bit | 易学教程

What does ~0 do?

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问题 Does ~0 mean its flipping 000000000 to 1111111111? printf("Check: %i", ~0); The printf results to -1, which is why I am confused. Does -1 essentially mean the same thing as 11111111111111111 bits? 回答1: Does ~0 mean its flipping 000000000 to 1111111111? Yes, it does. Does -1 essentially mean the same thing as 11111111111111111 bits? In 2s complement representation, it does. 回答2: Does ~0 mean its flipping 000000000 to 1111111111? Yes, that's what it means. printf("Check: %i", ~0); The printf

Java Iterate Bits in Byte Array

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问题 How can i iterate bits in a byte array? 回答1: You'd have to write your own implementation of Iterable<Boolean> which took an array of bytes, and then created Iterator<Boolean> values which remembered the current index into the byte array and the current index within the current byte. Then a utility method like this would come in handy: private static Boolean isBitSet(byte b, int bit) { return (b & (1 << bit)) != 0; } (where bit ranges from 0 to 7). Each time next() was called you'd have to

How can I cast an int to a bit in MySQL 5.1?

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问题 I am transitioning from SQL Server to MySQL 5.1 and seem to be tripped up trying to create a table using a select statement so that the column is a bit. Ideally the following would work: CREATE TABLE myNewTable AS SELECT cast(myIntThatIsZeroOrOne as bit) AS myBit FROM myOldtable However sql is very unhappy at casting as a bit. How can I tell it to select an int column (which I know only has 0s and 1s) as a bit? 回答1: You cannot! CAST and CONVERT only work to: BINARY[(N)] CHAR[(N)] DATE

IBM Single Precision Floating Point data conversion to intended value

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问题 I need to read values from a binary file, the data format is IBM single Precision Floating Point (4-byte Hexadecimal Exponent Data) and use the value as a decimal number. I have C++ code that reads from the file and takes out each byte and stores it like so unsigned char buf[BUF_LEN]; for (long position = 0; position < fileLength; position += BUF_LEN) { file.read((char* )(&buf[0]), BUF_LEN); // printf("\n%8ld: ", pos); for (int byte = 0; byte < BUF_LEN; byte++) { // printf(" 0x%-2x", buf[byte

Bitwise operator for simply flipping all bits in an integer?

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问题 I have to flip all bits in a binary representation of an integer. Given: 10101 The output should be 01010 What is the bitwise operator to accomplish this when used with an integer? For example, if I were writing a method like int flipBits(int n); , what would go in the body? I need to flip only what's already present in the number, not all 32 bits in the integer. 回答1: The ~ unary operator is bitwise negation. If you need fewer bits than what fits in an int then you'll need to mask it with &

What does “real*8” mean?

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问题 The manual of a program written in Fortran 90 says, "All real variables and parameters are specified in 64-bit precision (i.e. real*8 )." According to Wikipedia, single precision corresponds to 32-bit precision, whereas double precision corresponds to 64-bit precision, so apparently the program uses double precision. But what does real*8 mean? I thought that the 8 meant that 8 digits follow the decimal point. However, Wikipedia seems to say that single precision typically provides 6-9 digits

2019 SDN上机第7次作业 CWC

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1. 根据 P4教程，将basic和basic_tunnel两个案例程序补充完整，成功运行。 basic 完整之程序及运行截图 /* -*- P4_16 -*- */ #include <core.p4> #include <v1model.p4> const bit<16> TYPE_IPV4 = 0x800; /************************************************************************* *********************** H E A D E R S *********************************** *************************************************************************/ typedef bit<9> egressSpec_t; typedef bit<48> macAddr_t; typedef bit<32> ip4Addr_t; header ethernet_t { macAddr_t dstAddr; macAddr_t srcAddr; bit<16> etherType; } header ipv4_t { bit<4> version; bit<4> ihl; bit<8>

2019 SDN上机第7次作业

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1.补充并运行basic代码任务是实现基础的交换机转发数据包功能将basic.p4补充完整后，代码如下： #include <core.p4> #include <v1model.p4> const bit<16> TYPE_IPV4 = 0x800; /************************************************************************* *********************** H E A D E R S *********************************** *************************************************************************/ typedef bit<9> egressSpec_t; typedef bit<48> macAddr_t; typedef bit<32> ip4Addr_t; header ethernet_t { macAddr_t dstAddr; macAddr_t srcAddr; bit<16> etherType; } header ipv4_t { bit<4> version; bit<4> ihl; bit<8> diffserv; bit<16> totalLen; bit<16

2019 SDN上机第7次作业

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1.根据P4教程，将basic和basic_tunnel两个案例程序补充完整，成功运行。 i.basic /* -*- P4_16 -*- */ #include <core.p4> #include <v1model.p4> const bit<16> TYPE_IPV4 = 0x800; /************************************************************************* *********************** H E A D E R S *********************************** *************************************************************************/ typedef bit<9> egressSpec_t; typedef bit<48> macAddr_t; typedef bit<32> ip4Addr_t; header ethernet_t { macAddr_t dstAddr; macAddr_t srcAddr; bit<16> etherType; } header ipv4_t { bit<4> version; bit<4> ihl; bit<8> diffserv; bit<16

2019 SDN上机第7次作业

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1.根据P4教程，将basic和basic_tunnel两个案例程序补充完整，成功运行。补充并运行basic代码 #include <core.p4> #include <v1model.p4> const bit<16> TYPE_IPV4 = 0x800; /************************************************************************* *********************** H E A D E R S *********************************** *************************************************************************/ typedef bit<9> egressSpec_t; typedef bit<48> macAddr_t; typedef bit<32> ip4Addr_t; header ethernet_t { macAddr_t dstAddr; macAddr_t srcAddr; bit<16> etherType; } header ipv4_t { bit<4> version; bit<4> ihl; bit<8> diffserv; bit<16> totalLen; bit