79eea8208d
Add RLE encoding/decoding functions for byte arrays for the purpose of pre-processing arrays with large spans of (mostly) uniform values before storing them in a BArrayState. Part of a fix for #136737.
128 lines
4.6 KiB
C
128 lines
4.6 KiB
C
/* SPDX-FileCopyrightText: 2023 Blender Authors
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*
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* SPDX-License-Identifier: GPL-2.0-or-later */
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#pragma once
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/** \file
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* \ingroup bli
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* \brief Efficient in-memory storage of multiple similar arrays.
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*/
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#include "BLI_sys_types.h"
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typedef struct BArrayState BArrayState;
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typedef struct BArrayStore BArrayStore;
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/**
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* Create a new array store, which can store any number of arrays
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* as long as their stride matches.
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*
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* \param stride: `sizeof()` each element,
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*
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* \note while a stride of `1` will always work,
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* its less efficient since duplicate chunks of memory will be searched
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* at positions unaligned with the array data.
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*
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* \param chunk_count: Number of elements to split each chunk into.
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* - A small value increases the ability to de-duplicate chunks,
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* but adds overhead by increasing the number of chunks to look up when searching for duplicates,
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* as well as some overhead constructing the original array again, with more calls to `memcpy`.
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* - Larger values reduce the *book keeping* overhead,
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* but increase the chance a small,
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* isolated change will cause a larger amount of data to be duplicated.
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*
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* \return A new array store, to be freed with #BLI_array_store_destroy.
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*/
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BArrayStore *BLI_array_store_create(unsigned int stride, unsigned int chunk_count);
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/**
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* Free the #BArrayStore, including all states and chunks.
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*/
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void BLI_array_store_destroy(BArrayStore *bs);
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/**
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* Clear all contents, allowing reuse of \a bs.
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*/
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void BLI_array_store_clear(BArrayStore *bs);
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/**
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* Find the memory used by all states (expanded & real).
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*
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* \return the total amount of memory that would be used by getting the arrays for all states.
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*/
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size_t BLI_array_store_calc_size_expanded_get(const BArrayStore *bs);
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/**
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* \return the amount of memory used by all #BChunk.data
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* (duplicate chunks are only counted once).
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*/
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size_t BLI_array_store_calc_size_compacted_get(const BArrayStore *bs);
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/**
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* \param data: Data used to create
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* \param state_reference: The state to use as a reference when adding the new state,
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* typically this is the previous state,
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* however it can be any previously created state from this \a bs.
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*
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* \return The new state,
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* which is used by the caller as a handle to get back the contents of \a data.
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* This may be removed using #BLI_array_store_state_remove,
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* otherwise it will be removed with #BLI_array_store_destroy.
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*/
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BArrayState *BLI_array_store_state_add(BArrayStore *bs,
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const void *data,
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size_t data_len,
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const BArrayState *state_reference);
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/**
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* Remove a state and free any unused #BChunk data.
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*
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* The states can be freed in any order.
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*/
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void BLI_array_store_state_remove(BArrayStore *bs, BArrayState *state);
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/**
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* \return the expanded size of the array,
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* use this to know how much memory to allocate #BLI_array_store_state_data_get's argument.
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*/
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size_t BLI_array_store_state_size_get(const BArrayState *state);
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/**
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* Fill in existing allocated memory with the contents of \a state.
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*/
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void BLI_array_store_state_data_get(const BArrayState *state, void *data);
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/**
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* Allocate an array for \a state and return it.
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*/
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void *BLI_array_store_state_data_get_alloc(const BArrayState *state, size_t *r_data_len);
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/**
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* \note Only for tests.
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*/
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bool BLI_array_store_is_valid(BArrayStore *bs);
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/* `array_store_rle.cc` */
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/**
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* Return a run-length encoded copy of `data_dec`.
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*
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* \param data_dec: The data to encode.
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* \param data_dec_len: The size of the data to encode.
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* \param data_enc_extra_size: Allocate extra memory at the beginning of the array.
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* - This doesn't impact the value of `r_data_enc_len`.
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* - This must be skipped when decoding.
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* \param r_data_enc_len: The size of the resulting RLE encoded data.
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*/
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uint8_t *BLI_array_store_rle_encode(const uint8_t *data_dec,
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size_t data_dec_len,
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size_t data_enc_extra_size,
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size_t *r_data_enc_len);
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/**
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* Decode a run-length encoded array, writing the result into `data_dec_v`.
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*
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* \param data_enc: The data to encode (returned by #BLI_array_store_rle_encode).
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* \param data_enc_len: The size of `data_enc`.
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* \param data_dec: The destination for the decoded data to be written to.
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* \param data_dec_len: The size of the destination (as passed to #BLI_array_store_rle_encode).
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*/
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void BLI_array_store_rle_decode(const uint8_t *data_enc,
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const size_t data_enc_len,
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void *data_dec_v,
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const size_t data_dec_len);
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