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#include "sqliteint.h"

#include <assert.h>

** Bitmasks used by sqlite3GetVarint(). These precomputed constants

** are defined here rather than simply putting the constant expressions

** inline in order to work around bugs in the RVT compiler.

** SLOT_2_0 A mask for (0x7f<<14) | 0x7f

** SLOT_4_2_0 A mask for (0x7f<<28) | SLOT_2_0

#define SLOT_2_0 0x001fc07f

#define SLOT_4_2_0 0xf01fc07f

** SQLITE_MAX_U32 is a u64 constant that is the maximum u64 value

** that can be stored in a u32 without loss of data. The value

** is 0x00000000ffffffff. But because of quirks of some compilers, we

** have to specify the value in the less intuitive manner shown:

#define SQLITE_MAX_U32 ((((u64)1)<<32)-1)

** Read a 64-bit variable-length integer from memory starting at p[0].

** Return the number of bytes read. The value is stored in *v.

u8 sqlite3GetVarint(const unsigned char *p, u64 *v){

u32 a,b,s;

a = *p;

/* a: p0 (unmasked) */

if (!(a&0x80))

{

*v = a;

return 1;

}

p++;

b = *p;

/* b: p1 (unmasked) */

if (!(b&0x80))

{

a &= 0x7f;

a = a<<7;

a |= b;

*v = a;

return 2;

}

/* Verify that constants are precomputed correctly */

assert( SLOT_2_0 == ((0x7f<<14) | (0x7f)) );

assert( SLOT_4_2_0 == ((0xfU<<28) | (0x7f<<14) | (0x7f)) );

p++;

a = a<<14;

a |= *p;

/* a: p0<<14 | p2 (unmasked) */

if (!(a&0x80))

{

a &= SLOT_2_0;

b &= 0x7f;

b = b<<7;

a |= b;

*v = a;

return 3;

}

/* CSE1 from below */

a &= SLOT_2_0;

p++;

b = b<<14;

b |= *p;

/* b: p1<<14 | p3 (unmasked) */

if (!(b&0x80))

{

b &= SLOT_2_0;

/* moved CSE1 up */

/* a &= (0x7f<<14)|(0x7f); */

a = a<<7;

a |= b;

*v = a;

return 4;

}

/* a: p0<<14 | p2 (masked) */

/* b: p1<<14 | p3 (unmasked) */

/* 1:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked) */

/* moved CSE1 up */

/* a &= (0x7f<<14)|(0x7f); */

b &= SLOT_2_0;

s = a;

/* s: p0<<14 | p2 (masked) */

p++;

a = a<<14;

a |= *p;

/* a: p0<<28 | p2<<14 | p4 (unmasked) */

if (!(a&0x80))

{

/* we can skip these cause they were (effectively) done above

** while calculating s */

/* a &= (0x7f<<28)|(0x7f<<14)|(0x7f); */

/* b &= (0x7f<<14)|(0x7f); */

b = b<<7;

a |= b;

s = s>>18;

*v = ((u64)s)<<32 | a;

return 5;

}

/* 2:save off p0<<21 | p1<<14 | p2<<7 | p3 (masked) */

s = s<<7;

s |= b;

/* s: p0<<21 | p1<<14 | p2<<7 | p3 (masked) */

p++;

b = b<<14;

b |= *p;

/* b: p1<<28 | p3<<14 | p5 (unmasked) */

if (!(b&0x80))

{

/* we can skip this cause it was (effectively) done above in calc'ing s */

/* b &= (0x7f<<28)|(0x7f<<14)|(0x7f); */

a &= SLOT_2_0;

a = a<<7;

a |= b;

s = s>>18;

*v = ((u64)s)<<32 | a;

return 6;

}

p++;

a = a<<14;

a |= *p;

/* a: p2<<28 | p4<<14 | p6 (unmasked) */

if (!(a&0x80))

{

a &= SLOT_4_2_0;

b &= SLOT_2_0;

b = b<<7;

a |= b;

s = s>>11;

*v = ((u64)s)<<32 | a;

return 7;

}

/* CSE2 from below */

a &= SLOT_2_0;

p++;

b = b<<14;

b |= *p;

/* b: p3<<28 | p5<<14 | p7 (unmasked) */

if (!(b&0x80))

{

b &= SLOT_4_2_0;

/* moved CSE2 up */

/* a &= (0x7f<<14)|(0x7f); */

a = a<<7;

a |= b;

s = s>>4;

*v = ((u64)s)<<32 | a;

return 8;

}

p++;

a = a<<15;

a |= *p;

/* a: p4<<29 | p6<<15 | p8 (unmasked) */

/* moved CSE2 up */

/* a &= (0x7f<<29)|(0x7f<<15)|(0xff); */

b &= SLOT_2_0;

b = b<<8;

a |= b;

s = s<<4;

b = p[-4];

b &= 0x7f;

b = b>>3;

s |= b;

*v = ((u64)s)<<32 | a;

return 9;

}

** Read a 32-bit variable-length integer from memory starting at p[0].

** Return the number of bytes read. The value is stored in *v.

** If the varint stored in p[0] is larger than can fit in a 32-bit unsigned

** integer, then set *v to 0xffffffff.

** A MACRO version, getVarint32, is provided which inlines the

** single-byte case. All code should use the MACRO version as

** this function assumes the single-byte case has already been handled.

u8 sqlite3GetVarint32(const unsigned char *p, u32 *v){

u32 a,b;

/* The 1-byte case. Overwhelmingly the most common. Handled inline

** by the getVarin32() macro */

a = *p;

/* a: p0 (unmasked) */

#ifndef getVarint32

if (!(a&0x80))

{

/* Values between 0 and 127 */

*v = a;

return 1;

}

#endif

/* The 2-byte case */

p++;

b = *p;

/* b: p1 (unmasked) */

if (!(b&0x80))

{

/* Values between 128 and 16383 */

a &= 0x7f;

a = a<<7;

*v = a | b;

return 2;

}

/* The 3-byte case */

p++;

a = a<<14;

a |= *p;

/* a: p0<<14 | p2 (unmasked) */

if (!(a&0x80))

{

/* Values between 16384 and 2097151 */

a &= (0x7f<<14)|(0x7f);

b &= 0x7f;

b = b<<7;

*v = a | b;

return 3;

}

/* A 32-bit varint is used to store size information in btrees.

** Objects are rarely larger than 2MiB limit of a 3-byte varint.

** A 3-byte varint is sufficient, for example, to record the size

** of a 1048569-byte BLOB or string.

** We only unroll the first 1-, 2-, and 3- byte cases. The very

** rare larger cases can be handled by the slower 64-bit varint

** routine.

#if 1

{

u64 v64;

u8 n;

p -= 2;

n = sqlite3GetVarint(p, &v64);

assert( n>3 && n<=9 );

if( (v64 & SQLITE_MAX_U32)!=v64 ){

*v = 0xffffffff;

}else{

*v = (u32)v64;

}

return n;

}

#else

/* For following code (kept for historical record only) shows an

** unrolling for the 3- and 4-byte varint cases. This code is

** slightly faster, but it is also larger and much harder to test.

p++;

b = b<<14;

b |= *p;

/* b: p1<<14 | p3 (unmasked) */

if (!(b&0x80))

{

/* Values between 2097152 and 268435455 */

b &= (0x7f<<14)|(0x7f);

a &= (0x7f<<14)|(0x7f);

a = a<<7;

*v = a | b;

return 4;

}

p++;

a = a<<14;

a |= *p;

/* a: p0<<28 | p2<<14 | p4 (unmasked) */

if (!(a&0x80))

{

/* Values between 268435456 and 34359738367 */

a &= SLOT_4_2_0;

b &= SLOT_4_2_0;

b = b<<7;

*v = a | b;

return 5;

}

/* We can only reach this point when reading a corrupt database

** file. In that case we are not in any hurry. Use the (relatively

** slow) general-purpose sqlite3GetVarint() routine to extract the

** value. */

{

u64 v64;

u8 n;

p -= 4;

n = sqlite3GetVarint(p, &v64);

assert( n>5 && n<=9 );

*v = (u32)v64;

return n;

}

#endif

}

/* Load an unaligned and unsigned 32-bit integer */

#define SESSION_UINT32(x) (((u32)(x)[0]<<24)|((x)[1]<<16)|((x)[2]<<8)|(x)[3])

** Read a 64-bit big-endian integer value from buffer aRec[]. Return

** the value read.

sqlite3_int64 sessionGetI64(u8 *aRec){

u64 x = SESSION_UINT32(aRec);

u32 y = SESSION_UINT32(aRec+4);

x = (x<<32) + y;

return (sqlite3_int64)x;

}

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