关键就在这其中的bit-field是如何解释成-14和-2的。 从结果来看,可以知道:bitstruct的3个field都在同一个存储单元内,并且由于x86是little-endian的,数据从内存读到寄存器之后字节序就反了过来,高位字节到低位字节的顺序是“从右向左”;对应的,解释bitstruct中的各field时也从右向左来读。 寄存器中的b: 'n' ...
还是在C99规范的6.7.2.1节里,规范规定了可以对struct中的field显式指定宽度(以bit为单位);显式指定了宽度的field被称为bit-field。规范中同一小节中的第10点有如下说明: 引用 An implementation may allocate any addressable storage unit large enough to hold a bitfield. If enough space remains, a bit-fiel...
structiphdr {#ifdefined(__LITTLE_ENDIAN_BITFIELD)__u8 ihl:4, version:4;#elifdefined (__BIG_ENDIAN_BITFIELD)__u8 version:4, ihl:4;#else#error"Please fix <asm/byteorder.h>"#endif__u8 tos; __be16-tot_len; __be16-id; __be16-frag_off; __u8 ttl; __u8 protocol; __be16-ch...
问struct ip与struct iphdr的区别EN1. 基本解释 typedef为C语言的关键字，作用是为一种数据类型定...
#if defined(__LITTLE_ENDIAN_BITFIELD) __u8 ihl:4, version:4; #elif defined (__BIG_ENDIAN_BITFIELD) __u8 version:4, ihl:4; #else #error "Please fix<asm/byteorder.h>" #endif __u8 tos; __be16 -tot_len; __be16 -id; ...
* Indicates order in the buddy system if PageBuddy. */ unsigned long private; }; struct { /* page_pool used by netstack */ /** * @dma_addr: might require a 64-bit value even on * 32-bit architectures. */ dma_addr_t dma_addr; ...
Within a struct object, addresses of its elements (and the addresses of the bit field allocation units) increase in order in which the members were defined. A pointer to a struct can be cast to a pointer to its first member (or, if the member is a bit field, to its allocation unit)...
(That is, an implementation may sign-extend a bitfield when it's used in comparisons, passed as a parameter, and so on. The "1" you assigned to a 1-bit bitfield might turn into a -1.) It's up to the implementation what order bitfields are allocated in those ints, and whether ...
structiphdr {#ifdefined(__LITTLE_ENDIAN_BITFIELD)__u8 ihl:4, version:4;#elifdefined (__BIG_ENDIAN_BITFIELD)__u8 version:4, ihl:4;#else#error"Please fix <asm/byteorder.h>"#endif__u8 tos; __be16-tot_len; __be16-id; __be16-frag_off; ...
* Indicates order in the buddy system if PageBuddy. */ unsigned long private; }; struct { /* page_pool used by netstack */ /** * @dma_addr: might require a 64-bit value even on * 32-bit architectures. */ dma_addr_t dma_addr; ...