c_cpp 样本二进制表数据交换语言设置。

Posted 2021-05-14

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

/* prototype for binary dynamic table language
*/

/* @brief Used to traverse table data and dynamically type
 *        binary data.
 */
enum item_type_t {
	item_type_none,
	item_type_bool
};

/*
 * @brief Main object that encapsulates a table.
 * @data  An array of bytes holding the size, length,
 *        and object specific items of a table. 
 */
struct table_t {
	unsigned char* data;
	size_t size;
	size_t item_count;
};

// Fast inline function that writes sizing info to head of table.
static inline void
_write_size_info(unsigned char* b, size_t size, size_t items) {
	*(uint64_t*)(b) = (uint64_t)size;
	*(uint64_t*)(b + sizeof(uint64_t)) = (uint64_t)items;
}

static void
_table_init(struct table_t* table, size_t size, size_t items) {
	table->data = malloc(size);
	table->size = size;
	table->item_count = items;
	_write_size_info(table->data, size, items);
}


int main(int argc, char const *argv[])
{
	struct table_t foo;
	_table_init(&foo, 50, 5);
	printf("size is %llu, item count is %llu\n", *(uint64_t*)(foo.data), *(uint64_t*)(foo.data + sizeof(uint64_t)));
	return 0;
}