Module: ExtractTtc::Constants

Defined in:: lib/extract_ttc/constants.rb

Overview

Constants module containing immutable constant definitions for TTC/TTF font file operations.

This module defines all magic numbers, version identifiers, and file format constants used throughout the extract_ttc gem. These values are based on the TrueType Collection and TrueType Font specifications.

Constant Summary collapse

TTC_TAG = TrueType Collection file signature tag. All valid TTC files must begin with this 4-byte tag.

"ttcf"

TTC_VERSION_1 = TrueType Collection Version 1.0 identifier. Represents the original TTC format version.

0x00010000

TTC_VERSION_2 = TrueType Collection Version 2.0 identifier. Represents the extended TTC format with digital signature support.

0x00020000

HEAD_TAG = Head table tag identifier. The ‘head’ table contains global font header information including the checksum adjustment field.

"head"

CHECKSUM_ADJUSTMENT_MAGIC = Magic number used for font file checksum adjustment calculation. This constant is used in conjunction with the file checksum to compute the checksumAdjustment value stored in the ‘head’ table. Formula: checksumAdjustment = CHECKSUM_ADJUSTMENT_MAGIC - file_checksum

0xB1B0AFBA

SUPPORTED_VERSIONS = Supported TTC version numbers. An array of valid version identifiers for TrueType Collection files.

[TTC_VERSION_1, TTC_VERSION_2].freeze

TABLE_ALIGNMENT = Table data alignment boundary in bytes. All table data in TTF files must be aligned to 4-byte boundaries, with padding added as necessary.