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orkinCompare.cpp
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00037 
00038 #ifndef _MDB_
00039 #include "mdb.h"
00040 #endif
00041 
00042 #ifndef _MORK_
00043 #include "mork.h"
00044 #endif
00045 
00046 #ifndef _ORKINCOMPARE_
00047 #include "orkinCompare.h"
00048 #endif
00049 
00050 #ifndef _MORKENV_
00051 #include "morkEnv.h"
00052 #endif
00053 
00054 //3456789_123456789_123456789_123456789_123456789_123456789_123456789_123456789
00055 
00056 
00057 orkinCompare::orkinCompare() // does nothing
00058 {
00059 }
00060 
00061 /*virtual*/
00062 orkinCompare::~orkinCompare() // does nothing
00063 {
00064 }
00065 
00066 
00067 mdb_order // standard yarn comparison for nsIMdbCompare::Order()
00068 mdbYarn_Order(const mdbYarn* inSelf, morkEnv* ev, const mdbYarn* inYarn)
00069 {
00070   // This code is a close copy of public domain Mithril's AgYarn_CompareLen().
00071   // Note all comments are from the original public domain Mithril code.
00072   
00073   mork_u1* self = (mork_u1*) inSelf->mYarn_Buf;
00074   mork_u1* yarn = (mork_u1*) inYarn->mYarn_Buf;
00075   
00076   mdb_fill selfFill = inSelf->mYarn_Fill;
00077   mdb_fill yarnFill = inYarn->mYarn_Fill;
00078   
00079   if ( selfFill && yarnFill ) /* neither yarn is empty? */
00080   {
00081     register int a; /* a byte from self */
00082     register int b; /* a byte from yarn */
00083     
00084     /* predecrement is normally used in loop tests to minimize instructions: */
00085     ++selfFill; /* prepare for predecrement */
00086     ++yarnFill; /* prepare for predecrement */
00087     /* we check only self len at loop top, but yarn len check must follow: */
00088     
00089     while ( --selfFill ) /* another byte in self? */
00090     {
00091       if ( !--yarnFill ) /* yarn runs out first? self is greater (pos)? */
00092         return 1;
00093       
00094       b = (mork_u1) *yarn++;  /* next byte in other yarn */
00095       a = (mork_u1) *self++;  /* next byte in self yarn */
00096 
00097       if ( a != b ) /* found first different byte? */
00098         return ( a - b ); /* return relative order */
00099     }
00100     /* if remaining yarn len is exactly 1, it runs out at same time as self: */
00101     return ( yarnFill == 1 )? 0 : -1; /* yarn is same len? or self is less? */
00102   }
00103   else
00104     return ((mdb_order) selfFill) - ((mdb_order) yarnFill);
00105 }
00106 
00107 // { ===== begin nsIMdbCompare methods =====
00108 /*virtual*/ mdb_err
00109 orkinCompare::Order(nsIMdbEnv* mev, // compare first to second yarn
00110   const mdbYarn* inFirst,   // first yarn in comparison
00111   const mdbYarn* inSecond,  // second yarn in comparison
00112   mdb_order* outOrder)      // negative="<", zero="=", positive=">"
00113 {
00114   mdb_err outErr = 1; // nonzero means FAILURE
00115 
00116   morkEnv* ev = morkEnv::FromMdbEnv(mev);
00117   if ( ev )
00118   {
00119     if ( inFirst && inSecond && outOrder )
00120     {
00121       *outOrder = mdbYarn_Order(inFirst, ev, inSecond);
00122     }
00123     else
00124       ev->NilPointerError();
00125 
00126     outErr = ev->AsErr();
00127   }
00128   return outErr;
00129 }
00130 
00131 /*virtual*/ mdb_err
00132 orkinCompare::AddStrongRef(nsIMdbEnv* ev) // does nothing
00133 {
00134   MORK_USED_1(ev);
00135   return 0;
00136 }
00137 
00138 /*virtual*/ mdb_err
00139 orkinCompare::CutStrongRef(nsIMdbEnv* ev) // does nothing
00140 {
00141   MORK_USED_1(ev);
00142   return 0;
00143 }
00144 
00145 // } ===== end nsIMdbCompare methods =====
00146 
00147 //3456789_123456789_123456789_123456789_123456789_123456789_123456789_123456789