Chain invocation in C programming language

c-chain-invocation.c

#include <glib.h>
#include <stdlib.h>
#include <stdio.h>

// MyJIT homepage: http://myjit.sourceforge.net/index.htm
#include "myjit/jitlib.h"

struct string_builder{
    GString *gstring;

    struct string_builder * (*append)(const char *s);
    const char *(*to_string)();
};

static struct string_builder *string_builder_append(struct string_builder *sb, const char *s){
    sb->gstring = g_string_append(sb->gstring, s);
    return sb;
}

static const char *string_builder_to_string(struct string_builder *sb){
    return sb->gstring->str;
}

void bind_zero2one(void *ptr_to_func, void *call_func, void *self){
    struct jit *p = jit_init();
    jit_prolog(p, ptr_to_func);

    jit_prepare(p);
    jit_putargi(p, self);
    jit_call(p, call_func);
    jit_retval(p, R(0));

    jit_retr(p, R(0));

    jit_generate_code(p);

    jit_free(p);
}

void bind_one2one(void *ptr_to_func, void *call_func, void *self){
    struct jit *p = jit_init();
    jit_prolog(p, ptr_to_func);
    jit_declare_arg(p, JIT_PTR, sizeof(const char *));

    jit_getarg(p, R(0), 0);

    jit_prepare(p);
    jit_putargi(p, self);
    jit_putargr(p, R(0));
    jit_call(p, call_func);
    jit_retval(p, R(0));

    jit_retr(p, R(0));

    jit_generate_code(p);
}

struct string_builder *create_string_builder(){
    struct string_builder *sb = g_new(struct string_builder, 1);
    sb->gstring = g_string_new(NULL);

    bind_one2one(&sb->append, string_builder_append, sb);
    bind_zero2one(&sb->to_string, string_builder_to_string, sb);

    return sb;
}

void string_builder_free(struct string_builder *sb){
    g_free(sb->gstring);
    g_free(sb);
}

int main(int argc, char const *argv[]) {
    struct string_builder *sb = create_string_builder();

    const char *result = sb
        ->append("hello\n")
        ->append("world\n")
        ->to_string();

    printf("%s", result);

    string_builder_free(sb);

    return 0;
}

不过，如果每个函数都这么写，太麻烦了。