Re: [HACKERS] Collation rules and multi-lingual databases

[Joe Conway]

Joe Conway wrote:
What about something like this?
Oops! Forgot to restrore error handling. See below:

Joe

8<--------------------------------

#include <setjmp.h>
#include <string.h>
#include "postgres.h"
#include "fmgr.h"
#include "tcop/tcopprot.h"
#include "utils/builtins.h"
#define GET_STR(textp) \
  DatumGetCString(DirectFunctionCall1(textout, PointerGetDatum(textp)))
#define GET_BYTEA(str_) \
  DatumGetTextP(DirectFunctionCall1(byteain, CStringGetDatum(str_)))
#define MAX_BYTEA_LEN    0x3fffffff
/*
 * pg_strxfrm - Function to convert string similar to the strxfrm C
 * function using a specified locale.
 */
extern Datum pg_strxfrm(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(pg_strxfrm);
Datum
pg_strxfrm(PG_FUNCTION_ARGS)
{
  char       *str = GET_STR(PG_GETARG_TEXT_P(0));
  size_t      str_len = strlen(str);
  char       *localestr = GET_STR(PG_GETARG_TEXT_P(1));
  size_t      approx_trans_len = 4 + (str_len * 3);
  char       *trans = (char *) palloc(approx_trans_len + 1);
  size_t      actual_trans_len;
  char       *oldlocale;
  char       *newlocale;
  sigjmp_buf  save_restart;
  if (approx_trans_len > MAX_BYTEA_LEN)
    elog(ERROR, "source string too long to transform");
  oldlocale = setlocale(LC_COLLATE, NULL);
  if (!oldlocale)
    elog(ERROR, "setlocale failed to return a locale");
  /* catch elog while locale is set other than the default */
  memcpy(&save_restart, &Warn_restart, sizeof(save_restart));
  if (sigsetjmp(Warn_restart, 1) != 0)
  {
    memcpy(&Warn_restart, &save_restart, sizeof(Warn_restart));
    newlocale = setlocale(LC_COLLATE, oldlocale);
    if (!newlocale)
      elog(PANIC, "setlocale failed to reset locale: %s", localestr);
    siglongjmp(Warn_restart, 1);
  }
  newlocale = setlocale(LC_COLLATE, localestr);
  if (!newlocale)
    elog(ERROR, "setlocale failed to set a locale: %s", localestr);
  actual_trans_len = strxfrm(trans, str, approx_trans_len + 1);

  /* if the buffer was not large enough, resize it and try again */
  if (actual_trans_len >= approx_trans_len)
  {
    approx_trans_len = actual_trans_len + 1;
    if (approx_trans_len > MAX_BYTEA_LEN)
      elog(ERROR, "source string too long to transform");
    trans = (char *) repalloc(trans, approx_trans_len + 1);
    actual_trans_len = strxfrm(trans, str, approx_trans_len + 1);
    /* if the buffer still not large enough, punt */
    if (actual_trans_len >= approx_trans_len)
      elog(ERROR, "strxfrm failed, buffer insufficient");
  }
  newlocale = setlocale(LC_COLLATE, oldlocale);
  if (!newlocale)
    elog(PANIC, "setlocale failed to reset locale: %s", localestr);
  /* restore normal error handling */
  memcpy(&Warn_restart, &save_restart, sizeof(Warn_restart));
  PG_RETURN_BYTEA_P(GET_BYTEA(trans));
}
8<--------------------------------



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