diff options
Diffstat (limited to 'gcc/ada/sinput.ads')
| -rw-r--r-- | gcc/ada/sinput.ads | 30 |
1 files changed, 7 insertions, 23 deletions
diff --git a/gcc/ada/sinput.ads b/gcc/ada/sinput.ads index 585a8b95ea0..b842790bc10 100644 --- a/gcc/ada/sinput.ads +++ b/gcc/ada/sinput.ads @@ -6,7 +6,7 @@ -- -- -- S p e c -- -- -- --- $Revision: 1.69 $ +-- $Revision$ -- -- -- Copyright (C) 1992-2001 Free Software Foundation, Inc. -- -- -- @@ -274,34 +274,18 @@ package Sinput is -- minus-minus sequence starting a comment, and all control characters -- except ESC. - -- These characters are used to compute a 31-bit checksum which is stored - -- in the variable Scans.Checksum, as follows: - - -- If a character, C, is not part of a wide character sequence, then - -- either the character itself, or its lower case equivalent if it - -- is a letter outside a string literal is used in the computation: - - -- Checksum := Checksum + Checksum + Character'Pos (C); - -- if Checksum > 16#8000_0000# then - -- Checksum := (Checksum + 1) and 16#7FFF_FFFF#; - -- end if; - - -- For a wide character sequence, the checksum is computed using the - -- corresponding character code value C, as follows: - - -- Checksum := Checksum + Checksum + Char_Code'Pos (C); - -- if Checksum > 16#8000_0000# then - -- Checksum := (Checksum + 1) and 16#7FFF_FFFF#; - -- end if; + -- The checksum algorithm used is the standard CRC-32 algorithm, as + -- implemented by System.CRC32, except that we do not bother with the + -- final XOR with all 1 bits. -- This algorithm ensures that the checksum includes all semantically -- significant aspects of the program represented by the source file, -- but is insensitive to layout, presence or contents of comments, wide -- character representation method, or casing conventions outside strings. - -- Scans.Checksum is initialized to zero at the start of scanning a file, - -- and copied into the Source_Checksum field of the file table entry when - -- the end of file is encountered. + -- Scans.Checksum is initialized appropriately at the start of scanning + -- a file, and copied into the Source_Checksum field of the file table + -- entry when the end of file is encountered. ------------------------------------- -- Handling Generic Instantiations -- |