type-conversion

问题 I have been searching for a solution for quite a while now and couldn't find anything close. What I want to achieve: I have two strings, 'a' and 'b'. String 'a' contains a datatype, for example "Boolean". String b contains a value like "1" or "False", could be anything. I want to be able to store the value of string 'b' in a variable which has the datatype of string 'a'. If I would itterate trough a list of results with the same values as given in the example the results would be as following

问题 So I'm doing some CTF and one of the challenge is about php type juggling. The code looks something like this if($_GET['var1'] == hash('md4', $_GET['var1'])) { //print flag } So I was 80% sure that I need to pass in an integer so it'll be true but all I can manipulate is the url. I tried using python request to do it but still failed. import requests url = 'http://example.com' params = dict(var1=0) r = requests.get(url=url, params=params) Is there any special case where php will treat the

问题 I've got 2 chars. Char 128 and Char 2 . How do I turn these chars into the Short 640 in C? I've tried unsigned short getShort(unsigned char* array, int offset) { short returnVal; char* a = slice(array, offset, offset+2); memcpy(&returnVal, a, 2); free(a); return returnVal; } But that didn't work, it just displays it as 128 . What's the preferred method? 回答1: I found that the accepted answer was nearly correct, except i'd run into a bug where sometimes the top byte of the result would be 0xff

问题 I want to avoid all lvalue conversions from a type to another type: struct A {}; struct T { A a; operator A() { return a; } //operator A&() = delete; how to delete lvalue conversions to A? }; void bar(A) {} void foo(const A&) {} void foo2(A&) {} int main() { T t; bar(t); // fine foo(t); // should never convert to ref-to-const A foo2(t); // should never convert to ref-to A return 0; } Is this possible? How and which conversion operators do I need to delete? Example on godbolt 回答1: You might do

问题 I can't figure out how to open a dng file in opencv. The file was created when using the pro options of the Samsung Galaxy S7. The images that are created when using those options are a dng file as well as a jpg of size 3024 x 4032 (I believe that is the dimensions of the dng file as well). I tried using the answer from here (except with 3 colors instead of grayscale) like so: import numpy as np fd = open("image.dng", 'rb') rows = 4032 cols = 3024 colors = 3 f = np.fromfile(fd, dtype=np.uint8

问题 How to prevent such code from compiling? #include <vector> #include <limits> #include <iostream> #include <cstdint> int main() { std::vector<int16_t> v; v.emplace_back(std::numeric_limits<uint64_t>::max()); std::cout << v.back() << std::endl; return 0; } g++ and clang with -std=c++14 -Wall -Wextra -Werror -pedantic -Wold-style-cast -Wconversion -Wsign-conversion don't even warn about it. The example also compiles without warnings with std::vector<uint16_t> 回答1: Add -Wsystem-headers to the

问题 I used double.Parse and Convert.ToDouble and got the same error System.FormatException: Input string was not in a correct format. When I write in console 10.2 or any other double number. I learnt from a tutorial and I followed it step by step but I have no idea how to solve this. Also I am using Visual Studio. Console.WriteLine("Enter a number: "); double num1 = double.Parse(Console.ReadLine()); Console.Write("Enter operator: "); string op = Console.ReadLine(); Console.WriteLine("Enter a

问题 I used double.Parse and Convert.ToDouble and got the same error System.FormatException: Input string was not in a correct format. When I write in console 10.2 or any other double number. I learnt from a tutorial and I followed it step by step but I have no idea how to solve this. Also I am using Visual Studio. Console.WriteLine("Enter a number: "); double num1 = double.Parse(Console.ReadLine()); Console.Write("Enter operator: "); string op = Console.ReadLine(); Console.WriteLine("Enter a

问题 Excel's datetime values look like 42291.60493, which means MySQL sees them as strings and not as dates. Is there a MySQL code that can convert them to MySQL datetime? (i.e. like in MS SQL) 回答1: I can think of 2 solutions: Convert your dates within excel to a formatted date string that conforms to mysql's date and time format using text() function within excel. Convert the number using calculation to date within mysql: (the expression below may be simplified) select date_add(date_add(date(

问题 I have a problem converting from a varchar '000000113754' to decimal 1137.54 I'm comparing two expressions: 1. select STUFF('000000113754', LEN('000000113754') - 1, 0, '.') 2. select STUFF([dbo].fn_PrepareNumeric(('000000113754' + '-'), '+','-'), LEN('000000113754') - 1, 0, '.') The function fn_PrepareNumeric just checks for the sign and appends '-' in front if the sign is - . That's all. The problem is that the first expression gives me the correct varchar - 0000001137.54 , and the second