Class: Cabriolet::HLP::WinHelp::BTreeBuilder

Inherits:
Object
  • Object
show all
Defined in:
lib/cabriolet/hlp/winhelp/btree_builder.rb

Overview

B+ tree builder for WinHelp 4.x directory format

Builds B+ tree directory structure for WinHelp 4.x files. The directory maps filenames to file offsets using a B+ tree with fixed-size pages.

Constant Summary collapse

DEFAULT_PAGE_SIZE =

Default page size for WinHelp 4.x directory (1KB for catalog/directory)

0x0400
PAGE_TYPE_LEAF =

Page types

0
PAGE_TYPE_INDEX = 
1
BTREE_MAGIC =

B+ tree magic number

0x293B
FLAGS_MAGIC_BIT =

Flags for B+ tree header Bit 0x0002 is always 1 Bit 0x0400 is 1 for catalog/directory

0x0002
FLAGS_CATALOG_BIT = 
0x0400

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(page_size: DEFAULT_PAGE_SIZE, structure: "FFz") ⇒ BTreeBuilder

Initialize B+ tree builder

Parameters:

  • page_size (Integer) (defaults to: DEFAULT_PAGE_SIZE) —

    Page size in bytes (default: 1KB)

  • structure (String) (defaults to: "FFz") —

    Structure string describing data format



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# File 'lib/cabriolet/hlp/winhelp/btree_builder.rb', line 37

def initialize(page_size: DEFAULT_PAGE_SIZE, structure: "FFz")
  @page_size = page_size
  @structure = structure
  @entries = []
end

Instance Attribute Details

#page_size ⇒ Object (readonly)

Returns the value of attribute page_size.



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# File 'lib/cabriolet/hlp/winhelp/btree_builder.rb', line 31

def page_size
  @page_size
end

#structure ⇒ Object (readonly)

Returns the value of attribute structure.



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# File 'lib/cabriolet/hlp/winhelp/btree_builder.rb', line 31

def structure
  @structure
end

Instance Method Details

#add_entry(filename, offset, size) ⇒ Object

Add a file entry to the B+ tree

Parameters:

  • filename (String) —

    Internal filename (e.g., "|SYSTEM")

  • offset (Integer) —

    File offset in help file

  • size (Integer) —

    File size in bytes



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# File 'lib/cabriolet/hlp/winhelp/btree_builder.rb', line 48

def add_entry(filename, offset, size)
  @entries << { filename: filename, offset: offset, size: size }
end

#build ⇒ Hash

Build B+ tree structure

Returns:

  • (Hash) —

    Hash containing :header, :pages



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# File 'lib/cabriolet/hlp/winhelp/btree_builder.rb', line 55

def build
  return build_empty if @entries.empty?

  # Sort entries by filename
  sorted_entries = @entries.sort_by { |e| e[:filename] }

  # Build leaf pages
  leaf_pages = build_leaf_pages(sorted_entries)

  # Build index pages if needed
  if leaf_pages.size > 1
    index_pages = build_index_pages(leaf_pages)
    root_page = index_pages.first[:page_num]
    n_levels = 2
  else
    index_pages = []
    root_page = leaf_pages.first[:page_num]
    n_levels = 1
  end

  # Build B+ tree header
  header = build_header(
    total_pages: leaf_pages.size + index_pages.size,
    root_page: root_page,
    n_levels: n_levels,
    total_entries: @entries.size,
  )

  # Combine all pages
  all_pages = index_pages + leaf_pages

  { header: header, pages: all_pages }
end