Mach-O 文件解析：压缩格式的 ulint 数据解析函数

#include 'mach0data.h'

#ifdef UNIV_NONINL #include 'mach0data.ic' #endif

/*************************************************/ Reads a ulint in a compressed form if the log record fully contains it. @return pointer to end of the stored field, NULL if not complete / UNIV_INTERN byte mach_parse_compressed( /==================/ byte ptr, /!< in: pointer to buffer from where to read / byte end_ptr,/!< in: pointer to end of the buffer / ulint val) /!< out: read value (< 2^32) */ { ulint flag;

ut_ad(ptr && end_ptr && val);

if (ptr >= end_ptr) {

	return(NULL);
}

flag = mach_read_from_1(ptr);

if (flag < 0x80UL) {
	*val = flag;
	return(ptr + 1);

} else if (flag < 0xC0UL) {
	if (end_ptr < ptr + 2) {
		return(NULL);
	}

	*val = mach_read_from_2(ptr) & 0x7FFFUL;

	return(ptr + 2);

} else if (flag < 0xE0UL) {
	if (end_ptr < ptr + 3) {
		return(NULL);
	}

	*val = mach_read_from_3(ptr) & 0x3FFFFFUL;

	return(ptr + 3);
} else if (flag < 0xF0UL) {
	if (end_ptr < ptr + 4) {
		return(NULL);
	}

	*val = mach_read_from_4(ptr) & 0x1FFFFFFFUL;

	return(ptr + 4);
} else {
	ut_ad(flag == 0xF0UL);

	if (end_ptr < ptr + 5) {
		return(NULL);
	}

	*val = mach_read_from_4(ptr + 1);
	return(ptr + 5);
}

}