242 lines
7.4 KiB
C
242 lines
7.4 KiB
C
/*
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* Copyright (C) 2005-2015 Christoph Rupp (chris@crupp.de).
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/**
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* A fast implementation for Frame of Reference encoding.
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*
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* See the README.md file for more information, example code and references.
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*
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* Feel free to send comments/questions to chris@crupp.de. I am available
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* for consulting.
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*/
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#ifndef FOR_H_5580af15_4570_41f9_ba2b_8afb1400e81e
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#define FOR_H_5580af15_4570_41f9_ba2b_8afb1400e81e
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* Returns the size required to compress a sequence of |length| ints,
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* each compressed with |bits| bits
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*
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* This function will NOT include any overhead required by
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* for_compress_sorted() and for_compress_unsorted().
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*
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* Invariant: bits <= 32
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*/
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extern uint32_t
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for_compressed_size_bits(uint32_t length, uint32_t bits);
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/**
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* Returns the size required to compress an unsorted sequence of |length| ints.
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*
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* This routine scans |in| for the min/max values and then calls
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* for_compressed_size_bits().
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*
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* The returned size will include the overhead required for
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* for_compress_sorted() and for_compressed_unsorted().
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*/
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extern uint32_t
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for_compressed_size_unsorted(const uint32_t *in, uint32_t length);
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/**
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* Returns the size required to compress a sorted sequence of |length| ints.
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*
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* This routine extracts min/max values at the beginning and end of
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* the sequence, then calls for_compressed_size_bits(). It is therefore
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* slightly faster than for_compressed_size_unsorted().
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*
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* The returned size will include the overhead required for
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* for_compress_sorted() and for_compressed_unsorted().
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*/
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extern uint32_t
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for_compressed_size_sorted(const uint32_t *in, uint32_t length);
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/**
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* Compresses a sequence of |length| ints at |in| and stores the result
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* in |out|.
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*
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* |base| is the "offset" (or common delta value) of all ints. It is usually
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* set to the minimum value of the uncompressed sequence.
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*
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* |bits| are the bits required to store a single integer.
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*
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* Returns the number of bytes used for compression.
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*
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* This is for advanced users who opt for storing |base| and |bits| on their
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* own. This function is called by for_compress_sorted() and
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* for_compress_unsorted().
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*
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* Invariant: bits <= 32
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*/
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extern uint32_t
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for_compress_bits(const uint32_t *in, uint8_t *out, uint32_t length,
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uint32_t base, uint32_t bits);
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/**
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* Compresses an unsorted sequence of |length| ints at |in| and stores the
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* result in |out|.
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*
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* This routine scans |in| for the min/max values and then calls
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* for_compress_bits().
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*
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* The minimun value and the bits are stored as metadata in |out|.
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*/
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extern uint32_t
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for_compress_unsorted(const uint32_t *in, uint8_t *out, uint32_t length);
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/**
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* Compresses a sorted sequence of |length| ints at |in| and stores the
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* result in |out|.
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*
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* This routine extracts min/max values at the beginning and end of
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* the sequence, then calls for_compress_bits().
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*
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* The minimun value and the bits are stored as metadata in |out|.
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*/
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extern uint32_t
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for_compress_sorted(const uint32_t *in, uint8_t *out, uint32_t length);
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/**
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* Uncompresses a sequence of |length| ints at |in| and stores the
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* result in |out|.
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*
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* |base| is the "offset" (or common delta value) of all ints. It is usually
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* set to the minimum value of the uncompressed sequence.
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*
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* |bits| are the bits required to store a single integer.
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*
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* Returns the number of compressed bytes processed.
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*
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* This function is for advanced users. It is the counterpart of
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* for_compress_bits().
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*
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* Invariant: bits <= 32
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*/
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extern uint32_t
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for_uncompress_bits(const uint8_t *in, uint32_t *out, uint32_t length,
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uint32_t base, uint32_t bits);
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/**
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* Uncompresses a sequence of |length| ints at |in| and stores the
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* result in |out|.
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*
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* This function is a convenience wrapper for for_uncompress_bits(). It
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* expects metadata at the beginning of |in|. Use in combination with
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* for_compress_sorted() and for_compress_unsorted().
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*
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* Returns the number of compressed bytes processed.
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*/
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extern uint32_t
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for_uncompress(const uint8_t *in, uint32_t *out, uint32_t length);
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/**
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* Returns the value at the given |index| from a compressed sequence.
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*
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* Make sure that |index| does not exceed the length of the sequence.
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*
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* |base| is the "offset" (or common delta value) of all ints. It is usually
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* set to the minimum value of the uncompressed sequence.
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*
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* Invariant: bits <= 32
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*/
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extern uint32_t
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for_select_bits(const uint8_t *in, uint32_t base, uint32_t bits,
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uint32_t index);
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/**
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* Returns the value at the given |index| from a compressed sequence.
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*
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* Make sure that |index| does not exceed the length of the sequence.
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*
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* This function is a convenience wrapper for for_select_bits(). It
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* expects metadata at the beginning of |in|. Use in combination with
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* for_compress_sorted() and for_compress_unsorted().
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*/
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extern uint32_t
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for_select(const uint8_t *in, uint32_t index);
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/**
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* Performs a linear search for |value|.
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*
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* Returns the index of the found element, or |length| if the key was not
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* found.
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*
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* This function is a convenience wrapper for for_linear_search_bits(). It
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* expects metadata at the beginning of |in|. Use in combination with
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* for_compress_sorted() and for_compress_unsorted().
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*/
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extern uint32_t
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for_linear_search(const uint8_t *in, uint32_t length, uint32_t value);
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/**
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* Performs a linear search for |value|.
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*
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* Returns the index of the found element, or |length| if the key was not
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* found.
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*
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* |base| is the "offset" (or common delta value) of all ints. It is usually
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* set to the minimum value of the uncompressed sequence.
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*
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* Invariant: bits <= 32
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*/
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extern uint32_t
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for_linear_search_bits(const uint8_t *in, uint32_t length, uint32_t base,
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uint32_t bits, uint32_t value);
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/**
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* Performs lower bound binary search search for |value|.
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*
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* A lower bound search returns the first element in the sequence which does
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* not compare less than |value|.
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* The actual result is stored in |*actual|.
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*
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* This function is a convenience wrapper for for_lower_bound_search_bits(). It
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* expects metadata at the beginning of |in|. Use in combination with
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* for_compress_sorted() and for_compress_unsorted().
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*/
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extern uint32_t
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for_lower_bound_search(const uint8_t *in, uint32_t length, uint32_t value,
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uint32_t *actual);
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/**
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* Performs lower bound binary search search for |value|.
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*
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* A lower bound search returns the first element in the sequence which does
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* not compare less than |value|.
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* The actual result is stored in |*actual|.
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*
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* |base| is the "offset" (or common delta value) of all ints. It is usually
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* set to the minimum value of the uncompressed sequence.
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*
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* Invariant: bits <= 32
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*/
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extern uint32_t
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for_lower_bound_search_bits(const uint8_t *in, uint32_t length, uint32_t base,
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uint32_t bits, uint32_t value, uint32_t *actual);
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#ifdef __cplusplus
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} /* extern "C" */
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#endif
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#endif /* FOR_H_5580af15_4570_41f9_ba2b_8afb1400e81e */
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