X-Macros for serialization of C structs

example.c

#include <stdio.h>
#include <stdint.h>

typedef enum {
    enOne,
    enTwo,
    enThree,
    invalidMax = 2147483647
} MyEnum;

// automatically define a struct and its reader and writer functions simultaneously
// typedef { ... } MyStruct;
// void fread_MyStruct(MyStruct *obj, FILE *fp) { ... }
// void fwrite_MyStruct(MyStruct *obj, FILE *fp) { ... }
#define SERIALIZABLE_STRUCT_NAME MyStruct
#define SERIALIZABLE_STRUCT_MEMBERS \
    SERIALIZABLE_STRUCT_MEMBER(MyEnum, anEnum) \
    SERIALIZABLE_STRUCT_MEMBER(uint8_t, aChar) \
    SERIALIZABLE_STRUCT_MEMBER(float, aFloat)
#include "serializable-struct.h"

// repeat as many times as necessary
#define SERIALIZABLE_STRUCT_NAME AnotherStruct
#define SERIALIZABLE_STRUCT_MEMBERS \
    SERIALIZABLE_STRUCT_MEMBER(int, foo) \
    SERIALIZABLE_STRUCT_MEMBER(double, bar) \
    SERIALIZABLE_STRUCT_MEMBER(short, baz)
#include "serializable-struct.h"


int main(void)
{
    MyStruct s;
    s.anEnum = enTwo;
    s.aChar = 4;
    s.aFloat = 3.14f;
    
    FILE *fp = fopen("output.dat", "wb");
    fwrite_MyStruct(&s, fp);
    
    printf("file size: %ld\nstruct size: %zu\n", ftell(fp), sizeof(MyStruct));
    fclose(fp);
}

serialiazable-struct.h

#define SERIALIZABLE_STRUCT_MEMBER(type, identifier) \
    type identifier;

typedef struct {
    SERIALIZABLE_STRUCT_MEMBERS
} SERIALIZABLE_STRUCT_NAME;

#define SERIALIZABLE_STRUCT_MAKENAME(functype, structname) \
    functype ## _ ## structname

#define SERIALIZABLE_STRUCT_DECLAREFUNC2(functype, structname) \
    static inline void SERIALIZABLE_STRUCT_MAKENAME(functype, structname) \
      (structname *obj, FILE *fp)

#define SERIALIZABLE_STRUCT_DECLAREFUNC(functype) \
    SERIALIZABLE_STRUCT_DECLAREFUNC2(functype, SERIALIZABLE_STRUCT_NAME)

#undef SERIALIZABLE_STRUCT_MEMBER
#define SERIALIZABLE_STRUCT_MEMBER(type, identifier) \
    fread(&(obj->identifier), sizeof(type), 1, fp);
    
SERIALIZABLE_STRUCT_DECLAREFUNC(fread) {
    SERIALIZABLE_STRUCT_MEMBERS
}

#undef SERIALIZABLE_STRUCT_MEMBER
#define SERIALIZABLE_STRUCT_MEMBER(type, identifier) \
    fwrite(&(obj->identifier), sizeof(type), 1, fp);

SERIALIZABLE_STRUCT_DECLAREFUNC(fwrite) {
    SERIALIZABLE_STRUCT_MEMBERS
}

#undef SERIALIZABLE_STRUCT_MEMBER
#undef SERIALIZABLE_STRUCT_DECLAREFUNC
#undef SERIALIZABLE_STRUCT_DECLAREFUNC2
#undef SERIALIZABLE_STRUCT_MAKENAME
#undef SERIALIZABLE_STRUCT_MEMBERS
#undef SERIALIZABLE_STRUCT_NAME

zz_output.txt

file size: 9
struct size: 12