/src/postgres/src/backend/utils/mb/mbutils.c

Source
/*-------------------------------------------------------------------------
 *
 * mbutils.c
 *    This file contains functions for encoding conversion.
 *
 * The string-conversion functions in this file share some API quirks.
 * Note the following:
 *
 * The functions return a palloc'd, null-terminated string if conversion
 * is required.  However, if no conversion is performed, the given source
 * string pointer is returned as-is.
 *
 * Although the presence of a length argument means that callers can pass
 * non-null-terminated strings, care is required because the same string
 * will be passed back if no conversion occurs.  Such callers *must* check
 * whether result == src and handle that case differently.
 *
 * If the source and destination encodings are the same, the source string
 * is returned without any verification; it's assumed to be valid data.
 * If that might not be the case, the caller is responsible for validating
 * the string using a separate call to pg_verify_mbstr().  Whenever the
 * source and destination encodings are different, the functions ensure that
 * the result is validly encoded according to the destination encoding.
 *
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/mb/mbutils.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/xact.h"
#include "catalog/namespace.h"
#include "mb/pg_wchar.h"
#include "utils/fmgrprotos.h"
#include "utils/memdebug.h"
#include "utils/memutils.h"
#include "utils/relcache.h"
#include "varatt.h"

/*
 * We maintain a simple linked list caching the fmgr lookup info for the
 * currently selected conversion functions, as well as any that have been
 * selected previously in the current session.  (We remember previous
 * settings because we must be able to restore a previous setting during
 * transaction rollback, without doing any fresh catalog accesses.)
 *
 * Since we'll never release this data, we just keep it in TopMemoryContext.
 */
typedef struct ConvProcInfo
{
  int     s_encoding;   /* server and client encoding IDs */
  int     c_encoding;
  FmgrInfo  to_server_info; /* lookup info for conversion procs */
  FmgrInfo  to_client_info;
} ConvProcInfo;

static List *ConvProcList = NIL;  /* List of ConvProcInfo */

/*
 * These variables point to the currently active conversion functions,
 * or are NULL when no conversion is needed.
 */
static FmgrInfo *ToServerConvProc = NULL;
static FmgrInfo *ToClientConvProc = NULL;

/*
 * This variable stores the conversion function to convert from UTF-8
 * to the server encoding.  It's NULL if the server encoding *is* UTF-8,
 * or if we lack a conversion function for this.
 */
static FmgrInfo *Utf8ToServerConvProc = NULL;

/*
 * These variables track the currently-selected encodings.
 */
static const pg_enc2name *ClientEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
static const pg_enc2name *DatabaseEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
static const pg_enc2name *MessageEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];

/*
 * During backend startup we can't set client encoding because we (a)
 * can't look up the conversion functions, and (b) may not know the database
 * encoding yet either.  So SetClientEncoding() just accepts anything and
 * remembers it for InitializeClientEncoding() to apply later.
 */
static bool backend_startup_complete = false;
static int  pending_client_encoding = PG_SQL_ASCII;


/* Internal functions */
static char *perform_default_encoding_conversion(const char *src,
                         int len, bool is_client_to_server);
static int  cliplen(const char *str, int len, int limit);

pg_noreturn
static void report_invalid_encoding_int(int encoding, const char *mbstr,
                    int mblen, int len);

pg_noreturn
static void report_invalid_encoding_db(const char *mbstr, int mblen, int len);


/*
 * Prepare for a future call to SetClientEncoding.  Success should mean
 * that SetClientEncoding is guaranteed to succeed for this encoding request.
 *
 * (But note that success before backend_startup_complete does not guarantee
 * success after ...)
 *
 * Returns 0 if okay, -1 if not (bad encoding or can't support conversion)
 */
int
PrepareClientEncoding(int encoding)
{
  int     current_server_encoding;
  ListCell   *lc;

  if (!PG_VALID_FE_ENCODING(encoding))
    return -1;

  /* Can't do anything during startup, per notes above */
  if (!backend_startup_complete)
    return 0;

  current_server_encoding = GetDatabaseEncoding();

  /*
   * Check for cases that require no conversion function.
   */
  if (current_server_encoding == encoding ||
    current_server_encoding == PG_SQL_ASCII ||
    encoding == PG_SQL_ASCII)
    return 0;

  if (IsTransactionState())
  {
    /*
     * If we're in a live transaction, it's safe to access the catalogs,
     * so look up the functions.  We repeat the lookup even if the info is
     * already cached, so that we can react to changes in the contents of
     * pg_conversion.
     */
    Oid     to_server_proc,
          to_client_proc;
    ConvProcInfo *convinfo;
    MemoryContext oldcontext;

    to_server_proc = FindDefaultConversionProc(encoding,
                           current_server_encoding);
    if (!OidIsValid(to_server_proc))
      return -1;
    to_client_proc = FindDefaultConversionProc(current_server_encoding,
                           encoding);
    if (!OidIsValid(to_client_proc))
      return -1;

    /*
     * Load the fmgr info into TopMemoryContext (could still fail here)
     */
    convinfo = (ConvProcInfo *) MemoryContextAlloc(TopMemoryContext,
                             sizeof(ConvProcInfo));
    convinfo->s_encoding = current_server_encoding;
    convinfo->c_encoding = encoding;
    fmgr_info_cxt(to_server_proc, &convinfo->to_server_info,
            TopMemoryContext);
    fmgr_info_cxt(to_client_proc, &convinfo->to_client_info,
            TopMemoryContext);

    /* Attach new info to head of list */
    oldcontext = MemoryContextSwitchTo(TopMemoryContext);
    ConvProcList = lcons(convinfo, ConvProcList);
    MemoryContextSwitchTo(oldcontext);

    /*
     * We cannot yet remove any older entry for the same encoding pair,
     * since it could still be in use.  SetClientEncoding will clean up.
     */

    return 0;       /* success */
  }
  else
  {
    /*
     * If we're not in a live transaction, the only thing we can do is
     * restore a previous setting using the cache.  This covers all
     * transaction-rollback cases.  The only case it might not work for is
     * trying to change client_encoding on the fly by editing
     * postgresql.conf and SIGHUP'ing.  Which would probably be a stupid
     * thing to do anyway.
     */
    foreach(lc, ConvProcList)
    {
      ConvProcInfo *oldinfo = (ConvProcInfo *) lfirst(lc);

      if (oldinfo->s_encoding == current_server_encoding &&
        oldinfo->c_encoding == encoding)
        return 0;
    }

    return -1;       /* it's not cached, so fail */
  }
}

/*
 * Set the active client encoding and set up the conversion-function pointers.
 * PrepareClientEncoding should have been called previously for this encoding.
 *
 * Returns 0 if okay, -1 if not (bad encoding or can't support conversion)
 */
int
SetClientEncoding(int encoding)
{
  int     current_server_encoding;
  bool    found;
  ListCell   *lc;

  if (!PG_VALID_FE_ENCODING(encoding))
    return -1;

  /* Can't do anything during startup, per notes above */
  if (!backend_startup_complete)
  {
    pending_client_encoding = encoding;
    return 0;
  }

  current_server_encoding = GetDatabaseEncoding();

  /*
   * Check for cases that require no conversion function.
   */
  if (current_server_encoding == encoding ||
    current_server_encoding == PG_SQL_ASCII ||
    encoding == PG_SQL_ASCII)
  {
    ClientEncoding = &pg_enc2name_tbl[encoding];
    ToServerConvProc = NULL;
    ToClientConvProc = NULL;
    return 0;
  }

  /*
   * Search the cache for the entry previously prepared by
   * PrepareClientEncoding; if there isn't one, we lose.  While at it,
   * release any duplicate entries so that repeated Prepare/Set cycles don't
   * leak memory.
   */
  found = false;
  foreach(lc, ConvProcList)
  {
    ConvProcInfo *convinfo = (ConvProcInfo *) lfirst(lc);

    if (convinfo->s_encoding == current_server_encoding &&
      convinfo->c_encoding == encoding)
    {
      if (!found)
      {
        /* Found newest entry, so set up */
        ClientEncoding = &pg_enc2name_tbl[encoding];
        ToServerConvProc = &convinfo->to_server_info;
        ToClientConvProc = &convinfo->to_client_info;
        found = true;
      }
      else
      {
        /* Duplicate entry, release it */
        ConvProcList = foreach_delete_current(ConvProcList, lc);
        pfree(convinfo);
      }
    }
  }

  if (found)
    return 0;       /* success */
  else
    return -1;       /* it's not cached, so fail */
}

/*
 * Initialize client encoding conversions.
 *    Called from InitPostgres() once during backend startup.
 */
void
InitializeClientEncoding(void)
{
  int     current_server_encoding;

  Assert(!backend_startup_complete);
  backend_startup_complete = true;

  if (PrepareClientEncoding(pending_client_encoding) < 0 ||
    SetClientEncoding(pending_client_encoding) < 0)
  {
    /*
     * Oops, the requested conversion is not available. We couldn't fail
     * before, but we can now.
     */
    ereport(FATAL,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("conversion between %s and %s is not supported",
            pg_enc2name_tbl[pending_client_encoding].name,
            GetDatabaseEncodingName())));
  }

  /*
   * Also look up the UTF8-to-server conversion function if needed.  Since
   * the server encoding is fixed within any one backend process, we don't
   * have to do this more than once.
   */
  current_server_encoding = GetDatabaseEncoding();
  if (current_server_encoding != PG_UTF8 &&
    current_server_encoding != PG_SQL_ASCII)
  {
    Oid     utf8_to_server_proc;

    AssertCouldGetRelation();
    utf8_to_server_proc =
      FindDefaultConversionProc(PG_UTF8,
                    current_server_encoding);
    /* If there's no such conversion, just leave the pointer as NULL */
    if (OidIsValid(utf8_to_server_proc))
    {
      FmgrInfo   *finfo;

      finfo = (FmgrInfo *) MemoryContextAlloc(TopMemoryContext,
                          sizeof(FmgrInfo));
      fmgr_info_cxt(utf8_to_server_proc, finfo,
              TopMemoryContext);
      /* Set Utf8ToServerConvProc only after data is fully valid */
      Utf8ToServerConvProc = finfo;
    }
  }
}

/*
 * returns the current client encoding
 */
int
pg_get_client_encoding(void)
{
  return ClientEncoding->encoding;
}

/*
 * returns the current client encoding name
 */
const char *
pg_get_client_encoding_name(void)
{
  return ClientEncoding->name;
}

/*
 * Convert src string to another encoding (general case).
 *
 * See the notes about string conversion functions at the top of this file.
 */
unsigned char *
pg_do_encoding_conversion(unsigned char *src, int len,
              int src_encoding, int dest_encoding)
{
  unsigned char *result;
  Oid     proc;

  if (len <= 0)
    return src;       /* empty string is always valid */

  if (src_encoding == dest_encoding)
    return src;       /* no conversion required, assume valid */

  if (dest_encoding == PG_SQL_ASCII)
    return src;       /* any string is valid in SQL_ASCII */

  if (src_encoding == PG_SQL_ASCII)
  {
    /* No conversion is possible, but we must validate the result */
    (void) pg_verify_mbstr(dest_encoding, (const char *) src, len, false);
    return src;
  }

  if (!IsTransactionState()) /* shouldn't happen */
    elog(ERROR, "cannot perform encoding conversion outside a transaction");

  proc = FindDefaultConversionProc(src_encoding, dest_encoding);
  if (!OidIsValid(proc))
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_FUNCTION),
         errmsg("default conversion function for encoding \"%s\" to \"%s\" does not exist",
            pg_encoding_to_char(src_encoding),
            pg_encoding_to_char(dest_encoding))));

  /*
   * Allocate space for conversion result, being wary of integer overflow.
   *
   * len * MAX_CONVERSION_GROWTH is typically a vast overestimate of the
   * required space, so it might exceed MaxAllocSize even though the result
   * would actually fit.  We do not want to hand back a result string that
   * exceeds MaxAllocSize, because callers might not cope gracefully --- but
   * if we just allocate more than that, and don't use it, that's fine.
   */
  if ((Size) len >= (MaxAllocHugeSize / (Size) MAX_CONVERSION_GROWTH))
    ereport(ERROR,
        (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
         errmsg("out of memory"),
         errdetail("String of %d bytes is too long for encoding conversion.",
               len)));

  result = (unsigned char *)
    MemoryContextAllocHuge(CurrentMemoryContext,
                 (Size) len * MAX_CONVERSION_GROWTH + 1);

  (void) OidFunctionCall6(proc,
              Int32GetDatum(src_encoding),
              Int32GetDatum(dest_encoding),
              CStringGetDatum((char *) src),
              CStringGetDatum((char *) result),
              Int32GetDatum(len),
              BoolGetDatum(false));

  /*
   * If the result is large, it's worth repalloc'ing to release any extra
   * space we asked for.  The cutoff here is somewhat arbitrary, but we
   * *must* check when len * MAX_CONVERSION_GROWTH exceeds MaxAllocSize.
   */
  if (len > 1000000)
  {
    Size    resultlen = strlen((char *) result);

    if (resultlen >= MaxAllocSize)
      ereport(ERROR,
          (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
           errmsg("out of memory"),
           errdetail("String of %d bytes is too long for encoding conversion.",
                 len)));

    result = (unsigned char *) repalloc(result, resultlen + 1);
  }

  return result;
}

/*
 * Convert src string to another encoding.
 *
 * This function has a different API than the other conversion functions.
 * The caller should've looked up the conversion function using
 * FindDefaultConversionProc().  Unlike the other functions, the converted
 * result is not palloc'd.  It is written to the caller-supplied buffer
 * instead.
 *
 * src_encoding   - encoding to convert from
 * dest_encoding  - encoding to convert to
 * src, srclen    - input buffer and its length in bytes
 * dest, destlen  - destination buffer and its size in bytes
 *
 * The output is null-terminated.
 *
 * If destlen < srclen * MAX_CONVERSION_INPUT_LENGTH + 1, the converted output
 * wouldn't necessarily fit in the output buffer, and the function will not
 * convert the whole input.
 *
 * TODO: The conversion function interface is not great.  Firstly, it
 * would be nice to pass through the destination buffer size to the
 * conversion function, so that if you pass a shorter destination buffer, it
 * could still continue to fill up the whole buffer.  Currently, we have to
 * assume worst case expansion and stop the conversion short, even if there
 * is in fact space left in the destination buffer.  Secondly, it would be
 * nice to return the number of bytes written to the caller, to avoid a call
 * to strlen().
 */
int
pg_do_encoding_conversion_buf(Oid proc,
                int src_encoding,
                int dest_encoding,
                unsigned char *src, int srclen,
                unsigned char *dest, int destlen,
                bool noError)
{
  Datum   result;

  /*
   * If the destination buffer is not large enough to hold the result in the
   * worst case, limit the input size passed to the conversion function.
   */
  if ((Size) srclen >= ((destlen - 1) / (Size) MAX_CONVERSION_GROWTH))
    srclen = ((destlen - 1) / (Size) MAX_CONVERSION_GROWTH);

  result = OidFunctionCall6(proc,
                Int32GetDatum(src_encoding),
                Int32GetDatum(dest_encoding),
                CStringGetDatum((char *) src),
                CStringGetDatum((char *) dest),
                Int32GetDatum(srclen),
                BoolGetDatum(noError));
  return DatumGetInt32(result);
}

/*
 * Convert string to encoding encoding_name. The source
 * encoding is the DB encoding.
 *
 * BYTEA convert_to(TEXT string, NAME encoding_name)
 */
Datum
pg_convert_to(PG_FUNCTION_ARGS)
{
  Datum   string = PG_GETARG_DATUM(0);
  Datum   dest_encoding_name = PG_GETARG_DATUM(1);
  Datum   src_encoding_name = DirectFunctionCall1(namein,
                            CStringGetDatum(DatabaseEncoding->name));
  Datum   result;

  /*
   * pg_convert expects a bytea as its first argument. We're passing it a
   * text argument here, relying on the fact that they are both in fact
   * varlena types, and thus structurally identical.
   */
  result = DirectFunctionCall3(pg_convert, string,
                 src_encoding_name, dest_encoding_name);

  PG_RETURN_DATUM(result);
}

/*
 * Convert string from encoding encoding_name. The destination
 * encoding is the DB encoding.
 *
 * TEXT convert_from(BYTEA string, NAME encoding_name)
 */
Datum
pg_convert_from(PG_FUNCTION_ARGS)
{
  Datum   string = PG_GETARG_DATUM(0);
  Datum   src_encoding_name = PG_GETARG_DATUM(1);
  Datum   dest_encoding_name = DirectFunctionCall1(namein,
                             CStringGetDatum(DatabaseEncoding->name));
  Datum   result;

  result = DirectFunctionCall3(pg_convert, string,
                 src_encoding_name, dest_encoding_name);

  /*
   * pg_convert returns a bytea, which we in turn return as text, relying on
   * the fact that they are both in fact varlena types, and thus
   * structurally identical. Although not all bytea values are valid text,
   * in this case it will be because we've told pg_convert to return one
   * that is valid as text in the current database encoding.
   */
  PG_RETURN_DATUM(result);
}

/*
 * Convert string between two arbitrary encodings.
 *
 * BYTEA convert(BYTEA string, NAME src_encoding_name, NAME dest_encoding_name)
 */
Datum
pg_convert(PG_FUNCTION_ARGS)
{
  bytea    *string = PG_GETARG_BYTEA_PP(0);
  char     *src_encoding_name = NameStr(*PG_GETARG_NAME(1));
  int     src_encoding = pg_char_to_encoding(src_encoding_name);
  char     *dest_encoding_name = NameStr(*PG_GETARG_NAME(2));
  int     dest_encoding = pg_char_to_encoding(dest_encoding_name);
  const char *src_str;
  char     *dest_str;
  bytea    *retval;
  int     len;

  if (src_encoding < 0)
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("invalid source encoding name \"%s\"",
            src_encoding_name)));
  if (dest_encoding < 0)
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("invalid destination encoding name \"%s\"",
            dest_encoding_name)));

  /* make sure that source string is valid */
  len = VARSIZE_ANY_EXHDR(string);
  src_str = VARDATA_ANY(string);
  (void) pg_verify_mbstr(src_encoding, src_str, len, false);

  /* perform conversion */
  dest_str = (char *) pg_do_encoding_conversion((unsigned char *) unconstify(char *, src_str),
                          len,
                          src_encoding,
                          dest_encoding);


  /* return source string if no conversion happened */
  if (dest_str == src_str)
    PG_RETURN_BYTEA_P(string);

  /*
   * build bytea data type structure.
   */
  len = strlen(dest_str);
  retval = (bytea *) palloc(len + VARHDRSZ);
  SET_VARSIZE(retval, len + VARHDRSZ);
  memcpy(VARDATA(retval), dest_str, len);
  pfree(dest_str);

  /* free memory if allocated by the toaster */
  PG_FREE_IF_COPY(string, 0);

  PG_RETURN_BYTEA_P(retval);
}

/*
 * get the length of the string considered as text in the specified
 * encoding. Raises an error if the data is not valid in that
 * encoding.
 *
 * INT4 length (BYTEA string, NAME src_encoding_name)
 */
Datum
length_in_encoding(PG_FUNCTION_ARGS)
{
  bytea    *string = PG_GETARG_BYTEA_PP(0);
  char     *src_encoding_name = NameStr(*PG_GETARG_NAME(1));
  int     src_encoding = pg_char_to_encoding(src_encoding_name);
  const char *src_str;
  int     len;
  int     retval;

  if (src_encoding < 0)
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
         errmsg("invalid encoding name \"%s\"",
            src_encoding_name)));

  len = VARSIZE_ANY_EXHDR(string);
  src_str = VARDATA_ANY(string);

  retval = pg_verify_mbstr_len(src_encoding, src_str, len, false);

  PG_RETURN_INT32(retval);
}

/*
 * Get maximum multibyte character length in the specified encoding.
 *
 * Note encoding is specified numerically, not by name as above.
 */
Datum
pg_encoding_max_length_sql(PG_FUNCTION_ARGS)
{
  int     encoding = PG_GETARG_INT32(0);

  if (PG_VALID_ENCODING(encoding))
    PG_RETURN_INT32(pg_wchar_table[encoding].maxmblen);
  else
    PG_RETURN_NULL();
}

/*
 * Convert client encoding to server encoding.
 *
 * See the notes about string conversion functions at the top of this file.
 */
char *
pg_client_to_server(const char *s, int len)
{
  return pg_any_to_server(s, len, ClientEncoding->encoding);
}

/*
 * Convert any encoding to server encoding.
 *
 * See the notes about string conversion functions at the top of this file.
 *
 * Unlike the other string conversion functions, this will apply validation
 * even if encoding == DatabaseEncoding->encoding.  This is because this is
 * used to process data coming in from outside the database, and we never
 * want to just assume validity.
 */
char *
pg_any_to_server(const char *s, int len, int encoding)
{
  if (len <= 0)
    return unconstify(char *, s);  /* empty string is always valid */

  if (encoding == DatabaseEncoding->encoding ||
    encoding == PG_SQL_ASCII)
  {
    /*
     * No conversion is needed, but we must still validate the data.
     */
    (void) pg_verify_mbstr(DatabaseEncoding->encoding, s, len, false);
    return unconstify(char *, s);
  }

  if (DatabaseEncoding->encoding == PG_SQL_ASCII)
  {
    /*
     * No conversion is possible, but we must still validate the data,
     * because the client-side code might have done string escaping using
     * the selected client_encoding.  If the client encoding is ASCII-safe
     * then we just do a straight validation under that encoding.  For an
     * ASCII-unsafe encoding we have a problem: we dare not pass such data
     * to the parser but we have no way to convert it.  We compromise by
     * rejecting the data if it contains any non-ASCII characters.
     */
    if (PG_VALID_BE_ENCODING(encoding))
      (void) pg_verify_mbstr(encoding, s, len, false);
    else
    {
      int     i;

      for (i = 0; i < len; i++)
      {
        if (s[i] == '\0' || IS_HIGHBIT_SET(s[i]))
          ereport(ERROR,
              (errcode(ERRCODE_CHARACTER_NOT_IN_REPERTOIRE),
               errmsg("invalid byte value for encoding \"%s\": 0x%02x",
                  pg_enc2name_tbl[PG_SQL_ASCII].name,
                  (unsigned char) s[i])));
      }
    }
    return unconstify(char *, s);
  }

  /* Fast path if we can use cached conversion function */
  if (encoding == ClientEncoding->encoding)
    return perform_default_encoding_conversion(s, len, true);

  /* General case ... will not work outside transactions */
  return (char *) pg_do_encoding_conversion((unsigned char *) unconstify(char *, s),
                        len,
                        encoding,
                        DatabaseEncoding->encoding);
}

/*
 * Convert server encoding to client encoding.
 *
 * See the notes about string conversion functions at the top of this file.
 */
char *
pg_server_to_client(const char *s, int len)
{
  return pg_server_to_any(s, len, ClientEncoding->encoding);
}

/*
 * Convert server encoding to any encoding.
 *
 * See the notes about string conversion functions at the top of this file.
 */
char *
pg_server_to_any(const char *s, int len, int encoding)
{
  if (len <= 0)
    return unconstify(char *, s);  /* empty string is always valid */

  if (encoding == DatabaseEncoding->encoding ||
    encoding == PG_SQL_ASCII)
    return unconstify(char *, s);  /* assume data is valid */

  if (DatabaseEncoding->encoding == PG_SQL_ASCII)
  {
    /* No conversion is possible, but we must validate the result */
    (void) pg_verify_mbstr(encoding, s, len, false);
    return unconstify(char *, s);
  }

  /* Fast path if we can use cached conversion function */
  if (encoding == ClientEncoding->encoding)
    return perform_default_encoding_conversion(s, len, false);

  /* General case ... will not work outside transactions */
  return (char *) pg_do_encoding_conversion((unsigned char *) unconstify(char *, s),
                        len,
                        DatabaseEncoding->encoding,
                        encoding);
}

/*
 *  Perform default encoding conversion using cached FmgrInfo. Since
 *  this function does not access database at all, it is safe to call
 *  outside transactions.  If the conversion has not been set up by
 *  SetClientEncoding(), no conversion is performed.
 */
static char *
perform_default_encoding_conversion(const char *src, int len,
                  bool is_client_to_server)
{
  char     *result;
  int     src_encoding,
        dest_encoding;
  FmgrInfo   *flinfo;

  if (is_client_to_server)
  {
    src_encoding = ClientEncoding->encoding;
    dest_encoding = DatabaseEncoding->encoding;
    flinfo = ToServerConvProc;
  }
  else
  {
    src_encoding = DatabaseEncoding->encoding;
    dest_encoding = ClientEncoding->encoding;
    flinfo = ToClientConvProc;
  }

  if (flinfo == NULL)
    return unconstify(char *, src);

  /*
   * Allocate space for conversion result, being wary of integer overflow.
   * See comments in pg_do_encoding_conversion.
   */
  if ((Size) len >= (MaxAllocHugeSize / (Size) MAX_CONVERSION_GROWTH))
    ereport(ERROR,
        (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
         errmsg("out of memory"),
         errdetail("String of %d bytes is too long for encoding conversion.",
               len)));

  result = (char *)
    MemoryContextAllocHuge(CurrentMemoryContext,
                 (Size) len * MAX_CONVERSION_GROWTH + 1);

  FunctionCall6(flinfo,
          Int32GetDatum(src_encoding),
          Int32GetDatum(dest_encoding),
          CStringGetDatum(src),
          CStringGetDatum(result),
          Int32GetDatum(len),
          BoolGetDatum(false));

  /*
   * Release extra space if there might be a lot --- see comments in
   * pg_do_encoding_conversion.
   */
  if (len > 1000000)
  {
    Size    resultlen = strlen(result);

    if (resultlen >= MaxAllocSize)
      ereport(ERROR,
          (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
           errmsg("out of memory"),
           errdetail("String of %d bytes is too long for encoding conversion.",
                 len)));

    result = (char *) repalloc(result, resultlen + 1);
  }

  return result;
}

/*
 * Convert a single Unicode code point into a string in the server encoding.
 *
 * The code point given by "c" is converted and stored at *s, which must
 * have at least MAX_UNICODE_EQUIVALENT_STRING+1 bytes available.
 * The output will have a trailing '\0'.  Throws error if the conversion
 * cannot be performed.
 *
 * Note that this relies on having previously looked up any required
 * conversion function.  That's partly for speed but mostly because the parser
 * may call this outside any transaction, or in an aborted transaction.
 */
void
pg_unicode_to_server(char32_t c, unsigned char *s)
{
  unsigned char c_as_utf8[MAX_MULTIBYTE_CHAR_LEN + 1];
  int     c_as_utf8_len;
  int     server_encoding;

  /*
   * Complain if invalid Unicode code point.  The choice of errcode here is
   * debatable, but really our caller should have checked this anyway.
   */
  if (!is_valid_unicode_codepoint(c))
    ereport(ERROR,
        (errcode(ERRCODE_SYNTAX_ERROR),
         errmsg("invalid Unicode code point")));

  /* Otherwise, if it's in ASCII range, conversion is trivial */
  if (c <= 0x7F)
  {
    s[0] = (unsigned char) c;
    s[1] = '\0';
    return;
  }

  /* If the server encoding is UTF-8, we just need to reformat the code */
  server_encoding = GetDatabaseEncoding();
  if (server_encoding == PG_UTF8)
  {
    unicode_to_utf8(c, s);
    s[pg_utf_mblen(s)] = '\0';
    return;
  }

  /* For all other cases, we must have a conversion function available */
  if (Utf8ToServerConvProc == NULL)
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("conversion between %s and %s is not supported",
            pg_enc2name_tbl[PG_UTF8].name,
            GetDatabaseEncodingName())));

  /* Construct UTF-8 source string */
  unicode_to_utf8(c, c_as_utf8);
  c_as_utf8_len = pg_utf_mblen(c_as_utf8);
  c_as_utf8[c_as_utf8_len] = '\0';

  /* Convert, or throw error if we can't */
  FunctionCall6(Utf8ToServerConvProc,
          Int32GetDatum(PG_UTF8),
          Int32GetDatum(server_encoding),
          CStringGetDatum((char *) c_as_utf8),
          CStringGetDatum((char *) s),
          Int32GetDatum(c_as_utf8_len),
          BoolGetDatum(false));
}

/*
 * Convert a single Unicode code point into a string in the server encoding.
 *
 * Same as pg_unicode_to_server(), except that we don't throw errors,
 * but simply return false on conversion failure.
 */
bool
pg_unicode_to_server_noerror(char32_t c, unsigned char *s)
{
  unsigned char c_as_utf8[MAX_MULTIBYTE_CHAR_LEN + 1];
  int     c_as_utf8_len;
  int     converted_len;
  int     server_encoding;

  /* Fail if invalid Unicode code point */
  if (!is_valid_unicode_codepoint(c))
    return false;

  /* Otherwise, if it's in ASCII range, conversion is trivial */
  if (c <= 0x7F)
  {
    s[0] = (unsigned char) c;
    s[1] = '\0';
    return true;
  }

  /* If the server encoding is UTF-8, we just need to reformat the code */
  server_encoding = GetDatabaseEncoding();
  if (server_encoding == PG_UTF8)
  {
    unicode_to_utf8(c, s);
    s[pg_utf_mblen(s)] = '\0';
    return true;
  }

  /* For all other cases, we must have a conversion function available */
  if (Utf8ToServerConvProc == NULL)
    return false;

  /* Construct UTF-8 source string */
  unicode_to_utf8(c, c_as_utf8);
  c_as_utf8_len = pg_utf_mblen(c_as_utf8);
  c_as_utf8[c_as_utf8_len] = '\0';

  /* Convert, but without throwing error if we can't */
  converted_len = DatumGetInt32(FunctionCall6(Utf8ToServerConvProc,
                        Int32GetDatum(PG_UTF8),
                        Int32GetDatum(server_encoding),
                        CStringGetDatum((char *) c_as_utf8),
                        CStringGetDatum((char *) s),
                        Int32GetDatum(c_as_utf8_len),
                        BoolGetDatum(true)));

  /* Conversion was successful iff it consumed the whole input */
  return (converted_len == c_as_utf8_len);
}


/* convert a multibyte string to a wchar */
int
pg_mb2wchar(const char *from, pg_wchar *to)
{
  return pg_wchar_table[DatabaseEncoding->encoding].mb2wchar_with_len((const unsigned char *) from, to, strlen(from));
}

/* convert a multibyte string to a wchar with a limited length */
int
pg_mb2wchar_with_len(const char *from, pg_wchar *to, int len)
{
  return pg_wchar_table[DatabaseEncoding->encoding].mb2wchar_with_len((const unsigned char *) from, to, len);
}

/* same, with any encoding */
int
pg_encoding_mb2wchar_with_len(int encoding,
                const char *from, pg_wchar *to, int len)
{
  return pg_wchar_table[encoding].mb2wchar_with_len((const unsigned char *) from, to, len);
}

/* convert a wchar string to a multibyte */
int
pg_wchar2mb(const pg_wchar *from, char *to)
{
  return pg_wchar_table[DatabaseEncoding->encoding].wchar2mb_with_len(from, (unsigned char *) to, pg_wchar_strlen(from));
}

/* convert a wchar string to a multibyte with a limited length */
int
pg_wchar2mb_with_len(const pg_wchar *from, char *to, int len)
{
  return pg_wchar_table[DatabaseEncoding->encoding].wchar2mb_with_len(from, (unsigned char *) to, len);
}

/* same, with any encoding */
int
pg_encoding_wchar2mb_with_len(int encoding,
                const pg_wchar *from, char *to, int len)
{
  return pg_wchar_table[encoding].wchar2mb_with_len(from, (unsigned char *) to, len);
}

/*
 * Returns the byte length of a multibyte character sequence in a
 * null-terminated string.  Raises an illegal byte sequence error if the
 * sequence would hit a null terminator.
 *
 * The caller is expected to have checked for a terminator at *mbstr == 0
 * before calling, but some callers want 1 in that case, so this function
 * continues that tradition.
 *
 * This must only be used for strings that have a null-terminator to enable
 * bounds detection.
 */
int
pg_mblen_cstr(const char *mbstr)
{
  int     length = pg_wchar_table[DatabaseEncoding->encoding].mblen((const unsigned char *) mbstr);

  /*
   * The .mblen functions return 1 when given a pointer to a terminator.
   * Some callers depend on that, so we tolerate it for now.  Well-behaved
   * callers check the leading byte for a terminator *before* calling.
   */
  for (int i = 1; i < length; ++i)
    if (unlikely(mbstr[i] == 0))
      report_invalid_encoding_db(mbstr, length, i);

  /*
   * String should be NUL-terminated, but checking that would make typical
   * callers O(N^2), tripling Valgrind check-world time.  Unless
   * VALGRIND_EXPENSIVE, check 1 byte after each actual character.  (If we
   * found a character, not a terminator, the next byte must be a terminator
   * or the start of the next character.)  If the caller iterates the whole
   * string, the last call will diagnose a missing terminator.
   */
  if (mbstr[0] != '\0')
  {
#ifdef VALGRIND_EXPENSIVE
    VALGRIND_CHECK_MEM_IS_DEFINED(mbstr, strlen(mbstr));
#else
    VALGRIND_CHECK_MEM_IS_DEFINED(mbstr + length, 1);
#endif
  }

  return length;
}

/*
 * Returns the byte length of a multibyte character sequence bounded by a range
 * [mbstr, end) of at least one byte in size.  Raises an illegal byte sequence
 * error if the sequence would exceed the range.
 */
int
pg_mblen_range(const char *mbstr, const char *end)
{
  int     length = pg_wchar_table[DatabaseEncoding->encoding].mblen((const unsigned char *) mbstr);

  Assert(end > mbstr);

  if (unlikely(mbstr + length > end))
    report_invalid_encoding_db(mbstr, length, end - mbstr);

#ifdef VALGRIND_EXPENSIVE
  VALGRIND_CHECK_MEM_IS_DEFINED(mbstr, end - mbstr);
#else
  VALGRIND_CHECK_MEM_IS_DEFINED(mbstr, length);
#endif

  return length;
}

/*
 * Returns the byte length of a multibyte character sequence bounded by a range
 * extending for 'limit' bytes, which must be at least one.  Raises an illegal
 * byte sequence error if the sequence would exceed the range.
 */
int
pg_mblen_with_len(const char *mbstr, int limit)
{
  int     length = pg_wchar_table[DatabaseEncoding->encoding].mblen((const unsigned char *) mbstr);

  Assert(limit >= 1);

  if (unlikely(length > limit))
    report_invalid_encoding_db(mbstr, length, limit);

#ifdef VALGRIND_EXPENSIVE
  VALGRIND_CHECK_MEM_IS_DEFINED(mbstr, limit);
#else
  VALGRIND_CHECK_MEM_IS_DEFINED(mbstr, length);
#endif

  return length;
}


/*
 * Returns the length of a multibyte character sequence, without any
 * validation of bounds.
 *
 * PLEASE NOTE:  This function can only be used safely if the caller has
 * already verified the input string, since otherwise there is a risk of
 * overrunning the buffer if the string is invalid.  A prior call to a
 * pg_mbstrlen* function suffices.
 */
int
pg_mblen_unbounded(const char *mbstr)
{
  int     length = pg_wchar_table[DatabaseEncoding->encoding].mblen((const unsigned char *) mbstr);

  VALGRIND_CHECK_MEM_IS_DEFINED(mbstr, length);

  return length;
}

/*
 * Historical name for pg_mblen_unbounded().  Should not be used and will be
 * removed in a later version.
 */
int
pg_mblen(const char *mbstr)
{
  return pg_mblen_unbounded(mbstr);
}

/* returns the display length of a multibyte character */
int
pg_dsplen(const char *mbstr)
{
  return pg_wchar_table[DatabaseEncoding->encoding].dsplen((const unsigned char *) mbstr);
}

/* returns the length (counted in wchars) of a multibyte string */
int
pg_mbstrlen(const char *mbstr)
{
  int     len = 0;

  /* optimization for single byte encoding */
  if (pg_database_encoding_max_length() == 1)
    return strlen(mbstr);

  while (*mbstr)
  {
    mbstr += pg_mblen_cstr(mbstr);
    len++;
  }
  return len;
}

/*
 * returns the length (counted in wchars) of a multibyte string
 * (stops at the first of "limit" or a NUL)
 */
int
pg_mbstrlen_with_len(const char *mbstr, int limit)
{
  int     len = 0;

  /* optimization for single byte encoding */
  if (pg_database_encoding_max_length() == 1)
    return limit;

  while (limit > 0 && *mbstr)
  {
    int     l = pg_mblen_with_len(mbstr, limit);

    limit -= l;
    mbstr += l;
    len++;
  }
  return len;
}

/*
 * returns the byte length of a multibyte string
 * (not necessarily NULL terminated)
 * that is no longer than limit.
 * this function does not break multibyte character boundary.
 */
int
pg_mbcliplen(const char *mbstr, int len, int limit)
{
  return pg_encoding_mbcliplen(DatabaseEncoding->encoding, mbstr,
                 len, limit);
}

/*
 * pg_mbcliplen with specified encoding; string must be valid in encoding
 */
int
pg_encoding_mbcliplen(int encoding, const char *mbstr,
            int len, int limit)
{
  mblen_function mblen_fn;
  int     clen = 0;
  int     l;

  /* optimization for single byte encoding */
  if (pg_encoding_max_length(encoding) == 1)
    return cliplen(mbstr, len, limit);

  mblen_fn = pg_wchar_table[encoding].mblen;

  while (len > 0 && *mbstr)
  {
    l = (*mblen_fn) ((const unsigned char *) mbstr);
    if ((clen + l) > limit)
      break;
    clen += l;
    if (clen == limit)
      break;
    len -= l;
    mbstr += l;
  }
  return clen;
}

/*
 * Similar to pg_mbcliplen except the limit parameter specifies the
 * character length, not the byte length.
 */
int
pg_mbcharcliplen(const char *mbstr, int len, int limit)
{
  int     clen = 0;
  int     nch = 0;
  int     l;

  /* optimization for single byte encoding */
  if (pg_database_encoding_max_length() == 1)
    return cliplen(mbstr, len, limit);

  while (len > 0 && *mbstr)
  {
    l = pg_mblen_with_len(mbstr, len);
    nch++;
    if (nch > limit)
      break;
    clen += l;
    len -= l;
    mbstr += l;
  }
  return clen;
}

/* mbcliplen for any single-byte encoding */
static int
cliplen(const char *str, int len, int limit)
{
  int     l = 0;

  len = Min(len, limit);
  while (l < len && str[l])
    l++;
  return l;
}

void
SetDatabaseEncoding(int encoding)
{
  if (!PG_VALID_BE_ENCODING(encoding))
    elog(ERROR, "invalid database encoding: %d", encoding);

  DatabaseEncoding = &pg_enc2name_tbl[encoding];
  Assert(DatabaseEncoding->encoding == encoding);
}

void
SetMessageEncoding(int encoding)
{
  /* Some calls happen before we can elog()! */
  Assert(PG_VALID_ENCODING(encoding));

  MessageEncoding = &pg_enc2name_tbl[encoding];
  Assert(MessageEncoding->encoding == encoding);
}

#ifdef ENABLE_NLS
/*
 * Make one bind_textdomain_codeset() call, translating a pg_enc to a gettext
 * codeset.  Can fail for gettext-internal causes like out-of-memory.
 */
static bool
raw_pg_bind_textdomain_codeset(const char *domainname, int encoding)
{
  bool    elog_ok = (CurrentMemoryContext != NULL);

  if (!PG_VALID_ENCODING(encoding) || pg_enc2gettext_tbl[encoding] == NULL)
    return false;

  if (bind_textdomain_codeset(domainname,
                pg_enc2gettext_tbl[encoding]) != NULL)
    return true;

  if (elog_ok)
    elog(LOG, "bind_textdomain_codeset failed");
  else
    write_stderr("bind_textdomain_codeset failed");

  return false;
}

/*
 * Bind a gettext message domain to the codeset corresponding to the database
 * encoding.  For SQL_ASCII, instead bind to the codeset implied by LC_CTYPE.
 * Return the MessageEncoding implied by the new settings.
 *
 * On most platforms, gettext defaults to the codeset implied by LC_CTYPE.
 * When that matches the database encoding, we don't need to do anything.  In
 * CREATE DATABASE, we enforce or trust that the locale's codeset matches the
 * database encoding, except for the C locale.  (On Windows, we also permit a
 * discrepancy under the UTF8 encoding.)  For the C locale, explicitly bind
 * gettext to the right codeset.
 *
 * On Windows, gettext defaults to the Windows ANSI code page.  This is a
 * convenient departure for software that passes the strings to Windows ANSI
 * APIs, but we don't do that.  Compel gettext to use database encoding or,
 * failing that, the LC_CTYPE encoding as it would on other platforms.
 *
 * This function is called before elog() and palloc() are usable.
 */
int
pg_bind_textdomain_codeset(const char *domainname)
{
  bool    elog_ok = (CurrentMemoryContext != NULL);
  int     encoding = GetDatabaseEncoding();
  int     new_msgenc;

#ifndef WIN32
  const char *ctype = setlocale(LC_CTYPE, NULL);

  if (pg_strcasecmp(ctype, "C") == 0 || pg_strcasecmp(ctype, "POSIX") == 0)
#endif
    if (encoding != PG_SQL_ASCII &&
      raw_pg_bind_textdomain_codeset(domainname, encoding))
      return encoding;

  new_msgenc = pg_get_encoding_from_locale(NULL, elog_ok);
  if (new_msgenc < 0)
    new_msgenc = PG_SQL_ASCII;

#ifdef WIN32
  if (!raw_pg_bind_textdomain_codeset(domainname, new_msgenc))
    /* On failure, the old message encoding remains valid. */
    return GetMessageEncoding();
#endif

  return new_msgenc;
}
#endif

/*
 * The database encoding, also called the server encoding, represents the
 * encoding of data stored in text-like data types.  Affected types include
 * cstring, text, varchar, name, xml, and json.
 */
int
GetDatabaseEncoding(void)
{
  return DatabaseEncoding->encoding;
}

const char *
GetDatabaseEncodingName(void)
{
  return DatabaseEncoding->name;
}

Datum
getdatabaseencoding(PG_FUNCTION_ARGS)
{
  return DirectFunctionCall1(namein, CStringGetDatum(DatabaseEncoding->name));
}

Datum
pg_client_encoding(PG_FUNCTION_ARGS)
{
  return DirectFunctionCall1(namein, CStringGetDatum(ClientEncoding->name));
}

Datum
PG_char_to_encoding(PG_FUNCTION_ARGS)
{
  Name    s = PG_GETARG_NAME(0);

  PG_RETURN_INT32(pg_char_to_encoding(NameStr(*s)));
}

Datum
PG_encoding_to_char(PG_FUNCTION_ARGS)
{
  int32   encoding = PG_GETARG_INT32(0);
  const char *encoding_name = pg_encoding_to_char(encoding);

  return DirectFunctionCall1(namein, CStringGetDatum(encoding_name));
}

/*
 * gettext() returns messages in this encoding.  This often matches the
 * database encoding, but it differs for SQL_ASCII databases, for processes
 * not attached to a database.
 */
int
GetMessageEncoding(void)
{
  return MessageEncoding->encoding;
}


/*
 * Generic character incrementer function.
 *
 * Not knowing anything about the properties of the encoding in use, we just
 * keep incrementing the last byte until we get a validly-encoded result,
 * or we run out of values to try.  We don't bother to try incrementing
 * higher-order bytes, so there's no growth in runtime for wider characters.
 * (If we did try to do that, we'd need to consider the likelihood that 255
 * is not a valid final byte in the encoding.)
 */
static bool
pg_generic_charinc(unsigned char *charptr, int len)
{
  unsigned char *lastbyte = charptr + len - 1;
  mbverifychar_function mbverifychar;

  /* We can just invoke the character verifier directly. */
  mbverifychar = pg_wchar_table[GetDatabaseEncoding()].mbverifychar;

  while (*lastbyte < (unsigned char) 255)
  {
    (*lastbyte)++;
    if ((*mbverifychar) (charptr, len) == len)
      return true;
  }

  return false;
}

/*
 * UTF-8 character incrementer function.
 *
 * For a one-byte character less than 0x7F, we just increment the byte.
 *
 * For a multibyte character, every byte but the first must fall between 0x80
 * and 0xBF; and the first byte must be between 0xC0 and 0xF4.  We increment
 * the last byte that's not already at its maximum value.  If we can't find a
 * byte that's less than the maximum allowable value, we simply fail.  We also
 * need some special-case logic to skip regions used for surrogate pair
 * handling, as those should not occur in valid UTF-8.
 *
 * Note that we don't reset lower-order bytes back to their minimums, since
 * we can't afford to make an exhaustive search (see make_greater_string).
 */
static bool
pg_utf8_increment(unsigned char *charptr, int length)
{
  unsigned char a;
  unsigned char limit;

  switch (length)
  {
    default:
      /* reject lengths 5 and 6 for now */
      return false;
    case 4:
      a = charptr[3];
      if (a < 0xBF)
      {
        charptr[3]++;
        break;
      }
      pg_fallthrough;
    case 3:
      a = charptr[2];
      if (a < 0xBF)
      {
        charptr[2]++;
        break;
      }
      pg_fallthrough;
    case 2:
      a = charptr[1];
      switch (*charptr)
      {
        case 0xED:
          limit = 0x9F;
          break;
        case 0xF4:
          limit = 0x8F;
          break;
        default:
          limit = 0xBF;
          break;
      }
      if (a < limit)
      {
        charptr[1]++;
        break;
      }
      pg_fallthrough;
    case 1:
      a = *charptr;
      if (a == 0x7F || a == 0xDF || a == 0xEF || a == 0xF4)
        return false;
      charptr[0]++;
      break;
  }

  return true;
}

/*
 * EUC-JP character incrementer function.
 *
 * If the sequence starts with SS2 (0x8e), it must be a two-byte sequence
 * representing JIS X 0201 characters with the second byte ranging between
 * 0xa1 and 0xdf.  We just increment the last byte if it's less than 0xdf,
 * and otherwise rewrite the whole sequence to 0xa1 0xa1.
 *
 * If the sequence starts with SS3 (0x8f), it must be a three-byte sequence
 * in which the last two bytes range between 0xa1 and 0xfe.  The last byte
 * is incremented if possible, otherwise the second-to-last byte.
 *
 * If the sequence starts with a value other than the above and its MSB
 * is set, it must be a two-byte sequence representing JIS X 0208 characters
 * with both bytes ranging between 0xa1 and 0xfe.  The last byte is
 * incremented if possible, otherwise the second-to-last byte.
 *
 * Otherwise, the sequence is a single-byte ASCII character. It is
 * incremented up to 0x7f.
 */
static bool
pg_eucjp_increment(unsigned char *charptr, int length)
{
  unsigned char c1,
        c2;
  int     i;

  c1 = *charptr;

  switch (c1)
  {
    case SS2:       /* JIS X 0201 */
      if (length != 2)
        return false;

      c2 = charptr[1];

      if (c2 >= 0xdf)
        charptr[0] = charptr[1] = 0xa1;
      else if (c2 < 0xa1)
        charptr[1] = 0xa1;
      else
        charptr[1]++;
      break;

    case SS3:       /* JIS X 0212 */
      if (length != 3)
        return false;

      for (i = 2; i > 0; i--)
      {
        c2 = charptr[i];
        if (c2 < 0xa1)
        {
          charptr[i] = 0xa1;
          return true;
        }
        else if (c2 < 0xfe)
        {
          charptr[i]++;
          return true;
        }
      }

      /* Out of 3-byte code region */
      return false;

    default:
      if (IS_HIGHBIT_SET(c1)) /* JIS X 0208? */
      {
        if (length != 2)
          return false;

        for (i = 1; i >= 0; i--)
        {
          c2 = charptr[i];
          if (c2 < 0xa1)
          {
            charptr[i] = 0xa1;
            return true;
          }
          else if (c2 < 0xfe)
          {
            charptr[i]++;
            return true;
          }
        }

        /* Out of 2 byte code region */
        return false;
      }
      else
      {         /* ASCII, single byte */
        if (c1 > 0x7e)
          return false;
        (*charptr)++;
      }
      break;
  }

  return true;
}

/*
 * get the character incrementer for the encoding for the current database
 */
mbcharacter_incrementer
pg_database_encoding_character_incrementer(void)
{
  /*
   * Eventually it might be best to add a field to pg_wchar_table[], but for
   * now we just use a switch.
   */
  switch (GetDatabaseEncoding())
  {
    case PG_UTF8:
      return pg_utf8_increment;

    case PG_EUC_JP:
      return pg_eucjp_increment;

    default:
      return pg_generic_charinc;
  }
}

/*
 * fetch maximum length of the encoding for the current database
 */
int
pg_database_encoding_max_length(void)
{
  return pg_wchar_table[GetDatabaseEncoding()].maxmblen;
}

/*
 * Verify mbstr to make sure that it is validly encoded in the current
 * database encoding.  Otherwise same as pg_verify_mbstr().
 */
bool
pg_verifymbstr(const char *mbstr, int len, bool noError)
{
  return pg_verify_mbstr(GetDatabaseEncoding(), mbstr, len, noError);
}

/*
 * Verify mbstr to make sure that it is validly encoded in the specified
 * encoding.
 */
bool
pg_verify_mbstr(int encoding, const char *mbstr, int len, bool noError)
{
  int     oklen;

  Assert(PG_VALID_ENCODING(encoding));

  oklen = pg_wchar_table[encoding].mbverifystr((const unsigned char *) mbstr, len);
  if (oklen != len)
  {
    if (noError)
      return false;
    report_invalid_encoding(encoding, mbstr + oklen, len - oklen);
  }
  return true;
}

/*
 * Verify mbstr to make sure that it is validly encoded in the specified
 * encoding.
 *
 * mbstr is not necessarily zero terminated; length of mbstr is
 * specified by len.
 *
 * If OK, return length of string in the encoding.
 * If a problem is found, return -1 when noError is
 * true; when noError is false, ereport() a descriptive message.
 *
 * Note: We cannot use the faster encoding-specific mbverifystr() function
 * here, because we need to count the number of characters in the string.
 */
int
pg_verify_mbstr_len(int encoding, const char *mbstr, int len, bool noError)
{
  mbverifychar_function mbverifychar;
  int     mb_len;

  Assert(PG_VALID_ENCODING(encoding));

  /*
   * In single-byte encodings, we need only reject nulls (\0).
   */
  if (pg_encoding_max_length(encoding) <= 1)
  {
    const char *nullpos = memchr(mbstr, 0, len);

    if (nullpos == NULL)
      return len;
    if (noError)
      return -1;
    report_invalid_encoding(encoding, nullpos, 1);
  }

  /* fetch function pointer just once */
  mbverifychar = pg_wchar_table[encoding].mbverifychar;

  mb_len = 0;

  while (len > 0)
  {
    int     l;

    /* fast path for ASCII-subset characters */
    if (!IS_HIGHBIT_SET(*mbstr))
    {
      if (*mbstr != '\0')
      {
        mb_len++;
        mbstr++;
        len--;
        continue;
      }
      if (noError)
        return -1;
      report_invalid_encoding(encoding, mbstr, len);
    }

    l = (*mbverifychar) ((const unsigned char *) mbstr, len);

    if (l < 0)
    {
      if (noError)
        return -1;
      report_invalid_encoding(encoding, mbstr, len);
    }

    mbstr += l;
    len -= l;
    mb_len++;
  }
  return mb_len;
}

/*
 * check_encoding_conversion_args: check arguments of a conversion function
 *
 * "expected" arguments can be either an encoding ID or -1 to indicate that
 * the caller will check whether it accepts the ID.
 *
 * Note: the errors here are not really user-facing, so elog instead of
 * ereport seems sufficient.  Also, we trust that the "expected" encoding
 * arguments are valid encoding IDs, but we don't trust the actuals.
 */
void
check_encoding_conversion_args(int src_encoding,
                 int dest_encoding,
                 int len,
                 int expected_src_encoding,
                 int expected_dest_encoding)
{
  if (!PG_VALID_ENCODING(src_encoding))
    elog(ERROR, "invalid source encoding ID: %d", src_encoding);
  if (src_encoding != expected_src_encoding && expected_src_encoding >= 0)
    elog(ERROR, "expected source encoding \"%s\", but got \"%s\"",
       pg_enc2name_tbl[expected_src_encoding].name,
       pg_enc2name_tbl[src_encoding].name);
  if (!PG_VALID_ENCODING(dest_encoding))
    elog(ERROR, "invalid destination encoding ID: %d", dest_encoding);
  if (dest_encoding != expected_dest_encoding && expected_dest_encoding >= 0)
    elog(ERROR, "expected destination encoding \"%s\", but got \"%s\"",
       pg_enc2name_tbl[expected_dest_encoding].name,
       pg_enc2name_tbl[dest_encoding].name);
  if (len < 0)
    elog(ERROR, "encoding conversion length must not be negative");
}

/*
 * report_invalid_encoding: complain about invalid multibyte character
 *
 * note: len is remaining length of string, not length of character;
 * len must be greater than zero (or we'd neglect initializing "buf").
 */
void
report_invalid_encoding(int encoding, const char *mbstr, int len)
{
  int     l = pg_encoding_mblen_or_incomplete(encoding, mbstr, len);

  report_invalid_encoding_int(encoding, mbstr, l, len);
}

static void
report_invalid_encoding_int(int encoding, const char *mbstr, int mblen, int len)
{
  char    buf[8 * 5 + 1];
  char     *p = buf;
  int     j,
        jlimit;

  jlimit = Min(mblen, len);
  jlimit = Min(jlimit, 8);  /* prevent buffer overrun */

  for (j = 0; j < jlimit; j++)
  {
    p += sprintf(p, "0x%02x", (unsigned char) mbstr[j]);
    if (j < jlimit - 1)
      p += sprintf(p, " ");
  }

  ereport(ERROR,
      (errcode(ERRCODE_CHARACTER_NOT_IN_REPERTOIRE),
       errmsg("invalid byte sequence for encoding \"%s\": %s",
          pg_enc2name_tbl[encoding].name,
          buf)));
}

static void
report_invalid_encoding_db(const char *mbstr, int mblen, int len)
{
  report_invalid_encoding_int(GetDatabaseEncoding(), mbstr, mblen, len);
}

/*
 * report_untranslatable_char: complain about untranslatable character
 *
 * note: len is remaining length of string, not length of character;
 * len must be greater than zero (or we'd neglect initializing "buf").
 */
void
report_untranslatable_char(int src_encoding, int dest_encoding,
               const char *mbstr, int len)
{
  int     l;
  char    buf[8 * 5 + 1];
  char     *p = buf;
  int     j,
        jlimit;

  /*
   * We probably could use plain pg_encoding_mblen(), because
   * gb18030_to_utf8() verifies before it converts.  All conversions should.
   * For src_encoding!=GB18030, len>0 meets pg_encoding_mblen() needs.  Even
   * so, be defensive, since a buggy conversion might pass invalid data.
   * This is not a performance-critical path.
   */
  l = pg_encoding_mblen_or_incomplete(src_encoding, mbstr, len);
  jlimit = Min(l, len);
  jlimit = Min(jlimit, 8);  /* prevent buffer overrun */

  for (j = 0; j < jlimit; j++)
  {
    p += sprintf(p, "0x%02x", (unsigned char) mbstr[j]);
    if (j < jlimit - 1)
      p += sprintf(p, " ");
  }

  ereport(ERROR,
      (errcode(ERRCODE_UNTRANSLATABLE_CHARACTER),
       errmsg("character with byte sequence %s in encoding \"%s\" has no equivalent in encoding \"%s\"",
          buf,
          pg_enc2name_tbl[src_encoding].name,
          pg_enc2name_tbl[dest_encoding].name)));
}


#ifdef WIN32
/*
 * Convert from MessageEncoding to a palloc'ed, null-terminated utf16
 * string. The character length is also passed to utf16len if not
 * null. Returns NULL iff failed. Before MessageEncoding initialization, "str"
 * should be ASCII-only; this will function as though MessageEncoding is UTF8.
 */
WCHAR *
pgwin32_message_to_UTF16(const char *str, int len, int *utf16len)
{
  int     msgenc = GetMessageEncoding();
  WCHAR    *utf16;
  int     dstlen;
  UINT    codepage;

  if (msgenc == PG_SQL_ASCII)
    /* No conversion is possible, and SQL_ASCII is never utf16. */
    return NULL;

  codepage = pg_enc2name_tbl[msgenc].codepage;

  /*
   * Use MultiByteToWideChar directly if there is a corresponding codepage,
   * or double conversion through UTF8 if not.  Double conversion is needed,
   * for example, in an ENCODING=LATIN8, LC_CTYPE=C database.
   */
  if (codepage != 0)
  {
    utf16 = palloc_array(WCHAR, len + 1);
    dstlen = MultiByteToWideChar(codepage, 0, str, len, utf16, len);
    utf16[dstlen] = (WCHAR) 0;
  }
  else
  {
    char     *utf8;

    /*
     * XXX pg_do_encoding_conversion() requires a transaction.  In the
     * absence of one, hope for the input to be valid UTF8.
     */
    if (IsTransactionState())
    {
      utf8 = (char *) pg_do_encoding_conversion((unsigned char *) unconstify(char *, str),
                            len,
                            msgenc,
                            PG_UTF8);
      if (utf8 != str)
        len = strlen(utf8);
    }
    else
      utf8 = unconstify(char *, str);

    utf16 = palloc_array(WCHAR, len + 1);
    dstlen = MultiByteToWideChar(CP_UTF8, 0, utf8, len, utf16, len);
    utf16[dstlen] = (WCHAR) 0;

    if (utf8 != str)
      pfree(utf8);
  }

  if (dstlen == 0 && len > 0)
  {
    pfree(utf16);
    return NULL;      /* error */
  }

  if (utf16len)
    *utf16len = dstlen;
  return utf16;
}

#endif              /* WIN32 */

Coverage Report

Created: 2026-11-09 07:20