<template> replacement for linked list C

Question

Just finished a small linked list in C and realized that I have a problem. There are no template arguments for C, so at the beginning of the file I declare my data type for the list, for example:

typedef int LData;

So far so good, but I can’t use this linked list for 2 (or more) different data types in one program.

I can determine LDatahow void*and manually convert it to a specific data type according to the context. But I wonder if there are more elegant solutions?

Answer 1

LData void*. , , void* void* , .

Answer 2

union, .

Answer 3

:

struct datum;
typedef struct datum datum;
typedef datum *LData;

struct datum {
   int whatever;
};

Answer 4

#defines, , ""?

.

 #define TYPE_INT   0
 #define TYPE_FLOAT 1
 // etc

- :

 struct LinkedListLink
 {
      int    type;
      LData  data;
 };

, "", , ( LinkedListLink).

Answer 5

( , ), , . . , , . - , .

++, , .

// some representative bits of my linked list API
//
typedef void* PLINK;

extern PLINK LLAddToList(PLINK head, PLINK new);
extern PLINK LLNextItem(PLINK current); 

// the structure I want to use it with

typedef struct _foo {
   PLINK  pLink;
   int    data1; 
   int    data2;
} FOO;

// to allow for the link pointers to be some other than the first field
// we use this to go from link pointer to structure pointer.
FOO * FooFromPLink(PLINK current) {
    return (FOO *)((char *)&current - FIELD_OFFSET(FOO, pLink));
}

void MyFunction()
{
   // this idiom to use the linklist code with a FOO struct
   //
   FOO * pfoo = // allocate and initialize a foo
   LLAddToList(head, &pfoo->pLink);


   // this idiom to traverse a list of FOOs, etc.
   //
   PLINK next = LLNextItem(head);
   while (next)
      {
      pfoo = FooFromPLink(next);
      // operate on foo.
      next = LLNextItem(next);
      }

}