How to save nested c struct data to disk?

Question

I have nested struct data in c . How to save _zend_op_array to file?

struct _zend_op {
    const void *handler;
    znode_op op1;
    znode_op op2;
    znode_op result;
    uint32_t extended_value;
    uint32_t lineno;
    zend_uchar opcode;
    zend_uchar op1_type;
    zend_uchar op2_type;
    zend_uchar result_type;
};

struct _zend_op_array {
    /* Common elements */
    zend_uchar type;
    zend_uchar arg_flags[3]; /* bitset of arg_info.pass_by_reference */
    uint32_t fn_flags;
    zend_string *function_name;
    zend_class_entry *scope;
    zend_function *prototype;
    uint32_t num_args;
    uint32_t required_num_args;
    zend_arg_info *arg_info;
    /* END of common elements */

    int cache_size;     /* number of run_time_cache_slots * sizeof(void*) */
    int last_var;       /* number of CV variables */
    uint32_t T;         /* number of temporary variables */
    uint32_t last;      /* number of opcodes */

    zend_op *opcodes;
    ZEND_MAP_PTR_DEF(void **, run_time_cache);
    ZEND_MAP_PTR_DEF(HashTable *, static_variables_ptr);
    HashTable *static_variables;
    zend_string **vars; /* names of CV variables */

    uint32_t *refcount;

    int last_live_range;
    int last_try_catch;
    zend_live_range *live_range;
    zend_try_catch_element *try_catch_array;

    zend_string *filename;
    uint32_t line_start;
    uint32_t line_end;
    zend_string *doc_comment;

    int last_literal;
    zval *literals;

    void *reserved[ZEND_MAX_RESERVED_RESOURCES];
};

Answer 1

You have a complicated structure with many pointers inside. The method to store depends on the data elements. I will give some general suggestions here.

• If you can ensure that that the number of fields are always constant (eg arg_info has a known number of elements) and that you will not have a semicolon in your data (or if present it is properly escaped) then you can define some sort of CSV format with semicolons separating the fields.

  • You will also need to write the number of elements in array first and then the array elements.
  • You will need to write your own functions for encoding and parsing.

• Another approach is to go for a structured format like JSON or XML. Maybe you can use some open source encoders and parsers for this.