C struct中的位域 bitfield 结构体的成员可以限制其位域,每个成员可以使用用比字节还小的取值范围,下面的结构体s1中,四个成员每个成员都是2bit的值(0~3),整个结构体占据的空间依然是4个字节,但是第一个字节中表示了四个成员,后续三个字节没有用到。 struct{unsignedchara :2;unsignedcharb :2;unsignedcharc...
Bit Field Storage in C Consider the following structure to start a discussion on bit field storage: struct{unsignedcharis_married;unsignedcharis_graduated;}status0; This structure requires two bytes of memory space; however, we have to store either 0 or 1 in both fields. Let’s move ahead to...
How To Implement a Bit Field in the C Program 1 2 3 4 5 6 7 8 9 10 11 structdate { unsignedintd; unsignedintm; unsignedinty; }; Explanation The variable of type, “date”, takes 12 bytes on a compiler which are 32 bits on a 64-bit compiler, whereas “date” takes 6 bytes ...
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' ...
struct { /* field 4 bits wide */ unsigned field1 :4; /* * unnamed 3 bit field * unnamed fields allow for padding */ unsigned :3; /* * one-bit field * can only be 0 or -1 in two's complement! */ signed field2 :1; ...
Note An unnamed bit field of width 0 forces alignment of the next bit field to the next type boundary, where type is the type of the member. The following example declares a structure that contains bit fields struct Date{ unsigned nWeekDay : 3; // 0..7 (3 bits) unsigned nMonthDay ...
Bit-fields are a remnant of C and can only be used as struct or union fields. In my opinion, there is no situation where a static bit-field member would be beneficial. In my opinion, allowing static data to behave in a way that is entirely implementation defined is not a good idea,...
A bit field is interpreted as an integral type. Syntax struct-declarator: declarator type-specifier declaratoropt : constant-expression The constant-expression specifies the width of the field in bits. The type-specifier for the declarator must be unsigned int, signed int, or int, and ...
struct { unsigned int fieldA : 4 ; unsigned int fieldB : 2 ; unsigned int fieldC : 1 ; } ; 这是c语言的特性,很少人使用。 fieldA代表将占用4个二进制位,fieldB代表占用2个二进制位,fieldC代表占用1个二进制位。于是,fieldA可以表示0到127之间的值,fieldC可以表示0或1这俩个值。
C Bit Fields - Learn about C Bit Fields, their significance, and how to use them effectively in your C programming projects.