I used to have several open-source projects available on CodePlex. At the end of 2017, the site was put in read-only mode and it will probably be closed at some point. Therefore, I have decided to move the projects that could still be useful to GitHub.

MFC Collection Utilities
A small library that enables developers to use MFC containers (arrays, lists, maps) with range-based for loops. The library consists of a single header that you include in your MFC projects.

See:

 

cppconlib
A header-only C++ template library for manipulating the settings of a Windows console (colors, text position, input mode, etc.)

See:

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Four years ago I wrote a blog post that shown how to build a web server using the http_listener from the C++ REST SDK library as well as a client application that consumed the exposed resources. Over the years there have been various changes to the API from the library and some readers complained the code no longer compiled. Eventually, I decided to revisit that post and update my code to the latest version of the library, which at this time is 2.10.

I will not reiterate all the details described in the former article. However, in summary, the server maintains a dictionary of values (both keys and values are strings). Through HTTP calls a client can retrieve the content of the dictionary, add new values, update or delete existing ones.

HTTP method Description Request Response
GET retrieves all the key-value pair from the dictionary {"one" : "100", "two" : "200"}
POST retrieves the values of the specified keys from the dictionary ["one", "two", "three"] {"one" : "100", "three" : "", "two" : "200"}
PUT inserts new pairs of key-values in the dictionary; if a key is already found its value is updated {"one" : "100", "two" : "200"} {"one" : "", "two" : ""}
DELETE deletes the specified keys from the dictionary ["one"] {"one" : ""}

Here is the server code:

And this is the client code:

Notice there are slight changes in the way output is formatted, both in the server and the client application. The rest is mostly unchanged, except for the handling of JSON, that has changed significatly since version 1.1. Again, please see the original post for an explanation of the code.

The output from running these client and server applications is shown below. On the left is the client output, and on the right the server output.

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But why?

Today I wanted to rework an example that I wrote years ago. I was a client-server example using the C++ REST SDK. I haven’t worked with the library for a while, so I needed to install the latest version first.

If you go to the C++ REST SDK project page it says you need to run the following command to install it:

For that, you need the vckpg package management system for C and C++ libraries on Windows. Getting and installing it is not that hard: you have to either clone the git repo or download and unzip it locally. Then you need to run two commands:

So I did all that and then installed the C++ REST SDK. It took about one hour and 11GB (!!) of disk storage for this. It had to download, build and install the following libraries:

  • boost:x86-windows
  • boost:x64-windows
  • bzip2:x86-windows
  • bzip2:x64-windows
  • cpprestsdk:x86-windows
  • cpprestsdk:x64-windows
  • openssl:x86-windows
  • openssl:x64-windows
  • websocketpp:x86-windows
  • websocketpp:x64-windows
  • zlib:x86-windows
  • zlib:x64-windows

This is utterly insane. All that I want is some headers and a few static and dynamic libraries. But instead I got 11GB of God knows what and waited about one hour before I could start to work.

Why is all this necessary? Why do I have to care about all this provisioning process? We don’t care about your time and resources, we’re cool we can do this with scripts? Seriously? What happened to the good old fashion of downloading an archive with everything you needed already built for you? Now you first need to install 400MB of Perl to be able to build and get going with a C++ library. It’s sad.

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Computing day of year in C++

I have been recently asked on my post on the date library if the library has a function for computing the day of the year. It actually does not, although it is fairly simple to compute it.

UPDATE: Howard Hinnant has shown in a comment below how to write a day_of_year() function using the date libray.

Let’s look at the days of the year.

Day Day of year
January 1 1
January 2 2
January 31 31
February 1 32
February 28 59

Here is where things complicate a bit, because during leap years February has 29 days. So we actually need to have two counts of days.

Day Day of non-leap year Day of leap year
January 1 1 1
January 2 2 2
January 31 31 31
February 1 32 32
February 28 59 59
February 29 N/A 60
March 1 60 61
December 31 365 366

It is fairly simple to compute the day of the year based on the day of the month if we knew the day of the year of each first day of the month. That can be also put in a table.

Day of month Day of non-leap year Day of leap year
January 1 1 1
February 1 32 32
March 1 60 61
April 1 91 92
May 1 121 122
June 1 152 153
July 1 182 183
August 1 213 214
September 1 244 245
October 1 274 275
November 1 305 306
December 1 335 336

So we can compute the day of the year as:

We can simplify that a bit by subtracking 1 from the day of the year values in the table above, such that January 1st is the day 0, February 1st is day 31, etc.

The following code sample shows how this can be written in C++:

And how it can be used:

This day_of_year() function can be used with the date library too. I’ll just add one more utility function that takes a date::year_month_day value and returns the day of the year.

And we want to know what day of the year today is then we can do that too:

The day_of_year() function is very simple and does not do any argument checks. That makes it possible to compute dates such as 2017.08.55 or 2017.55.100. Obviously, these not only that do not make sense, but indexing the days_to_month array beyond its bounds is undefined behavior. That means that in practice you should write a function that validates the arguments and throws an exception upon error. However, in this case, the day_of_year() can not be constexpr anymore.

This would throw an exception on dates like 2017.13.1 or 2017.1.50, but would not do so for 2017.2.30 or 2017.11.31 that are also invalid dates. That can be further corrected by verifying that the day of the month does not exceed the number of days that month can have in the given year.

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C++11 added a date and time utility library called chrono, available in namespace std::chrono and header <chrono>. The problem with it is that the library is a general purpose one and therefore lacks many useful features, such as working with dates, weeks, calendars, timezones and other related features. Fortunately, a rich date and time library based on chrono has been created by Howard Hinnant and is available on github. The library is called date and is actually a collection of several small libraries:

  • date: the main library, available in header date.h, defines new date and time classes and operations with them. All the other libraries are based on this one.
  • timezones: a library for timezones, available in files tz.h/tz.cpp, based on the IANA timezone database
  • chrono_io: a library for streaming durations, available in header chrono_io.h
  • iso_week: a library that implements the ISO week calendar, available in header iso_week.h
  • julian and islamic: libraries that implement the Julian and Islamic calendars, available in headers julian.h and islamic.h

You can find all the necessary documentation on github. Here are several links:

In this article we will look at some examples for working with dates and ISO weeks. This library introduces many new types to handle various date and time representations. Among these we will look at:

  • sys_days: A count of days since std::system_clock‘s epoch. This is a time_point with a resolution of a day, and is implicitly convertible to std::system_clock::time_point, that has a much smaller resolution (millisecond or nanosecond), but not the other way around. To go the other way you must use floor().
  • year_month_day: A type that holds a day with fields for year, month (1 to 12) and day (1 to 31).
  • year_month_weekday: A type that holds a day with fields for year, month (1 to 12), a day of the week (0 to 6), and an index in the range [1, 5] that indicates the number of the week in the month.
  • year_weeknum_weekday: A type that hold a year, a weeknum (1 to 53) and a weekday (0 to 6). This can convert implicitly to and from a sys_days.

For using the library we need the following:

  • include header date.h and namespaces date and date::literals
  • for iso weeks we also need header iso_week.h and namespaces iso_week and iso_week::literals
  • NOTICE: The namespaces date::literals and iso_week::literals define types and literal operators with the same name and therefore can lead to name collisions; therefore you should only include them in the scope where you need them.

We will use the following lambda expression to print various dates to the console:

NOTICE: All the ‘today’ and related dates below are based on 2016-10-31.

Let us look at some examples:

  • create sys_days objects (including literals):

  • create year_month_day objects (including literals):

  • creating year_month_weekday literals and converting to year_month_day

  • create year_month_day values for today, yesterday and tomorrow

  • create year_month_day values for first and last day of the month

    Update: The following, as indicated by Howard Hinnant in the comments, can also be used:

  • create iso_week literals

  • get the iso week number for today

We will look at more utilities and examples in another post.

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This project has been moved to GitHub.

New location: https://github.com/mariusbancila/cppconlib

Many years ago I published on my blog a helper class for working with the Windows console that was wrapping the Windows console API. Looking back at it I realized it was a pretty naive implementation. So I decided to start a new and make something more flexible and easier to use. Hopefully, I was more successful. The result is a small C++ template library called cppconlib, available on codeplex.

cppconlib is built with C++11 features and requires Visual Studio 2012 or newer. The library is available in a single header called conmanip.h and provides a set of helper classes, functions and constants for manipulating a Windows console (using the Windows console functions). The library features the following components:

  • console_context<T>: represents a context object for console operations; its main purpose is restoring console settings; typedefs for the three consoles are available (console_in_context, console_out_context and console_err_context)
  • console<T>: represents a console objects providing operations such as changing the foreground and background colors, the input mode, screen buffer size, title, and others; typedefs for the three consoles are available (console_in, console_out and console_err)
  • manipulating functions that can be used with cout/wcout and cin/wcin: settextcolor()/restoretextcolor(), setbgcolor()/restorebgcolor(), setcolors(), setmode()/clearmode(), setposx()/setposy()/setpos().

The library can be downloaded from here. Detailed documentation is available here.

cppconlib

Examples

The following example prints some text in custom colors and then reads text in a different set of colors.

cppconlib2

The following code prints a rhomb to the console:

cppconlib3

For more details and updates check the project at codeplex: https://cppconlib.codeplex.com.

UPDATE: A NuGet package for cppconlib is available.

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NuGet has recently added support for native projects. This simplifies a lot deployment of native libraries. Even though cpplinq is not a big library (in fact is just a header file) I have created a NuGet package so that you are able to automatically add it to your project.

Here is what you have to do.

  1. Make sure you have NuGet 2.5 or newer, otherwise the NuGet package manager won’t show up in your VC++ projects.
  2. In the context menu for your project choose Manage NuGet Packages…
    cpplinqdemo1
  3. Search for cpplinq and install the package.
    cpplinqdemo2
  4. Include the cpplinq.hpp header and start using the library. Here is a sample to test that everything is all right.

Notice that all the settings for library (such as adding the proper entry for the include directories or defining NOMINMAX so that min and max macros will not be defined for the project) are automatically performed, so you can focus on coding.

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cpplinq new operators

There are some new operators available in cpplinq: singleton, generate, pairwise and zip_with.

singleton
This operator create a range with a single element, specified as argument. Using the operator is straight forward.

generate
This operator creates a range using a given predicate.

pairwise
Generates a new range of pairs by grouping adjacent elements of an input range. On an empty range it yields an empty range.

zip_with
Generates a new range of pairs by grouping together elements from two different ranges. If the two input ranges have different sizes, the result has the size of the smallest range. If any of the input ranges is empty, the result is an empty range.

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cpplinq: set operators

In the previous posts I introduced cpplinq, a C++ template library that provides .NET-like query operators for sequences of objects in C++11. In this third installment I will discuss the set operators the library provides.

There are four set operators: distinct, union_with (called so because union is a keyword in C++), intersect_with (suffix _with is for consistency with the union operator) and except. These operators should be pretty straight forward: distinct eliminates the duplicate elements from a sequence, yielding a new sequence with only the distinct elements (in the order their original order), union_with produces the set union of two sequences, intersect_with produces the set intersection of two sequences and except produces the set difference of two sequences.

Before seeing some examples, it worth nothing that all these operators delay the traversal of the sequences until the resulting object is enumerated.

Let’s see some examples:

You can learn more about these operators (and the others that are implemented) by reading the cpplinq query operators documentation.

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cpplinq: An introduction

cpplinq is a C++ template library that provides .NET-like query operators for sequences of objects in C++11. cpplinq is an open-source library that works both with VC++ compilers (2010 and 2012) and gcc (4.7.0 is the version used for unit tests). The library supports most of the .NET query operators and is extendable with additional operators that can suite some particular use. If you’re not familiar with .NET query operators, this article, http://msdn.microsoft.com/en-us/library/bb394939.aspx, lists and explain them.

The light-weighted library consists of a series of template classes and helper methods, provided in a single header under the namespace cpplinq.

This is a short introduction to the library. More posts will follow. Let’s see some examples.

The following code retrieves all the prime numbers from an array.

A slightly variation produces a sequence of first N prime numbers and transforms them into strings.

The next sample retrieves all the orders from a customer.

Callinq print_orders_by_cust() with argument 1 would print:

On the other hand, if you want to print the last order from a particular customer, the function above would change to something like this:

Calling print_last_order_for_customer() with argument 1 would print:

Hopefully this provides a quick view over the capabilities of the library. In following posts I will show more examples and discuss some of the query operators. To learn more about the library see the following articles:

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