Skip to content
Snippets Groups Projects
Select Git revision
  • v1.0rc3
  • passt default
  • master
  • pu
  • todo
  • next
  • maint
  • v2.8.0-rc1
  • v2.8.0-rc0
  • v2.7.2
  • v2.7.1
  • v2.7.0
  • v2.6.5
  • v2.7.0-rc3
  • v2.7.0-rc2
  • v2.7.0-rc1
  • v2.7.0-rc0
  • v2.6.4
  • v2.6.3
  • v2.6.2
  • v2.6.1
  • v2.3.10
  • v2.5.4
  • v2.4.10
  • v2.6.0
  • v2.6.0-rc3
  • v2.5.3
27 results

diffcore-break.c

Blame
  • diff-delta.c 7.14 KiB
    /*
     * diff-delta.c: generate a delta between two buffers
     *
     *  Many parts of this file have been lifted from LibXDiff version 0.10.
     *  http://www.xmailserver.org/xdiff-lib.html
     *
     *  LibXDiff was written by Davide Libenzi <davidel@xmailserver.org>
     *  Copyright (C) 2003	Davide Libenzi
     *
     *  Many mods for GIT usage by Nicolas Pitre <nico@cam.org>, (C) 2005.
     *
     *  This file is free software; you can redistribute it and/or
     *  modify it under the terms of the GNU Lesser General Public
     *  License as published by the Free Software Foundation; either
     *  version 2.1 of the License, or (at your option) any later version.
     *
     *  Use of this within git automatically means that the LGPL
     *  licensing gets turned into GPLv2 within this project.
     */
    
    #include <stdlib.h>
    #include "delta.h"
    
    
    /* block size: min = 16, max = 64k, power of 2 */
    #define BLK_SIZE 16
    
    #define MIN(a, b) ((a) < (b) ? (a) : (b))
    
    #define GR_PRIME 0x9e370001
    #define HASH(v, b) (((unsigned int)(v) * GR_PRIME) >> (32 - (b)))
    	
    /* largest prime smaller than 65536 */
    #define BASE 65521
    
    /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
    #define NMAX 5552
    
    #define DO1(buf, i)  { s1 += buf[i]; s2 += s1; }
    #define DO2(buf, i)  DO1(buf, i); DO1(buf, i + 1);
    #define DO4(buf, i)  DO2(buf, i); DO2(buf, i + 2);
    #define DO8(buf, i)  DO4(buf, i); DO4(buf, i + 4);
    #define DO16(buf)    DO8(buf, 0); DO8(buf, 8);
    
    static unsigned int adler32(unsigned int adler, const unsigned char *buf, int len)
    {
    	int k;
    	unsigned int s1 = adler & 0xffff;
    	unsigned int s2 = adler >> 16;
    
    	while (len > 0) {
    		k = MIN(len, NMAX);
    		len -= k;
    		while (k >= 16) {
    			DO16(buf);
    			buf += 16;
    			k -= 16;
    		}
    		if (k != 0)
    			do {
    				s1 += *buf++;
    				s2 += s1;
    			} while (--k);
    		s1 %= BASE;
    		s2 %= BASE;
    	}
    
    	return (s2 << 16) | s1;
    }
    
    static unsigned int hashbits(unsigned int size)
    {
    	unsigned int val = 1, bits = 0;
    	while (val < size && bits < 32) {
    		val <<= 1;
    	       	bits++;
    	}
    	return bits ? bits: 1;
    }
    
    typedef struct s_chanode {
    	struct s_chanode *next;
    	int icurr;
    } chanode_t;
    
    typedef struct s_chastore {
    	chanode_t *head, *tail;
    	int isize, nsize;
    	chanode_t *ancur;
    	chanode_t *sncur;
    	int scurr;
    } chastore_t;
    
    static void cha_init(chastore_t *cha, int isize, int icount)
    {
    	cha->head = cha->tail = NULL;
    	cha->isize = isize;
    	cha->nsize = icount * isize;
    	cha->ancur = cha->sncur = NULL;
    	cha->scurr = 0;
    }
    
    static void *cha_alloc(chastore_t *cha)
    {
    	chanode_t *ancur;
    	void *data;
    
    	ancur = cha->ancur;
    	if (!ancur || ancur->icurr == cha->nsize) {
    		ancur = malloc(sizeof(chanode_t) + cha->nsize);
    		if (!ancur)
    			return NULL;
    		ancur->icurr = 0;
    		ancur->next = NULL;
    		if (cha->tail)
    			cha->tail->next = ancur;
    		if (!cha->head)
    			cha->head = ancur;
    		cha->tail = ancur;
    		cha->ancur = ancur;
    	}
    
    	data = (void *)ancur + sizeof(chanode_t) + ancur->icurr;
    	ancur->icurr += cha->isize;
    	return data;
    }
    
    static void cha_free(chastore_t *cha)
    {
    	chanode_t *cur = cha->head;
    	while (cur) {
    		chanode_t *tmp = cur;
    		cur = cur->next;
    		free(tmp);
    	}
    }
    
    typedef struct s_bdrecord {
    	struct s_bdrecord *next;
    	unsigned int fp;
    	const unsigned char *ptr;
    } bdrecord_t;
    
    typedef struct s_bdfile {
    	const unsigned char *data, *top;
    	chastore_t cha;
    	unsigned int fphbits;
    	bdrecord_t **fphash;
    } bdfile_t;
    
    static int delta_prepare(const unsigned char *buf, int bufsize, bdfile_t *bdf)
    {
    	unsigned int fphbits;
    	int i, hsize;
    	const unsigned char *base, *data, *top;
    	bdrecord_t *brec;
    	bdrecord_t **fphash;
    
    	fphbits = hashbits(bufsize / BLK_SIZE + 1);
    	hsize = 1 << fphbits;
    	fphash = malloc(hsize * sizeof(bdrecord_t *));
    	if (!fphash)
    		return -1;
    	for (i = 0; i < hsize; i++)
    		fphash[i] = NULL;
    	cha_init(&bdf->cha, sizeof(bdrecord_t), hsize / 4 + 1);
    
    	bdf->data = data = base = buf;
    	bdf->top = top = buf + bufsize;
    	data += (bufsize / BLK_SIZE) * BLK_SIZE;
    	if (data == top)
    		data -= BLK_SIZE;
    
    	for ( ; data >= base; data -= BLK_SIZE) {
    		brec = cha_alloc(&bdf->cha);
    		if (!brec) {
    			cha_free(&bdf->cha);
    			free(fphash);
    			return -1;
    		}
    		brec->fp = adler32(0, data, MIN(BLK_SIZE, top - data));
    		brec->ptr = data;
    		i = HASH(brec->fp, fphbits);
    		brec->next = fphash[i];
    		fphash[i] = brec;
    	}
    
    	bdf->fphbits = fphbits;
    	bdf->fphash = fphash;
    
    	return 0;
    }
    
    static void delta_cleanup(bdfile_t *bdf)
    {
    	free(bdf->fphash);
    	cha_free(&bdf->cha);
    }
    
    #define COPYOP_SIZE(o, s) \
        (!!(o & 0xff) + !!(o & 0xff00) + !!(o & 0xff0000) + !!(o & 0xff000000) + \
         !!(s & 0xff) + !!(s & 0xff00) + 1)
    
    void *diff_delta(void *from_buf, unsigned long from_size,
    		 void *to_buf, unsigned long to_size,
    		 unsigned long *delta_size,
    		 unsigned long max_size)
    {
    	int i, outpos, outsize, inscnt, csize, msize, moff;
    	unsigned int fp;
    	const unsigned char *data, *top, *ptr1, *ptr2;
    	unsigned char *out, *orig;
    	bdrecord_t *brec;
    	bdfile_t bdf;
    
    	if (!from_size || !to_size || delta_prepare(from_buf, from_size, &bdf))
    		return NULL;
    	
    	outpos = 0;
    	outsize = 8192;
    	out = malloc(outsize);
    	if (!out) {
    		delta_cleanup(&bdf);
    		return NULL;
    	}
    
    	data = to_buf;
    	top = to_buf + to_size;
    
    	/* store reference buffer size */
    	out[outpos++] = from_size;
    	from_size >>= 7;
    	while (from_size) {
    		out[outpos - 1] |= 0x80;
    		out[outpos++] = from_size;
    		from_size >>= 7;
    	}
    
    	/* store target buffer size */
    	out[outpos++] = to_size;
    	to_size >>= 7;
    	while (to_size) {
    		out[outpos - 1] |= 0x80;
    		out[outpos++] = to_size;
    		to_size >>= 7;
    	}
    
    	inscnt = 0;
    	moff = 0;
    	while (data < top) {
    		msize = 0;
    		fp = adler32(0, data, MIN(top - data, BLK_SIZE));
    		i = HASH(fp, bdf.fphbits);
    		for (brec = bdf.fphash[i]; brec; brec = brec->next) {
    			if (brec->fp == fp) {
    				csize = bdf.top - brec->ptr;
    				if (csize > top - data)
    					csize = top - data;
    				for (ptr1 = brec->ptr, ptr2 = data; 
    				     csize && *ptr1 == *ptr2;
    				     csize--, ptr1++, ptr2++);
    
    				csize = ptr1 - brec->ptr;
    				if (csize > msize) {
    					moff = brec->ptr - bdf.data;
    					msize = csize;
    					if (msize >= 0x10000) {
    						msize = 0x10000;
    						break;
    					}
    				}
    			}
    		}
    
    		if (!msize || msize < COPYOP_SIZE(moff, msize)) {
    			if (!inscnt)
    				outpos++;
    			out[outpos++] = *data++;
    			inscnt++;
    			if (inscnt == 0x7f) {
    				out[outpos - inscnt - 1] = inscnt;
    				inscnt = 0;
    			}
    		} else {
    			if (inscnt) {
    				out[outpos - inscnt - 1] = inscnt;
    				inscnt = 0;
    			}
    
    			data += msize;
    			orig = out + outpos++;
    			i = 0x80;
    
    			if (moff & 0xff) { out[outpos++] = moff; i |= 0x01; }
    			moff >>= 8;
    			if (moff & 0xff) { out[outpos++] = moff; i |= 0x02; }
    			moff >>= 8;
    			if (moff & 0xff) { out[outpos++] = moff; i |= 0x04; }
    			moff >>= 8;
    			if (moff & 0xff) { out[outpos++] = moff; i |= 0x08; }
    
    			if (msize & 0xff) { out[outpos++] = msize; i |= 0x10; }
    			msize >>= 8;
    			if (msize & 0xff) { out[outpos++] = msize; i |= 0x20; }
    
    			*orig = i;
    		}
    
    		if (max_size && outpos > max_size) {
    			free(out);
    			delta_cleanup(&bdf);
    			return NULL;
    		}
    
    		/* next time around the largest possible output is 1 + 4 + 3 */
    		if (outpos > outsize - 8) {
    			void *tmp = out;
    			outsize = outsize * 3 / 2;
    			out = realloc(out, outsize);
    			if (!out) {
    				free(tmp);
    				delta_cleanup(&bdf);
    				return NULL;
    			}
    		}
    	}
    
    	if (inscnt)
    		out[outpos - inscnt - 1] = inscnt;
    
    	delta_cleanup(&bdf);
    	*delta_size = outpos;
    	return out;
    }