/*
** Copyright (c) 2007 D. Richard Hipp
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of the GNU General Public
** License version 2 as published by the Free Software Foundation.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
** General Public License for more details.
**
** You should have received a copy of the GNU General Public
** License along with this library; if not, write to the
** Free Software Foundation, Inc., 59 Temple Place - Suite 330,
** Boston, MA 02111-1307, USA.
**
** Author contact information:
** drh@hwaci.com
** http://www.hwaci.com/drh/
**
*******************************************************************************
**
** This module implements a 3-way merge
*/
#include "config.h"
#include "merge3.h"
#if 0
#define DEBUG(X) X
#define ISDEBUG 1
#else
#define DEBUG(X)
#define ISDEBUG 0
#endif
/* The minimum of two integers */
#define min(A,B) (A<B?A:B)
/*
** Compare N lines of text from pV1 and pV2. If the lines
** are the same, return true. Return false if they are different.
**
** The cursor on both pV1 and pV2 is unchanged.
*/
static int sameLines(Blob *pV1, Blob *pV2, int N){
char *z1, *z2;
int i;
if( N==0 ) return 1;
z1 = &blob_buffer(pV1)[blob_tell(pV1)];
z2 = &blob_buffer(pV2)[blob_tell(pV2)];
for(i=0; z1[i]==z2[i]; i++){
if( z1[i]=='\n' ){
N--;
if( N==0 ) return 1;
}
}
return 0;
}
/*
** Look at the next edit triple in both aC1 and aC2. If they describe
** an identical edit, then return 1. If the edits are different,
** return 0.
*/
static int sameEdit(int *aC1, int *aC2, Blob *pV1, Blob *pV2){
if( aC1[0]!=aC2[0] ) return 0;
if( aC1[1]!=aC2[1] ) return 0;
if( aC1[2]!=aC2[2] ) return 0;
if( sameLines(pV1, pV2, aC1[2]) ) return 1;
return 0;
}
/*
** The aC[] array contains triples of integers. Within each triple, the
** elements are:
**
** (0) The number of lines to copy
** (1) The number of lines to delete
** (2) The number of liens to insert
**
** Suppose we want to advance over sz lines of the pivot. This routine
** returns true if that advance would land us on a copy operation. It
** returns false if the advance would end on a delete.
*/
static int ends_at_CPY(int *aC, int sz){
while( sz>0 && (aC[0]>0 || aC[1]>0 || aC[2]>0) ){
if( aC[0]>=sz ) return 1;
sz -= aC[0];
if( aC[1]>sz ) return 0;
sz -= aC[1];
aC += 3;
}
return 1;
}
/*
** pSrc contains an edited file where aC[] describes the edit. Part of
** pSrc has already been output. This routine outputs additional lines
** of pSrc - lines that correspond to the next sz lines of the original
** unedited file.
**
** The aC[] array is updated and the new index into aC[] is returned.
*/
static int output_one_side(
Blob *pOut, /* Write to this blob */
Blob *pSrc, /* The edited file that is to be copied to pOut */
int *aC, /* Array of integer triples describing the edit */
int i, /* Index in aC[] of current location in pSrc */
int sz /* Number of lines in unedited source to output */
){
while( sz>0 ){
if( aC[i]==0 && aC[i+1]==0 && aC[i+2]==0 ) break;
if( aC[i]>=sz ){
blob_copy_lines(pOut, pSrc, sz);
aC[i] -= sz;
break;
}
blob_copy_lines(pOut, pSrc, aC[i]);
blob_copy_lines(pOut, pSrc, aC[i+2]);
sz -= aC[i] + aC[i+1];
i += 3;
}
return i;
}
/*
** Do a three-way merge. Initialize pOut to contain the result.
**
** The merge is an edit against pV2. Both pV1 and pV2 have a
** common origin at pPivot. Apply the changes of pPivot ==> pV1
** to pV2.
**
** The return is 0 upon complete success. If any input file is binary,
** -1 is returned and pOut is unmodified. If there are merge
** conflicts, the merge proceeds as best as it can and the number
** of conflicts is returns
*/
int blob_merge(Blob *pPivot, Blob *pV1, Blob *pV2, Blob *pOut){
int *aC1; /* Changes from pPivot to pV1 */
int *aC2; /* Changes from pPivot to pV2 */
int i1, i2; /* Index into aC1[] and aC2[] */
int nCpy, nDel, nIns; /* Number of lines to copy, delete, or insert */
int limit1, limit2; /* Sizes of aC1[] and aC2[] */
int nConflict = 0; /* Number of merge conflicts seen so far */
static const char zBegin[] = ">>>>>>> BEGIN MERGE CONFLICT\n";
static const char zMid[] = "============================\n";
static const char zEnd[] = "<<<<<<< END MERGE CONFLICT\n";
/* Compute the edits that occur from pPivot => pV1 and pPivot => pV2 */
aC1 = text_diff(pPivot, pV1, 0, 0);
aC2 = text_diff(pPivot, pV2, 0, 0);
if( aC2==0 || aC2==0 ){
free(aC1);
free(aC2);
return -1;
}
blob_zero(pOut); /* Merge results stored in pOut */
blob_rewind(pV1); /* Rewind inputs: Needed to reconstruct output */
blob_rewind(pV2);
blob_rewind(pPivot);
/* Determine the length of the aC1[] and aC2[] change vectors */
for(i1=0; aC1[i1] || aC1[i1+1] || aC1[i1+2]; i1+=3){}
limit1 = i1;
for(i2=0; aC2[i2] || aC2[i2+1] || aC2[i2+2]; i2+=3){}
limit2 = i2;
DEBUG(
for(i1=0; i1<limit1; i1+=3){
printf("c1: %4d %4d %4d\n", aC1[i1], aC1[i1+1], aC1[i1+2]);
}
for(i2=0; i2<limit2; i2+=3){
printf("c2: %4d %4d %4d\n", aC2[i2], aC2[i2+1], aC2[i2+2]);
}
)
i1 = i2 = 0;
while( i1<limit1 && i2<limit2 ){
DEBUG( printf("%d: %2d %2d %2d %d: %2d %2d %2d\n",
i1/3, aC1[i1], aC1[i1+1], aC1[i1+2],
i2/3, aC2[i2], aC2[i2+1], aC2[i2+2]); )
if( aC1[i1]>0 && aC2[i2]>0 ){
nCpy = min(aC1[i1], aC2[i2]);
DEBUG( printf("COPY %d\n", nCpy); )
blob_copy_lines(pOut, pPivot, nCpy);
blob_copy_lines(0, pV1, nCpy);
blob_copy_lines(0, pV2, nCpy);
aC1[i1] -= nCpy;
aC2[i2] -= nCpy;
}else
if( aC1[i1] >= aC2[i2+1] && aC1[i1]>0 && aC2[i2+1]+aC2[i2+2]>0 ){
nDel = aC2[i2+1];
nIns = aC2[i2+2];
DEBUG( printf("EDIT -%d+%d left\n", nDel, nIns); )
blob_copy_lines(0, pPivot, nDel);
blob_copy_lines(0, pV1, nDel);
blob_copy_lines(pOut, pV2, nIns);
aC1[i1] -= nDel;
i2 += 3;
}else
if( aC2[i2] >= aC1[i1+1] && aC2[i2]>0 && aC1[i1+1]+aC1[i1+2]>0 ){
nDel = aC1[i1+1];
nIns = aC1[i1+2];
DEBUG( printf("EDIT -%d+%d right\n", nDel, nIns); )
blob_copy_lines(0, pPivot, nDel);
blob_copy_lines(0, pV2, nDel);
blob_copy_lines(pOut, pV1, nIns);
aC2[i2] -= nDel;
i1 += 3;
}else
if( sameEdit(&aC1[i1], &aC2[i2], pV1, pV2) ){
assert( aC1[i1]==0 );
nDel = aC1[i1+1];
nIns = aC1[i1+2];
DEBUG( printf("EDIT -%d+%d both\n", nDel, nIns); )
blob_copy_lines(0, pPivot, nDel);
blob_copy_lines(pOut, pV1, nIns);
blob_copy_lines(0, pV2, nIns);
i1 += 3;
i2 += 3;
}else
{
int sz = 1; /* Size of the conflict in lines */
nConflict++;
while( !ends_at_CPY(&aC1[i1], sz) || !ends_at_CPY(&aC2[i2], sz) ){
sz++;
}
DEBUG( printf("CONFLICT %d\n", sz); )
blob_appendf(pOut, zBegin);
i1 = output_one_side(pOut, pV1, aC1, i1, sz);
blob_appendf(pOut, zMid);
i2 = output_one_side(pOut, pV2, aC2, i2, sz);
blob_appendf(pOut, zEnd);
blob_copy_lines(0, pPivot, sz);
}
if( i1<limit1 && aC1[i1]==0 && aC1[i1+1]==0 && aC1[i1+2]==0 ) i1+=3;
if( i2<limit2 && aC2[i2]==0 && aC2[i2+1]==0 && aC2[i2+2]==0 ) i2+=3;
}
DEBUG( printf("%d: %2d %2d %2d %d: %2d %2d %2d\n",
i1/3, aC1[i1], aC1[i1+1], aC1[i1+2],
i2/3, aC2[i2], aC2[i2+1], aC2[i2+2]); )
if( i1<limit1 && aC1[i1+2]>0 ){
DEBUG( printf("INSERT +%d left\n", aC1[i1+2]); )
blob_copy_lines(pOut, pV1, aC1[i1+2]);
}else if( i2<limit2 && aC2[i2+2]>0 ){
DEBUG( printf("INSERT +%d right\n", aC2[i2+2]); )
blob_copy_lines(pOut, pV2, aC2[i2+2]);
}
free(aC1);
free(aC2);
return nConflict;
}
/*
** COMMAND: test-3-way-merge
**
** Combine change in going from PIVOT->VERSION1 with the change going
** from PIVOT->VERSION2 and write the combined changes into MERGED.
*/
void delta_3waymerge_cmd(void){
Blob pivot, v1, v2, merged;
if( g.argc!=6 ){
fprintf(stderr,"Usage: %s %s PIVOT V1 V2 MERGED\n", g.argv[0], g.argv[1]);
exit(1);
}
if( blob_read_from_file(&pivot, g.argv[2])<0 ){
fprintf(stderr,"cannot read %s\n", g.argv[2]);
exit(1);
}
if( blob_read_from_file(&v1, g.argv[3])<0 ){
fprintf(stderr,"cannot read %s\n", g.argv[3]);
exit(1);
}
if( blob_read_from_file(&v2, g.argv[4])<0 ){
fprintf(stderr,"cannot read %s\n", g.argv[4]);
exit(1);
}
blob_merge(&pivot, &v1, &v2, &merged);
if( blob_write_to_file(&merged, g.argv[5])<blob_size(&merged) ){
fprintf(stderr,"cannot write %s\n", g.argv[4]);
exit(1);
}
blob_reset(&pivot);
blob_reset(&v1);
blob_reset(&v2);
blob_reset(&merged);
}