Types are passed as follows:

//The following typedefs are used below:
typedef unsigned size32_t;
typedef wchar_t UChar; [ unsigned short in linux ]

The following list describes the mappings from ECL to C++. For embedded C++ the parameters are always converted to lower case, and capitalized in conjunctions (see below).

ECL                  C++ [Linux in brackets]
BOOOLEAN xyz         bool xyz
INTEGER1 xyz         signed char xyz
INTEGER2 xyz         signed short xyz
INTEGER4 xyz         signed int xyz
INTEGER8 xyz         signed __int64 xyz [ long long ]
UNSIGNED1 xyz        unsigned char xyz
UNSIGNED2 xyz        unsigned short xyz
UNSIGNED4 xyz        unsigned int xyz
UNSIGNED8 xyz        unsigned __int64 xyz [ unsigned long long xyz ]
REAL4 xyz            float xyz
REAL/REAL8 xyz       double xyz
DATA xyz             size32_t lenXyz, void * xyz
STRING xyz           size32_t lenXyz, char * xyz
VARSTRING xyz        char * xyz;
QSTRING xyz          size32_t lenXyz, char * xyz
UNICODE xyz          size32_t lenXyz, UChar * xyz
VARUNICODE xyz       UChar * xyz
DATA<nn> xyz         void * xyz
STRING<nn> xyz       char * xyz
QSTRING<nn> xyz      char * xyz
UNICODE<nn> xyz      UChar * xyz
SET OF ... xyz       bool isAllXyz, size32_t lenXyz, void *  xyz

Note that strings of unknown length are passed differently from those with a known length. A variable length input string is passed as a number of characters, not the size (i.e. qstring/unicode), followed by a pointer to the data, like this (size32_t is an UNSIGNED4):

string ABC -> size32_t lenAbc, const char * abc;
unicode ABC -> size32_t lenABC, const UChar * abc;

A dataset is passed as a size/pointer pair. The length gives the size of the following dataset in bytes. The same naming convention is used:

dataset(r) ABC -> size32_t lenAbc, const void * abc

NOTE: variable length strings within a record are stored as a 4 byte number of characters, followed by the string data.

Sets are passed as a set of parameters (all, size, pointer):

set of unsigned4 ABC -> bool isAllAbc, size32_t lenAbc, const void * abc

Return types are handled as C++ functions returning the same types with some exceptions. The exceptions have some extra initial parameters to return the results in:

ECL                C++ [Linux in brackets]
DATA xyz           size32_t & __lenResult, void * & __result
STRING xyz         size32_t & __lenResult, char * & __result
QSTRING xyz        size32_t & __lenResult, char * & __result
UNICODE xyz        size32_t & __lenResult, UChar * & __result
DATA<nn> xyz       void * __result
STRING<nn> xyz     char * __result
QSTRING<nn> xyz    char * __result
UNICODE<nn> xyz    UChar * __result
SET OF ... xyz     bool __isAllResult, size32_t &  __lenResult,
                      void * & __result

For example,

STRING process(STRING value, INTEGER4 len)

has the prototype:

void process(size32_t & __lenResult, char * & __result,
             size32_t lenValue, char * value, int len);

#option pureBy default, embedded C++ functions are assumed to have side-effects, which means the generated code won't be as efficient as it might be since the calls can't be shared. Adding #option pure inside the embedded C++ code causes it to be treated as a pure function without side effects.

#option onceIndicates the function has no side effects and is evaluated at query execution time, even if the parameters are constant, allowing the optimizer to make more efficient calls to the function in some cases.

#option actionIndicates side effects, requiring the optimizer to keep all calls to the function.

#body Delimits the beginning of executable code. All code that precedes #body (such as #include) is generated outside the function definition; all code that follows it is generated inside the function definition.

Example:

//static int add(int x,int y) {
INTEGER4 add(INTEGER4 x, INTEGER4 y) := BEGINC++
  #option pure
  return x + y;
ENDC++;
         
OUTPUT(add(10,20));
          
//static void reverseString(size32_t & __lenResult,char *  & __result,
// size32_t lenValue,char * value) {
STRING reverseString(STRING value) := BEGINC++
   size32_t len = lenValue;
   char * out = (char *)rtlMalloc(len);
   for (unsigned i= 0; i < len; i++)
        out[i] = value[len-1-i];
   __lenResult = len;
   __result = out;
ENDC++;
OUTPUT(reverseString('Kevin'));
// This is a function returning an unknown length string via the
// special reference parameters __lenResult and  __result
         
//this function demonstrates #body, allowing #include to be  used
BOOLEAN nocaseInList(STRING search,
          SET OF STRING values) := BEGINC++
#include <string.h>
#body 
  if (isAllValues)
    return true; 
  const byte * cur = (const byte *)values; 
  const byte * end = cur + lenValues; 
  while (cur != end) 
  { 
  unsigned len = *(unsigned *)cur; 
  cur += sizeof(unsigned); 
  if (lenSearch == len && memicmp(search, cur, len) == 0) 
      return true; 
  cur += len; 
  } 
  return false;
ENDC++;
          
//and another example, generating a variable number of Xes
STRING buildString(INTEGER4 value) := BEGINC++
   char * out = (char *)rtlMalloc(value);
   for (unsigned i= 0; i < value; i++)
     out[i] = 'X';
     __lenResult = value;
     __result = out;
ENDC++;

See Also: External Service Implementation