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varintgb.h
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/*
* varintgb.h
*
* Created on: Jul 25, 2013
* Author: lemire
*/
#ifndef VARINTGB_H_
#define VARINTGB_H_
#include "common.h"
#include "codecs.h"
#include "variablebyte.h"
namespace FastPForLib {
/**
* Group VarInt.
*
* Implemented and designed by D. Lemire based on a talk by Jeff Dean (Google),
* optimized by N. Kurz.
*/
template <bool delta = false> class VarIntGB : public IntegerCODEC {
public:
void encodeArray(const uint32_t *in, const size_t length, uint32_t *out,
size_t &nvalue) {
uint32_t prev = 0; // for delta
uint8_t *bout = reinterpret_cast<uint8_t *>(out);
const uint8_t *const initbout = reinterpret_cast<uint8_t *>(out);
*out = static_cast<uint32_t>(length);
bout += 4;
size_t k = 0;
for (; k + 3 < length; k += 4) {
uint8_t *keyp = bout++;
*keyp = 0;
{
const uint32_t val = delta ? in[k] - prev : in[k];
if (delta)
prev = in[k];
if (val < (1U << 8)) {
*bout++ = static_cast<uint8_t>(val);
} else if (val < (1U << 16)) {
*bout++ = static_cast<uint8_t>(val);
*bout++ = static_cast<uint8_t>(val >> 8);
*keyp = static_cast<uint8_t>(1);
} else if (val < (1U << 24)) {
*bout++ = static_cast<uint8_t>(val);
*bout++ = static_cast<uint8_t>(val >> 8);
*bout++ = static_cast<uint8_t>(val >> 16);
*keyp = static_cast<uint8_t>(2);
} else {
// the compiler will do the right thing
*reinterpret_cast<uint32_t *>(bout) = val;
bout += 4;
*keyp = static_cast<uint8_t>(3);
}
}
{
const uint32_t val = delta ? in[k + 1] - prev : in[k + 1];
if (delta)
prev = in[k + 1];
if (val < (1U << 8)) {
*bout++ = static_cast<uint8_t>(val);
} else if (val < (1U << 16)) {
*bout++ = static_cast<uint8_t>(val);
*bout++ = static_cast<uint8_t>(val >> 8);
*keyp |= static_cast<uint8_t>(1 << 2);
} else if (val < (1U << 24)) {
*bout++ = static_cast<uint8_t>(val);
*bout++ = static_cast<uint8_t>(val >> 8);
*bout++ = static_cast<uint8_t>(val >> 16);
*keyp |= static_cast<uint8_t>(2 << 2);
} else {
// the compiler will do the right thing
*reinterpret_cast<uint32_t *>(bout) = val;
bout += 4;
*keyp |= static_cast<uint8_t>(3 << 2);
}
}
{
const uint32_t val = delta ? in[k + 2] - prev : in[k + 2];
if (delta)
prev = in[k + 2];
if (val < (1U << 8)) {
*bout++ = static_cast<uint8_t>(val);
} else if (val < (1U << 16)) {
*bout++ = static_cast<uint8_t>(val);
*bout++ = static_cast<uint8_t>(val >> 8);
*keyp |= static_cast<uint8_t>(1 << 4);
} else if (val < (1U << 24)) {
*bout++ = static_cast<uint8_t>(val);
*bout++ = static_cast<uint8_t>(val >> 8);
*bout++ = static_cast<uint8_t>(val >> 16);
*keyp |= static_cast<uint8_t>(2 << 4);
} else {
// the compiler will do the right thing
*reinterpret_cast<uint32_t *>(bout) = val;
bout += 4;
*keyp |= static_cast<uint8_t>(3 << 4);
}
}
{
const uint32_t val = delta ? in[k + 3] - prev : in[k + 3];
if (delta)
prev = in[k + 3];
if (val < (1U << 8)) {
*bout++ = static_cast<uint8_t>(val);
} else if (val < (1U << 16)) {
*bout++ = static_cast<uint8_t>(val);
*bout++ = static_cast<uint8_t>(val >> 8);
*keyp |= static_cast<uint8_t>(1 << 6);
} else if (val < (1U << 24)) {
*bout++ = static_cast<uint8_t>(val);
*bout++ = static_cast<uint8_t>(val >> 8);
*bout++ = static_cast<uint8_t>(val >> 16);
*keyp |= static_cast<uint8_t>(2 << 6);
} else {
// the compiler will do the right thing
*reinterpret_cast<uint32_t *>(bout) = val;
bout += 4;
*keyp |= static_cast<uint8_t>(3 << 6);
}
}
}
if (k < length) {
uint8_t *keyp = bout++;
*keyp = 0;
for (int j = 0; k < length && j < 8; j += 2, ++k) {
const uint32_t val = delta ? in[k] - prev : in[k];
if (delta)
prev = in[k];
if (val < (1U << 8)) {
*bout++ = static_cast<uint8_t>(val);
} else if (val < (1U << 16)) {
*bout++ = static_cast<uint8_t>(val);
*bout++ = static_cast<uint8_t>(val >> 8);
*keyp |= static_cast<uint8_t>(1 << j);
} else if (val < (1U << 24)) {
*bout++ = static_cast<uint8_t>(val);
*bout++ = static_cast<uint8_t>(val >> 8);
*bout++ = static_cast<uint8_t>(val >> 16);
*keyp |= static_cast<uint8_t>(2 << j);
} else {
// the compiler will do the right thing
*reinterpret_cast<uint32_t *>(bout) = val;
bout += 4;
*keyp |= static_cast<uint8_t>(3 << j);
}
}
}
while (needPaddingTo32Bits(bout)) {
*bout++ = 0;
}
const size_t storageinbytes = bout - initbout;
assert((storageinbytes % 4) == 0);
nvalue = storageinbytes / 4;
}
const uint32_t *decodeArray(const uint32_t *in, const size_t length,
uint32_t *out, size_t &nvalue) {
uint32_t prev = 0; // for delta
const uint8_t *inbyte = reinterpret_cast<const uint8_t *>(in);
nvalue = *in;
inbyte += 4;
const uint8_t *const endbyte =
reinterpret_cast<const uint8_t *>(in + length);
const uint32_t *const endout(out + nvalue);
uint32_t val;
while (endbyte > inbyte + 1 + 4 * 4) {
inbyte = delta ? decodeGroupVarIntDelta(inbyte, &prev, out)
: decodeGroupVarInt(inbyte, out);
out += 4;
}
while (endbyte > inbyte) {
uint8_t key = *inbyte++;
for (int k = 0; out < endout and k < 4; k++) {
const uint32_t howmanybyte = key & 3;
key = static_cast<uint8_t>(key >> 2);
val = static_cast<uint32_t>(*inbyte++);
if (howmanybyte >= 1) {
val |= (static_cast<uint32_t>(*inbyte++) << 8);
if (howmanybyte >= 2) {
val |= (static_cast<uint32_t>(*inbyte++) << 16);
if (howmanybyte >= 3) {
val |= (static_cast<uint32_t>(*inbyte++) << 24);
}
}
}
prev = (delta ? prev : 0) + val;
*out++ = prev;
}
assert(inbyte <= endbyte);
}
inbyte = padTo32bits(inbyte);
return reinterpret_cast<const uint32_t *>(inbyte);
}
std::string name() const {
if (delta)
return "varintgbdelta";
else
return "varintgb";
}
private:
static uint32_t mask[4]; // { { 0xFF, 0xFFFF, 0xFFFFFF, 0xFFFFFFFF } };
const uint8_t *decodeGroupVarInt(const uint8_t *in, uint32_t *out) {
const uint32_t sel = *in++;
if (sel == 0) {
out[0] = static_cast<uint32_t>(in[0]);
out[1] = static_cast<uint32_t>(in[1]);
out[2] = static_cast<uint32_t>(in[2]);
out[3] = static_cast<uint32_t>(in[3]);
return in + 4;
}
const uint32_t sel1 = (sel & 3);
*out++ = *(reinterpret_cast<const uint32_t *>(in)) & mask[sel1];
in += sel1 + 1;
const uint32_t sel2 = ((sel >> 2) & 3);
*out++ = *(reinterpret_cast<const uint32_t *>(in)) & mask[sel2];
in += sel2 + 1;
const uint32_t sel3 = ((sel >> 4) & 3);
*out++ = *(reinterpret_cast<const uint32_t *>(in)) & mask[sel3];
in += sel3 + 1;
const uint32_t sel4 = (sel >> 6);
*out++ = *(reinterpret_cast<const uint32_t *>(in)) & mask[sel4];
in += sel4 + 1;
return in;
}
const uint8_t *decodeGroupVarIntDelta(const uint8_t *in, uint32_t *val,
uint32_t *out) {
const uint32_t sel = *in++;
if (sel == 0) {
out[0] = (*val += static_cast<uint32_t>(in[0]));
out[1] = (*val += static_cast<uint32_t>(in[1]));
out[2] = (*val += static_cast<uint32_t>(in[2]));
out[3] = (*val += static_cast<uint32_t>(in[3]));
return in + 4;
}
const uint32_t sel1 = (sel & 3);
*val += *(reinterpret_cast<const uint32_t *>(in)) & mask[sel1];
*out++ = *val;
in += sel1 + 1;
const uint32_t sel2 = ((sel >> 2) & 3);
*val += *(reinterpret_cast<const uint32_t *>(in)) & mask[sel2];
*out++ = *val;
in += sel2 + 1;
const uint32_t sel3 = ((sel >> 4) & 3);
*val += *(reinterpret_cast<const uint32_t *>(in)) & mask[sel3];
*out++ = *val;
in += sel3 + 1;
const uint32_t sel4 = (sel >> 6);
*val += *(reinterpret_cast<const uint32_t *>(in)) & mask[sel4];
*out++ = *val;
in += sel4 + 1;
return in;
}
};
template <bool delta>
uint32_t VarIntGB<delta>::mask[4] = {0xFF, 0xFFFF, 0xFFFFFF, 0xFFFFFFFF};
}
#endif /* VARINTGB_H_ */