Buffer in Lexical Analysis

Buffer in Lexical Analysis

• Purpose: To read input source code efficiently and provide characters to the lexer.
• Lexical analyzer works on one character at a time, but reading file character by character is slow.

• Buffering improves speed by reading chunks of data at once.

Common Technique – Two Buffer Scheme:

1. Two buffers of size N each (front and back).
2. Forward pointer: Scans characters for the current lexeme.
3. Lexeme beginning pointer: Marks the start of the current token.
4. When forward reaches end of first buffer, load second buffer, and vice versa.
5. Helps recognize tokens spanning across buffer boundary.

Benefits:

• Efficient reading from source file.
• Handles large source files without storing whole file in memory.
• Supports lookahead for token recognition.

Flow:

[Lexeme Begin] ---> [Forward Pointer scanning] ---> End of buffer? ---> Load next buffer if needed

I can also draw a small two-buffer diagram to make it easy to visualize. Do you want me to?