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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT COMPILER COMPONENTS --
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4 -- --
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5 -- S Y S T E M . S T R I N G _ H A S H --
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6 -- --
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7 -- S p e c --
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8 -- --
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145
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9 -- Copyright (C) 2009-2019, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 -- This package provides a generic hashing function over strings, suitable for
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33 -- use with a string keyed hash table. In particular, it is the basis for the
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34 -- string hash functions in Ada.Containers.
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35 --
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36 -- The algorithm used here is not appropriate for applications that require
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37 -- cryptographically strong hashes, or for application which wish to use very
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38 -- wide hash values as pseudo unique identifiers. In such cases please refer
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39 -- to GNAT.SHA1 and GNAT.MD5.
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40 --
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41 -- Note: this package is in the System hierarchy so that it can be directly
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42 -- be used by other predefined packages. User access to this package is via
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43 -- a renaming of this package in GNAT.String_Hash (file g-strhas.ads).
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44
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45 package System.String_Hash is
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46 pragma Pure;
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47
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48 generic
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49 type Char_Type is (<>);
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50 -- The character type composing the key string type
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51
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52 type Key_Type is array (Positive range <>) of Char_Type;
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53 -- The string type to use as a hash key
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54
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55 type Hash_Type is mod <>;
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56 -- The type to be returned as a hash value. This must be a 32-bit
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57 -- unsigned type with full range 0 .. 2**32-1, no other type is allowed
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58 -- for this instantiation (checked in the body by Compile_Time_Error).
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59
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60 function Hash (Key : Key_Type) return Hash_Type;
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61 pragma Inline (Hash);
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62 -- Compute a hash value for a key
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63
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64 end System.String_Hash;
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