Json on Lloyd Rochester's Geek Blog

Improved Scanning of JSON with Flex/Bison

Tue, 27 Oct 2020 00:00:00 +0000

Improved Scanning of JSON with Flex/Bison

Using Flex/Bison in the last post we Parsed JSON into an AST. In the first post we setup a Simple Example to Parse JSON. In this post we will improve our Flex Scanner to tokenize and validate more JSON cases. We will continue to align with the grammar at json.org. We will add rules and tokens for DQUOTE (double-quote), string, HEX, and CHARACTERS not in our previous implementation.

Parse JSON into an Abstract Syntax Tree using Flex/Bison

Sun, 25 Oct 2020 00:00:00 +0000

Parse JSON into an Abstract Syntax Tree using Flex/Bison

In a previous post we Parsed JSON using Flex/Bison. This example was very basic. We used a FLEX scanner to tokenize our JSON and created grammar rules in BISON to parse this token stream. This post will take it further and create an Abstract Syntax Tree (AST). The AST is a power data structure typically used in compilers that will store the structure of our JSON. Effectively we will read in the JSON structure a tree-like data structure in C.

Parse JSON with Flex and Bison

Sat, 22 Feb 2020 00:00:00 +0000

Parse JSON with Flex and Bison

A simple example that will parse JSON in C using Flex and Bison. Forewarning, while this example works well it’s not going to handle every JSON case. I’ll highlight the limitations of what cannot be parsed towards the end of the post. It’s a perfect example to build upon and extend though.

FLEX Scanner to Parse JSON

The scanner will create a token stream. Tokens are just regex matches made by flex that can also have values. For example a DECIMAL token we return a float by calling atof(yytext). Whereas, we also tokenize { to LCURLY, but there is no value. The ECHO macro is turned off, and can be turned on for further debug info.