binary.sa


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-- Copyright (C) 2000 by K Hopper, University of Waikato, New Zealand        --
-- This file is part of the GNU Sather library. It is free software; you may --
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abstract class $BINARY

abstract class $BINARY is -- This abstract class specifies three routines which sub-classes must -- provide in order to convert the value into a form suitable for -- manipulation as a sequence of storage units and vice-versa. Both -- transformations must satisfy the identity -- -- -- create(Value.binstr) = Value -- Version 1.0 Feb 98. Copyright K Hopper, U of Waikato -- Development History -- ------------------- -- Date Who By Detail -- ---- ------ ------ -- 25 Feb 98 kh Original create(storage : BINSTR) : SAME ; -- Provided that the size of the storage argument is exactly the amount -- of storage required for an object of this class as produced by the binstr -- routine, then storage is converted into an object of this class which is -- returned. build(cursor : BIN_CURSOR) : SAME ; -- Provided that there are at least the number of storaqge units -- required to produce a value of this class then the number of storage units -- required are used to do so and the cursor is moved to the next position on -- the binary string. read(cursor : BIN_CURSOR) : SAME ; -- This routine returns the next object in the file providing that the -- next item in the file is the boolean value for true, otherwise it returns -- void having moved past the item in the string. binstr : BINSTR ; -- This returns a sequence of storage units which is suitable for -- conversion back into a value of the class concerned.. write(fyle : BIN_FILE) ; -- This routine appends self to the given binary file. end ; -- $BINARY

partial class BINARY < $BINARY

partial class BINARY < $BINARY is -- This class specifies defines those components of the binary -- reading/writing mechanism which are the same irrespective of the class -- involved. -- Version 1.0 Jul 98. Copyright K Hopper, U of Waikato -- Development History -- ------------------- -- Date Who By Detail -- ---- ------ ------ -- 22 Jul 98 kh Original stub build(cursor : BIN_CURSOR) : SAME ; -- Provided that there are at least the number of storage units -- required to produce a value of this class then the number of storage units -- required are used to do so and the cursor is moved to the next position on -- the binary string. create(str : BINSTR) : SAME pre (str.size > 0) post true -- ~void(result) (but immutables -- could be ZERO!! is -- This routine requires that the binary string argument contains -- exactly the correct number of octets in the right format for it to create -- and return a value, otherwise void is returned. loc_cursor : BIN_CURSOR := str.cursor ; me : SAME := build(loc_cursor) ; if loc_cursor.remaining > 0 then -- string too long! return void else return me -- may be void if too short! end end ; read(index : BIN_CURSOR) : SAME pre ~void(index) and ~index.is_done post true is -- This routine assumes that the next octet in the binary string -- represents a boolean value. If this value is true then the appropriate -- number of octets is used to create and return a new object. if BOOL::build(index) then return build(index) else return void end end ; stub binstr : BINSTR ; -- This returns a sequence of storage units which is suitable for -- conversion back into a value of the class concerned.. write(fyle : BIN_FILE) pre ~void(self) and ~void(fyle) post (fyle.size = initial(fyle.size) + binstr.size) is -- This routine writes a binary representation of self to the given binary file. fyle := fyle + binstr ; fyle.flush end ; end ; -- BINARY