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// SPDX-License-Identifier: Apache-2.0
// ----------------------------------------------------------------------------
// Copyright 2011-2024 Arm Limited
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy
// of the License at:
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.
// ----------------------------------------------------------------------------
/**
* @brief Functions for encoding/decoding Bounded Integer Sequence Encoding.
*/
#include "astcenc_internal.h"
#include <array>
/** @brief Unpacked quint triplets <low,middle,high> for each packed value */
// TODO: Bitpack these into a uint16_t?
static const uint8_t quints_of_integer[128][3] {
{0, 0, 0}, {1, 0, 0}, {2, 0, 0}, {3, 0, 0},
{4, 0, 0}, {0, 4, 0}, {4, 4, 0}, {4, 4, 4},
{0, 1, 0}, {1, 1, 0}, {2, 1, 0}, {3, 1, 0},
{4, 1, 0}, {1, 4, 0}, {4, 4, 1}, {4, 4, 4},
{0, 2, 0}, {1, 2, 0}, {2, 2, 0}, {3, 2, 0},
{4, 2, 0}, {2, 4, 0}, {4, 4, 2}, {4, 4, 4},
{0, 3, 0}, {1, 3, 0}, {2, 3, 0}, {3, 3, 0},
{4, 3, 0}, {3, 4, 0}, {4, 4, 3}, {4, 4, 4},
{0, 0, 1}, {1, 0, 1}, {2, 0, 1}, {3, 0, 1},
{4, 0, 1}, {0, 4, 1}, {4, 0, 4}, {0, 4, 4},
{0, 1, 1}, {1, 1, 1}, {2, 1, 1}, {3, 1, 1},
{4, 1, 1}, {1, 4, 1}, {4, 1, 4}, {1, 4, 4},
{0, 2, 1}, {1, 2, 1}, {2, 2, 1}, {3, 2, 1},
{4, 2, 1}, {2, 4, 1}, {4, 2, 4}, {2, 4, 4},
{0, 3, 1}, {1, 3, 1}, {2, 3, 1}, {3, 3, 1},
{4, 3, 1}, {3, 4, 1}, {4, 3, 4}, {3, 4, 4},
{0, 0, 2}, {1, 0, 2}, {2, 0, 2}, {3, 0, 2},
{4, 0, 2}, {0, 4, 2}, {2, 0, 4}, {3, 0, 4},
{0, 1, 2}, {1, 1, 2}, {2, 1, 2}, {3, 1, 2},
{4, 1, 2}, {1, 4, 2}, {2, 1, 4}, {3, 1, 4},
{0, 2, 2}, {1, 2, 2}, {2, 2, 2}, {3, 2, 2},
{4, 2, 2}, {2, 4, 2}, {2, 2, 4}, {3, 2, 4},
{0, 3, 2}, {1, 3, 2}, {2, 3, 2}, {3, 3, 2},
{4, 3, 2}, {3, 4, 2}, {2, 3, 4}, {3, 3, 4},
{0, 0, 3}, {1, 0, 3}, {2, 0, 3}, {3, 0, 3},
{4, 0, 3}, {0, 4, 3}, {0, 0, 4}, {1, 0, 4},
{0, 1, 3}, {1, 1, 3}, {2, 1, 3}, {3, 1, 3},
{4, 1, 3}, {1, 4, 3}, {0, 1, 4}, {1, 1, 4},
{0, 2, 3}, {1, 2, 3}, {2, 2, 3}, {3, 2, 3},
{4, 2, 3}, {2, 4, 3}, {0, 2, 4}, {1, 2, 4},
{0, 3, 3}, {1, 3, 3}, {2, 3, 3}, {3, 3, 3},
{4, 3, 3}, {3, 4, 3}, {0, 3, 4}, {1, 3, 4}
};
/** @brief Packed quint values for each unpacked value, indexed [hi][mid][lo]. */
static const uint8_t integer_of_quints[5][5][5] {
{
{0, 1, 2, 3, 4},
{8, 9, 10, 11, 12},
{16, 17, 18, 19, 20},
{24, 25, 26, 27, 28},
{5, 13, 21, 29, 6}
},
{
{32, 33, 34, 35, 36},
{40, 41, 42, 43, 44},
{48, 49, 50, 51, 52},
{56, 57, 58, 59, 60},
{37, 45, 53, 61, 14}
},
{
{64, 65, 66, 67, 68},
{72, 73, 74, 75, 76},
{80, 81, 82, 83, 84},
{88, 89, 90, 91, 92},
{69, 77, 85, 93, 22}
},
{
{96, 97, 98, 99, 100},
{104, 105, 106, 107, 108},
{112, 113, 114, 115, 116},
{120, 121, 122, 123, 124},
{101, 109, 117, 125, 30}
},
{
{102, 103, 70, 71, 38},
{110, 111, 78, 79, 46},
{118, 119, 86, 87, 54},
{126, 127, 94, 95, 62},
{39, 47, 55, 63, 31}
}
};
/** @brief Unpacked trit quintuplets <low,...,high> for each packed value */
// TODO: Bitpack these into a uint16_t?
static const uint8_t trits_of_integer[256][5] {
{0, 0, 0, 0, 0}, {1, 0, 0, 0, 0}, {2, 0, 0, 0, 0}, {0, 0, 2, 0, 0},
{0, 1, 0, 0, 0}, {1, 1, 0, 0, 0}, {2, 1, 0, 0, 0}, {1, 0, 2, 0, 0},
{0, 2, 0, 0, 0}, {1, 2, 0, 0, 0}, {2, 2, 0, 0, 0}, {2, 0, 2, 0, 0},
{0, 2, 2, 0, 0}, {1, 2, 2, 0, 0}, {2, 2, 2, 0, 0}, {2, 0, 2, 0, 0},
{0, 0, 1, 0, 0}, {1, 0, 1, 0, 0}, {2, 0, 1, 0, 0}, {0, 1, 2, 0, 0},
{0, 1, 1, 0, 0}, {1, 1, 1, 0, 0}, {2, 1, 1, 0, 0}, {1, 1, 2, 0, 0},
{0, 2, 1, 0, 0}, {1, 2, 1, 0, 0}, {2, 2, 1, 0, 0}, {2, 1, 2, 0, 0},
{0, 0, 0, 2, 2}, {1, 0, 0, 2, 2}, {2, 0, 0, 2, 2}, {0, 0, 2, 2, 2},
{0, 0, 0, 1, 0}, {1, 0, 0, 1, 0}, {2, 0, 0, 1, 0}, {0, 0, 2, 1, 0},
{0, 1, 0, 1, 0}, {1, 1, 0, 1, 0}, {2, 1, 0, 1, 0}, {1, 0, 2, 1, 0},
{0, 2, 0, 1, 0}, {1, 2, 0, 1, 0}, {2, 2, 0, 1, 0}, {2, 0, 2, 1, 0},
{0, 2, 2, 1, 0}, {1, 2, 2, 1, 0}, {2, 2, 2, 1, 0}, {2, 0, 2, 1, 0},
{0, 0, 1, 1, 0}, {1, 0, 1, 1, 0}, {2, 0, 1, 1, 0}, {0, 1, 2, 1, 0},
{0, 1, 1, 1, 0}, {1, 1, 1, 1, 0}, {2, 1, 1, 1, 0}, {1, 1, 2, 1, 0},
{0, 2, 1, 1, 0}, {1, 2, 1, 1, 0}, {2, 2, 1, 1, 0}, {2, 1, 2, 1, 0},
{0, 1, 0, 2, 2}, {1, 1, 0, 2, 2}, {2, 1, 0, 2, 2}, {1, 0, 2, 2, 2},
{0, 0, 0, 2, 0}, {1, 0, 0, 2, 0}, {2, 0, 0, 2, 0}, {0, 0, 2, 2, 0},
{0, 1, 0, 2, 0}, {1, 1, 0, 2, 0}, {2, 1, 0, 2, 0}, {1, 0, 2, 2, 0},
{0, 2, 0, 2, 0}, {1, 2, 0, 2, 0}, {2, 2, 0, 2, 0}, {2, 0, 2, 2, 0},
{0, 2, 2, 2, 0}, {1, 2, 2, 2, 0}, {2, 2, 2, 2, 0}, {2, 0, 2, 2, 0},
{0, 0, 1, 2, 0}, {1, 0, 1, 2, 0}, {2, 0, 1, 2, 0}, {0, 1, 2, 2, 0},
{0, 1, 1, 2, 0}, {1, 1, 1, 2, 0}, {2, 1, 1, 2, 0}, {1, 1, 2, 2, 0},
{0, 2, 1, 2, 0}, {1, 2, 1, 2, 0}, {2, 2, 1, 2, 0}, {2, 1, 2, 2, 0},
{0, 2, 0, 2, 2}, {1, 2, 0, 2, 2}, {2, 2, 0, 2, 2}, {2, 0, 2, 2, 2},
{0, 0, 0, 0, 2}, {1, 0, 0, 0, 2}, {2, 0, 0, 0, 2}, {0, 0, 2, 0, 2},
{0, 1, 0, 0, 2}, {1, 1, 0, 0, 2}, {2, 1, 0, 0, 2}, {1, 0, 2, 0, 2},
{0, 2, 0, 0, 2}, {1, 2, 0, 0, 2}, {2, 2, 0, 0, 2}, {2, 0, 2, 0, 2},
{0, 2, 2, 0, 2}, {1, 2, 2, 0, 2}, {2, 2, 2, 0, 2}, {2, 0, 2, 0, 2},
{0, 0, 1, 0, 2}, {1, 0, 1, 0, 2}, {2, 0, 1, 0, 2}, {0, 1, 2, 0, 2},
{0, 1, 1, 0, 2}, {1, 1, 1, 0, 2}, {2, 1, 1, 0, 2}, {1, 1, 2, 0, 2},
{0, 2, 1, 0, 2}, {1, 2, 1, 0, 2}, {2, 2, 1, 0, 2}, {2, 1, 2, 0, 2},
{0, 2, 2, 2, 2}, {1, 2, 2, 2, 2}, {2, 2, 2, 2, 2}, {2, 0, 2, 2, 2},
{0, 0, 0, 0, 1}, {1, 0, 0, 0, 1}, {2, 0, 0, 0, 1}, {0, 0, 2, 0, 1},
{0, 1, 0, 0, 1}, {1, 1, 0, 0, 1}, {2, 1, 0, 0, 1}, {1, 0, 2, 0, 1},
{0, 2, 0, 0, 1}, {1, 2, 0, 0, 1}, {2, 2, 0, 0, 1}, {2, 0, 2, 0, 1},
{0, 2, 2, 0, 1}, {1, 2, 2, 0, 1}, {2, 2, 2, 0, 1}, {2, 0, 2, 0, 1},
{0, 0, 1, 0, 1}, {1, 0, 1, 0, 1}, {2, 0, 1, 0, 1}, {0, 1, 2, 0, 1},
{0, 1, 1, 0, 1}, {1, 1, 1, 0, 1}, {2, 1, 1, 0, 1}, {1, 1, 2, 0, 1},
{0, 2, 1, 0, 1}, {1, 2, 1, 0, 1}, {2, 2, 1, 0, 1}, {2, 1, 2, 0, 1},
{0, 0, 1, 2, 2}, {1, 0, 1, 2, 2}, {2, 0, 1, 2, 2}, {0, 1, 2, 2, 2},
{0, 0, 0, 1, 1}, {1, 0, 0, 1, 1}, {2, 0, 0, 1, 1}, {0, 0, 2, 1, 1},
{0, 1, 0, 1, 1}, {1, 1, 0, 1, 1}, {2, 1, 0, 1, 1}, {1, 0, 2, 1, 1},
{0, 2, 0, 1, 1}, {1, 2, 0, 1, 1}, {2, 2, 0, 1, 1}, {2, 0, 2, 1, 1},
{0, 2, 2, 1, 1}, {1, 2, 2, 1, 1}, {2, 2, 2, 1, 1}, {2, 0, 2, 1, 1},
{0, 0, 1, 1, 1}, {1, 0, 1, 1, 1}, {2, 0, 1, 1, 1}, {0, 1, 2, 1, 1},
{0, 1, 1, 1, 1}, {1, 1, 1, 1, 1}, {2, 1, 1, 1, 1}, {1, 1, 2, 1, 1},
{0, 2, 1, 1, 1}, {1, 2, 1, 1, 1}, {2, 2, 1, 1, 1}, {2, 1, 2, 1, 1},
{0, 1, 1, 2, 2}, {1, 1, 1, 2, 2}, {2, 1, 1, 2, 2}, {1, 1, 2, 2, 2},
{0, 0, 0, 2, 1}, {1, 0, 0, 2, 1}, {2, 0, 0, 2, 1}, {0, 0, 2, 2, 1},
{0, 1, 0, 2, 1}, {1, 1, 0, 2, 1}, {2, 1, 0, 2, 1}, {1, 0, 2, 2, 1},
{0, 2, 0, 2, 1}, {1, 2, 0, 2, 1}, {2, 2, 0, 2, 1}, {2, 0, 2, 2, 1},
{0, 2, 2, 2, 1}, {1, 2, 2, 2, 1}, {2, 2, 2, 2, 1}, {2, 0, 2, 2, 1},
{0, 0, 1, 2, 1}, {1, 0, 1, 2, 1}, {2, 0, 1, 2, 1}, {0, 1, 2, 2, 1},
{0, 1, 1, 2, 1}, {1, 1, 1, 2, 1}, {2, 1, 1, 2, 1}, {1, 1, 2, 2, 1},
{0, 2, 1, 2, 1}, {1, 2, 1, 2, 1}, {2, 2, 1, 2, 1}, {2, 1, 2, 2, 1},
{0, 2, 1, 2, 2}, {1, 2, 1, 2, 2}, {2, 2, 1, 2, 2}, {2, 1, 2, 2, 2},
{0, 0, 0, 1, 2}, {1, 0, 0, 1, 2}, {2, 0, 0, 1, 2}, {0, 0, 2, 1, 2},
{0, 1, 0, 1, 2}, {1, 1, 0, 1, 2}, {2, 1, 0, 1, 2}, {1, 0, 2, 1, 2},
{0, 2, 0, 1, 2}, {1, 2, 0, 1, 2}, {2, 2, 0, 1, 2}, {2, 0, 2, 1, 2},
{0, 2, 2, 1, 2}, {1, 2, 2, 1, 2}, {2, 2, 2, 1, 2}, {2, 0, 2, 1, 2},
{0, 0, 1, 1, 2}, {1, 0, 1, 1, 2}, {2, 0, 1, 1, 2}, {0, 1, 2, 1, 2},
{0, 1, 1, 1, 2}, {1, 1, 1, 1, 2}, {2, 1, 1, 1, 2}, {1, 1, 2, 1, 2},
{0, 2, 1, 1, 2}, {1, 2, 1, 1, 2}, {2, 2, 1, 1, 2}, {2, 1, 2, 1, 2},
{0, 2, 2, 2, 2}, {1, 2, 2, 2, 2}, {2, 2, 2, 2, 2}, {2, 1, 2, 2, 2}
};
/** @brief Packed trit values for each unpacked value, indexed [hi][][][][lo]. */
static const uint8_t integer_of_trits[3][3][3][3][3] {
{
{
{
{0, 1, 2},
{4, 5, 6},
{8, 9, 10}
},
{
{16, 17, 18},
{20, 21, 22},
{24, 25, 26}
},
{
{3, 7, 15},
{19, 23, 27},
{12, 13, 14}
}
},
{
{
{32, 33, 34},
{36, 37, 38},
{40, 41, 42}
},
{
{48, 49, 50},
{52, 53, 54},
{56, 57, 58}
},
{
{35, 39, 47},
{51, 55, 59},
{44, 45, 46}
}
},
{
{
{64, 65, 66},
{68, 69, 70},
{72, 73, 74}
},
{
{80, 81, 82},
{84, 85, 86},
{88, 89, 90}
},
{
{67, 71, 79},
{83, 87, 91},
{76, 77, 78}
}
}
},
{
{
{
{128, 129, 130},
{132, 133, 134},
{136, 137, 138}
},
{
{144, 145, 146},
{148, 149, 150},
{152, 153, 154}
},
{
{131, 135, 143},
{147, 151, 155},
{140, 141, 142}
}
},
{
{
{160, 161, 162},
{164, 165, 166},
{168, 169, 170}
},
{
{176, 177, 178},
{180, 181, 182},
{184, 185, 186}
},
{
{163, 167, 175},
{179, 183, 187},
{172, 173, 174}
}
},
{
{
{192, 193, 194},
{196, 197, 198},
{200, 201, 202}
},
{
{208, 209, 210},
{212, 213, 214},
{216, 217, 218}
},
{
{195, 199, 207},
{211, 215, 219},
{204, 205, 206}
}
}
},
{
{
{
{96, 97, 98},
{100, 101, 102},
{104, 105, 106}
},
{
{112, 113, 114},
{116, 117, 118},
{120, 121, 122}
},
{
{99, 103, 111},
{115, 119, 123},
{108, 109, 110}
}
},
{
{
{224, 225, 226},
{228, 229, 230},
{232, 233, 234}
},
{
{240, 241, 242},
{244, 245, 246},
{248, 249, 250}
},
{
{227, 231, 239},
{243, 247, 251},
{236, 237, 238}
}
},
{
{
{28, 29, 30},
{60, 61, 62},
{92, 93, 94}
},
{
{156, 157, 158},
{188, 189, 190},
{220, 221, 222}
},
{
{31, 63, 127},
{159, 191, 255},
{252, 253, 254}
}
}
}
};
/**
* @brief The number of bits, trits, and quints needed for a quant level.
*/
struct btq_count
{
/** @brief The number of bits. */
uint8_t bits:6;
/** @brief The number of trits. */
uint8_t trits:1;
/** @brief The number of quints. */
uint8_t quints:1;
};
/**
* @brief The table of bits, trits, and quints needed for a quant encode.
*/
static const std::array<btq_count, 21> btq_counts {{
{ 1, 0, 0 }, // QUANT_2
{ 0, 1, 0 }, // QUANT_3
{ 2, 0, 0 }, // QUANT_4
{ 0, 0, 1 }, // QUANT_5
{ 1, 1, 0 }, // QUANT_6
{ 3, 0, 0 }, // QUANT_8
{ 1, 0, 1 }, // QUANT_10
{ 2, 1, 0 }, // QUANT_12
{ 4, 0, 0 }, // QUANT_16
{ 2, 0, 1 }, // QUANT_20
{ 3, 1, 0 }, // QUANT_24
{ 5, 0, 0 }, // QUANT_32
{ 3, 0, 1 }, // QUANT_40
{ 4, 1, 0 }, // QUANT_48
{ 6, 0, 0 }, // QUANT_64
{ 4, 0, 1 }, // QUANT_80
{ 5, 1, 0 }, // QUANT_96
{ 7, 0, 0 }, // QUANT_128
{ 5, 0, 1 }, // QUANT_160
{ 6, 1, 0 }, // QUANT_192
{ 8, 0, 0 } // QUANT_256
}};
/**
* @brief The sequence scale, round, and divisors needed to compute sizing.
*
* The length of a quantized sequence in bits is:
* (scale * <sequence_len> + round) / divisor
*/
struct ise_size
{
/** @brief The scaling parameter. */
uint8_t scale:6;
/** @brief The divisor parameter. */
uint8_t divisor:2;
};
/**
* @brief The table of scale, round, and divisors needed for quant sizing.
*/
static const std::array<ise_size, 21> ise_sizes {{
{ 1, 0 }, // QUANT_2
{ 8, 2 }, // QUANT_3
{ 2, 0 }, // QUANT_4
{ 7, 1 }, // QUANT_5
{ 13, 2 }, // QUANT_6
{ 3, 0 }, // QUANT_8
{ 10, 1 }, // QUANT_10
{ 18, 2 }, // QUANT_12
{ 4, 0 }, // QUANT_16
{ 13, 1 }, // QUANT_20
{ 23, 2 }, // QUANT_24
{ 5, 0 }, // QUANT_32
{ 16, 1 }, // QUANT_40
{ 28, 2 }, // QUANT_48
{ 6, 0 }, // QUANT_64
{ 19, 1 }, // QUANT_80
{ 33, 2 }, // QUANT_96
{ 7, 0 }, // QUANT_128
{ 22, 1 }, // QUANT_160
{ 38, 2 }, // QUANT_192
{ 8, 0 } // QUANT_256
}};
/* See header for documentation. */
unsigned int get_ise_sequence_bitcount(
unsigned int character_count,
quant_method quant_level
) {
// Cope with out-of bounds values - input might be invalid
if (static_cast<size_t>(quant_level) >= ise_sizes.size())
{
// Arbitrary large number that's more than an ASTC block can hold
return 1024;
}
auto& entry = ise_sizes[quant_level];
unsigned int divisor = (entry.divisor << 1) + 1;
return (entry.scale * character_count + divisor - 1) / divisor;
}
/**
* @brief Write up to 8 bits at an arbitrary bit offset.
*
* The stored value is at most 8 bits, but can be stored at an offset of between 0 and 7 bits so may
* span two separate bytes in memory.
*
* @param value The value to write.
* @param bitcount The number of bits to write, starting from LSB.
* @param bitoffset The bit offset to store at, between 0 and 7.
* @param[in,out] ptr The data pointer to write to.
*/
static inline void write_bits(
unsigned int value,
unsigned int bitcount,
unsigned int bitoffset,
uint8_t ptr[2]
) {
unsigned int mask = (1 << bitcount) - 1;
value &= mask;
ptr += bitoffset >> 3;
bitoffset &= 7;
value <<= bitoffset;
mask <<= bitoffset;
mask = ~mask;
ptr[0] &= mask;
ptr[0] |= value;
ptr[1] &= mask >> 8;
ptr[1] |= value >> 8;
}
/**
* @brief Read up to 16 bits from two bytes.
*
* This function reads a packed N-bit field from two bytes in memory. The stored value must exist
* within the two bytes, but can start at an arbitary bit offset and span the two bytes in memory.
*
* @param bitcount The number of bits to read.
* @param bitoffset The bit offset to read from, between 0 and 7.
* @param[in,out] ptr The data pointer to read from.
*
* @return The read value.
*/
static inline unsigned int read_bits(
unsigned int bitcount,
unsigned int bitoffset,
const uint8_t* ptr
) {
unsigned int mask = (1 << bitcount) - 1;
ptr += bitoffset >> 3;
bitoffset &= 7;
unsigned int value = ptr[0] | (ptr[1] << 8);
value >>= bitoffset;
value &= mask;
return value;
}
/* See header for documentation. */
void encode_ise(
quant_method quant_level,
unsigned int character_count,
const uint8_t* input_data,
uint8_t* output_data,
unsigned int bit_offset
) {
promise(character_count > 0);
unsigned int bits = btq_counts[quant_level].bits;
unsigned int trits = btq_counts[quant_level].trits;
unsigned int quints = btq_counts[quant_level].quints;
unsigned int mask = (1 << bits) - 1;
// Write out trits and bits
if (trits)
{
unsigned int i = 0;
unsigned int full_trit_blocks = character_count / 5;
for (unsigned int j = 0; j < full_trit_blocks; j++)
{
unsigned int i4 = input_data[i + 4] >> bits;
unsigned int i3 = input_data[i + 3] >> bits;
unsigned int i2 = input_data[i + 2] >> bits;
unsigned int i1 = input_data[i + 1] >> bits;
unsigned int i0 = input_data[i + 0] >> bits;
uint8_t T = integer_of_trits[i4][i3][i2][i1][i0];
// The max size of a trit bit count is 6, so we can always safely
// pack a single MX value with the following 1 or 2 T bits.
uint8_t pack;
// Element 0 + T0 + T1
pack = (input_data[i++] & mask) | (((T >> 0) & 0x3) << bits);
write_bits(pack, bits + 2, bit_offset, output_data);
bit_offset += bits + 2;
// Element 1 + T2 + T3
pack = (input_data[i++] & mask) | (((T >> 2) & 0x3) << bits);
write_bits(pack, bits + 2, bit_offset, output_data);
bit_offset += bits + 2;
// Element 2 + T4
pack = (input_data[i++] & mask) | (((T >> 4) & 0x1) << bits);
write_bits(pack, bits + 1, bit_offset, output_data);
bit_offset += bits + 1;
// Element 3 + T5 + T6
pack = (input_data[i++] & mask) | (((T >> 5) & 0x3) << bits);
write_bits(pack, bits + 2, bit_offset, output_data);
bit_offset += bits + 2;
// Element 4 + T7
pack = (input_data[i++] & mask) | (((T >> 7) & 0x1) << bits);
write_bits(pack, bits + 1, bit_offset, output_data);
bit_offset += bits + 1;
}
// Loop tail for a partial block
if (i != character_count)
{
// i4 cannot be present - we know the block is partial
// i0 must be present - we know the block isn't empty
unsigned int i4 = 0;
unsigned int i3 = i + 3 >= character_count ? 0 : input_data[i + 3] >> bits;
unsigned int i2 = i + 2 >= character_count ? 0 : input_data[i + 2] >> bits;
unsigned int i1 = i + 1 >= character_count ? 0 : input_data[i + 1] >> bits;
unsigned int i0 = input_data[i + 0] >> bits;
uint8_t T = integer_of_trits[i4][i3][i2][i1][i0];
for (unsigned int j = 0; i < character_count; i++, j++)
{
// Truncated table as this iteration is always partital
static const uint8_t tbits[4] { 2, 2, 1, 2 };
static const uint8_t tshift[4] { 0, 2, 4, 5 };
uint8_t pack = (input_data[i] & mask) |
(((T >> tshift[j]) & ((1 << tbits[j]) - 1)) << bits);
write_bits(pack, bits + tbits[j], bit_offset, output_data);
bit_offset += bits + tbits[j];
}
}
}
// Write out quints and bits
else if (quints)
{
unsigned int i = 0;
unsigned int full_quint_blocks = character_count / 3;
for (unsigned int j = 0; j < full_quint_blocks; j++)
{
unsigned int i2 = input_data[i + 2] >> bits;
unsigned int i1 = input_data[i + 1] >> bits;
unsigned int i0 = input_data[i + 0] >> bits;
uint8_t T = integer_of_quints[i2][i1][i0];
// The max size of a quint bit count is 5, so we can always safely
// pack a single M value with the following 2 or 3 T bits.
uint8_t pack;
// Element 0
pack = (input_data[i++] & mask) | (((T >> 0) & 0x7) << bits);
write_bits(pack, bits + 3, bit_offset, output_data);
bit_offset += bits + 3;
// Element 1
pack = (input_data[i++] & mask) | (((T >> 3) & 0x3) << bits);
write_bits(pack, bits + 2, bit_offset, output_data);
bit_offset += bits + 2;
// Element 2
pack = (input_data[i++] & mask) | (((T >> 5) & 0x3) << bits);
write_bits(pack, bits + 2, bit_offset, output_data);
bit_offset += bits + 2;
}
// Loop tail for a partial block
if (i != character_count)
{
// i2 cannot be present - we know the block is partial
// i0 must be present - we know the block isn't empty
unsigned int i2 = 0;
unsigned int i1 = i + 1 >= character_count ? 0 : input_data[i + 1] >> bits;
unsigned int i0 = input_data[i + 0] >> bits;
uint8_t T = integer_of_quints[i2][i1][i0];
for (unsigned int j = 0; i < character_count; i++, j++)
{
// Truncated table as this iteration is always partital
static const uint8_t tbits[2] { 3, 2 };
static const uint8_t tshift[2] { 0, 3 };
uint8_t pack = (input_data[i] & mask) |
(((T >> tshift[j]) & ((1 << tbits[j]) - 1)) << bits);
write_bits(pack, bits + tbits[j], bit_offset, output_data);
bit_offset += bits + tbits[j];
}
}
}
// Write out just bits
else
{
for (unsigned int i = 0; i < character_count; i++)
{
write_bits(input_data[i], bits, bit_offset, output_data);
bit_offset += bits;
}
}
}
/* See header for documentation. */
void decode_ise(
quant_method quant_level,
unsigned int character_count,
const uint8_t* input_data,
uint8_t* output_data,
unsigned int bit_offset
) {
promise(character_count > 0);
// Note: due to how the trit/quint-block unpacking is done in this function, we may write more
// temporary results than the number of outputs. The maximum actual number of results is 64 bit,
// but we keep 4 additional character_count of padding.
uint8_t results[68];
uint8_t tq_blocks[22] { 0 }; // Trit-blocks or quint-blocks, must be zeroed
unsigned int bits = btq_counts[quant_level].bits;
unsigned int trits = btq_counts[quant_level].trits;
unsigned int quints = btq_counts[quant_level].quints;
unsigned int lcounter = 0;
unsigned int hcounter = 0;
// Collect bits for each element, as well as bits for any trit-blocks and quint-blocks.
for (unsigned int i = 0; i < character_count; i++)
{
results[i] = static_cast<uint8_t>(read_bits(bits, bit_offset, input_data));
bit_offset += bits;
if (trits)
{
static const uint8_t bits_to_read[5] { 2, 2, 1, 2, 1 };
static const uint8_t block_shift[5] { 0, 2, 4, 5, 7 };
static const uint8_t next_lcounter[5] { 1, 2, 3, 4, 0 };
static const uint8_t hcounter_incr[5] { 0, 0, 0, 0, 1 };
unsigned int tdata = read_bits(bits_to_read[lcounter], bit_offset, input_data);
bit_offset += bits_to_read[lcounter];
tq_blocks[hcounter] |= tdata << block_shift[lcounter];
hcounter += hcounter_incr[lcounter];
lcounter = next_lcounter[lcounter];
}
if (quints)
{
static const uint8_t bits_to_read[3] { 3, 2, 2 };
static const uint8_t block_shift[3] { 0, 3, 5 };
static const uint8_t next_lcounter[3] { 1, 2, 0 };
static const uint8_t hcounter_incr[3] { 0, 0, 1 };
unsigned int tdata = read_bits(bits_to_read[lcounter], bit_offset, input_data);
bit_offset += bits_to_read[lcounter];
tq_blocks[hcounter] |= tdata << block_shift[lcounter];
hcounter += hcounter_incr[lcounter];
lcounter = next_lcounter[lcounter];
}
}
// Unpack trit-blocks or quint-blocks as needed
if (trits)
{
unsigned int trit_blocks = (character_count + 4) / 5;
promise(trit_blocks > 0);
for (unsigned int i = 0; i < trit_blocks; i++)
{
const uint8_t *tritptr = trits_of_integer[tq_blocks[i]];
results[5 * i ] |= tritptr[0] << bits;
results[5 * i + 1] |= tritptr[1] << bits;
results[5 * i + 2] |= tritptr[2] << bits;
results[5 * i + 3] |= tritptr[3] << bits;
results[5 * i + 4] |= tritptr[4] << bits;
}
}
if (quints)
{
unsigned int quint_blocks = (character_count + 2) / 3;
promise(quint_blocks > 0);
for (unsigned int i = 0; i < quint_blocks; i++)
{
const uint8_t *quintptr = quints_of_integer[tq_blocks[i]];
results[3 * i ] |= quintptr[0] << bits;
results[3 * i + 1] |= quintptr[1] << bits;
results[3 * i + 2] |= quintptr[2] << bits;
}
}
for (unsigned int i = 0; i < character_count; i++)
{
output_data[i] = results[i];
}
}