d := make([]byte, 4096)
conn.Read(d)
I created a fixed array to get data from the socket.
But I want to get the data in a flexible size rather than a fixed size.
The reason is that i need to unmarshal the data received from the socket, but the data is fixed in size, so calling the unmarshal function will not work.
So what I want to ask is how to get the data from the socket in a flexible size or how to delete empty values from a fixed size.
ex)
data := make([]byte, 4096)
conn.Read(data)
fmt.Println(len(data)) ===> 105 (Actual data length)
or
data([4, 128, 16, 8, 7, 0, 0, 0, 0, 7, 9, 128, 0...])
↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓↓
data([4, 128, 16, 8, 7, 0, 0, 0, 0, 7, 9, 128])
For example,
data := make([]byte, 0, 4096)
n, err := conn.Read(data[:cap(data)])
data = data[:n]
if err != nil {
// handle error
}
fmt.Println(len(data))
Related
I have a list of int like the following.
List<int> data = [52, 24, 40, 0, 198, 7, 98, 0, 0, 0, 40, 223, 30, 0, 203, 244, 0, 0]
I would like to generate 8/16/32 Uint so that I can process them. For example, bytes 2 & 3 is actually a 16 bit value, so both bytes need to be added, in the right order which in this case is 00000000 00101000 .
Question: How can I target specific index to add to a specific Uint type?
eg.. Uint16 powerValue = data[2] data[3];
Presuming that your List<int> is meant to be a list of bytes, convert your List<int> into a Uint8List with Uint8List.fromList. Note that your List<int> might already be a Uint8List; if so, just cast it with as Uint8List to avoid an unnecessary copy.
Access the Uint8List.buffer getter to obtain the underlying ByteBuffer.
You then can use methods such as ByteBuffer.asUint16List, ByteBuffer.asUint32List, etc. These methods allow you to specify a starting offset and length.
Alternatively, if you need more control (for example, if you want to interpret bytes using the non-native endianness), then you can use ByteBuffer.asByteData to obtain a ByteData view that provides methods such as getUint16, getUint32, etc.
Putting it all together, for your specific example:
import 'dart:typed_data';
void main() {
List<int> data = [
52,
24,
40,
0,
198,
7,
98,
0,
0,
0,
40,
223,
30,
0,
203,
244,
0,
0
];
var bytes = Uint8List.fromList(data);
var powerValue = bytes.buffer.asByteData().getUint16(2, Endian.little);
print(value); // Prints: 40
}
Of course, if this is just something you need to do as a one-off case, you also could just do bitwise operations yourself:
var powerValue = (data[3] << 8) | data[2];
I'm developing a flutter app using the flutter_blue library to interface a BlueNRG-tile from STMicroelectronics. I'm receiving the the raw data from the desired caracteristics then i'm note able ble to convert them to string using the utf8.decode() function.
This is the received data as a list and the issue.
I/flutter (32277): Teste conversion : [121, 85, 0, 0, 209, 133, 1, 0, 5, 10, 237, 0, 0, 0]
E/flutter (32277): [ERROR:flutter/lib/ui/ui_dart_state.cc(199)] Unhandled Exception: FormatException: Missing extension byte (at offset 11).
the code from the in the st board:
tBleStatus Environmental_Update(int32_t Press,int32_t Press2,uint16_t Hum, int16_t Temp,int16_t Temp2) {
uint8_t BuffPos = 0;
STORE_LE_16(buff, (getTimestamp()));
BuffPos = 2;
STORE_LE_32(buff + BuffPos, Press);
BuffPos += 4;
STORE_LE_16(buff + BuffPos, Hum);
BuffPos += 2;
STORE_LE_16(buff + BuffPos, Temp);
BuffPos += 2;
STORE_LE_16(buff + BuffPos, Temp2);
return aci_gatt_update_char_value(HWServW2STHandle, EnvironmentalCharHandle, 0, EnvironmentalCharSize, buff);
}
Environmental_Update(PressToSend,PressToSend2, HumToSend, TempToSend,TempToSend2);
Thank You.
You are not able to convert your RAW data to string because you are not sending it as string but in form of bytes.
Take your temperature for example:
You receive the temperature as int16_t, a 16-bit number storing values from –32768 to 32767. This number needs two bytes to be stored, that's why you used BuffPos += 2; and increased the position by 2 bytes.
You need to extract the values from your received array the same way, bytewise. Have a look at this example:
import 'dart:typed_data';
int fromBytesToInt16(int b1, int b0) {
final int8List = new Int8List(2)
..[1] = b1
..[0] = b0;
return ByteData.sublistView(int8List).getInt16(0);
}
void main() {
var received = [121, 85, 0, 0, 209, 133, 1, 0, 5, 10, 237, 0, 0, 0];
var temp = fromBytesToInt16(received[8], received[9]) / 100;
print('temperature: $temp');
}
The temperature was stored as a int16 at index 8 and 9 so I converted it the same way. This results in a temp value of 2565, which divided by 100 would give a pretty nice temperature of 25.65 degree
I'm getting a byte array like this one:
[60, 2, 0, 0, 0]
In the documentation there is written this:
uint16 -> heartBeatNum;
uint8 -> rawDataFilesNum;
uint8 -> alertNum
uint8 -> fallsNum
I will explain a little about the device so that you understand and then I ask my question.
The bluetooth device sends an object every minute that is called heartbeat. If this is the first time the object is to use the array looks like this:
After first minute:
[1, 0, 0, 0, 0]
After two minute:
[2, 0, 0, 0, 0]
After three minute:
[3, 0, 0, 0, 0]
After for minute:
[4, 0, 0, 0, 0]
...
Now there are more than 12 that have passed and the array is:
[60, 2, 0, 0, 0]
So I try to understand from the documentation the heartbeat count is the first 16 bytes. I can not figure out how to collect the 60's and the 2's to have the exact heartbeat number.
How does this function?
According to my calculation if I do 60 * 12 = 720
So I should have about 700
Can someone enlighten me how to gather the 16 bytes in int?
Say I have an array of Ints and all elements equal zero. It'd look something like this:
let arr: [Int] = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
There are 11 elements in this array in total. I want three of the elements in this array to be the number one. I want these one values to be distributed evenly throughout the array so that it looks something like this:
[0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0]
I want to be able to add however many one's and distribute them evenly (or as close to evenly as possible) no matter how many total elements there are. How could I do this?
Note: For anyone wondering why I need this, I have a collection of strings that when joined together make up a large body of text. Think of the zeroes as the pieces of text and think of the ones as advertisements I am adding in between the text. I wanted to distribute these ads as evenly as possible. I figured this would be a simple way of expressing what I needed.
Maybe you can try this.
var arr: [Int] = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
let distribution = arr.count / 3 // 3 is the number of 1s
for (index, value) in arr.enumerated() {
arr[index] = (index + 1) % distribution == 0 ? 1 : value
}
print(arr) // [0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0]
Assuming that the value distribution > 1
I'm using textscan to import data. I can get to it successfully import properly formatted data. I can't get it to properly handle data that isn't properly formatted. Below is the format of the data.
JeB2021Da 12-13 and stuff, 1, 1, 0, 1, 0, 1, 1, 1, 3, 1, 99, 0, 0, 0,
JoB2021Ha 12-13 and stuff, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 99, 2, 1, 0,
JoP2021Co 12-13 and stuff, not enough samples
MaA2021Be 12-13 and stuff, 1, 1, 0, 0, 0, 1, 1, 0, 1, 0, 99, 1, 0, 0,
MaA2021Ma 12-13 and stuff, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 99, 1, 0, 0,
How would I handle the data that is, not enough samples? Because currently the data structures don't line up. The data structures that are being produced are 17 x 1 and 16 x 14. I'd like to import the string as it is in the data. So not enough samples would be imported. Below is the code that I'm using.
fid = fopen('./file.txt','r');
fmt = ['%s %d %d %d %d %d %d %d %d %d %d %d %d %d %d'];
d = textscan(fid, fmt, 'CollectOutput', 1,'Delimiter',',','headerLines', 1, 'EmptyValue', 0);
I'm trying to handle it with the EmptyValue flag but it's not working. Any help is greatly appreciated.
I am not sure what exactly you mean by I'd like to import the string as it is in the data, or more exactly where you would like to have that string stored.
But about just reading your data as a whole you can use the 'TreatAsEmpty' argument:
d = textscan(fid, fmt, 'CollectOutput', 1,'Delimiter',',','headerLines', 1,'TreatAsEmpty','not enough samples');
Then you can modify the input further by looking for the rows in the imported data array that solely consist of zeros.