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Convert byte slice to int slice
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I have written a LZW decoder algorithm in Go for a programming task required as part of a job application. A LZW code is a sequence of integers which can be decoded as a string. I have basically written a function that looks like this:
func LZWdecoder(code []int) string {
// * perform decoding *
return decodedString
}
They have provided me with a .z file which is encoded using LZW encoding so I can test my algorithm on it (it decodes to human readable text).
However, I don't know how to "load" that file into an integer slice that I can run through my function. Any help would be greatly appreciated.
Use import os then os.ReadFile("filename.z") should return a slice of bytes, which you can then convert to a slice of int using the method described here: Convert byte slice to int slice
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How do I convert a string to a structure?
The line looks like this: Name[data1] Name2[data1 data2 data3] Name3[data1 data2] ...
The data can be of type Int, String, or Float. In general, this is not important, you can write everything as string.
Data in brackets is separated by a space
What I got using regexp:
func Parse() {
str := "Version[2f0] Terminal[10002] Machine[10.1.1.1] DH[0.137%] Temp[45] Fan[0] Vo[4074 4042 4058 4098] CRC[0 0 0 0]"
j := make(map[string][]string)
re, err := regexp.Compile(`(?P<Name>[^ \[]*)\[(?P<Value>[^\]]*)`)
if err != nil {
log.Fatal(err)
}
res := re.FindAllSubmatch([]byte(str), -1)
for _, match := range res {
j[string(match[1])] = strings.Split(string(match[2]), " ")
}
log.Printf("%+v", j)
}
Could there be a more elegant way using json.Unmarshal?
You need to define a specific format for the serializing the data. A key part of that will be how to encode specific special characters, such as the [ and ]. You generally do not want to do this.
If you want to use any string as a temporary textual representation of your data and the format doesn't matter, you can just use JSON and use json.Marshal() and json.Unmarshal().
I'm not sure what you are trying to achieve (what's this struct data? what generated it? why are you trying to decode it into a struct?) but it seems that going through the fundamentals might be helpful:
https://en.wikipedia.org/wiki/Serialization will tell you what that is
https://betterprogramming.pub/serialization-and-deserialization-ba12fc3fbe23 is a very short guide that will give you the very basics (in JavaScript)
I already mentioned json.Marshal and json.Unmarshal - reading their docs in the standard library will be helpful as well.
I'm sure you can google the more in-depth articles when you identify what you need to know for your specific purposes.
If you're free to use any tool you like, a regular expression might make this fairly easy.
(?P<Name>\[^\[\]*)\[(?P<Values>\[^\]\]*)\]
That matches each of the named value sets.
and then you could split the Values group at the spaces with string.Split
To create a dynamic struct you'd need to use reflection. Avoid reflection, though, as you learn Go. A struct in Go is unlike an object in say Javascript or Python, where fields are dynamic at runtime. Go structs are meant to have static fields.
For this purpose, a map[string][]string would be a more appropriate type. The key would be the Name fields, and the value would be the data fields.
I am working on unpacking a binary file for the first time in Ruby. Already found the unpack method which works pretty nice. Which according to the docs works perfect for 8(1 byte),16(2 byte),32(4 byte) and 64 bit(8 byte).
But now I have to unpack 5 bytes. How do I do this?
Thx in advance!
To literally unpack five bytes: str.unpack 'C5'
That gives you five byte values as unsigned ints. The question is how to reinterpret those ints as a single data type. Pack/unpack only recognize the standard power of two sizes, so you'll have to do that part manually.
For example, to get a little endian unsigned 40-bit int
bytes = str.unpack 'C5'
int = bytes.map.with_index { |byte, i| byte << (i * 8) }.reduce(:+)
If you need to do something more sophisticated like a signed type or a float... good luck.
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How do I convert a String object into a Hash object?
(16 answers)
Closed 4 years ago.
I stored my nested hash in a file, and while retrieving it, I want to it back in a hash form instead of string. When I read a file it will give me a string and then how can I parse it back to a hash.
This is the string hash in the file:
{"SONGS"=>{1=>["2018-05-29 18:19:14 +0530", "HAPPY", "Meri Sapnon Ki Rani"]}}
Already in SO.
WARNING SECURITY RISK!
For your string you need to pass to eval, but this is a SECURITY RISK
string = '{"SONGS"=>{1=>["2018-05-29 18:19:14 +0530", "HAPPY", "Meri Sapnon Ki Rani"]}}'
p eval(string).class
If you need to store data structures in files, I suggest you to take a look at YAML module. Look at this post, for example.
As suggested in comments:
Consider also security concerns, look this post.
Consider to change a little bit the string syntax to use a JSON structure. See below.
Use of JSON:
require 'json'
json_string = '{"songs":{"1":{"date": "2018-05-29 18:19:14 +0530", "title":"HAPPY", "name":"Meri Sapnon Ki Rani"}}}'
p JSON::parse(json_string).class
This question already has an answer here:
Unable to decode gob data
(1 answer)
Closed 5 years ago.
Here is my playground where I am trying to serialize a list of structures and read back from the file.
https://play.golang.org/p/8x0uciOd1Sq
I was expecting the object to be decoded successfully. What am I doing wrong?
Export the field names by capitalizing the first letter.
type REntry struct {
Key string
Value []string
}
The gob package and other similar packages ignore unexported fields.
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VBScript equals problems
(1 answer)
Closed 8 years ago.
I am working on a VBScript login/signup program I already have the signup part done but then while logging in it has to read a line from a file with ReadLine() but the file must see if the line read and the text typed are equal variables and I don't know how to do this
For simple cases, the = operator
If sInput = sRead Then
...
Else
...
End If
works well; if you have to care for case(in)sensitivity, use StrComp().
The comparison is not affected by the way you obtained the strings. If your file justs contains the string that has to be matched,
sRead = tsIn.ReadLine()
before the comparisons will 'work'; if your file contains more than that, you'll have to publish (relevant parts of) its content and how the relevant data can be identified.