Category Archives: HxD design and implementation

Compressing arrays of integers while keeping fast indexing

While adding support for editing and viewing text encoded in UTF-8 to HxD’s hex editor control itself, it turns out I have to query Unicode property tables, that go beyond the basic ones included with Delphi (and most other languages / default libraries).

Parsing the structured text files, provided by the Unicode consortium, at each startup is too inefficient, and merely storing the parsed text into a simple integer array wastes too much memory.

A more efficient storage uses a dictionary-like approach, to compress the needed data using a few layers of indirections, while still giving array-like performance with constant (and negligible) overhead.

In the following, I’ll briefly present the solution I found.

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Character encoding confusion

HxD will extend character encoding support, and I am looking for the best way to name character encodings. So far, you can only pick between the following four to affect the text display in the editor window:

  • Windows (ANSI)
  • DOS/IBM-PC (OEM)
  • Macintosh
  • EBCDIC

Additionally, in the Search window, Unicode (UCS-2LE) can be selected using a checkbox to override the current editor window encoding. I’d like the character encoding selection to be more uniform, flexible, and clear in future. Continue reading

Reading process memory / RAM

RAM

One of the most common questions I get regarding HxD is about obtaining source code to understand and reproduce some of its basic functionality. The most frequent points of interest are how the RAM editor reads / writes memory of other running programs (i.e., processes) and how the disk editor reads from / writes to storage media.

Yesterday, when Mohamed A. Mansour, who will teach an Operating Systems class, suggested this information might be useful for his students, I thought it was a good opportunity to start my blog and write it up in a proper way.

This post is about reading memory that belongs to another running program (aka. process), and will be the first in a series of posts about the implementation and design of HxD.

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