fromcode) == 0) break;
-               from = from->next;
-       }
+       /* check if we have a builtin function for this conversion */
+       from = find_charset_functions(fromcode);
+       if(from)ret->pull = from->pull;
+       
+       to = find_charset_functions(tocode);
+       if(to)ret->push = to->push;
 
-       while (to) {
-               if (strcasecmp(to->name, tocode) == 0) break;
-               to = to->next;
+       /* check if we can use iconv for this conversion */
+#ifdef HAVE_NATIVE_ICONV
+       if (!ret->pull) {
+               ret->cd_pull = iconv_open("UTF-16LE", fromcode);
+               if (ret->cd_pull == (iconv_t)-1)
+                       ret->cd_pull = iconv_open("UCS-2LE", fromcode);
+               if (ret->cd_pull != (iconv_t)-1)
+                       ret->pull = sys_iconv;
        }
 
-#ifdef HAVE_NATIVE_ICONV
-       if (!from) {
-               ret->pull = sys_iconv;
-               ret->cd_pull = iconv_open("UCS-2LE", fromcode);
-               if (ret->cd_pull == (iconv_t)-1) goto failed;
+       if (!ret->push) {
+               ret->cd_push = iconv_open(tocode, "UTF-16LE");
+               if (ret->cd_push == (iconv_t)-1)
+                       ret->cd_push = iconv_open(tocode, "UCS-2LE");
+               if (ret->cd_push != (iconv_t)-1)
+                       ret->push = sys_iconv;
+       }
+#endif
+       
+       /* check if there is a module available that can do this conversion */
+       if (!ret->pull && NT_STATUS_IS_OK(smb_probe_module("charset", fromcode))) {
+               if(!(from = find_charset_functions(fromcode)))
+                       DEBUG(0, ("Module %s doesn't provide charset %s!\n", fromcode, fromcode));
+               else 
+                       ret->pull = from->pull;
        }
 
-       if (!to) {
-               ret->push = sys_iconv;
-               ret->cd_push = iconv_open(tocode, "UCS-2LE");
-               if (ret->cd_push == (iconv_t)-1) goto failed;
+       if (!ret->push && NT_STATUS_IS_OK(smb_probe_module("charset", tocode))) {
+               if(!(to = find_charset_functions(tocode)))
+                       DEBUG(0, ("Module %s doesn't provide charset %s!\n", tocode, tocode));
+               else 
+                       ret->push = to->push;
        }
-#else
-       if (!from || !to) {
-               goto failed;
+
+       if (!ret->push || !ret->pull) {
+               SAFE_FREE(ret->from_name);
+               SAFE_FREE(ret->to_name);
+               SAFE_FREE(ret);
+               errno = EINVAL;
+               return (smb_iconv_t)-1;
        }
-#endif
 
        /* check for conversion to/from ucs2 */
-       if (strcasecmp(fromcode, "UCS-2LE") == 0 && to) {
+       if (is_utf16(fromcode) && to) {
                ret->direct = to->push;
+               ret->push = ret->pull = NULL;
                return ret;
        }
-       if (strcasecmp(tocode, "UCS-2LE") == 0 && from) {
+
+       if (is_utf16(tocode) && from) {
                ret->direct = from->pull;
+               ret->push = ret->pull = NULL;
                return ret;
        }
 
+       /* Check if we can do the conversion direct */
 #ifdef HAVE_NATIVE_ICONV
-       if (strcasecmp(fromcode, "UCS-2LE") == 0) {
+       if (is_utf16(fromcode)) {
                ret->direct = sys_iconv;
                ret->cd_direct = ret->cd_push;
                ret->cd_push = NULL;
                return ret;
        }
-       if (strcasecmp(tocode, "UCS-2LE") == 0) {
+       if (is_utf16(tocode)) {
                ret->direct = sys_iconv;
                ret->cd_direct = ret->cd_pull;
                ret->cd_pull = NULL;
@@ -211,15 +303,7 @@ smb_iconv_t smb_iconv_open(const char *tocode, const char *fromcode)
        }
 #endif
 
-       /* the general case has to go via a buffer */
-       if (!ret->pull) ret->pull = from->pull;
-       if (!ret->push) ret->push = to->push;
        return ret;
-
-failed:
-       SAFE_FREE(ret);
-       errno = EINVAL;
-       return (smb_iconv_t)-1;
 }
 
 /*
@@ -248,7 +332,7 @@ int smb_iconv_close (smb_iconv_t cd)
  multi-byte character set support for english users
 ***********************************************************************/
 
-static size_t ascii_pull(void *cd, char **inbuf, size_t *inbytesleft,
+static size_t ascii_pull(void *cd, const char **inbuf, size_t *inbytesleft,
                         char **outbuf, size_t *outbytesleft)
 {
        while (*inbytesleft >= 1 && *outbytesleft >= 2) {
@@ -268,7 +352,7 @@ static size_t ascii_pull(void *cd, char **inbuf, size_t *inbytesleft,
        return 0;
 }
 
-static size_t ascii_push(void *cd, char **inbuf, size_t *inbytesleft,
+static size_t ascii_push(void *cd, const char **inbuf, size_t *inbytesleft,
                         char **outbuf, size_t *outbytesleft)
 {
        int ir_count=0;
@@ -295,8 +379,34 @@ static size_t ascii_push(void *cd, char **inbuf, size_t *inbytesleft,
        return ir_count;
 }
 
+static size_t latin1_push(void *cd, const char **inbuf, size_t *inbytesleft,
+                        char **outbuf, size_t *outbytesleft)
+{
+       int ir_count=0;
+
+       while (*inbytesleft >= 2 && *outbytesleft >= 1) {
+               (*outbuf)[0] = (*inbuf)[0];
+               if ((*inbuf)[1]) ir_count++;
+               (*inbytesleft)  -= 2;
+               (*outbytesleft) -= 1;
+               (*inbuf)  += 2;
+               (*outbuf) += 1;
+       }
 
-static size_t ucs2hex_pull(void *cd, char **inbuf, size_t *inbytesleft,
+       if (*inbytesleft == 1) {
+               errno = EINVAL;
+               return -1;
+       }
+
+       if (*inbytesleft > 1) {
+               errno = E2BIG;
+               return -1;
+       }
+       
+       return ir_count;
+}
+
+static size_t ucs2hex_pull(void *cd, const char **inbuf, size_t *inbytesleft,
                         char **outbuf, size_t *outbytesleft)
 {
        while (*inbytesleft >= 1 && *outbytesleft >= 2) {
@@ -339,7 +449,7 @@ static size_t ucs2hex_pull(void *cd, char **inbuf, size_t *inbytesleft,
        return 0;
 }
 
-static size_t ucs2hex_push(void *cd, char **inbuf, size_t *inbytesleft,
+static size_t ucs2hex_push(void *cd, const char **inbuf, size_t *inbytesleft,
                           char **outbuf, size_t *outbytesleft)
 {
        while (*inbytesleft >= 2 && *outbytesleft >= 1) {
@@ -380,8 +490,32 @@ static size_t ucs2hex_push(void *cd, char **inbuf, size_t *inbytesleft,
        return 0;
 }
 
+static size_t iconv_swab(void *cd, const char **inbuf, size_t *inbytesleft,
+                        char **outbuf, size_t *outbytesleft)
+{
+       int n;
+
+       n = MIN(*inbytesleft, *outbytesleft);
+
+       swab(*inbuf, *outbuf, (n&~1));
+       if (n&1) {
+               (*outbuf)[n-1] = 0;
+       }
 
-static size_t iconv_copy(void *cd, char **inbuf, size_t *inbytesleft,
+       (*inbytesleft) -= n;
+       (*outbytesleft) -= n;
+       (*inbuf) += n;
+       (*outbuf) += n;
+
+       if (*inbytesleft > 0) {
+               errno = E2BIG;
+               return -1;
+       }
+
+       return 0;
+}
+
+static size_t iconv_copy(void *cd, const char **inbuf, size_t *inbytesleft,
                         char **outbuf, size_t *outbytesleft)
 {
        int n;
@@ -403,103 +537,234 @@ static size_t iconv_copy(void *cd, char **inbuf, size_t *inbytesleft,
        return 0;
 }
 
-static size_t utf8_pull(void *cd, char **inbuf, size_t *inbytesleft,
+static size_t utf8_pull(void *cd, const char **inbuf, size_t *inbytesleft,
                         char **outbuf, size_t *outbytesleft)
 {
-       while (*inbytesleft >= 1 && *outbytesleft >= 2) {
-               unsigned char *c = (unsigned char *)*inbuf;
-               unsigned char *uc = (unsigned char *)*outbuf;
-               int len = 1;
+       size_t in_left=*inbytesleft, out_left=*outbytesleft;
+       const uint8 *c = (const uint8 *)*inbuf;
+       uint8 *uc = (uint8 *)*outbuf;
 
+       while (in_left >= 1 && out_left >= 2) {
                if ((c[0] & 0x80) == 0) {
                        uc[0] = c[0];
                        uc[1] = 0;
-               } else if ((c[0] & 0xf0) == 0xe0) {
-                       if (*inbytesleft < 3) {
-                               DEBUG(0,("short utf8 char\n"));
-                               goto badseq;
+                       c  += 1;
+                       in_left  -= 1;
+                       out_left -= 2;
+                       uc += 2;
+                       continue;
+               }
+
+               if ((c[0] & 0xe0) == 0xc0) {
+                       if (in_left < 2 ||
+                           (c[1] & 0xc0) != 0x80) {
+                               errno = EILSEQ;
+                               goto error;
+                       }
+                       uc[1] = (c[0]>>2) & 0x7;
+                       uc[0] = (c[0]<<6) | (c[1]&0x3f);
+                       c  += 2;
+                       in_left  -= 2;
+                       out_left -= 2;
+                       uc += 2;
+                       continue;
+               }
+
+               if ((c[0] & 0xf0) == 0xe0) {
+                       if (in_left < 3 ||
+                           (c[1] & 0xc0) != 0x80 || 
+                           (c[2] & 0xc0) != 0x80) {
+                               errno = EILSEQ;
+                               goto error;
                        }
                        uc[1] = ((c[0]&0xF)<<4) | ((c[1]>>2)&0xF);
                        uc[0] = (c[1]<<6) | (c[2]&0x3f);
-                       len = 3;
-               } else if ((c[0] & 0xe0) == 0xc0) {
-                       if (*inbytesleft < 2) {
-                               DEBUG(0,("short utf8 char\n"));
-                               goto badseq;
+                       c  += 3;
+                       in_left  -= 3;
+                       out_left -= 2;
+                       uc += 2;
+                       continue;
+               }
+
+               if ((c[0] & 0xf8) == 0xf0) {
+                       unsigned int codepoint;
+                       if (in_left < 4 ||
+                           (c[1] & 0xc0) != 0x80 || 
+                           (c[2] & 0xc0) != 0x80 ||
+                           (c[3] & 0xc0) != 0x80) {
+                               errno = EILSEQ;
+                               goto error;
                        }
-                       uc[1] = (c[0]>>2) & 0x7;
-                       uc[0] = (c[0]<<6) | (c[1]&0x3f);
-                       len = 2;
+                       codepoint = 
+                               (c[3]&0x3f) | 
+                               ((c[2]&0x3f)<<6) | 
+                               ((c[1]&0x3f)<<12) |
+                               ((c[0]&0x7)<<18);
+                       if (codepoint < 0x10000) {
+                               /* accept UTF-8 characters that are not
+                                  minimally packed, but pack the result */
+                               uc[0] = (codepoint & 0xFF);
+                               uc[1] = (codepoint >> 8);
+                               c += 4;
+                               in_left -= 4;
+                               out_left -= 2;
+                               uc += 2;
+                               continue;
+                       }
+
+                       codepoint -= 0x10000;
+
+                       if (out_left < 4) {
+                               errno = E2BIG;
+                               goto error;
+                       }
+
+                       uc[0] = (codepoint>>10) & 0xFF;
+                       uc[1] = (codepoint>>18) | 0xd8;
+                       uc[2] = codepoint & 0xFF;
+                       uc[3] = ((codepoint>>8) & 0x3) | 0xdc;
+                       c  += 4;
+                       in_left  -= 4;
+                       out_left -= 4;
+                       uc += 4;
+                       continue;
                }
 
-               (*inbuf)  += len;
-               (*inbytesleft)  -= len;
-               (*outbytesleft) -= 2;
-               (*outbuf) += 2;
+               /* we don't handle 5 byte sequences */
+               errno = EINVAL;
+               goto error;
        }
 
-       if (*inbytesleft > 0) {
+       if (in_left > 0) {
                errno = E2BIG;
-               return -1;
+               goto error;
        }
-       
+
+       *inbytesleft = in_left;
+       *outbytesleft = out_left;
+       *inbuf = c;
+       *outbuf = uc;   
        return 0;
 
-badseq:
-       errno = EINVAL;
+error:
+       *inbytesleft = in_left;
+       *outbytesleft = out_left;
+       *inbuf = c;
+       *outbuf = uc;
        return -1;
 }
 
-static size_t utf8_push(void *cd, char **inbuf, size_t *inbytesleft,
-                        char **outbuf, size_t *outbytesleft)
+static size_t utf8_push(void *cd, const char **inbuf, size_t *inbytesleft,
+                       char **outbuf, size_t *outbytesleft)
 {
-       while (*inbytesleft >= 2 && *outbytesleft >= 1) {
-               unsigned char *c = (unsigned char *)*outbuf;
-               unsigned char *uc = (unsigned char *)*inbuf;
-               int len=1;
-
-               if (uc[1] & 0xf8) {
-                       if (*outbytesleft < 3) {
-                               DEBUG(0,("short utf8 write\n"));
-                               goto toobig;
+       size_t in_left=*inbytesleft, out_left=*outbytesleft;
+       uint8 *c = (uint8 *)*outbuf;
+       const uint8 *uc = (const uint8 *)*inbuf;
+
+       while (in_left >= 2 && out_left >= 1) {
+               unsigned int codepoint;
+
+               if (uc[1] == 0 && !(uc[0] & 0x80)) {
+                       /* simplest case */
+                       c[0] = uc[0];
+                       in_left  -= 2;
+                       out_left -= 1;
+                       uc += 2;
+                       c  += 1;
+                       continue;
+               }
+
+               if ((uc[1]&0xf8) == 0) {
+                       /* next simplest case */
+                       if (out_left < 2) {
+                               errno = E2BIG;
+                               goto error;
                        }
-                       c[0] = 0xe0 | (uc[1]>>4);
-                       c[1] = 0x80 | ((uc[1]&0xF)<<2) | (uc[0]>>6);
-                       c[2] = 0x80 | (uc[0]&0x3f);
-                       len = 3;
-               } else if (uc[1] | (uc[0] & 0x80)) {
-                       if (*outbytesleft < 2) {
-                               DEBUG(0,("short utf8 write\n"));
-                               goto toobig;
+                       c[0] = 0xc0 | (uc[0]>>6) | (uc[1]<<2);
+                       c[1] = 0x80 | (uc[0] & 0x3f);
+                       in_left  -= 2;
+                       out_left -= 2;
+                       uc += 2;
+                       c  += 2;
+                       continue;
+               }
+
+               if ((uc[1] & 0xfc) == 0xdc) {
+                       /* its the second part of a 4 byte sequence. Illegal */
+                       if (in_left < 4) {
+                               errno = EINVAL;
+                       } else {
+                               errno = EILSEQ;
                        }
-                       c[0] = 0xc0 | (uc[1]<<2) | (uc[0]>>6);
-                       c[1] = 0x80 | (uc[0]&0x3f);
-                       len = 2;
-               } else {
-                       c[0] = uc[0];
+                       goto error;
                }
 
+               if ((uc[1] & 0xfc) != 0xd8) {
+                       codepoint = uc[0] | (uc[1]<<8);
+                       if (out_left < 3) {
+                               errno = E2BIG;
+                               goto error;
+                       }
+                       c[0] = 0xe0 | (codepoint >> 12);
+                       c[1] = 0x80 | ((codepoint >> 6) & 0x3f);
+                       c[2] = 0x80 | (codepoint & 0x3f);
+                       
+                       in_left  -= 2;
+                       out_left -= 3;
+                       uc  += 2;
+                       c   += 3;
+                       continue;
+               }
 
-               (*inbytesleft)  -= 2;
-               (*outbytesleft) -= len;
-               (*inbuf)  += 2;
-               (*outbuf) += len;
+               /* its the first part of a 4 byte sequence */
+               if (in_left < 4) {
+                       errno = EINVAL;
+                       goto error;
+               }
+               if ((uc[3] & 0xfc) != 0xdc) {
+                       errno = EILSEQ;
+                       goto error;
+               }
+               codepoint = 0x10000 + (uc[2] | ((uc[3] & 0x3)<<8) | 
+                                      (uc[0]<<10) | ((uc[1] & 0x3)<<18));
+               
+               if (out_left < 4) {
+                       errno = E2BIG;
+                       goto error;
+               }
+               c[0] = 0xf0 | (codepoint >> 18);
+               c[1] = 0x80 | ((codepoint >> 12) & 0x3f);
+               c[2] = 0x80 | ((codepoint >> 6) & 0x3f);
+               c[3] = 0x80 | (codepoint & 0x3f);
+               
+               in_left  -= 4;
+               out_left -= 4;
+               uc       += 4;
+               c        += 4;
        }
 
-       if (*inbytesleft == 1) {
+       if (in_left == 1) {
                errno = EINVAL;
-               return -1;
+               goto error;
        }
 
-       if (*inbytesleft > 1) {
+       if (in_left > 1) {
                errno = E2BIG;
-               return -1;
+               goto error;
        }
+
+       *inbytesleft = in_left;
+       *outbytesleft = out_left;
+       *inbuf  = uc;
+       *outbuf = c;
        
        return 0;
 
-toobig:
-       errno = E2BIG;
+error:
+       *inbytesleft = in_left;
+       *outbytesleft = out_left;
+       *inbuf  = uc;
+       *outbuf = c;
        return -1;
 }