/*
** 2020年04月14日
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
******************************************************************************
**
** This SQLite extension implements the UINT collating sequence.
**
** UINT works like BINARY for text, except that embedded strings
** of digits compare in numeric order.
**
** * Leading zeros are handled properly, in the sense that
** they do not mess of the maginitude comparison of embedded
** strings of digits. "x00123y" is equal to "x123y".
**
** * Only unsigned integers are recognized. Plus and minus
** signs are ignored. Decimal points and exponential notation
** are ignored.
**
** * Embedded integers can be of arbitrary length. Comparison
** is *not* limited integers that can be expressed as a
** 64-bit machine integer.
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
#include <ctype.h>

/*
** Compare text in lexicographic order, except strings of digits
** compare in numeric order.
*/
static int uintCollFunc(
 void *notUsed,
 int nKey1, const void *pKey1,
 int nKey2, const void *pKey2
){
 const unsigned char *zA = (const unsigned char*)pKey1;
 const unsigned char *zB = (const unsigned char*)pKey2;
 int i=0, j=0, x;
 (void)notUsed;
 while( i<nKey1 && j<nKey2 ){
 x = zA[i] - zB[j];
 if( isdigit(zA[i]) ){
 int k;
 if( !isdigit(zB[j]) ) return x;
 while( i<nKey1 && zA[i]=='0' ){ i++; }
 while( j<nKey2 && zB[j]=='0' ){ j++; }
 k = 0;
 while( i+k<nKey1 && isdigit(zA[i+k])
 && j+k<nKey2 && isdigit(zB[j+k]) ){
 k++;
 }
 if( i+k<nKey1 && isdigit(zA[i+k]) ){
 return +1;
 }else if( j+k<nKey2 && isdigit(zB[j+k]) ){
 return -1;
 }else{
 x = memcmp(zA+i, zB+j, k);
 if( x ) return x;
 i += k;
 j += k;
 }
 }else if( x ){
 return x;
 }else{
 i++;
 j++;
 }
 }
 return (nKey1 - i) - (nKey2 - j);
}

#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_uint_init(
 sqlite3 *db, 
 char **pzErrMsg, 
 const sqlite3_api_routines *pApi
){
 SQLITE_EXTENSION_INIT2(pApi);
 (void)pzErrMsg; /* Unused parameter */
 return sqlite3_create_collation(db, "uint", SQLITE_UTF8, 0, uintCollFunc);
}