93 lines
2.5 KiB
C
93 lines
2.5 KiB
C
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/*
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** 2020-04-14
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**
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** The author disclaims copyright to this source code. In place of
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** a legal notice, here is a blessing:
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**
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** May you do good and not evil.
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** May you find forgiveness for yourself and forgive others.
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** May you share freely, never taking more than you give.
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**
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******************************************************************************
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**
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** This SQLite extension implements the UINT collating sequence.
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**
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** UINT works like BINARY for text, except that embedded strings
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** of digits compare in numeric order.
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**
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** * Leading zeros are handled properly, in the sense that
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** they do not mess of the maginitude comparison of embedded
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** strings of digits. "x00123y" is equal to "x123y".
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**
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** * Only unsigned integers are recognized. Plus and minus
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** signs are ignored. Decimal points and exponential notation
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** are ignored.
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**
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** * Embedded integers can be of arbitrary length. Comparison
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** is *not* limited integers that can be expressed as a
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** 64-bit machine integer.
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*/
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#include "sqlite3ext.h"
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SQLITE_EXTENSION_INIT1
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#include <assert.h>
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#include <string.h>
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#include <ctype.h>
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/*
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** Compare text in lexicographic order, except strings of digits
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** compare in numeric order.
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*/
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static int uintCollFunc(
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void *notUsed,
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int nKey1, const void *pKey1,
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int nKey2, const void *pKey2
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){
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const unsigned char *zA = (const unsigned char*)pKey1;
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const unsigned char *zB = (const unsigned char*)pKey2;
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int i=0, j=0, x;
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(void)notUsed;
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while( i<nKey1 && j<nKey2 ){
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x = zA[i] - zB[j];
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if( isdigit(zA[i]) ){
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int k;
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if( !isdigit(zB[j]) ) return x;
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while( i<nKey1 && zA[i]=='0' ){ i++; }
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while( j<nKey2 && zB[j]=='0' ){ j++; }
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k = 0;
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while( i+k<nKey1 && isdigit(zA[i+k])
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&& j+k<nKey2 && isdigit(zB[j+k]) ){
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k++;
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}
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if( i+k<nKey1 && isdigit(zA[i+k]) ){
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return +1;
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}else if( j+k<nKey2 && isdigit(zB[j+k]) ){
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return -1;
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}else{
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x = memcmp(zA+i, zB+j, k);
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if( x ) return x;
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i += k;
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j += k;
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}
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}else if( x ){
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return x;
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}else{
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i++;
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j++;
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}
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}
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return (nKey1 - i) - (nKey2 - j);
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}
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#ifdef _WIN32
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__declspec(dllexport)
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#endif
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int sqlite3_uint_init(
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sqlite3 *db,
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char **pzErrMsg,
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const sqlite3_api_routines *pApi
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){
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SQLITE_EXTENSION_INIT2(pApi);
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(void)pzErrMsg; /* Unused parameter */
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return sqlite3_create_collation(db, "uint", SQLITE_UTF8, 0, uintCollFunc);
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}
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