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ext/for/for.h

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+/*
+ * Copyright (C) 2005-2015 Christoph Rupp (chris@crupp.de).
+ *
+ * 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.
+ */
+
+/**
+ * A fast implementation for Frame of Reference encoding.
+ *
+ * See the README.md file for more information, example code and references.
+ *
+ * Feel free to send comments/questions to chris@crupp.de. I am available
+ * for consulting.
+ */
+
+#ifndef FOR_H_5580af15_4570_41f9_ba2b_8afb1400e81e
+#define FOR_H_5580af15_4570_41f9_ba2b_8afb1400e81e
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/**
+ * Returns the size required to compress a sequence of |length| ints,
+ * each compressed with |bits| bits
+ *
+ * This function will NOT include any overhead required by
+ * for_compress_sorted() and for_compress_unsorted().
+ *
+ * Invariant: bits <= 32
+ */
+extern uint32_t
+for_compressed_size_bits(uint32_t length, uint32_t bits);
+
+/**
+ * Returns the size required to compress an unsorted sequence of |length| ints.
+ * 
+ * This routine scans |in| for the min/max values and then calls
+ * for_compressed_size_bits().
+ *
+ * The returned size will include the overhead required for
+ * for_compress_sorted() and for_compressed_unsorted().
+ */
+extern uint32_t
+for_compressed_size_unsorted(const uint32_t *in, uint32_t length);
+
+/**
+ * Returns the size required to compress a sorted sequence of |length| ints.
+ * 
+ * This routine extracts min/max values at the beginning and end of
+ * the sequence, then calls for_compressed_size_bits(). It is therefore
+ * slightly faster than for_compressed_size_unsorted().
+ *
+ * The returned size will include the overhead required for
+ * for_compress_sorted() and for_compressed_unsorted().
+ */
+extern uint32_t
+for_compressed_size_sorted(const uint32_t *in, uint32_t length);
+
+/**
+ * Compresses a sequence of |length| ints at |in| and stores the result
+ * in |out|.
+ *
+ * |base| is the "offset" (or common delta value) of all ints. It is usually
+ * set to the minimum value of the uncompressed sequence.
+ *
+ * |bits| are the bits required to store a single integer.
+ *
+ * Returns the number of bytes used for compression.
+ *
+ * This is for advanced users who opt for storing |base| and |bits| on their
+ * own. This function is called by for_compress_sorted() and
+ * for_compress_unsorted().
+ *
+ * Invariant: bits <= 32
+ */
+extern uint32_t
+for_compress_bits(const uint32_t *in, uint8_t *out, uint32_t length,
+                uint32_t base, uint32_t bits);
+
+/**
+ * Compresses an unsorted sequence of |length| ints at |in| and stores the
+ * result in |out|.
+ *
+ * This routine scans |in| for the min/max values and then calls
+ * for_compress_bits().
+ *
+ * The minimun value and the bits are stored as metadata in |out|.
+ */
+extern uint32_t
+for_compress_unsorted(const uint32_t *in, uint8_t *out, uint32_t length);
+
+/**
+ * Compresses a sorted sequence of |length| ints at |in| and stores the
+ * result in |out|.
+ *
+ * This routine extracts min/max values at the beginning and end of
+ * the sequence, then calls for_compress_bits().
+ *
+ * The minimun value and the bits are stored as metadata in |out|.
+ */
+extern uint32_t
+for_compress_sorted(const uint32_t *in, uint8_t *out, uint32_t length);
+
+/**
+ * Uncompresses a sequence of |length| ints at |in| and stores the
+ * result in |out|.
+ *
+ * |base| is the "offset" (or common delta value) of all ints. It is usually
+ * set to the minimum value of the uncompressed sequence.
+ *
+ * |bits| are the bits required to store a single integer.
+ *
+ * Returns the number of compressed bytes processed.
+ *
+ * This function is for advanced users. It is the counterpart of
+ * for_compress_bits().
+ *
+ * Invariant: bits <= 32
+ */
+extern uint32_t
+for_uncompress_bits(const uint8_t *in, uint32_t *out, uint32_t length,
+                uint32_t base, uint32_t bits);
+
+/**
+ * Uncompresses a sequence of |length| ints at |in| and stores the
+ * result in |out|.
+ *
+ * This function is a convenience wrapper for for_uncompress_bits(). It
+ * expects metadata at the beginning of |in|. Use in combination with
+ * for_compress_sorted() and for_compress_unsorted().
+ *
+ * Returns the number of compressed bytes processed.
+ */
+extern uint32_t
+for_uncompress(const uint8_t *in, uint32_t *out, uint32_t length);
+
+/**
+ * Returns the value at the given |index| from a compressed sequence.
+ *
+ * Make sure that |index| does not exceed the length of the sequence.
+ *
+ * |base| is the "offset" (or common delta value) of all ints. It is usually
+ * set to the minimum value of the uncompressed sequence.
+ *
+ * Invariant: bits <= 32
+ */
+extern uint32_t
+for_select_bits(const uint8_t *in, uint32_t base, uint32_t bits,
+                uint32_t index);
+
+/**
+ * Returns the value at the given |index| from a compressed sequence.
+ *
+ * Make sure that |index| does not exceed the length of the sequence.
+ *
+ * This function is a convenience wrapper for for_select_bits(). It
+ * expects metadata at the beginning of |in|. Use in combination with
+ * for_compress_sorted() and for_compress_unsorted().
+ */
+extern uint32_t
+for_select(const uint8_t *in, uint32_t index);
+
+/**
+ * Performs a linear search for |value|.
+ *
+ * Returns the index of the found element, or |length| if the key was not
+ * found.
+ *
+ * This function is a convenience wrapper for for_linear_search_bits(). It
+ * expects metadata at the beginning of |in|. Use in combination with
+ * for_compress_sorted() and for_compress_unsorted().
+ */
+extern uint32_t
+for_linear_search(const uint8_t *in, uint32_t length, uint32_t value);
+
+/**
+ * Performs a linear search for |value|.
+ *
+ * Returns the index of the found element, or |length| if the key was not
+ * found.
+ *
+ * |base| is the "offset" (or common delta value) of all ints. It is usually
+ * set to the minimum value of the uncompressed sequence.
+ *
+ * Invariant: bits <= 32
+ */
+extern uint32_t
+for_linear_search_bits(const uint8_t *in, uint32_t length, uint32_t base,
+                uint32_t bits, uint32_t value);
+
+/**
+ * Performs lower bound binary search search for |value|.
+ * 
+ * A lower bound search returns the first element in the sequence which does
+ * not compare less than |value|.
+ * The actual result is stored in |*actual|.
+ *
+ * This function is a convenience wrapper for for_lower_bound_search_bits(). It
+ * expects metadata at the beginning of |in|. Use in combination with
+ * for_compress_sorted() and for_compress_unsorted().
+ */
+extern uint32_t
+for_lower_bound_search(const uint8_t *in, uint32_t length, uint32_t value,
+                uint32_t *actual);
+
+/**
+ * Performs lower bound binary search search for |value|.
+ * 
+ * A lower bound search returns the first element in the sequence which does
+ * not compare less than |value|.
+ * The actual result is stored in |*actual|.
+ *
+ * |base| is the "offset" (or common delta value) of all ints. It is usually
+ * set to the minimum value of the uncompressed sequence.
+ *
+ * Invariant: bits <= 32
+ */
+extern uint32_t
+for_lower_bound_search_bits(const uint8_t *in, uint32_t length, uint32_t base,
+                uint32_t bits, uint32_t value, uint32_t *actual);
+
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif /* FOR_H_5580af15_4570_41f9_ba2b_8afb1400e81e */