#include <stdlib.h>
#include <string.h>
#include <sqlcli.h>
#include <sqludf.h>

/*
CREATE FUNCTION CRC32(STR VARCHAR(4000))
RETURNS BIGINT
SPECIFIC CRC32
EXTERNAL NAME 'crc32!crc32'
LANGUAGE C
PARAMETER STYLE SQL
FENCED THREADSAFE
DETERMINISTIC
NOT NULL CALL
NO SQL
NO EXTERNAL ACTION
ALLOW PARALLEL;
*/

void make_crc_table(
  SQLUINTEGER crc_table[]
) {
  int i, j;
  for (i = 0; i < 256; i++) {
    SQLUINTEGER c = i;
    for (j = 0; j < 8; j++)
      c = (c & 1) ? (0xEDB88320 ^ (c >> 1)) : (c >> 1);
    crc_table[i] = c;
  }
}
 
SQLUINTEGER get_crc32(
  SQLUDF_VARCHAR *buf
, int len
, SQLUINTEGER crc_table[256]
) {
  int i;
  SQLUINTEGER c = 0xFFFFFFFF;

  for (i = 0; i < len; i++)
    c = crc_table[(c ^ buf[i]) & 0xFF] ^ (c >> 8);
  return c ^ 0xFFFFFFFF;
}

#ifdef __cplusplus
extern "C"
#endif
void SQL_API_FN crc32( 
  SQLUDF_VARCHAR    *inStr
, SQLUDF_BIGINT     *outRes
, SQLUDF_NULLIND    *inStrNullInd
, SQLUDF_NULLIND    *outResNullInd
, SQLUDF_TRAIL_ARGS
) {
  SQLUINTEGER crc_table[256];

  if ((*outResNullInd = *inStrNullInd) == -1) return;
  make_crc_table(crc_table);
  *outRes = get_crc32(inStr, strlen(inStr), crc_table);
}

@echo off
setlocal
@CALL "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\bin\vcvars64.bat" 
set INCLUDE=%DB2PATH%\include;%INCLUDE%
rem Microsoft C/C++ Compiler
set BLDCOMP=cl

if "%BITWIDTH%" == "32onWin64" set LIB=%DB2PATH%\lib\Win32;%LIB%
if "%1" == "" goto error

if exist "%1.cpp" goto cpp
%BLDCOMP% -Zi -Od -c -W2 -DWIN32 -MD -D_CRT_SECURE_NO_DEPRECATE %1.c
goto link_step
:cpp
%BLDCOMP% -Zi -Od -c -W2 -DWIN32 -MD -D_CRT_SECURE_NO_DEPRECATE /EHsc %1.cpp

rem Link the program.
:link_step
set BUFFEROVERFLOWLIB=
if "%CPU%" == "AMD64" set BUFFEROVERFLOWLIB=bufferoverflowU.lib
link -debug -dll -out:%1.dll %1.obj db2api.lib %BUFFEROVERFLOWLIB% -def:%1.def
if EXIST %1.dll.manifest MT -manifest %1.dll.manifest -outputresource:%1.dll;#2

rem Copy the stored procedure DLL to the 'function' directory
copy %1.dll "%DB2PATH%\function"

goto exit
:error
echo Usage: bldrtn prog_name
:exit

endlocal
@echo on