This hands-on session will give you an overview of the techniques needed to parse and work with JSON data in the C++ language. Bring your laptop and join in the coding.

2. Coding 210
Parsing JSON in C++
Mike Maas, Technical Evangelist – IoE, DevNet, @mike_maas

3. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• Introductions
• Overview
• Requirements
• C++ Primer
• Requesting Content
• Parsing Content
• Resources
Agenda
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4. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Introductions
• Who Am I?
• Mike Maas, Technical Evangelist – Internet of Everything, DevNet
• Why this session? Why C++?
• It is not going away
• http://stackoverflow.com/research/developer-survey-2015#tech
• http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html
• http://langpop.com/
• C > C++ > C++11 > C++14
• Great for constrained applications
• Better performance and control of resources
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Overview
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6. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Overview
• Goals
• Build upon Coding 101 and Coding 201
• Briefest introduction to C++ and application compilation
• Deeper understanding of using C++ to collect information from the network
• Further inspection of JSON and the tools available to evaluate JSON content
• Understand the methods and implementation of parsing JSON
• What we won't be covering
• Many C/C++ Features, Integrated Development Environments (IDEs) and other tools
• Authentication
• Oauth, Digest/Form/etc.

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Overview
• What we are going to work on
• Using Postman
• Learning a little bit about CMX
• Understanding how to use C++ and useful libraries to parse data
• Understanding some of the challenges of parsing data
• Seeing some of the errors you might encounter

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Requirements
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9. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Requirements: Tools
• A web browser (Chrome)
• http://getchrome.com
• C/C++ Compiler
• Text Editor
• Git (Optional)
• http://git-scm.com/
• Postman (Optional)
• Get from the Chrome Web Store or the standalone version at
http://www.getpostman.com/

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Requirements: Expertise
• Basic computer skills / Accessing web sites
• Using the command-line for your Operating System
• Some skills in scripting or computer automation

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Requirements: OS X
• Install the G++ C/C++ Compiler
• Install XCode
• Install Command Line Developer Tools for OS X
• Open a Terminal
• Launch a terminal via Spotlight > Terminal
• Type g++ --version
• We should get something like "Apple LLVM version 6.1.0"
• If we don't
• On OS X : Verify you have XCode and the command line tools installed
Pre-Flight Check: C/C++ Compiler

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Requirements: Windows
• Install Cygwin on your computer
• Install the g++ C/C++ Compiler
• Run Cygwin, Install from Internet,
• Within the Cygwin setup, install the following:
• gcc-g++, openssl-devel, libssh2-devel, libcurl-devel, libcurl4
• Open a console
• Locate and start the Cygwin terminal
• Type g++ --version
• We should get something like "g++ (GCC) 4.9.2"
• If we don't
• Verify you are running it from a Cygwin terminal
Pre-Flight Check: C/C++ Compiler

13. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Requirements
• Install Postman if you don't already have it installed
• This isn't required but it is a very useful tool
• Available at http://www.getpostman.com/
• If you are used to a different tool (SoapUI, Chrome DevTools, etc.) – Feel free
• Browser-based version or Standalone packaged application is fine
Pre-Flight Check: Postman

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Requirements: Code
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• GitHub
• https://github.com/CiscoDevNet/coding-skills-sample-code
• coding210-parsing-json-c++
• To Clone locally run the following command:
• git clone https://github.com/CiscoDevNet/coding-skills-sample-code.git
• Within our source directory we will also need to clone libcurl and RapidJSON
• git clone https://github.com/bagder/curl.git
• git clone https://github.com/miloyip/rapidjson.git
All the samples used are available online

15. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Optional: Tools
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• JSON Test
• http://www.jsontest.com/
• JSON Lint
• http://jsonlint.com/
• JSON Placeholder
• http://jsonplaceholder.typicode.com/
Other online resources for our foray into JSON parsing

16. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
C++ Primer
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17. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
C++ is a standardized, object-oriented
programming language. It is designed
for efficiency, performance, and
flexibility of use.
What is C++?
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18. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• C/C++ has a notable barriers to entry
• Broad Syntax / Deep Feature Set
• Pointers/References, Generics
• Object Oriented Conceptualization, Programming, and Design
• Class > Object, Inheritance/Polymorphism, etc.
• Compilation
• Many different compilation tools and toolchains
• http://en.wikipedia.org/wiki/List_of_compilers#C.2B.2B_compilers
• GUIs are not it's primary concern
• Lots of Dragons and Grognards be there
C++ Primer
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• Typed Programming Languages
• Static / Compile-Time / Strong
• Ada, C, C++, C#, Java, Pascal, …
• Dynamic / Run-Time / Weak
• JavaScript, Lisp, Lua, Python, Ruby, Perl, Smalltalk, …
• Optionally Both
• Objective-C, TypeScript, …
• Runtimes
• Java, Python, Common Language Runtime (CLR), etc use an interpreter executable
for a particular platform
• C/C++ Create a executable for a particular platform
C++ Primer – Compare and Contrast
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• C#
• Compiles to Common Intermediate
Language (CIL)
• Uses the CLR
• Garbage Collected
• Platform includes Standard Libraries
• Syntax Differences
• Types
• Object versions of types
• long = 8 bytes
• Control
• switch explicit
• Inheritance
• …
• C++
• Compiles to a platform machine code
• Not Garbage Collected
• Developer includes Standard Libraries
• Syntax Differences
• Types
• Fundamental types
• long = 4 bytes
• Control
• switch falls through
• Inheritance
• …
C++ Primer – Compare and Contrast
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21. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• To just get something to the screen…
• Create a syntactically correct source code file with a main entry point
• Compile that source code file
• Link the resultant object code into an Application
• Run the resultant Application
C++ Primer – Compare and Contrast : HelloWorld!
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22. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• C#
using System;
public class HelloWorld
{
static public void Main()
{
Console.WriteLine("Hello World!");
Console.WriteLine("How are you?");
}
}
• C++
#include <iostream>
int main()
{
std::cout << "Hello World!n";
std::cout << "How are you?n";
return 0;
}
C++ Primer – Compare and Contrast : HelloWorld!
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23. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Activity 1 : Compilation
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24. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Creating an application via C++
• Get Code Via Git
• Git clone the following command:
• git clone https://github.com/
CiscoDevNet/coding-skills-sample-
code.git
Let’s get something to look at in our console
• Get Code Via Download
• Download the following file:
• https://github.com/CiscoDevNet/coding-
skills-sample-code/archive/master.zip
• When you get a coding-skills-sample-code directory/folder
• Launch a terminal and navigate to coding-skills-sample-code
• Locate the coding210-parsing-json-c++ directory/folder
• We will execute commands directly from this folder

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Basic Construction via C++
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.c
.cpp
Compiler Linker
.lib
.o
.dll
.exe
.lib
Source

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• Source Files
• hello-world.cpp (valid C++ instructions)
• Compilation (compiler, assembler, and linker)
g++ -c hello-world.cpp -o hello-world.o
g++ -o hello hello-world.o
- or -
g++ -o hello hello-world.cpp
• Output
• hello (OS X), hello.exe (Windows)
Basic Construction
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27. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Requesting Content
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28. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Request and Response
• Request
• What you want
• Parameters
• Response results can often be controlled via Request elements
• URL query params
• Form-based transactions
• HTTP Headers
• Pseudo Extensions (https://stream.twitter.com/1.1/statuses/sample.json)
• Response
• What you get
• Content
• Can often return the same data in different formats per request
• XML, JSON, ATOM, …
What you want; what you get

29. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
HTTP
• What does HTTP stand for? (HT) & (TP)
• What is the most relevant part of the definition for us today?
• Headers
• Authorization
• Accept
• Charset, Encoding, Language
• Actions
• GET – Actually get content
• POST – Create new content
• DELETE – Delete content
• PUT – Update content
• Content Description
• MIME Types
• For HTTP the content is negotiated
A brief word about HTTP

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Requesting Content via Postman
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• From Postman
• In the Request field enter our test URL
• http://jsonplaceholder.typicode.com/users
• Click Send
• From a Browser
• Just put http://jsonplaceholder.typicode.com/users in as the URL
• We should get some JSON returned
Let’s get something to look at
http://jsonplaceholder.typicode.com/users
http://jsonplaceholder.typicode.com/todos

31. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Understanding the structure of the Response
[
{
"id" : 1,
"name": "Leanne Graham"
},
{
"id": 2,
"name": "Ervin Howell"
}
]
Let's look at this in JSON Lint and then JSON.org.
Let’s look at what we got (Condensed)

32. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Understanding the structure of the Response
[ (Array)
{ (Object)
"id" : 1, (Value)
"name": "Leanne Graham" (Value)
},
{ (Object)
"id": 2, (Value)
"name": "Ervin Howell" (Value)
}
]
Let’s look at what we got (Condensed)

33. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Activity 2: Requesting Content

34. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• What needs to happen?
• Establish a HyperText Transport Protocol (HTTP) connection
• Sockets
• Network Library
• Send and Receive data against the HyperText Transport Protocol (HTTP)
• Synchronous/Blocking or Asynchronous/Non-Blocking
• Parse and handle the Response data
Requesting Content via C++
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35. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• Get the libcurl source
• http://curl.haxx.se/dev/source.html
• Execute the following command in your source directory:
• git clone https://github.com/bagder/curl.git
• Use the cURL functionality
• Include headers to add libcurl support
• Use the cURL Easy interface (Synchronous)
- or -
• Use the cURL Multi interface (Asynchronous)
Requesting Content via C++ using libcurl
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36. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• A basic HTTP application
• main-http.cpp
• Code available at https://github.com/CiscoDevNet/coding-skills-sample-code
• Compile the main-http application
• g++ -o main-http main-http.cpp –lcurl
• How do we know what these flags are?
• curl-config
• Evaluate the returned results
Requesting Content via C++ using libcurl
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37. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Activity 3: Requesting JSON

38. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• A basic HTTP application that returns JSON
• main-json.cpp
• Code available at https://github.com/CiscoDevNet/coding-skills-sample-code
• Compile the main-http application
• g++ -o main-json main-json.cpp –lcurl
• Evaluate the returned results
Requesting JSON via C++ using libcurl
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39. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Parsing Content
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40. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• Why Parse?
• Methods of Parsing
• Don't Parse
• Output is truly human-readable
• Do-It-Yourself (DIY) String Parsing
• Useful for really, really simple string extraction
• Build or Use a Framework
• A lot of ready-made libraries and tools are already available
Parsing Content
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41. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• Available Libraries
• jsoncpp
• rapidjson
• LibJSON
• JSON++
• …
• JSON.org has lists of utilities at http://json.org/
Methods of Parsing Content
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42. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Activity 4: Parsing Content

43. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• What needs to happen?
• Need to establish a Data source
• Identify the Data to extract
• Walk the String
• Regular Expressions
• Parsing Library
• Extract the Data
• Instance Counts
• Copy of the Data itself
• Do something with the Data
Parsing Content via C++
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44. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• Get the RapidJSON source
• https://github.com/miloyip/rapidjson
• Execute the following command in your source directory:
• git clone https://github.com/miloyip/rapidjson.git
• Use the RapidJSON functionality
• Include headers to add rapidjson support
Parsing Content via C++ using RapidJSON
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45. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• An application that pretties the JSON output
• main-json-lib
• Code available at https://github.com/CiscoDevNet/coding-skills-sample-code
• Compile the main-http application
• g++ -o main-json-lib main-json-lib.cpp -Irapidjson/include –lcurl
• Do something with the returned results
• Like Prettify!
Parsing Content via C++ using RapidJSON
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46. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Activity 5: Extracting Content

47. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• An application that extracts data from the JSON output
• main
• Code available at https://github.com/CiscoDevNet/coding-skills-sample-code
• Compile the main-http application
• g++ -o main main.cpp -Irapidjson/include –lcurl
• Do something with the returned results
• Like Get AccessPoint names from your CMX installation!
Parsing Content via C++ using RapidJSON
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48. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Demo: IOx
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49. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• IOx
• Edge Computing
• C++ on the Edge
• Cross-Compilation Toolchain
• x86 > PowerPC
Demonstration
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50. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Resources

51. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Resources
• On-Site
• Learning Labs
• https://learninglabs.cisco.com
• DevNetizens
Information to help you on your way

52. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
Resources
• On-Line
• Learning Labs
• https://learninglabs.cisco.com
• C++
• http://www.cplusplus.com/
• http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list/
• JSON : JSON.org
• JSON Test : http://www.jsontest.com/
• JSON Lint : http://jsonlint.com/
• JSON Placeholder : http://jsonplaceholder.typicode.com/
Information to help you on your way

53. © 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicCoding 210: Parsing JSON in C++
• Try it yourself
• Do a Learning Lab
• Go Online
• Read a book
Where to go from here?
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54. Thank you
© 2015 Cisco and/or its affiliates. All rights reserved. Cisco PublicPresentation ID 54