CSS-Parser

This project implements a simple CSS processing engine. It reads CSS rules and command sections from standard input. The CSS sections are parsed and stored in appropriate data structures. The project was created for university purposes.

Project Description

CSS Parsing:

• The processing begins by reading CSS declarations. The CSS is syntactically correct and consists of attribute blocks, optionally preceded by selectors. A lack of selectors is valid (it would mean that attributes apply to everything).

• Selectors are separated by commas. Legal CSS selectors are accepted, and it's assumed that they don’t contain commas or curly braces.

• Each block of attributes is enclosed in curly braces {}.

• Attributes are separated by semicolons and consist of a property name and a value, separated by a colon. The last attribute in a block may or may not be followed by a semicolon.

• Attribute values may be valid CSS constructs, but it's assumed that any strings will not contain malicious content such as escaped quotes, curly braces, or semicolons.

• If a specific attribute appears more than once in a block, it’s treated as a single occurrence, with the last value being significant.

• Selectors, property names, and values are treated as-is (after trimming leading and trailing whitespace), meaning no semantic interpretation is needed. For example, "margin-left: 8px" and "margin: 4px 7px 4px 7px" are treated as separate attributes with the names margin-left and margin, and values 8px and 4px 7px 4px 7px respectively.

• Simplifications:

  • No comments are present in the CSS.
  • No @ selectors.
  • Blocks cannot be nested.

• For testing purposes, it's assumed that no selector or attribute spans multiple lines (although multiple separators and attributes can appear on the same line).

Commands:

Commands are described in the format ???, followed by actions for processing the CSS. These commands use integers i and j (positive integers) and n (a valid attribute name). Some possible commands include:

• ****: Resume reading CSS.
• ?: Output the number of CSS blocks.
• i,S,?: Output the number of selectors for block i. If block i doesn't exist, skip.
• i,A,?: Output the number of attributes for block i. If block i doesn't exist, skip.
• i,S,j: Output the j-th selector for block i. Skip if no such block or selector exists.
• i,A,n: Output the value of attribute n for block i. Skip if no such block or attribute exists.
• n,A,?: Output the total number of occurrences of attribute n across all blocks.
• z,S,?: Output the total number of occurrences of selector z across all blocks.
• z,E,n: Output the value of attribute n for selector z. If multiple occurrences exist, use the last one. Skip if none.
• i,D,*: Delete block i entirely. If successful, print deleted.
• i,D,n: Delete attribute n from block i. If the block is empty after the operation, it should be deleted as well. If successful, print deleted.

Implementation Notes:

• Selectors and attributes are stored as lists.
• CSS blocks are organized as a doubly linked list (to efficiently handle the E command – retrieving the last occurrence of an attribute).
• To optimize memory usage, a node in the list should include an array T of size 8 representing a block. The count of used structures should help in speeding up operations.
• When allocating a new node, an array of T elements is created. If there's space in a node, new elements should be added to it before allocating a new node.
• If deleting elements leaves a node empty, the node should be removed.

Example:

Input:

#breadcrumb 
{
	width: 80%;
	font-size: 9pt;
}

h1, body {
	min-width: 780px;
	margin: 0;
	padding: 0;
	font-family: "Trebuchet MS", "Lucida Grande", Arial;
	font-size: 85%;
	color: #666666;
}

h1, h2, h3, h4, h5, h6 {color: #0066CB;}
????
?
1,S,?
1,S,1
1,A,?
2,A,font-family
h1,S,?
color,A,?
h1,E,color
1,A,padding
1,D,*
?
2,D,color
?

****
h1, h2, h3, h4, h5, h6 {color: #0066FF;}
????
?

Output:

? == 3
1,S,? == 1
1,S,1 == #breadcrumb
1,A,? == 2
2,A,font-family == "Trebuchet MS", "Lucida Grande", Arial
h1,S,? == 2
color,A,? == 2
h1,E,color == #0066CB
1,D,* == deleted
? == 2
2,D, color == deleted
? == 1
? == 2