I am using Z-stack-CC2530-2.5 for developing Zigbee-based application. I've come across a timestmap conversion problem.
I am using osal_ConvertUTCTime method to convert a uint32 timestamp value to timestampStruct as follows:
osal_ConvertUTCTime(& timestampStruct, timestamp);
The Struct is defined as follows:
typedef struct{
uint8 seconds;
uint8 min;
uint8 hour;
uint8 day;
uint8 month;
uint16 year;
} UTCTimeStruct
My Question:
How to convert the Struct's content to be written on the UART port in a human readable format ?
Example:
HalUARTWrite (Port0, timestampStruct, len) // Output: 22/1/2013 12:05:45
Thank you.
I do not have the prototype of the function HalUartWrite at the moment, but I googled it and someone used it as this:
HalUARTWrite(DEBUG_UART_PORT, "12345", 6);
so I guess the second argument must be a pointer to char. You can't just pass a struct UTCTimeStruct variable into the second argument. If you just need to output the raw data to the serial port. You need to cast the struct into char * in order to make the compiler happy. But generally, this is bad practice. This might not be a problem in your case as you work in a 8-bit processor that all the struct fields are either a char or a short. In general, if you cast a struct into a char * and print it out, due to struct padding, you get a lot of nonsense characters between your struct fields.
OK. A bit off topic. Back to your question, you need to convert the struct into a friendly string yourself. Because you know your output string is of format "22/1/2013 12:05:45" which has fixed length, you can simply declare a char[] of that length. And manually fill in the numbers by bit-manipulating the uint32 timestamp value. After that, you can pass the char[] into the second argument and the exact length into the third argument.
Related
I am exposing a PyMemoryView in C on a set of data, like so:
PyMemoryView_FromMemory((char *)ibuf->rect, pixels * sizeof(uint), PyBUF_WRITE);
That data is floating-point data, however, so attempting to do this:
mv = get_my_memory_view()
mv[0] = 3.141
yields the following error:
TypeError: memoryview: invalid type for format 'B'
This is, of course, because the memoryview assumes the underlying data to be byte data, not float. How would I ensure that the memoryview returned from my module has a float specifier?
The easiest way would probably be to use the cast method of the memoryview to get a new memoryview with the correct format. There isn't a direct C-API method to do it, so just call it like any other Python method:
mview_double = PyObject_CallMethod(mview_bytes, "cast", "s", "d");
this assumes double data - if it's float data then you should change the "d".
In the original call to PyMemoryView_FromMemory I think pixels * sizeof(uint) is wrong since you've told us the data-type is a floating-point type. Maybe pixels*sizeof(ibuf->rect[0])?
I am well aware that one is able to assign a value to an array or constant in Swift and have those value represented in different formats.
For Integer: One can declare in the formats of decimal, binary, octal or hexadecimal.
For Float or Double: One can declare in the formats of either decimal or hexadecimal and able to make use of the exponent too.
For instance:
var decInt = 17
var binInt = 0b10001
var octInt = 0o21
var hexInt = 0x11
All of the above variables gives the same result which is 17.
But what's the catch? Why bother using those other than decimal?
There are some notations that can be way easier to understand for people even if the result in the end is the same. You can for example think in cases like colour notation (hexadecimal) or file permission notation (octal).
Code is best written in the most meaningful way.
Using the number format that best matches the domain of your program, is just one example. You don't want to obscure domain specific details and want to minimize the mental effort for the reader of your code.
Two other examples:
Do not simplify calculations. For example: To convert a scaled integer value in 1/10000 arc minutes to a floating point in degrees, do not write the conversion factor as 600000.0, but instead write 10000.0 * 60.0.
Chose a code structure that matches the nature of your data. For example: If you have a function with two return values, determine if it's a symmetrical or asymmetrical situation. For a symmetrical situation always write a full if (condition) { return A; } else { return B; }. It's a common mistake to write if (condition) { return A; } return B; (simply because 'it works').
Meaning matters!
I am just not able to convert different datatypes in c++,I know that c++ is a strong type language so,I
used here static_cast but I am facing a problem the error messages are
invalid static_cast from type 'std::string {aka std::basic_string}' to type 'int'
invalid conversion from 'int' to 'const char*' [-fpermissive]
#include <vector>
#include <iostream>
using namespace std;
int main()
{
string time;
string t2;
cin >> time;
int hrs;
for(int i=0;i!=':';i++)
{
t2[i]=time[i];
}
hrs=static_cast<int>(t2);
hrs=hrs+12;
t2=static_cast<string>(hrs);
for(int i=0;i!=':';i++)
{
time[i]=t2[i];
}
cout<<time;
return 0;
}
Making a string from an int (and the converse) is not a cast.
A cast is taking an object of one type and using it, unmodified, as if it were another type.
A string is a pointer to a complex structure including at least an array of characters.
An int is a CPU level structure that directly represents a numeric value.
An int can be expressed as a string for display purposes, but the representation requires significant computation. On a given platform, all ints use exactly the same amount of memory (64 bits for example). However, the string representations can vary significantly, and for any given int value there are several common string representations.
Zero, as an int on a 64 bit platform, consists of 64 bits at low voltage. As a string, it can be represented with a single byte "0" (high voltage on bits 4 and 5, low voltage on all other bits), the text "zero", the text "0x0000000000000000", or any of several other conventions that exist for various reasons. Then you get into the question of which character encoding scheme is being used - EBCDIC, ASCII, UTF-8, Simplified Chinese, UCS-2, etc.
Determining the int from a string requires a parser, and producing a string from an int requires a formatter.
I am a complete beginner with the D language.
How to get, as an uint unsigned 32 bits integer in the D language, some hash of a string...
I need a quick and dirty hash code (I don't care much about the "randomness" or the "lack of collision", I care slightly more about performance).
import std.digest.crc;
uint string_hash(string s) {
return crc320f(s);
}
is not good...
(using gdc-5 on Linux/x86-64 with phobos-2)
While Adams answer does exactly what you're looking for, you can also use a union to do the casting.
This is a pretty useful trick so may as well put it here:
/**
* Returns a crc32Of hash of a string
* Uses a union to store the ubyte[]
* And then simply reads that memory as a uint
*/
uint string_hash(string s){
import std.digest.crc;
union hashUnion{
ubyte[4] hashArray;
uint hashNumber;
}
hashUnion x;
x.hashArray = crc32Of(s); // stores the result of crc32Of into the array.
return x.hashNumber; // reads the exact same memory as the hashArray
// but reads it as a uint.
}
A really quick thing could just be this:
uint string_hash(string s) {
import std.digest.crc;
auto r = crc32Of(s);
return *(cast(uint*) r.ptr);
}
Since crc32Of returns a ubyte[4] instead of the uint you want, a conversion is necessary, but since ubyte[4] and uint are the same thing to the machine, we can just do a reinterpret cast with the pointer trick seen there to convert types for free at runtime.
I have a struct in matlab called mystruct
It has the following fields with the following classes:
Field Class
a single
b single
c double
I want to convert all fields of mystruct to class double, but when I try:
double(mystruct)
I get the following output from MATLAB:
??? Error using ==> double
Conversion to double from struct is not possible.
Futhermore, I am giving mystruct as just an example. I realize I could just individually cast each field manually since there are only 3 fields in this example. I am wondering how do this this conversion to double for any structure in matlab with many fields and subfields.
For scalar structs (numel(mystruct) is 1) the answer of Luis Mendo is probably the best solution. For other structs use this code:
cell2struct(cellfun(#double,struct2cell(mystruct),'uni',false),fieldnames(mystruct),1)
It converts the struct to a cell, then converts each element to double and converts back to a struct.
You can use structfun for that:
mystruct = structfun(#double, mystruct, 'uniformoutput', 0);