ext/misc/uint.c

   1 /*
   2 ** 2020-04-14
   3 **
   4 ** The author disclaims copyright to this source code.  In place of
   5 ** a legal notice, here is a blessing:
   6 **
   7 **    May you do good and not evil.
   8 **    May you find forgiveness for yourself and forgive others.
   9 **    May you share freely, never taking more than you give.
  10 **
  11 ******************************************************************************
  12 **
  13 ** This SQLite extension implements the UINT collating sequence.
  14 **
  15 ** UINT works like BINARY for text, except that embedded strings
  16 ** of digits compare in numeric order.
  17 **
  18 **     *   Leading zeros are handled properly, in the sense that
  19 **         they do not mess of the maginitude comparison of embedded
  20 **         strings of digits.  "x00123y" is equal to "x123y".
  21 **
  22 **     *   Only unsigned integers are recognized.  Plus and minus
  23 **         signs are ignored.  Decimal points and exponential notation
  24 **         are ignored.
  25 **
  26 **     *   Embedded integers can be of arbitrary length.  Comparison
  27 **         is *not* limited integers that can be expressed as a
  28 **         64-bit machine integer.
  29 */
  30 #include "sqlite3ext.h"
  31 SQLITE_EXTENSION_INIT1
  32 #include <assert.h>
  33 #include <string.h>
  34 #include <ctype.h>
  35
  36 /*
  37 ** Compare text in lexicographic order, except strings of digits
  38 ** compare in numeric order.
  39 */
  40 static int uintCollFunc(
  41   void *notUsed,
  42   int nKey1, const void *pKey1,
  43   int nKey2, const void *pKey2
  44 ){
  45   const unsigned char *zA = (const unsigned char*)pKey1;
  46   const unsigned char *zB = (const unsigned char*)pKey2;
  47   int i=0, j=0, x;
  48   (void)notUsed;
  49   while( i<nKey1 && j<nKey2 ){
  50     x = zA[i] - zB[j];
  51     if( isdigit(zA[i]) ){
  52       int k;
  53       if( !isdigit(zB[j]) ) return x;
  54       while( i<nKey1 && zA[i]=='0' ){ i++; }
  55       while( j<nKey2 && zB[j]=='0' ){ j++; }
  56       k = 0;
  57       while( i+k<nKey1 && isdigit(zA[i+k])
  58              && j+k<nKey2 && isdigit(zB[j+k]) ){
  59         k++;
  60       }
  61       if( i+k<nKey1 && isdigit(zA[i+k]) ){
  62         return +1;
  63       }else if( j+k<nKey2 && isdigit(zB[j+k]) ){
  64         return -1;
  65       }else{
  66         x = memcmp(zA+i, zB+j, k);
  67         if( x ) return x;
  68         i += k;
  69         j += k;
  70       }
  71     }else if( x ){
  72       return x;
  73     }else{
  74       i++;
  75       j++;
  76     }
  77   }
  78   return (nKey1 - i) - (nKey2 - j);
  79 }
  80
  81 #ifdef _WIN32
  82 __declspec(dllexport)
  83 #endif
  84 int sqlite3_uint_init(
  85   sqlite3 *db,
  86   char **pzErrMsg,
  87   const sqlite3_api_routines *pApi
  88 ){
  89   SQLITE_EXTENSION_INIT2(pApi);
  90   (void)pzErrMsg;  /* Unused parameter */
  91   return sqlite3_create_collation(db, "uint", SQLITE_UTF8, 0, uintCollFunc);
  92 }