Calculating the TrueType Checksum

 Last reviewed: November 2, 1995
Article ID: Q102354
The information in this article applies to:
  • Microsoft Win32 Application Programming Interface (API) included with: 

        - Microsoft Windows NT versions 3.1, 3.5, and 3.51
    - Microsoft Windows 95 version 4.0

SUMMARY

To calculate a TrueType checksum:

  1. Sum all the ULONGS in the .TTF file, except the checkSumAdjust field (which contains the calculated checksum). Note that TrueType files are big-endian, while Windows and Windows NT are little-endian, so the bytes must be swapped before they are summed.

  2. Subtract the result from the magic number 0xb1b0afba.

MORE INFORMATION

Example

  1. Open the SYMBOL.TTF distributed with Windows NT. It is 64492 bytes long.

  2. Step through the 16123 ULONGS, summing each one, except for the checkSumAdjust field for the file (which in this case is 0xa7a81151).

  3. Subtract the result from 0xb1b0afba. The result is 0xa7a81151.

The TrueType font file specification is available from several sources, including the Microsoft Software Library (query on the word TTSPEC1).

Additional reference words: 3.10 3.50 4.00 95
KBCategory: kbgraphic
KBSubcategory: GdiFnt

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Last reviewed: November 2, 1995
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