[Source] Compresor mejor y mas rápido que FreeARC, en C.

[sabeeee]

Un regalo para ustedes que encontré por ahí   después de tanta ayuda prestada, muchos ya lo deben conocer, es un derivado de PAQ8 ¿Se acuerdan del famoso KGB archiver?, bueno este código usa casi el mismo método pero es mucho mas rápido y funciono en mi Android con CppDroid. Excepto WAV (Tiene un algoritmo especial), es muy superior que FreeARC.

Uso:

Código [Seleccionar] Expandir

paq9a a "saliente.paq9a" -0...9 "entrante.archivo"

Compilación:

Código [Seleccionar] Expandir

@path C:\MinGw\bin;%path%
g++ -fpermissive -O3 -s paq9a.cpp -o paq9a
pause
Web (muy buena): http://mattmahoney.net/dc/

Código (cpp) [Seleccionar] Expandir

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <ctype.h>
#define NDEBUG  // remove for debugging
#include <assert.h>

int allocated=0;  // Total memory allocated by alloc()

// Create an array p of n elements of type T
template <class T> void alloc(T*&p, int n) {
 p=(T*)calloc(n, sizeof(T));
 if (!p) printf("Out of memory\n"), exit(1);
 allocated+=n*sizeof(T);
}

// 8, 16, 32 bit unsigned types (adjust as appropriate)
typedef unsigned char  U8;
typedef unsigned short U16;
typedef unsigned int   U32;

///////////////////////////// Squash //////////////////////////////

// return p = 1/(1 + exp(-d)), d scaled by 8 bits, p scaled by 12 bits
class Squash {
 short t[4096];
public:
 Squash();
 int operator()(int p) const {
   if (p>2047) return 4095;
 if (p<-2047) return 0;
   return t[p+2048];
 }
} squash;

Squash::Squash() {
int ts[33]={1,2,3,6,10,16,27,45,73,120,194,310,488,747,1101,
   1546,2047,2549,2994,3348,3607,3785,3901,3975,4022,
   4050,4068,4079,4085,4089,4092,4093,4094};
int w,d;
 for (int i=-2047; i<=2047; ++i){
   w=i&127;
   d=(i>>7)+16;
   t[i+2048]=(ts[d]*(128-w)+ts[(d+1)]*w+64) >> 7;
   }
}

//////////////////////////// Stretch ///////////////////////////////

// Inverse of squash. stretch(d) returns ln(p/(1-p)), d scaled by 8 bits,
// p by 12 bits.  d has range -2047 to 2047 representing -8 to 8.  
// p has range 0 to 4095 representing 0 to 1.

class Stretch {
 short t[4096];
public:
 Stretch();
 int operator()(int p) const {
   assert(p>=0 && p<4096);
   return t[p];
 }
} stretch;

Stretch::Stretch() {
 int pi=0;
 for (int x=-2047; x<=2047; ++x) {  // invert squash()
   int i=squash(x);
   for (int j=pi; j<=i; ++j)
     t[j]=x;
   pi=i+1;
 }
 t[4095]=2047;
}

///////////////////////////// ilog //////////////////////////////

// ilog(x) = round(log2(x) * 16), 0 <= x < 64K
class Ilog {
 U8* t;
public:
 int operator()(U16 x) const {return t[x];}
 Ilog();
} ilog;

// Compute lookup table by numerical integration of 1/x
Ilog::Ilog(): t(65536) {
 U32 x=14155776;
 for (int i=2; i<65536; ++i) {
   x+=774541002/(i*2-1);  // numerator is 2^29/ln 2
   t[i]=x>>24;
 }
}

// llog(x) accepts 32 bits
inline int llog(U32 x) {
 if (x>=0x1000000)
   return 256+ilog(x>>16);
 else if (x>=0x10000)
   return 128+ilog(x>>8);
 else
   return ilog(x);
}

///////////////////////// state table ////////////////////////

// State table:
//   nex(state, 0) = next state if bit y is 0, 0 <= state < 256
//   nex(state, 1) = next state if bit y is 1
//
// States represent a bit history within some context.
// State 0 is the starting state (no bits seen).
// States 1-30 represent all possible sequences of 1-4 bits.
// States 31-252 represent a pair of counts, (n0,n1), the number
//   of 0 and 1 bits respectively.  If n0+n1 < 16 then there are
//   two states for each pair, depending on if a 0 or 1 was the last
//   bit seen.
// If n0 and n1 are too large, then there is no state to represent this
// pair, so another state with about the same ratio of n0/n1 is substituted.
// Also, when a bit is observed and the count of the opposite bit is large,
// then part of this count is discarded to favor newer data over old.

static const U8 State_table[256][4]={
 {  1,  2, 0, 0},{  3,  5, 1, 0},{  4,  6, 0, 1},{  7, 10, 2, 0}, // 0-3
 {  8, 12, 1, 1},{  9, 13, 1, 1},{ 11, 14, 0, 2},{ 15, 19, 3, 0}, // 4-7
 { 16, 23, 2, 1},{ 17, 24, 2, 1},{ 18, 25, 2, 1},{ 20, 27, 1, 2}, // 8-11
 { 21, 28, 1, 2},{ 22, 29, 1, 2},{ 26, 30, 0, 3},{ 31, 33, 4, 0}, // 12-15
 { 32, 35, 3, 1},{ 32, 35, 3, 1},{ 32, 35, 3, 1},{ 32, 35, 3, 1}, // 16-19
 { 34, 37, 2, 2},{ 34, 37, 2, 2},{ 34, 37, 2, 2},{ 34, 37, 2, 2}, // 20-23
 { 34, 37, 2, 2},{ 34, 37, 2, 2},{ 36, 39, 1, 3},{ 36, 39, 1, 3}, // 24-27
 { 36, 39, 1, 3},{ 36, 39, 1, 3},{ 38, 40, 0, 4},{ 41, 43, 5, 0}, // 28-31
 { 42, 45, 4, 1},{ 42, 45, 4, 1},{ 44, 47, 3, 2},{ 44, 47, 3, 2}, // 32-35
 { 46, 49, 2, 3},{ 46, 49, 2, 3},{ 48, 51, 1, 4},{ 48, 51, 1, 4}, // 36-39
 { 50, 52, 0, 5},{ 53, 43, 6, 0},{ 54, 57, 5, 1},{ 54, 57, 5, 1}, // 40-43
 { 56, 59, 4, 2},{ 56, 59, 4, 2},{ 58, 61, 3, 3},{ 58, 61, 3, 3}, // 44-47
 { 60, 63, 2, 4},{ 60, 63, 2, 4},{ 62, 65, 1, 5},{ 62, 65, 1, 5}, // 48-51
 { 50, 66, 0, 6},{ 67, 55, 7, 0},{ 68, 57, 6, 1},{ 68, 57, 6, 1}, // 52-55
 { 70, 73, 5, 2},{ 70, 73, 5, 2},{ 72, 75, 4, 3},{ 72, 75, 4, 3}, // 56-59
 { 74, 77, 3, 4},{ 74, 77, 3, 4},{ 76, 79, 2, 5},{ 76, 79, 2, 5}, // 60-63
 { 62, 81, 1, 6},{ 62, 81, 1, 6},{ 64, 82, 0, 7},{ 83, 69, 8, 0}, // 64-67
 { 84, 71, 7, 1},{ 84, 71, 7, 1},{ 86, 73, 6, 2},{ 86, 73, 6, 2}, // 68-71
 { 44, 59, 5, 3},{ 44, 59, 5, 3},{ 58, 61, 4, 4},{ 58, 61, 4, 4}, // 72-75
 { 60, 49, 3, 5},{ 60, 49, 3, 5},{ 76, 89, 2, 6},{ 76, 89, 2, 6}, // 76-79
 { 78, 91, 1, 7},{ 78, 91, 1, 7},{ 80, 92, 0, 8},{ 93, 69, 9, 0}, // 80-83
 { 94, 87, 8, 1},{ 94, 87, 8, 1},{ 96, 45, 7, 2},{ 96, 45, 7, 2}, // 84-87
 { 48, 99, 2, 7},{ 48, 99, 2, 7},{ 88,101, 1, 8},{ 88,101, 1, 8}, // 88-91
 { 80,102, 0, 9},{103, 69,10, 0},{104, 87, 9, 1},{104, 87, 9, 1}, // 92-95
 {106, 57, 8, 2},{106, 57, 8, 2},{ 62,109, 2, 8},{ 62,109, 2, 8}, // 96-99
 { 88,111, 1, 9},{ 88,111, 1, 9},{ 80,112, 0,10},{113, 85,11, 0}, // 100-103
 {114, 87,10, 1},{114, 87,10, 1},{116, 57, 9, 2},{116, 57, 9, 2}, // 104-107
 { 62,119, 2, 9},{ 62,119, 2, 9},{ 88,121, 1,10},{ 88,121, 1,10}, // 108-111
 { 90,122, 0,11},{123, 85,12, 0},{124, 97,11, 1},{124, 97,11, 1}, // 112-115
 {126, 57,10, 2},{126, 57,10, 2},{ 62,129, 2,10},{ 62,129, 2,10}, // 116-119
 { 98,131, 1,11},{ 98,131, 1,11},{ 90,132, 0,12},{133, 85,13, 0}, // 120-123
 {134, 97,12, 1},{134, 97,12, 1},{136, 57,11, 2},{136, 57,11, 2}, // 124-127
 { 62,139, 2,11},{ 62,139, 2,11},{ 98,141, 1,12},{ 98,141, 1,12}, // 128-131
 { 90,142, 0,13},{143, 95,14, 0},{144, 97,13, 1},{144, 97,13, 1}, // 132-135
 { 68, 57,12, 2},{ 68, 57,12, 2},{ 62, 81, 2,12},{ 62, 81, 2,12}, // 136-139
 { 98,147, 1,13},{ 98,147, 1,13},{100,148, 0,14},{149, 95,15, 0}, // 140-143
 {150,107,14, 1},{150,107,14, 1},{108,151, 1,14},{108,151, 1,14}, // 144-147
 {100,152, 0,15},{153, 95,16, 0},{154,107,15, 1},{108,155, 1,15}, // 148-151
 {100,156, 0,16},{157, 95,17, 0},{158,107,16, 1},{108,159, 1,16}, // 152-155
 {100,160, 0,17},{161,105,18, 0},{162,107,17, 1},{108,163, 1,17}, // 156-159
 {110,164, 0,18},{165,105,19, 0},{166,117,18, 1},{118,167, 1,18}, // 160-163
 {110,168, 0,19},{169,105,20, 0},{170,117,19, 1},{118,171, 1,19}, // 164-167
 {110,172, 0,20},{173,105,21, 0},{174,117,20, 1},{118,175, 1,20}, // 168-171
 {110,176, 0,21},{177,105,22, 0},{178,117,21, 1},{118,179, 1,21}, // 172-175
 {110,180, 0,22},{181,115,23, 0},{182,117,22, 1},{118,183, 1,22}, // 176-179
 {120,184, 0,23},{185,115,24, 0},{186,127,23, 1},{128,187, 1,23}, // 180-183
 {120,188, 0,24},{189,115,25, 0},{190,127,24, 1},{128,191, 1,24}, // 184-187
 {120,192, 0,25},{193,115,26, 0},{194,127,25, 1},{128,195, 1,25}, // 188-191
 {120,196, 0,26},{197,115,27, 0},{198,127,26, 1},{128,199, 1,26}, // 192-195
 {120,200, 0,27},{201,115,28, 0},{202,127,27, 1},{128,203, 1,27}, // 196-199
 {120,204, 0,28},{205,115,29, 0},{206,127,28, 1},{128,207, 1,28}, // 200-203
 {120,208, 0,29},{209,125,30, 0},{210,127,29, 1},{128,211, 1,29}, // 204-207
 {130,212, 0,30},{213,125,31, 0},{214,137,30, 1},{138,215, 1,30}, // 208-211
 {130,216, 0,31},{217,125,32, 0},{218,137,31, 1},{138,219, 1,31}, // 212-215
 {130,220, 0,32},{221,125,33, 0},{222,137,32, 1},{138,223, 1,32}, // 216-219
 {130,224, 0,33},{225,125,34, 0},{226,137,33, 1},{138,227, 1,33}, // 220-223
 {130,228, 0,34},{229,125,35, 0},{230,137,34, 1},{138,231, 1,34}, // 224-227
 {130,232, 0,35},{233,125,36, 0},{234,137,35, 1},{138,235, 1,35}, // 228-231
 {130,236, 0,36},{237,125,37, 0},{238,137,36, 1},{138,239, 1,36}, // 232-235
 {130,240, 0,37},{241,125,38, 0},{242,137,37, 1},{138,243, 1,37}, // 236-239
 {130,244, 0,38},{245,135,39, 0},{246,137,38, 1},{138,247, 1,38}, // 240-243
 {140,248, 0,39},{249,135,40, 0},{250, 69,39, 1},{ 80,251, 1,39}, // 244-247
 {140,252, 0,40},{249,135,41, 0},{250, 69,40, 1},{ 80,251, 1,40}, // 248-251
 {140,252, 0,41}};  // 252, 253-255 are reserved

#define nex(state,sel) State_table[state][sel]

//////////////////////////// StateMap //////////////////////////

// A StateMap maps a context to a probability.  Methods:
//
// Statemap sm(n) creates a StateMap with n contexts using 4*n bytes memory.
// sm.p(cx, limit) converts state cx (0..n-1) to a probability (0..4095)
//     that the next updated bit y=1.
//     limit (1..1023, default 255) is the maximum count for computing a
//     prediction.  Larger values are better for stationary sources.
// sm.update(y) updates the model with actual bit y (0..1).

class StateMap {
protected:
 const int N;  // Number of contexts
 int cxt;      // Context of last prediction
 U32 *t;       // cxt -> prediction in high 22 bits, count in low 10 bits
 static int dt[1024];  // i -> 16K/(i+3)
public:
 StateMap(int n=256);

 // update bit y (0..1)
 void update(int y, int limit=255) {
   assert(cxt>=0 && cxt<N);
   int n=t[cxt]&1023, p=t[cxt]>>10;  // count, prediction
   if (n<limit) ++t[cxt];
   else t[cxt]=t[cxt]&0xfffffc00|limit;
   t[cxt]+=(((y<<22)-p)>>3)*dt[n]&0xfffffc00;
 }

 // predict next bit in context cx
 int p(int cx) {
   assert(cx>=0 && cx<N);
   return t[cxt=cx]>>20;
 }
};

int StateMap::dt[1024]={0};

StateMap::StateMap(int n): N(n), cxt(0) {
 alloc(t, N);
 for (int i=0; i<N; ++i)
   t[i]=1<<31;
 if (dt[0]==0)
   for (int i=0; i<1024; ++i)
     dt[i]=16384/(i+i+3);
}

//////////////////////////// Mix, APM /////////////////////////

// Mix combines 2 predictions and a context to produce a new prediction.
// Methods:
// Mix m(n) -- creates allowing with n contexts.
// m.pp(p1, p2, cx) -- inputs 2 stretched predictions and a context cx
//   (0..n-1) and returns a stretched prediction.  Stretched predictions
//   are fixed point numbers with an 8 bit fraction, normally -2047..2047
//   representing -8..8, such that 1/(1+exp(-p) is the probability that
//   the next update will be 1.
// m.update(y) updates the model after a prediction with bit y (0..1).

class Mix {
protected:
 const int N;  // n
 int* wt;  // weights, scaled 24 bits
 int x1, x2;    // inputs, scaled 8 bits (-2047 to 2047)
 int cxt;  // last context (0..n-1)
 int pr;   // last output
public:
 Mix(int n=512);
 int pp(int p1, int p2, int cx) {
   assert(cx>=0 && cx<N);
   cxt=cx*2;
   return pr=(x1=p1)*(wt[cxt]>>16)+(x2=p2)*(wt[cxt+1]>>16)+128>>8;
 }
 void update(int y) {
   assert(y==0 || y==1);
   int err=((y<<12)-squash(pr));
   if ((wt[cxt]&3)<3)
     err*=4-(++wt[cxt]&3);
   err=err+8>>4;
   wt[cxt]+=x1*err&-4;
   wt[cxt+1]+=x2*err;
 }
};

Mix::Mix(int n): N(n), x1(0), x2(0), cxt(0), pr(0) {
 alloc(wt, n*2);
 for (int i=0; i<N*2; ++i)
   wt[i]=1<<23;
}

// An APM is a Mix optimized for a constant in place of p1, used to
// refine a stretched prediction given a context cx.
// Normally p1 is in the range (0..4095) and p2 is doubled.

class APM: public Mix {
public:
 APM(int n);
};

APM::APM(int n): Mix(n) {
 for (int i=0; i<n; ++i)
   wt[2*i]=0;
}

//////////////////////////// HashTable /////////////////////////

// A HashTable maps a 32-bit index to an array of B bytes.
// The first byte is a checksum using the upper 8 bits of the
// index.  The second byte is a priority (0 = empty) for hash
// replacement.  The index need not be a hash.

// HashTable<B> h(n) - create using n bytes  n and B must be
//     powers of 2 with n >= B*4, and B >= 2.
// h[i] returns array [1..B-1] of bytes indexed by i, creating and
//     replacing another element if needed.  Element 0 is the
//     checksum and should not be modified.

template <int B>
class HashTable {
 U8* t;  // table: 1 element = B bytes: checksum priority data data
 const U32 N;  // size in bytes
public:
 HashTable(int n);
 ~HashTable();
 U8* operator[](U32 i);
};

template <int B>
HashTable<B>::HashTable(int n): t(0), N(n) {
 assert(B>=2 && (B&B-1)==0);
 assert(N>=B*4 && (N&N-1)==0);
 alloc(t, N+B*4+64);
 t+=64-int(((long)t)&63);  // align on cache line boundary
}

template <int B>
inline U8* HashTable<B>::operator[](U32 i) {
 i*=123456791;
 i=i<<16|i>>16;
 i*=234567891;
 int chk=i>>24;
 i=i*B&N-B;
 if (t[i]==chk) return t+i;
 if (t[i^B]==chk) return t+(i^B);
 if (t[i^B*2]==chk) return t+(i^B*2);
 if (t[i+1]>t[i+1^B] || t[i+1]>t[i+1^B*2]) i^=B;
 if (t[i+1]>t[i+1^B^B*2]) i^=B^B*2;
 memset(t+i, 0, B);
 t[i]=chk;
 return t+i;
}

template <int B>
HashTable<B>::~HashTable() {
 int c=0, c0=0;
 for (U32 i=0; i<N; ++i) {
   if (t[i]) {
     ++c;
     if (i%B==0) ++c0;
   }
 }
 printf("HashTable<%d> %1.4f%% full, %1.4f%% utilized of %d KiB\n",
   B, 100.0*c0*B/N, 100.0*c/N, N>>10);
}

////////////////////////// LZP /////////////////////////

U32 MEM=1<<29;  // Global memory limit, 1 << 22+(memory option)

// LZP predicts the next byte and maintains context.  Methods:
// c() returns the predicted byte for the next update, or -1 if none.
// p() returns the 12 bit probability (0..4095) that c() is next.
// update(ch) updates the model with actual byte ch (0..255).
// c(i) returns the i'th prior byte of context, i > 0.
// c4() returns the order 4 context, shifted into the LSB.
// c8() returns a hash of the order 8 context, shifted 4 bits into LSB.
// word0, word1 are hashes of the current and previous word (a-z).

class LZP {
private:
 const int N, H; // buf, t sizes
 enum {MINLEN=12};  // minimum match length
 U8* buf;     // Rotating buffer of size N
 U32* t;      // hash table of pointers in high 24 bits, state in low 8 bits
 int match;   // start of match
 int len;     // length of match
 int pos;     // position of next ch to write to buf
 U32 h;       // context hash
 U32 h1;      // hash of last 8 byte updates, shifting 4 bits to MSB
 U32 h2;      // last 4 updates, shifting 8 bits to MSB
 StateMap sm1; // len+offset -> p
 APM a1, a2, a3;   // p, context -> p
 int literals, matches;  // statistics
public:
 U32 word0, word1;  // hashes of last 2 words (case insensitive a-z)
 LZP();
 ~LZP();
 int c();     // predicted char
 int c(int i);// context
 int c4() {return h2;}  // order 4 context, c(1) in LSB
 int c8() {return h1;}  // hashed order 8 context
 int p();     // probability that next char is c() * 4096
 void update(int ch);  // update model with actual char ch
};

// Initialize
LZP::LZP(): N(MEM/8), H(MEM/32),
   match(-1), len(0), pos(0), h(0), h1(0), h2(0),
   sm1(0x200), a1(0x10000), a2(0x40000), a3(0x100000),
   literals(0), matches(0), word0(0), word1(0) {
 assert(MEM>0);
 assert(H>0);
 alloc(buf, N);
 alloc(t, H);
}

// Print statistics
LZP::~LZP() {
 int c=0;
 for (int i=0; i<H; ++i)
   c+=(t[i]!=0);
 printf("LZP hash table %1.4f%% full of %d KiB\n"
   "LZP buffer %1.4f%% full of %d KiB\n",
   100.0*c/H, H>>8, pos<N?100.0*pos/N:100.0, N>>10);
 printf("LZP %d literals, %d matches (%1.4f%% matched)\n",
   literals, matches,
   literals+matches>0?100.0*matches/(literals+matches):0.0);
}

// Predicted next byte, or -1 for no prediction
inline int LZP::c() {
 return len>=MINLEN ? buf[match&N-1] : -1;
}

// Return i'th byte of context (i > 0)
inline int LZP::c(int i) {
 assert(i>0);
 return buf[pos-i&N-1];
}

// Return prediction that c() will be the next byte (0..4095)
int LZP::p() {
 if (len<MINLEN) return 0;
 int cxt=len;
 if (len>28) cxt=28+(len>=32)+(len>=64)+(len>=128);
 int pc=c();
 int pr=sm1.p(cxt);
 pr=stretch(pr);
 pr=a1.pp(2048, pr*2, h2*256+pc&0xffff)*3+pr>>2;
 pr=a2.pp(2048, pr*2, h1*(11<<6)+pc&0x3ffff)*3+pr>>2;
 pr=a3.pp(2048, pr*2, h1*(7<<4)+pc&0xfffff)*3+pr>>2;
 pr=squash(pr);
 return pr;
}

// Update model with predicted byte ch (0..255)
void LZP::update(int ch) {
 int y=c()==ch;     // 1 if prediction of ch was right, else 0
 h1=h1*(3<<4)+ch+1; // update context hashes
 h2=h2<<8|ch;
 h=h*(5<<2)+ch+1&H-1;
 if (len>=MINLEN) {
   sm1.update(y);
   a1.update(y);
   a2.update(y);
   a3.update(y);
 }
 if (isalpha(ch))
   word0=word0*(29<<2)+tolower(ch);
 else if (word0)
   word1=word0, word0=0;
 buf[pos&N-1]=ch;   // update buf
 ++pos;
 if (y) {  // extend match
   ++len;
   ++match;
   ++matches;
 }
 else {  // find new match, try order 6 context first
   ++literals;
   y=0;
   len=1;
   match=t[h];
   if (!((match^pos)&N-1)) --match;
   while (len<=128 && buf[match-len&N-1]==buf[pos-len&N-1]) ++len;
   --len;
 }
 t[h]=pos;
}

LZP* lzp=0;

//////////////////////////// Predictor /////////////////////////

// A Predictor estimates the probability that the next bit of
// uncompressed data is 1.  Methods:
// Predictor() creates.
// p() returns P(1) as a 12 bit number (0-4095).
// update(y) trains the predictor with the actual bit (0 or 1).

class Predictor {
 enum {N=11}; // number of contexts
 int c0;      // last 0-7 bits with leading 1, 0 before LZP flag
 int nibble;  // last 0-3 bits with leading 1 (1..15)
 int bcount;  // number of bits in c0 (0..7)
 HashTable<16> t;  // context -> state
 StateMap sm[N];   // state -> prediction
 U8* cp[N];   // i -> state array of bit histories for i'th context
 U8* sp[N];   // i -> pointer to bit history for i'th context
 Mix m[N-1];  // combines 2 predictions given a context
 APM a1, a2, a3;  // adjusts a prediction given a context
 U8* t2;      // order 1 contexts -> state

public:
 Predictor();
 int p();
 void update(int y);
};

// Initialize
Predictor::Predictor():
   c0(0), nibble(1), bcount(0), t(MEM/2),
   a1(0x10000), a2(0x10000), a3(0x10000) {
 alloc(t2, 0x40000);
 for (int i=0; i<N; ++i)
   sp[i]=cp[i]=t2;
}

// Update model
void Predictor::update(int y) {
 assert(y==0 || y==1);
 assert(bcount>=0 && bcount<8);
 assert(c0>=0 && c0<256);
 assert(nibble>=1 && nibble<=15);
 if (c0==0)
   c0=1-y;
 else {
   *sp[0]=nex(*sp[0], y);
   sm[0].update(y);
   for (int i=1; i<N; ++i) {
     *sp[i]=nex(*sp[i], y);
     sm[i].update(y);
     m[i-1].update(y);
   }
   c0+=c0+y;
   if (++bcount==8) bcount=c0=0;
   if ((nibble+=nibble+y)>=16) nibble=1;
   a1.update(y);
   a2.update(y);
   a3.update(y);
 }
}

// Predict next bit
int Predictor::p() {
 assert(lzp);
 if (c0==0)
   return lzp->p();
 else {

   // Set context pointers
   int pc=lzp->c();  // mispredicted byte
   int r=pc+256>>8-bcount==c0;  // c0 consistent with mispredicted byte?
   U32 c4=lzp->c4();  // last 4 whole context bytes, shifted into LSB
   U32 c8=(lzp->c8()<<4)-1;  // hash of last 7 bytes with 4 trailing 1 bits
   if ((bcount&3)==0) {  // nibble boundary?  Update context pointers
     pc&=-r;
     U32 c4p=c4<<8;
     if (bcount==0) {  // byte boundary?  Update order-1 context pointers
       cp[0]=t2+(c4>>16&0xff00);
       cp[1]=t2+(c4>>8 &0xff00)+0x10000;
       cp[2]=t2+(c4    &0xff00)+0x20000;
       cp[3]=t2+(c4<<8 &0xff00)+0x30000;
     }
     cp[4]=t[(c4p&0xffff00)-c0];
     cp[5]=t[(c4p&0xffffff00)*3+c0];
     cp[6]=t[c4*7+c0];
     cp[7]=t[(c8*5&0xfffffc)+c0];
     cp[8]=t[(c8*11&0xffffff0)+c0+pc*13];
     cp[9]=t[lzp->word0*5+c0+pc*17];
     cp[10]=t[lzp->word1*7+lzp->word0*11+c0+pc*37];
   }

   // Mix predictions
   r<<=8;
   sp[0]=&cp[0][c0];
   int pr=stretch(sm[0].p(*sp[0]));
   for (int i=1; i<N; ++i) {
     sp[i]=&cp[i][i<4?c0:nibble];
     int st=*sp[i];
     pr=m[i-1].pp(pr, stretch(sm[i].p(st)), st+r)*3+pr>>2;
   }
   pr=a1.pp(512, pr*2, c0+pc*256&0xffff)*3+pr>>2;  // Adjust prediction
   pr=a2.pp(512, pr*2, c4<<8&0xff00|c0)*3+pr>>2;
   pr=a3.pp(512, pr*2, c4*3+c0&0xffff)*3+pr>>2;
   return squash(pr);
 }
}

Predictor* predictor=0;

/////////////////////////// get4, put4 //////////////////////////

// Read/write a 4 byte big-endian number
int get4(FILE* in) {
 int r=getc(in);
 r=r*256+getc(in);
 r=r*256+getc(in);
 r=r*256+getc(in);
 return r;
}

void put4(U32 c, FILE* out) {
 fprintf(out, "%c%c%c%c", c>>24, c>>16, c>>8, c);
}

//////////////////////////// Encoder ////////////////////////////

// An Encoder arithmetic codes in blocks of size BUFSIZE.  Methods:
// Encoder(COMPRESS, f) creates encoder for compression to archive f, which
//     must be open past any header for writing in binary mode.
// Encoder(DECOMPRESS, f) creates encoder for decompression from archive f,
//     which must be open past any header for reading in binary mode.
// code(i) in COMPRESS mode compresses bit i (0 or 1) to file f.
// code() in DECOMPRESS mode returns the next decompressed bit from file f.
// count() should be called after each byte is compressed.
// flush() should be called after compression is done.  It is also called
//   automatically when a block is written.

typedef enum {COMPRESS, DECOMPRESS} Mode;
class Encoder {
private:
 const Mode mode;       // Compress or decompress?
 FILE* archive;         // Compressed data file
 U32 x1, x2;            // Range, initially [0, 1), scaled by 2^32
 U32 x;                 // Decompress mode: last 4 input bytes of archive
 enum {BUFSIZE=0x20000};
 static unsigned char* buf; // Compression output buffer, size BUFSIZE
 int usize, csize;      // Buffered uncompressed and compressed sizes
 double usum, csum;     // Total of usize, csize

public:
 Encoder(Mode m, FILE* f);
 void flush();  // call this when compression is finished

 // Compress bit y or return decompressed bit
 int code(int y=0) {
   assert(predictor);
   int p=predictor->p();
   assert(p>=0 && p<4096);
   p+=p<2048;
   U32 xmid=x1 + (x2-x1>>12)*p + ((x2-x1&0xfff)*p>>12);
   assert(xmid>=x1 && xmid<x2);
   if (mode==DECOMPRESS) y=x<=xmid;
   y ? (x2=xmid) : (x1=xmid+1);
   predictor->update(y);
   while (((x1^x2)&0xff000000)==0) {  // pass equal leading bytes of range
     if (mode==COMPRESS) buf[csize++]=x2>>24;
     x1<<=8;
     x2=(x2<<8)+255;
     if (mode==DECOMPRESS) x=(x<<8)+getc(archive);
   }
   return y;
 }

 // Count one byte
 void count() {
   assert(mode==COMPRESS);
   ++usize;
   if (csize>BUFSIZE-256)
     flush();
 }
};
unsigned char* Encoder::buf=0;

// Create in mode m (COMPRESS or DECOMPRESS) with f opened as the archive.
Encoder::Encoder(Mode m, FILE* f):
   mode(m), archive(f), x1(0), x2(0xffffffff), x(0),
   usize(0), csize(0), usum(0), csum(0) {
 if (mode==DECOMPRESS) {  // x = first 4 bytes of archive
   for (int i=0; i<4; ++i)
     x=(x<<8)+(getc(archive)&255);
   csize=4;
 }
 else if (!buf)
   alloc(buf, BUFSIZE);
}

// Write a compressed block and reinitialize the encoder.  The format is:
//   uncompressed size (usize, 4 byte, MSB first)
//   compressed size (csize, 4 bytes, MSB first)
//   compressed data (csize bytes)
void Encoder::flush() {
 if (mode==COMPRESS) {
   buf[csize++]=x1>>24;
   buf[csize++]=255;
   buf[csize++]=255;
   buf[csize++]=255;
   putc(0, archive);
   putc('c', archive);
   put4(usize, archive);
   put4(csize, archive);
   fwrite(buf, 1, csize, archive);
   usum+=usize;
   csum+=csize+10;
   printf("%15.0f -> %15.0f"
     "\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b",
     usum, csum);
   x1=x=usize=csize=0;
   x2=0xffffffff;
 }
}

/////////////////////////// paq9a ////////////////////////////////

// Compress or decompress from in to out, depending on whether mode
// is COMPRESS or DECOMPRESS.  A byte c is encoded as a 1 bit if it
// is predicted by LZP, otherwise a 0 followed by 8 bits from MSB to LSB.
void paq9a(FILE* in, FILE* out, Mode mode) {
 if (!lzp && !predictor) {
   lzp=new LZP;
   predictor=new Predictor;
   printf("%8d KiB\b\b\b\b\b\b\b\b\b\b\b\b", allocated>>10);
 }
 if (mode==COMPRESS) {
   Encoder e(COMPRESS, out);
   int c;
   while ((c=getc(in))!=EOF) {
     int cp=lzp->c();
     if (c==cp)
       e.code(1);
     else
       for (int i=8; i>=0; --i)
         e.code(c>>i&1);
     e.count();
     lzp->update(c);
   }
   e.flush();
 }
 else {  // DECOMPRESS
   int usize=get4(in);
   get4(in);  // csize
   Encoder e(DECOMPRESS, in);
   while (usize--) {
     int c=lzp->c();
     if (e.code()==0) {
       c=1;
       while (c<256) c+=c+e.code();
       c&=255;
     }
     if (out) putc(c, out);
     lzp->update(c);
   }
 }
}


///////////////////////////// store ///////////////////////////

// Store a file in blocks as: {'\0' mode usize csize contents}...
void store(FILE* in, FILE* out) {
 assert(in);
 assert(out);

 // Store in blocks
 const int BLOCKSIZE=0x100000;
 static char* buf=0;
 if (!buf) alloc(buf, BLOCKSIZE);
 bool first=true;
 while (true) {
   int n=fread(buf, 1, BLOCKSIZE, in);
   if (!first && n<=0) break;
   fprintf(out, "%c%c", 0, 's');
   put4(n, out);  // usize
   put4(n, out);  // csize
   fwrite(buf, 1, n, out);
   first=false;
 }

 // Close file
 fclose(in);
}

// Write usize == csize bytes of an uncompressed block from in to out
void unstore(FILE* in, FILE* out) {
 assert(in);
 int usize=get4(in);
 int csize=get4(in);
 if (usize!=csize)
   printf("Bad archive format: usize=%d csize=%d\n", usize, csize);
 static char* buf=0;
 const int BUFSIZE=0x1000;
 if (!buf) alloc(buf, BUFSIZE);
 while (csize>0) {
   usize=csize;
   if (usize>BUFSIZE) usize=BUFSIZE;
   if (int(fread(buf, 1, usize, in))!=usize)
     printf("Unexpected end of archive\n"), exit(1);
   if (out) fwrite(buf, 1, usize, out);
   csize-=usize;
 }
}

//////////////////////// Archiving functions ////////////////////////

const int MAXNAMELEN=1023;  // max filename length

// Return true if the first 4 bytes of in are a valid archive
bool check_archive(FILE* in) {
 return getc(in)=='p' && getc(in)=='Q' && getc(in)=='9' && getc(in)==1;
}

// Open archive and check for valid archive header, exit if bad.
// Set MEM to memory option '1' through '9'
FILE* open_archive(const char* filename) {
 FILE* in=fopen(filename, "rb");
 if (!in)
   printf("Cannot find archive %s\n", filename), exit(1);
 if (!check_archive(in) || (MEM=getc(in))<'1' || MEM>'9') {
   fclose(in);
   printf("%s: Not a paq9a archive\n", filename);
   exit(1);
 }
 return in;
}

// Compress filename to out.  option is 'c' to compress or 's' to store.
void compress(const char* filename, FILE* out, int option) {

 // Open input file
 FILE* in=fopen(filename, "rb");
 if (!in) {
   printf("File not found: %s\n", filename);
   return;
 }
 fprintf(out, "%s", filename);
 printf("%-40s ", filename);

 // Compress depending on option
 if (option=='s')
   store(in, out);
 else if (option=='c')
   paq9a(in, out, COMPRESS);
 printf("\n");
}

// List archive contents
void list(const char* archive) {
 double usum=0, csum=0;  // uncompressed and compressed size per file
 double utotal=0, ctotal=4;  // total size in archive
 static char filename[MAXNAMELEN+1];
 int mode=0;

 FILE* in=open_archive(archive);
 printf("\npaq9a -%c\n", MEM);
 while (true) {

   // Get filename, mode
   int c=getc(in);
   if (c==EOF) break;
   if (c) {   // start of new file?  Print previous file
     if (mode)
       printf("%10.0f -> %10.0f %c %s\n", usum, csum, mode, filename);
     int len=0;
     filename[len++]=c;
     while ((c=getc(in))!=EOF && c)
       if (len<MAXNAMELEN) filename[len++]=c;
     filename[len]=0;
     utotal+=usum;
     ctotal+=csum;
     usum=0;
     csum=len;
   }

   // Get uncompressed size
   mode=getc(in);
   int usize=get4(in);
   usum+=usize;

   // Get compressed size
   int csize=get4(in);
   csum+=csize+10;

   if (usize<0 || csize<0 || mode!='c' && mode!='s')
     printf("Archive corrupted usize=%d csize=%d mode=%d at %ld\n",
       usize, csize, mode, ftell(in)), exit(1);

   // Skip csize bytes
   const int BUFSIZE=0x1000;
   char buf[BUFSIZE];
   while (csize>BUFSIZE)
     csize-=fread(buf, 1, BUFSIZE, in);
   fread(buf, 1, csize, in);
 }
 printf("%10.0f -> %10.0f %c %s\n", usum, csum, mode, filename);
 utotal+=usum;
 ctotal+=csum;
 printf("%10.0f -> %10.0f total\n", utotal, ctotal);
 fclose(in);
}

// Extract files given command line arguments
// Input format is: [filename {'\0' mode usize csize contents}...]...
void extract(int argc, char** argv) {
 assert(argc>2);
 assert(argv[1][0]=='x');
 static char filename[MAXNAMELEN+1];  // filename from archive

 // Open archive
 FILE* in=open_archive(argv[2]);
 MEM=1<<22+MEM-'0';

 // Extract files
 argc-=3;
 argv+=3;
 FILE* out=0;
 while (true) {  // for each block

   // Get filename
   int c;
   for (int i=0;; ++i) {
     c=getc(in);
     if (c==EOF) break;
     if (i<MAXNAMELEN) filename[i]=c;
     if (!c) break;
   }
   if (c==EOF) break;

   // Open output file
   if (filename[0]) {  // new file?
     const char* fn=filename;
     if (argc>0) fn=argv[0], --argc, ++argv;
     if (out) fclose(out);
     out=fopen(fn, "rb");
     if (out) {
       printf("\nCannot overwrite file, skipping: %s ", fn);
       fclose(out);
       out=0;
     }
     else {
       out=fopen(fn, "wb");
       if (!out) printf("\nCannot create file: %s ", fn);
     }
     if (out) {
       if (fn==filename) printf("\n%s ", filename);
       else printf("\n%s -> %s ", filename, fn);
     }
   }

   // Extract block
   int mode=getc(in);
   if (mode=='s')
     unstore(in, out);
   else if (mode=='c')
     paq9a(in, out, DECOMPRESS);
   else
     printf("\nUnsupported compression mode %c %d at %ld\n",
       mode, mode, ftell(in)), exit(1);
 }
 printf("\n");
 if (out) fclose(out);
}

// Command line is: paq9a {a|x|l} archive [[-option] files...]...
int main(int argc, char** argv) {
 clock_t start=clock();

 // Check command line arguments
 if (argc<3 || argv[1][1] || (argv[1][0]!='a' && argv[1][0]!='x'
     && argv[1][0]!='l') || (argv[1][0]=='a' && argc<4) || argv[2][0]=='-')
 {
   printf("paq9a archiver (C) 2007, Matt Mahoney\n"
     "Free software under GPL, http://www.gnu.org/copyleft/gpl.html\n"
     "\n"
     "To create archive: paq9a a archive [-1..-9] [[-s|-c] files...]...\n"
     "  -1..-9 = use 18 to 1585 MiB memory (default -7 = 408 MiB)\n"
     "  -s = store, -c = compress (default)\n"
     "To extract files:  paq9a x archive [files...]\n"
     "To list contents:  paq9a l archive\n");
   exit(1);
 }

 // Create archive
 if (argv[1][0]=='a') {
   int option = 'c';  // -c or -s
   FILE* out=fopen(argv[2], "rb");
   if (out) printf("Cannot overwrite archive %s\n", argv[2]), exit(1);
   out=fopen(argv[2], "wb");
   if (!out) printf("Cannot create archive %s\n", argv[2]), exit(1);
   fprintf(out, "pQ9%c", 1);
   int i=3;
   if (argc>3 && argv[3][0]=='-' && argv[3][1]>='1' && argv[3][1]<='9'
       && argv[3][2]==0) {
     putc(argv[3][1], out);
     MEM=1<<22+argv[3][1]-'0';
     ++i;
   }
   else
     putc('7', out);
   for (; i<argc; ++i) {
     if (argv[i][0]=='-' && (argv[i][1]=='c' || argv[i][1]=='s')
         && argv[i][2]==0)
       option=argv[i][1];
     else
       compress(argv[i], out, option);
   }
   printf("-> %ld in %1.2f sec\n", ftell(out),
     double(clock()-start)/CLOCKS_PER_SEC);
 }

 // List archive contents
 else if (argv[1][0]=='l')
   list(argv[2]);

 // Extract from archive
 else if (argv[1][0]=='x') {
   extract(argc, argv);
   printf("%1.2f sec\n", double(clock()-start)/CLOCKS_PER_SEC);
 }

 // Report statistics
 delete predictor;
 delete lzp;
 printf("Used %d KiB memory\n", allocated>>10);
 return 0;
}