Modified source engine (2017) developed by valve and leaked in 2020. Not for commercial purporses
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//========= Copyright Valve Corporation, All rights reserved. ============//
//
// Purpose:
//
// $NoKeywords: $
//=============================================================================//
#include "tier0/platform.h"
#include "tier0/dbg.h"
#include "tier1/diff.h"
#include "mathlib/mathlib.h"
// memdbgon must be the last include file in a .cpp file!!!
#include "tier0/memdbgon.h"
// format of diff output:
// 0NN (N=1..127) copy next N literaly
//
// 1NN (N=1..127) ofs (-128..127) copy next N bytes from original, changin offset by N bytes from
// last copy end
// 100 N ofs(-32768..32767) copy next N, with larger delta offset
// 00 NNNN(1..65535) ofs(-32768..32767) big copy from old
// 80 00 NN NN NN big raw copy
//
// available codes (could be used for additonal compression ops)
// long offset form whose offset could have fit in short offset
// note - this algorithm uses storage equal to 8* the old buffer size. 64k=.5mb
#define MIN_MATCH_LEN 8
#define ACCEPTABLE_MATCH_LEN 4096
struct BlockPtr
{
BlockPtr *Next;
uint8 const *dataptr;
};
template<class T,class V> static inline void AddToHead(T * & head, V * node)
{
node->Next=head;
head=node;
}
void Fail(char const *msg)
{
Assert(0);
}
void ApplyDiffs(uint8 const *OldBlock, uint8 const *DiffList,
int OldSize, int DiffListSize, int &ResultListSize,uint8 *Output,uint32 OutSize)
{
uint8 const *copy_src=OldBlock;
uint8 const *end_of_diff_list=DiffList+DiffListSize;
uint8 const *obuf=Output;
while(DiffList<end_of_diff_list)
{
// printf("dptr=%x ",DiffList-d);
uint8 op=*(DiffList++);
if (op==0)
{
uint16 copy_sz=DiffList[0]+256*DiffList[1];
int copy_ofs=DiffList[2]+DiffList[3]*256;
if (copy_ofs>32767)
copy_ofs|=0xffff0000;
// printf("long cp from %x to %x len=%d\n", copy_src+copy_ofs-OldBlock,Output-obuf,copy_sz);
memcpy(Output,copy_src+copy_ofs,copy_sz);
Output+=copy_sz;
copy_src=copy_src+copy_ofs+copy_sz;
DiffList+=4;
}
else
{
if (op & 0x80)
{
int copy_sz=op & 0x7f;
int copy_ofs;
if (copy_sz==0)
{
copy_sz=DiffList[0];
if (copy_sz==0)
{
// big raw copy
copy_sz=DiffList[1]+256*DiffList[2]+65536*DiffList[3];
memcpy(Output,DiffList+4,copy_sz);
// printf("big rawcopy to %x len=%d\n", Output-obuf,copy_sz);
DiffList+=copy_sz+4;
Output+=copy_sz;
}
else
{
copy_ofs=DiffList[1]+(DiffList[2]*256);
if (copy_ofs>32767)
copy_ofs|=0xffff0000;
// printf("long ofs cp from %x to %x len=%d\n", copy_src+copy_ofs-OldBlock,Output-obuf,copy_sz);
memcpy(Output,copy_src+copy_ofs,copy_sz);
Output+=copy_sz;
copy_src=copy_src+copy_ofs+copy_sz;
DiffList+=3;
}
}
else
{
copy_ofs=DiffList[0];
if (copy_ofs>127)
copy_ofs|=0xffffff80;
// printf("cp from %x to %x len=%d\n", copy_src+copy_ofs-OldBlock,Output-obuf,copy_sz);
memcpy(Output,copy_src+copy_ofs,copy_sz);
Output+=copy_sz;
copy_src=copy_src+copy_ofs+copy_sz;
DiffList++;
}
}
else
{
// printf("raw copy %d to %x\n",op & 127,Output-obuf);
memcpy(Output,DiffList,op & 127);
Output+=op & 127;
DiffList+=(op & 127);
}
}
}
ResultListSize=Output-obuf;
}
static void CopyPending(int len, uint8 const *rawbytes,uint8 * &outbuf, uint8 const *limit)
{
// printf("copy raw len=%d\n",len);
if (len<128)
{
if (limit-outbuf < len+1)
Fail("diff buffer overrun");
*(outbuf++)=len;
memcpy(outbuf,rawbytes,len);
outbuf+=len;
}
else
{
if (limit-outbuf < len+5)
Fail("diff buffer overrun");
*(outbuf++)=0x80;
*(outbuf++)=0x00;
*(outbuf++)=(len & 255);
*(outbuf++)=((len>>8) & 255);
*(outbuf++)=((len>>16) & 255);
memcpy(outbuf,rawbytes,len);
outbuf+=len;
}
}
static uint32 hasher(uint8 const *mdata)
{
// attempt to scramble the bits of h1 and h2 together
uint32 ret=0;
for(int i=0;i<MIN_MATCH_LEN;i++)
{
ret=ret<<4;
ret+=(*mdata++);
}
return ret;
}
int FindDiffsForLargeFiles(uint8 const *NewBlock, uint8 const *OldBlock,
int NewSize, int OldSize, int &DiffListSize,uint8 *Output,
uint32 OutSize,
int hashsize)
{
int ret=0;
if (OldSize!=NewSize)
ret=1;
// first, build the hash table
BlockPtr **HashedMatches=new BlockPtr* [hashsize];
memset(HashedMatches,0,sizeof(HashedMatches[0])*hashsize);
BlockPtr *Blocks=0;
if (OldSize)
Blocks=new BlockPtr[OldSize];
BlockPtr *FreeList=Blocks;
// now, build the hash table
uint8 const *walk=OldBlock;
if (OldBlock && OldSize)
while(walk<OldBlock+OldSize-MIN_MATCH_LEN)
{
uint32 hash1=hasher(walk);
hash1 &=(hashsize-1);
BlockPtr *newnode=FreeList;
FreeList++;
newnode->dataptr=walk;
AddToHead(HashedMatches[hash1],newnode);
walk++;
}
else
ret=1;
// now, we have the hash table which may be used to search. begin the output step
int pending_raw_len=0;
walk=NewBlock;
uint8 *outbuf=Output;
uint8 const *lastmatchend=OldBlock;
while(walk<NewBlock+NewSize)
{
int longest=0;
BlockPtr *longest_block=0;
if (walk<NewBlock+NewSize-MIN_MATCH_LEN)
{
// check for a match
uint32 hash1=hasher(walk);
hash1 &= (hashsize-1);
// now, find the longest match in the hash table. If we find one >MIN_MATCH_LEN, take it
for(BlockPtr *b=HashedMatches[hash1];b;b=b->Next)
{
// find the match length
int match_of=b->dataptr-lastmatchend;
if ((match_of>-32768) && (match_of<32767))
{
int max_mlength=min(65535,(int)((ptrdiff_t)OldBlock+OldSize-(ptrdiff_t)b->dataptr));
max_mlength=min(max_mlength,(int)((ptrdiff_t)NewBlock+NewSize-(ptrdiff_t)walk));
int i;
for(i=0;i<max_mlength;i++)
if (walk[i]!=b->dataptr[i])
break;
if ((i>MIN_MATCH_LEN) && (i>longest))
{
longest=i;
longest_block=b;
if (longest>ACCEPTABLE_MATCH_LEN)
break;
}
}
}
}
// now, we have a match maybe
if (longest_block)
{
if (pending_raw_len) // must output
{
ret=1;
CopyPending(pending_raw_len,walk-pending_raw_len,outbuf,Output+OutSize);
pending_raw_len=0;
}
// now, output copy block
int match_of=longest_block->dataptr-lastmatchend;
int nremaining=OutSize-(outbuf-Output);
if (match_of)
ret=1;
// printf("copy from %x to %x len=%d\n", match_of,outbuf-Output,longest);
if (longest>127)
{
// use really long encoding
if (nremaining<5)
Fail("diff buff needs increase");
*(outbuf++)=00;
*(outbuf++)=(longest & 255);
*(outbuf++)=((longest>>8) & 255);
*(outbuf++)=(match_of & 255);
*(outbuf++)=((match_of>>8) & 255);
}
else
{
if ((match_of>=-128) && (match_of<128))
{
if (nremaining<2)
Fail("diff buff needs increase");
*(outbuf++)=128+longest;
*(outbuf++)=(match_of&255);
}
else
{
// use long encoding
if (nremaining<4)
Fail("diff buff needs increase");
*(outbuf++)=0x80;
*(outbuf++)=longest;
*(outbuf++)=(match_of & 255);
*(outbuf++)=((match_of>>8) & 255);
}
}
lastmatchend=longest_block->dataptr+longest;
walk+=longest;
}
else
{
walk++;
pending_raw_len++;
}
}
// now, flush pending raw copy
if (pending_raw_len) // must output
{
ret=1;
CopyPending(pending_raw_len,walk-pending_raw_len,outbuf,Output+OutSize);
pending_raw_len=0;
}
delete[] HashedMatches;
if (Blocks)
delete[] Blocks;
DiffListSize=outbuf-Output;
return ret;
}
int FindDiffs(uint8 const *NewBlock, uint8 const *OldBlock,
int NewSize, int OldSize, int &DiffListSize,uint8 *Output,uint32 OutSize)
{
int ret=0;
if (OldSize!=NewSize)
ret=1;
// first, build the hash table
BlockPtr *HashedMatches[65536];
memset(HashedMatches,0,sizeof(HashedMatches));
BlockPtr *Blocks=0;
if (OldSize)
Blocks=new BlockPtr[OldSize];
BlockPtr *FreeList=Blocks;
// now, build the hash table
uint8 const *walk=OldBlock;
if (OldBlock && OldSize)
while(walk<OldBlock+OldSize-MIN_MATCH_LEN)
{
uint16 hash1=*((uint16 const *) walk)+*((uint16 const *) walk+2);
BlockPtr *newnode=FreeList;
FreeList++;
newnode->dataptr=walk;
AddToHead(HashedMatches[hash1],newnode);
walk++;
}
else
ret=1;
// now, we have the hash table which may be used to search. begin the output step
int pending_raw_len=0;
walk=NewBlock;
uint8 *outbuf=Output;
uint8 const *lastmatchend=OldBlock;
while(walk<NewBlock+NewSize)
{
int longest=0;
BlockPtr *longest_block=0;
if (walk<NewBlock+NewSize-MIN_MATCH_LEN)
{
// check for a match
uint16 hash1=*((uint16 const *) walk)+*((uint16 const *) walk+2);
// now, find the longest match in the hash table. If we find one >MIN_MATCH_LEN, take it
for(BlockPtr *b=HashedMatches[hash1];b;b=b->Next)
{
// find the match length
int match_of=b->dataptr-lastmatchend;
if ((match_of>-32768) && (match_of<32767))
{
int max_mlength=min(65535,(int)((ptrdiff_t)OldBlock+OldSize-(ptrdiff_t)b->dataptr));
max_mlength=min(max_mlength,(int)((ptrdiff_t)NewBlock+NewSize-(ptrdiff_t)walk));
int i;
for(i=0;i<max_mlength;i++)
if (walk[i]!=b->dataptr[i])
break;
if ((i>MIN_MATCH_LEN) && (i>longest))
{
longest=i;
longest_block=b;
}
}
}
}
// now, we have a match maybe
if (longest_block)
{
if (pending_raw_len) // must output
{
ret=1;
CopyPending(pending_raw_len,walk-pending_raw_len,outbuf,Output+OutSize);
pending_raw_len=0;
}
// now, output copy block
int match_of=longest_block->dataptr-lastmatchend;
int nremaining=OutSize-(outbuf-Output);
if (match_of)
ret=1;
if (longest>127)
{
// use really long encoding
if (nremaining<5)
Fail("diff buff needs increase");
*(outbuf++)=00;
*(outbuf++)=(longest & 255);
*(outbuf++)=((longest>>8) & 255);
*(outbuf++)=(match_of & 255);
*(outbuf++)=((match_of>>8) & 255);
}
else
{
if ((match_of>=-128) && (match_of<128))
{
if (nremaining<2)
Fail("diff buff needs increase");
*(outbuf++)=128+longest;
*(outbuf++)=(match_of&255);
}
else
{
// use long encoding
if (nremaining<4)
Fail("diff buff needs increase");
*(outbuf++)=0x80;
*(outbuf++)=longest;
*(outbuf++)=(match_of & 255);
*(outbuf++)=((match_of>>8) & 255);
}
}
lastmatchend=longest_block->dataptr+longest;
walk+=longest;
}
else
{
walk++;
pending_raw_len++;
}
}
// now, flush pending raw copy
if (pending_raw_len) // must output
{
ret=1;
CopyPending(pending_raw_len,walk-pending_raw_len,outbuf,Output+OutSize);
pending_raw_len=0;
}
if (Blocks)
delete[] Blocks;
DiffListSize=outbuf-Output;
return ret;
}
int FindDiffsLowMemory(uint8 const *NewBlock, uint8 const *OldBlock,
int NewSize, int OldSize, int &DiffListSize,uint8 *Output,uint32 OutSize)
{
int ret=0;
if (OldSize!=NewSize)
ret=1;
uint8 const *old_data_hash[256];
memset(old_data_hash,0,sizeof(old_data_hash));
int pending_raw_len=0;
uint8 const *walk=NewBlock;
uint8 const *oldptr=OldBlock;
uint8 *outbuf=Output;
uint8 const *lastmatchend=OldBlock;
while(walk<NewBlock+NewSize)
{
while( (oldptr-OldBlock<walk-NewBlock+40) && (oldptr-OldBlock<OldSize-MIN_MATCH_LEN))
{
uint16 hash1=(oldptr[0]+oldptr[1]+oldptr[2]+oldptr[3]) & (NELEMS(old_data_hash)-1);
old_data_hash[hash1]=oldptr;
oldptr++;
}
int longest=0;
uint8 const *longest_block=0;
if (walk<NewBlock+NewSize-MIN_MATCH_LEN)
{
// check for a match
uint16 hash1=(walk[0]+walk[1]+walk[2]+walk[3]) & (NELEMS(old_data_hash)-1);
if (old_data_hash[hash1])
{
int max_bytes_to_compare=min(NewBlock+NewSize-walk,OldBlock+OldSize-old_data_hash[hash1]);
int nmatches;
for(nmatches=0;nmatches<max_bytes_to_compare;nmatches++)
if (walk[nmatches]!=old_data_hash[hash1][nmatches])
break;
if (nmatches>MIN_MATCH_LEN)
{
longest_block=old_data_hash[hash1];
longest=nmatches;
}
}
}
// now, we have a match maybe
if (longest_block)
{
if (pending_raw_len) // must output
{
ret=1;
CopyPending(pending_raw_len,walk-pending_raw_len,outbuf,Output+OutSize);
pending_raw_len=0;
}
// now, output copy block
int match_of=longest_block-lastmatchend;
int nremaining=OutSize-(outbuf-Output);
if (match_of)
ret=1;
if (longest>127)
{
// use really long encoding
if (nremaining<5)
Fail("diff buff needs increase");
*(outbuf++)=00;
*(outbuf++)=(longest & 255);
*(outbuf++)=((longest>>8) & 255);
*(outbuf++)=(match_of & 255);
*(outbuf++)=((match_of>>8) & 255);
}
else
{
if ((match_of>=-128) && (match_of<128))
{
if (nremaining<2)
Fail("diff buff needs increase");
*(outbuf++)=128+longest;
*(outbuf++)=(match_of&255);
}
else
{
// use long encoding
if (nremaining<4)
Fail("diff buff needs increase");
*(outbuf++)=0x80;
*(outbuf++)=longest;
*(outbuf++)=(match_of & 255);
*(outbuf++)=((match_of>>8) & 255);
}
}
lastmatchend=longest_block+longest;
walk+=longest;
}
else
{
walk++;
pending_raw_len++;
}
}
// now, flush pending raw copy
if (pending_raw_len) // must output
{
ret=1;
CopyPending(pending_raw_len,walk-pending_raw_len,outbuf,Output+OutSize);
pending_raw_len=0;
}
DiffListSize=outbuf-Output;
return ret;
}