Krunching Method (GNAT User’s Guide for Native Platforms)

#### 3.3.5.3 Krunching Method ¶

The initial file name is determined by the name of the unit that the file contains. The name is formed by taking the full expanded name of the unit and replacing the separating dots with hyphens and using lowercase for all letters, except that a hyphen in the second character position is replaced by a tilde if the first character is `a`, `i`, `g`, or `s`. The extension is `.ads` for a spec and `.adb` for a body. Krunching does not affect the extension, but the file name is shortened to the specified length by following these rules:

- The name is divided into segments separated by hyphens, tildes, or underscores and all hyphens, tildes, and underscores are eliminated. If this leaves the name short enough, we are done.
- If the name is too long, the longest segment is located (left-most if there are two of equal length) and shortened by dropping its last character. This is repeated until the name is short enough.

  As an example, consider the krunching of `our-strings-wide_fixed.adb` to fit the name into 8 characters, as required by some operating systems:

      our-strings-wide_fixed 22
      our strings wide fixed 19
      our string  wide fixed 18
      our strin   wide fixed 17
      our stri    wide fixed 16
      our stri    wide fixe  15
      our str     wide fixe  14
      our str     wid  fixe  13
      our str     wid  fix   12
      ou  str     wid  fix   11
      ou  st      wid  fix   10
      ou  st      wi   fix   9
      ou  st      wi   fi    8
      Final file name: oustwifi.adb

- The file names for all predefined units are always krunched to eight characters. The krunching of these predefined units uses the following special prefix replacements:

  Prefix | Replacement
  `ada-` | `a-`
  `gnat-` | `g-`
  `interfac es-` | `i-`
  `system-` | `s-`

  These system files have a hyphen in the second character position. That’s is why normal user files replace such a character with a tilde.

  As an example of this special rule, consider `ada-strings-wide_fixed.adb`, which gets krunched as follows:

      ada-strings-wide_fixed 22
      a-  strings wide fixed 18
      a-  string  wide fixed 17
      a-  strin   wide fixed 16
      a-  stri    wide fixed 15
      a-  stri    wide fixe  14
      a-  str     wide fixe  13
      a-  str     wid  fixe  12
      a-  str     wid  fix   11
      a-  st      wid  fix   10
      a-  st      wi   fix   9
      a-  st      wi   fi    8
      Final file name: a-stwifi.adb

Of course, no file shortening algorithm can guarantee uniqueness over all possible unit names. If file name krunching is used, it’is your responsibility to ensure that no name clashes occur. The utility program `gnatkr` is supplied so that you can conveniently determine the krunched name of a file.