bsdifflib.c

/*-
 * Copyright 2010, Peter Vaskovic, (petervaskovic@yahoo.de)
 * Copyright 2007 Andreas John <dynacore@tesla.inka.de>
 * Copyright 2003-2005 Colin Percival
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted providing that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
*/

#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <bzlib.h>
#include "bsdifflib.h"

typedef unsigned char u_char;

#define MIN(x,y) (((x)<(y)) ? (x) : (y))

static void split(off_t *I,off_t *V,off_t start,off_t len,off_t h)
{
	off_t i,j,k,x,tmp,jj,kk;

	if(len<16)
	{
		for(k=start; k<start+len; k+=j)
		{
			j=1;
			x=V[I[k]+h];

			for(i=1; k+i<start+len; i++)
			{
				if(V[I[k+i]+h]<x)
				{
					x=V[I[k+i]+h];
					j=0;
				};

				if(V[I[k+i]+h]==x)
				{
					tmp=I[k+j];
					I[k+j]=I[k+i];
					I[k+i]=tmp;
					j++;
				};
			};

			for(i=0; i<j; i++)
			{
				V[I[k+i]]=k+j-1;
			}

			if(j==1)
			{
				I[k]=-1;
			}
		};

		return;
	};

	x=V[I[start+len/2]+h];

	jj=0;

	kk=0;

	for(i=start; i<start+len; i++)
	{
		if(V[I[i]+h]<x)
		{
			jj++;
		}

		if(V[I[i]+h]==x)
		{
			kk++;
		}
	};

	jj+=start;

	kk+=jj;

	i=start;

	j=0;

	k=0;

	while(i<jj)
	{
		if(V[I[i]+h]<x)
		{
			i++;
		}
		else if(V[I[i]+h]==x)
		{
			tmp=I[i];
			I[i]=I[jj+j];
			I[jj+j]=tmp;
			j++;
		}
		else
		{
			tmp=I[i];
			I[i]=I[kk+k];
			I[kk+k]=tmp;
			k++;
		};
	};

	while(jj+j<kk)
	{
		if(V[I[jj+j]+h]==x)
		{
			j++;
		}
		else
		{
			tmp=I[jj+j];
			I[jj+j]=I[kk+k];
			I[kk+k]=tmp;
			k++;
		};
	};

	if(jj>start)
	{
		split(I,V,start,jj-start,h);
	}

	for(i=0; i<kk-jj; i++)
	{
		V[I[jj+i]]=kk-1;
	}

	if(jj==kk-1)
	{
		I[jj]=-1;
	}

	if(start+len>kk)
	{
		split(I,V,kk,start+len-kk,h);
	}
}

static void qsufsort(off_t *I,off_t *V,u_char *old,off_t oldsize)
{
	off_t buckets[256];
	off_t i,h,len;

	for(i=0; i<256; i++)
	{
		buckets[i]=0;
	}

	for(i=0; i<oldsize; i++)
	{
		buckets[old[i]]++;
	}

	for(i=1; i<256; i++)
	{
		buckets[i]+=buckets[i-1];
	}

	for(i=255; i>0; i--)
	{
		buckets[i]=buckets[i-1];
	}

	buckets[0]=0;

	for(i=0; i<oldsize; i++)
	{
		I[++buckets[old[i]]]=i;
	}

	I[0]=oldsize;

	for(i=0; i<oldsize; i++)
	{
		V[i]=buckets[old[i]];
	}

	V[oldsize]=0;

	for(i=1; i<256; i++) if(buckets[i]==buckets[i-1]+1)
		{
			I[buckets[i]]=-1;
		}

	I[0]=-1;

	for(h=1; I[0]!=-(oldsize+1); h+=h)
	{
		len=0;

		for(i=0; i<oldsize+1;)
		{
			if(I[i]<0)
			{
				len-=I[i];
				i-=I[i];
			}
			else
			{
				if(len)
				{
					I[i-len]=-len;
				}

				len=V[I[i]]+1-i;
				split(I,V,i,len,h);
				i+=len;
				len=0;
			};
		};

		if(len)
		{
			I[i-len]=-len;
		}
	};

	for(i=0; i<oldsize+1; i++)
	{
		I[V[i]]=i;
	}
}

static off_t matchlen(u_char *old,off_t oldsize,u_char *_new,off_t newsize)
{
	off_t i;

	for(i=0; (i<oldsize)&&(i<newsize); i++)
		if(old[i]!=_new[i])
		{
			break;
		}

	return i;
}

static off_t search(off_t *I,u_char *old,off_t oldsize,
                    u_char *_new,off_t newsize,off_t st,off_t en,off_t *pos)
{
	off_t x,y;

	if(en-st<2)
	{
		x=matchlen(old+I[st],oldsize-I[st],_new,newsize);
		y=matchlen(old+I[en],oldsize-I[en],_new,newsize);

		if(x>y)
		{
			*pos=I[st];
			return x;
		}
		else
		{
			*pos=I[en];
			return y;
		}
	};

	x=st+(en-st)/2;

	if(memcmp(old+I[x],_new,MIN(oldsize-I[x],newsize))<0)
	{
		return search(I,old,oldsize,_new,newsize,x,en,pos);
	}
	else
	{
		return search(I,old,oldsize,_new,newsize,st,x,pos);
	};
}

static void offtout(off_t x,u_char *buf)
{
	off_t y;

	if(x<0)
	{
		y=-x;
	}
	else
	{
		y=x;
	}

	buf[0]=y%256;
	y-=buf[0];
	y=y/256;
	buf[1]=y%256;
	y-=buf[1];
	y=y/256;
	buf[2]=y%256;
	y-=buf[2];
	y=y/256;
	buf[3]=y%256;
	y-=buf[3];
	y=y/256;
	buf[4]=y%256;
	y-=buf[4];
	y=y/256;
	buf[5]=y%256;
	y-=buf[5];
	y=y/256;
	buf[6]=y%256;
	y-=buf[6];
	y=y/256;
	buf[7]=y%256;

	if(x<0)
	{
		buf[7]|=0x80;
	}
}

char *bsdiff(const char *oldfile, const char *newfile,
             const char *patchfile)
{
	u_char *old = NULL;
	u_char *_new = NULL;
	off_t oldsize,newsize;
	off_t *I = NULL;
	off_t *V = NULL;
	off_t scan, len;
	off_t pos = 0;
	off_t lastscan,lastpos,lastoffset;
	off_t oldscore,scsc;
	off_t s,Sf,lenf,Sb,lenb;
	off_t overlap,Ss,lens;
	off_t i;
	off_t dblen,eblen;
	u_char *db = NULL;
	u_char *eb = NULL;
	u_char buf[8];
	u_char header[32];
	FILE * pf, * fp;
	BZFILE * pfbz2;
	int bz2err;
	static char	errstr[1024];

	/* Allocate oldsize+1 bytes instead of oldsize bytes to ensure
		that we never try to malloc(0) and get a NULL pointer */
	if(((fp=fopen(oldfile,"rb")) == NULL) ||
	        (fseek(fp,0,SEEK_END)!=0) ||
	        ((oldsize=ftell(fp))==-1) ||
	        ((old=(u_char*)malloc(oldsize+1))==NULL) ||
	        (fseek(fp,0,SEEK_SET)!=0) ||
	        ((off_t)fread(old,1,oldsize,fp)!=oldsize))
	{
		sprintf(errstr,"Cannot process file \"%s\".",oldfile);
		free(old);

		if(fp)
		{
			fclose(fp);
		}

		return errstr;
	}

	if(fclose(fp)!=0)
	{
		sprintf(errstr,"Cannot close file \"%s\".",oldfile);
		free(old);
		return errstr;
	}

	if(((I=(off_t*)malloc((oldsize+1)*sizeof(off_t)))==NULL) ||
	        ((V=(off_t*)malloc((oldsize+1)*sizeof(off_t)))==NULL))
	{
		sprintf(errstr,"Cannot allocate memory.");
		free(I);
		free(V);
		free(old);
		return errstr;
	}

	qsufsort(I,V,old,oldsize);
	free(V);

	/* Allocate newsize+1 bytes instead of newsize bytes to ensure
		that we never try to malloc(0) and get a NULL pointer */
	if(((fp=fopen(newfile,"rb")) == NULL) ||
	        (fseek(fp,0,SEEK_END)!=0) ||
	        ((newsize=ftell(fp))==-1) ||
	        ((_new=(u_char*)malloc(newsize+1))==NULL) ||
	        (fseek(fp,0,SEEK_SET)!=0) ||
	        ((off_t)fread(_new,1,newsize,fp)!=newsize))
	{
		sprintf(errstr,"Cannot process file \"%s\".",newfile);
		free(I);
		free(_new);
		free(old);

		if(fp)
		{
			fclose(fp);
		}

		return errstr;
	}

	if(fclose(fp)!=0)
	{
		sprintf(errstr,"Cannot process file \"%s\".",newfile);
		free(I);
		free(_new);
		free(old);
		return errstr;
	}

	if(((db=(u_char*)malloc(newsize+1))==NULL) ||
	        ((eb=(u_char*)malloc(newsize+1))==NULL))
	{
		sprintf(errstr,"Cannot allocate memory.");
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		return errstr;
	}

	dblen=0;
	eblen=0;

	/* Create the patch file */
	if ((pf = fopen(patchfile, "wb")) == NULL)
	{
		sprintf(errstr,"Cannot open file \"%s\".",patchfile);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		return errstr;
	}

	/* Header is
		0	8	 "BSDIFF40"
		8	8	length of bzip2ed ctrl block
		16	8	length of bzip2ed diff block
		24	8	length of new file */
	/* File is
		0	32	Header
		32	??	Bzip2ed ctrl block
		??	??	Bzip2ed diff block
		??	??	Bzip2ed extra block */
	memcpy(header,"BSDIFF40",8);
	offtout(0, header + 8);
	offtout(0, header + 16);
	offtout(newsize, header + 24);

	if (fwrite(header, 32, 1, pf) != 1)
	{
		sprintf(errstr,"Cannot write file \"%s\".",patchfile);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		fclose(pf);
		return errstr;
	}

	/* Compute the differences, writing ctrl as we go */
	if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)
	{
		sprintf(errstr,"BZ2_bzWriteOpen, bz2err = %d", bz2err);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		fclose(pf);
		return errstr;
	}

	scan=0;
	len=0;
	lastscan=0;
	lastpos=0;
	lastoffset=0;

	while(scan<newsize)
	{
		oldscore=0;

		for(scsc=scan+=len; scan<newsize; scan++)
		{
			len=search(I,old,oldsize,_new+scan,newsize-scan,
			           0,oldsize,&pos);

			for(; scsc<scan+len; scsc++)
				if((scsc+lastoffset<oldsize) &&
				        (old[scsc+lastoffset] == _new[scsc]))
				{
					oldscore++;
				}

			if(((len==oldscore) && (len!=0)) ||
			        (len>oldscore+8))
			{
				break;
			}

			if((scan+lastoffset<oldsize) &&
			        (old[scan+lastoffset] == _new[scan]))
			{
				oldscore--;
			}
		};

		if((len!=oldscore) || (scan==newsize))
		{
			s=0;
			Sf=0;
			lenf=0;

			for(i=0; (lastscan+i<scan)&&(lastpos+i<oldsize);)
			{
				if(old[lastpos+i]==_new[lastscan+i])
				{
					s++;
				}

				i++;

				if(s*2-i>Sf*2-lenf)
				{
					Sf=s;
					lenf=i;
				};
			};

			lenb=0;

			if(scan<newsize)
			{
				s=0;
				Sb=0;

				for(i=1; (scan>=lastscan+i)&&(pos>=i); i++)
				{
					if(old[pos-i]==_new[scan-i])
					{
						s++;
					}

					if(s*2-i>Sb*2-lenb)
					{
						Sb=s;
						lenb=i;
					};
				};
			};

			if(lastscan+lenf>scan-lenb)
			{
				overlap=(lastscan+lenf)-(scan-lenb);
				s=0;
				Ss=0;
				lens=0;

				for(i=0; i<overlap; i++)
				{
					if(_new[lastscan+lenf-overlap+i]==
					        old[lastpos+lenf-overlap+i])
					{
						s++;
					}

					if(_new[scan-lenb+i]==
					        old[pos-lenb+i])
					{
						s--;
					}

					if(s>Ss)
					{
						Ss=s;
						lens=i+1;
					};
				};

				lenf+=lens-overlap;

				lenb-=lens;
			};

			for(i=0; i<lenf; i++)
			{
				db[dblen+i]=_new[lastscan+i]-old[lastpos+i];
			}

			for(i=0; i<(scan-lenb)-(lastscan+lenf); i++)
			{
				eb[eblen+i]=_new[lastscan+lenf+i];
			}

			dblen+=lenf;
			eblen+=(scan-lenb)-(lastscan+lenf);
			offtout(lenf,buf);
			BZ2_bzWrite(&bz2err, pfbz2, buf, 8);

			if (bz2err != BZ_OK)
			{
				sprintf(errstr,"BZ2_bzWrite, bz2err = %d", bz2err);
				free(I);
				free(_new);
				free(old);
				free(db);
				free(eb);
				BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
				fclose(pf);
				return errstr;
			}

			offtout((scan-lenb)-(lastscan+lenf),buf);
			BZ2_bzWrite(&bz2err, pfbz2, buf, 8);

			if (bz2err != BZ_OK)
			{
				sprintf(errstr,"BZ2_bzWrite, bz2err = %d", bz2err);
				free(I);
				free(_new);
				free(old);
				free(db);
				free(eb);
				BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
				fclose(pf);
				return errstr;
			}

			offtout((pos-lenb)-(lastpos+lenf),buf);
			BZ2_bzWrite(&bz2err, pfbz2, buf, 8);

			if (bz2err != BZ_OK)
			{
				sprintf(errstr,"BZ2_bzWrite, bz2err = %d", bz2err);
				free(I);
				free(_new);
				free(old);
				free(db);
				free(eb);
				BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
				fclose(pf);
				return errstr;
			}

			lastscan=scan-lenb;
			lastpos=pos-lenb;
			lastoffset=pos-scan;
		};
	};

	BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);

	if (bz2err != BZ_OK)
	{
		sprintf(errstr,"BZ2_bzWriteClose, bz2err = %d", bz2err);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		fclose(pf);
		return errstr;
	}

	/* Compute size of compressed ctrl data */
	if ((len = ftell(pf)) == -1)
	{
		sprintf(errstr,"Cannot return current value of the position indicator in file \"%s\".",patchfile);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		fclose(pf);
		return errstr;
	}

	offtout(len-32, header + 8);

	/* Write compressed diff data */
	if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)
	{
		sprintf(errstr,"BZ2_bzWriteOpen, bz2err = %d", bz2err);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		fclose(pf);
		return errstr;
	}

	BZ2_bzWrite(&bz2err, pfbz2, db, dblen);

	if (bz2err != BZ_OK)
	{
		sprintf(errstr,"BZ2_bzWrite, bz2err = %d", bz2err);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
		fclose(pf);
		return errstr;
	}

	BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);

	if (bz2err != BZ_OK)
	{
		sprintf(errstr,"BZ2_bzWriteClose, bz2err = %d", bz2err);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		fclose(pf);
		return errstr;
	}

	/* Compute size of compressed diff data */
	if ((newsize = ftell(pf)) == -1)
	{
		sprintf(errstr,"Cannot return current value of the position indicator in file \"%s\".",patchfile);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		fclose(pf);
		return errstr;
	}

	offtout(newsize - len, header + 16);

	/* Write compressed extra data */
	if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)
	{
		sprintf(errstr,"BZ2_bzWriteOpen, bz2err = %d", bz2err);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		fclose(pf);
		return errstr;
	}

	BZ2_bzWrite(&bz2err, pfbz2, eb, eblen);

	if (bz2err != BZ_OK)
	{
		sprintf(errstr,"BZ2_bzWrite, bz2err = %d", bz2err);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
		fclose(pf);
		return errstr;
	}

	BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);

	if (bz2err != BZ_OK)
	{
		sprintf(errstr,"BZ2_bzWriteClose, bz2err = %d", bz2err);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		fclose(pf);
		return errstr;
	}

	/* Seek to the beginning, write the header, and close the file */
	if (fseek(pf, 0, SEEK_SET))
	{
		sprintf(errstr,"Cannot change the file position indicator in file \"%s\".",patchfile);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		fclose(pf);
		return errstr;
	}

	if (fwrite(header, 32, 1, pf) != 1)
	{
		sprintf(errstr,"Cannot write file \"%s\".",patchfile);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		fclose(pf);
		return errstr;
	}

	if (fclose(pf))
	{
		sprintf(errstr,"Cannot close file \"%s\".",patchfile);
		free(I);
		free(_new);
		free(old);
		free(db);
		free(eb);
		return errstr;
	}

	/* Free the memory we used */
	free(db);
	free(eb);
	free(I);
	free(old);
	free(_new);
	return NULL;
}