On 2023-02-28 19:46, Tyler Retzlaff wrote:
> On Tue, Feb 28, 2023 at 10:39:15AM +0100, Mattias Rönnblom wrote:
>> Introduce a set of functions and macros that operate on sets of bits,
>> kept in arrays of 64-bit elements.
>>
>> RTE bitset is designed for bitsets which are larger than what fits in
>> a single machine word (i.e., 64 bits). For very large bitsets, the
>> <rte_bitmap.h> API may be a more appropriate choice.
>>
>> Signed-off-by: Mattias Rönnblom <mattias.ronnb...@ericsson.com>
>> ---
>
> ...
>
>> diff --git a/lib/eal/include/rte_bitset.h b/lib/eal/include/rte_bitset.h
>> new file mode 100644
>> index 0000000000..e333e527e5
>> --- /dev/null
>> +++ b/lib/eal/include/rte_bitset.h
>> @@ -0,0 +1,878 @@
>> +/* SPDX-License-Identifier: BSD-3-Clause
>> + * Copyright(c) 2023 Ericsson AB
>> + */
>> +
>> +#ifndef _RTE_BITSET_H_
>> +#define _RTE_BITSET_H_
>> +
>> +/**
>> + * @file
>> + * RTE Bitset
>> + *
>> + * This file provides functions and macros for querying and
>> + * manipulating sets of bits kept in arrays of @c uint64_t-sized
>> + * elements.
>> + *
>> + * The bits in a bitset are numbered from 0 to @c size - 1, with the
>> + * lowest index being the least significant bit.
>> + *
>> + * The bitset array must be properly aligned.
>> + *
>> + * For optimal performance, the @c size parameter, required by
>> + * many of the API's functions, should be a compile-time constant.
>> + *
>> + * For large bitsets, the rte_bitmap.h API may be more appropriate.
>> + *
>> + * @warning
>> + * All functions modifying a bitset may overwrite any unused bits of
>> + * the last word. Such unused bits are ignored by all functions reading
>> + * bits.
>> + *
>> + */
>> +
>> +#include <limits.h>
>> +#include <stdbool.h>
>> +#include <stdint.h>
>> +#include <sys/types.h>
>
> windows has no sys/types.h if there is a shim being picked up somewhere
> portable code shouldn't depend on sys/types.h
>
That include was a misdirected attempt to get the 'size_t' definition. I
will replaced it with <stddef.h>. Thanks.
>> +
>> +#include <rte_branch_prediction.h>
>> +#include <rte_common.h>
>> +#include <rte_debug.h>
>> +#include <rte_memcpy.h>
>> +
>> +#ifdef __cplusplus
>> +extern "C" {
>> +#endif
>> +
>> +/**
>> + * The size (in bytes) of each element in the array used to represent
>> + * a bitset.
>> + */
>> +#define RTE_BITSET_WORD_SIZE (sizeof(uint64_t))
>> +
>> +/**
>> + * The size (in bits) of each element in the array used to represent
>> + * a bitset.
>> + */
>> +#define RTE_BITSET_WORD_BITS (RTE_BITSET_WORD_SIZE * CHAR_BIT)
>> +
>> +/**
>> + * Computes the number of words required to store @c size bits.
>> + */
>> +#define RTE_BITSET_NUM_WORDS(size) \
>> + ((size + RTE_BITSET_WORD_BITS - 1) / RTE_BITSET_WORD_BITS)
>> +
>> +/**
>> + * Computes the amount of memory (in bytes) required to fit a bitset
>> + * holding @c size bits.
>> + */
>> +#define RTE_BITSET_SIZE(size) \
>> + ((size_t)(RTE_BITSET_NUM_WORDS(size) * RTE_BITSET_WORD_SIZE))
>> +
>> +#define __RTE_BITSET_WORD_IDX(bit_num) ((bit_num) / RTE_BITSET_WORD_BITS)
>> +#define __RTE_BITSET_BIT_OFFSET(bit_num) ((bit_num) % RTE_BITSET_WORD_BITS)
>> +#define __RTE_BITSET_UNUSED(size) \
>> + ((RTE_BITSET_NUM_WORDS(size) * RTE_BITSET_WORD_BITS) \
>> + - (size))
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Declare a bitset.
>> + *
>> + * Declare (e.g., as a struct field) or define (e.g., as a stack
>> + * variable) a bitset of the specified size.
>> + *
>> + * @param size
>> + * The number of bits the bitset must be able to represent. Must be
>> + * a compile-time constant.
>> + * @param name
>> + * The field or variable name of the resulting definition.
>> + */
>> +#define RTE_BITSET_DECLARE(name, size) \
>> + uint64_t name[RTE_BITSET_NUM_WORDS(size)]
>> +
>> +/* XXX: should one include flags here and use to avoid a comparison? */
>> +/* XXX: would this be better off as a function? */
>> +
>> +#define __RTE_BITSET_FOREACH_LEFT(var, size, start_bit, len) \
>> + ((len) - 1 - ((var) >= (start_bit) ? (var) - (start_bit) : \
>> + (size) - (start_bit) + (var)))
>> +
>> +#define __RTE_BITSET_FOREACH(var, bitset, size, start_bit, len, flags) \
>> + for ((var) = __rte_bitset_find(bitset, size, start_bit, len, \
>> + flags); \
>> + (var) != -1; \
>> + (var) = __RTE_BITSET_FOREACH_LEFT(var, size, start_bit, \
>> + len) > 0 ? \
>> + __rte_bitset_find(bitset, size, \
>> + ((var) + 1) % (size), \
>> + __RTE_BITSET_FOREACH_LEFT(var, \
>> + size, \
>> + start_bit, \
>> + len), \
>> + flags) : -1)
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Iterate over all bits set.
>> + *
>> + * This macro iterates over all bits set (i.e., all ones) in the
>> + * bitset, in the forward direction (i.e., starting with the least
>> + * significant '1').
>> + *
>> + * @param var
>> + * An iterator variable of type @c ssize_t. For each sucessive iteration,
>> + * this variable will hold the bit index of a set bit.
>> + * @param bitset
>> + * A <tt>const uint64_t *</tt> pointer to the bitset array.
>> + * @param size
>> + * The size of the bitset (in bits).
>> + */
>> +
>> +#define RTE_BITSET_FOREACH_SET(var, bitset, size) \
>> + __RTE_BITSET_FOREACH(var, bitset, size, 0, size, 0)
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Iterate over all bits cleared.
>> + *
>> + * This macro iterates over all bits cleared in the bitset, in the
>> + * forward direction (i.e., starting with the lowest-indexed set bit).
>> + *
>> + * @param var
>> + * An iterator variable of type @c ssize_t. For each successive iteration,
>> + * this variable will hold the bit index of a cleared bit.
>> + * @param bitset
>> + * A <tt>const uint64_t *</tt> pointer to the bitset array.
>> + * @param size
>> + * The size of the bitset (in bits).
>> + */
>> +
>> +#define RTE_BITSET_FOREACH_CLEAR(var, bitset, size) \
>> + __RTE_BITSET_FOREACH(var, bitset, size, 0, size, \
>> + __RTE_BITSET_FIND_FLAG_FIND_CLEAR)
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Iterate over all bits set within a range.
>> + *
>> + * This macro iterates over all bits set (i.e., all ones) in the
>> + * specified range, in the forward direction (i.e., starting with the
>> + * least significant '1').
>> + *
>> + * @param var
>> + * An iterator variable of type @c ssize_t. For each sucessive iteration,
>> + * this variable will hold the bit index of a set bit.
>> + * @param bitset
>> + * A <tt>const uint64_t *</tt> pointer to the bitset array.
>> + * @param size
>> + * The size of the bitset (in bits).
>> + * @param start_bit
>> + * The index of the first bit to check. Must be less than @c size.
>> + * @param len
>> + * The length (in bits) of the range. @c start_bit + @c len must be less
>> + * than or equal to @c size.
>> + */
>> +
>> +#define RTE_BITSET_FOREACH_SET_RANGE(var, bitset, size, start_bit, \
>> + len) \
>> + __RTE_BITSET_FOREACH(var, bitset, size, start_bit, len, 0)
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Iterate over all cleared bits within a range.
>> + *
>> + * This macro iterates over all bits cleared (i.e., all zeroes) in the
>> + * specified range, in the forward direction (i.e., starting with the
>> + * least significant '0').
>> + *
>> + * @param var
>> + * An iterator variable of type @c ssize_t. For each sucessive iteration,
>> + * this variable will hold the bit index of a set bit.
>> + * @param bitset
>> + * A <tt>const uint64_t *</tt> pointer to the bitset array.
>> + * @param size
>> + * The size of the bitset (in bits).
>> + * @param start_bit
>> + * The index of the first bit to check. Must be less than @c size.
>> + * @param len
>> + * The length (in bits) of the range. @c start_bit + @c len must be less
>> + * than or equal to @c size.
>> + */
>> +
>> +#define RTE_BITSET_FOREACH_CLEAR_RANGE(var, bitset, size, start_bit,
>> \
>> + len) \
>> + __RTE_BITSET_FOREACH(var, bitset, size, start_bit, len, \
>> + __RTE_BITSET_FIND_FLAG_FIND_CLEAR)
>> +
>> +#define RTE_BITSET_FOREACH_SET_WRAP(var, bitset, size, start_bit, \
>> + len) \
>> + __RTE_BITSET_FOREACH(var, bitset, size, start_bit, len, \
>> + __RTE_BITSET_FIND_FLAG_WRAP)
>> +
>> +#define RTE_BITSET_FOREACH_CLEAR_WRAP(var, bitset, size, start_bit, \
>> + len) \
>> + __RTE_BITSET_FOREACH(var, bitset, size, start_bit, len, \
>> + __RTE_BITSET_FIND_FLAG_WRAP | \
>> + __RTE_BITSET_FIND_FLAG_FIND_CLEAR)
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Initializes a bitset.
>> + *
>> + * All bits are cleared.
>> + *
>> + * @param bitset
>> + * A pointer to the array of bitset 64-bit words.
>> + * @param size
>> + * The size of the bitset (in bits).
>> + */
>> +
>> +__rte_experimental
>> +static inline void
>> +rte_bitset_init(uint64_t *bitset, size_t size)
>> +{
>> + memset(bitset, 0, RTE_BITSET_SIZE(size));
>> +}
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Set a bit in the bitset.
>> + *
>> + * Bits are numbered from 0 to (size - 1) (inclusive).
>> + *
>> + * @param bitset
>> + * A pointer to the array words making up the bitset.
>> + * @param bit_num
>> + * The index of the bit to be set.
>> + */
>> +
>> +__rte_experimental
>> +static inline void
>> +rte_bitset_set(uint64_t *bitset, size_t bit_num)
>> +{
>> + size_t word;
>> + size_t offset;
>> + uint64_t mask;
>> +
>> + word = __RTE_BITSET_WORD_IDX(bit_num);
>> + offset = __RTE_BITSET_BIT_OFFSET(bit_num);
>> + mask = UINT64_C(1) << offset;
>> +
>> + bitset[word] |= mask;
>> +}
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Clear a bit in the bitset.
>> + *
>> + * Bits are numbered 0 to (size - 1) (inclusive).
>> + *
>> + * @param bitset
>> + * A pointer to the array words making up the bitset.
>> + * @param bit_num
>> + * The index of the bit to be cleared.
>> + */
>> +
>> +__rte_experimental
>> +static inline void
>> +rte_bitset_clear(uint64_t *bitset, size_t bit_num)
>> +{
>> + size_t word;
>> + size_t offset;
>> + uint64_t mask;
>> +
>> + word = __RTE_BITSET_WORD_IDX(bit_num);
>> + offset = __RTE_BITSET_BIT_OFFSET(bit_num);
>> + mask = ~(UINT64_C(1) << offset);
>> +
>> + bitset[word] &= mask;
>> +}
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Set all bits in the bitset.
>> + *
>> + * @param bitset
>> + * A pointer to the array of words making up the bitset.
>> + * @param size
>> + * The size of the bitset (in bits).
>> + */
>> +
>> +__rte_experimental
>> +static inline void
>> +rte_bitset_set_all(uint64_t *bitset, size_t size)
>> +{
>> + memset(bitset, 0xFF, RTE_BITSET_SIZE(size));
>> +}
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Clear all bits in the bitset.
>> + *
>> + * @param bitset
>> + * A pointer to the array of words making up the bitset.
>> + * @param size
>> + * The size of the bitset (in bits).
>> + */
>> +
>> +__rte_experimental
>> +static inline void
>> +rte_bitset_clear_all(uint64_t *bitset, size_t size)
>> +{
>> + rte_bitset_init(bitset, size);
>> +}
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Count all set bits.
>> + *
>> + * @param bitset
>> + * A pointer to the array of words making up the bitset.
>> + * @param size
>> + * The size of the bitset (in bits).
>> + * @return
>> + * Returns the number of '1' bits in the bitset.
>> + */
>> +
>> +__rte_experimental
>> +static inline size_t
>> +rte_bitset_count_set(const uint64_t *bitset, size_t size)
>> +{
>> + size_t i;
>> + size_t total = 0;
>> + uint64_t unused_mask;
>> +
>> + /*
>> + * Unused bits in a rte_bitset are always '0', and thus are
>> + * not included in this count.
>> + */
>> + for (i = 0; i < RTE_BITSET_NUM_WORDS(size) - 1; i++)
>> + total += __builtin_popcountll(bitset[i]);
>> +
>> + unused_mask = UINT64_MAX >> __RTE_BITSET_UNUSED(size);
>> + total += __builtin_popcountll(bitset[i] & unused_mask);
>> +
>> + return total;
>> +}
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Count all cleared bits.
>> + *
>> + * @param bitset
>> + * A pointer to the array of words making up the bitset.
>> + * @param size
>> + * The size of the bitset (in bits).
>> + * @return
>> + * Returns the number of '0' bits in the bitset.
>> + */
>> +
>> +__rte_experimental
>> +static inline size_t
>> +rte_bitset_count_clear(const uint64_t *bitset, size_t size)
>> +{
>> + return size - rte_bitset_count_set(bitset, size);
>> +}
>> +
>> +/**
>> + * @warning
>> + * @b EXPERIMENTAL: this API may change without prior notice.
>> + *
>> + * Test if a bit is set.
>> + *
>> + * @param bitset
>> + * A pointer to the array of words making up the bitset.
>> + * @param bit_num
>> + * Index of the bit to test. Index 0 is the least significant bit.
>> + * @return
>> + * Returns true if the bit is '1', and false if the bit is '0'.
>> + */
>> +
>> +__rte_experimental
>> +static inline bool
>> +rte_bitset_test(const uint64_t *bitset, size_t bit_num)
>> +{
>> + size_t word;
>> + size_t offset;
>> +
>> + word = __RTE_BITSET_WORD_IDX(bit_num);
>> + offset = __RTE_BITSET_BIT_OFFSET(bit_num);
>> +
>> + return (bitset[word] >> offset) & 1;
>> +}
>> +
>> +#define __RTE_BITSET_FIND_FLAG_FIND_CLEAR (1U << 0)
>> +#define __RTE_BITSET_FIND_FLAG_WRAP (1U << 1)
>> +
>> +__rte_experimental
>> +static inline ssize_t
>> +__rte_bitset_find_nowrap(const uint64_t *bitset, size_t __rte_unused size,
>> + size_t start_bit, size_t len, bool find_clear)
>
> ^^ seems like the intent here is for this to be internal (not part of
> public api) i wonder do we have to mark it __rte_experimental?
>
> or better can we prevent visibility / consumption outside of the
> inline functions in this header?
>
It is supposed to be internal (although you can question the DPDK habit
of using the reserved __ namespace for such symbols).
I don't know of any way to prevent its use. I'm not sure it's needed.
Those who don't heed the "___" prefix warning, are on their own.
>> +{
>> + size_t word_idx;
>> + size_t offset;
>> + size_t end_bit = start_bit + len;
>> +
>> + RTE_ASSERT(end_bit <= size);
>> +
>> + if (unlikely(len == 0))
>> + return -1;
>> +
>> + word_idx = __RTE_BITSET_WORD_IDX(start_bit);
>> + offset = __RTE_BITSET_BIT_OFFSET(start_bit);
>> +
>> + while (word_idx <= __RTE_BITSET_WORD_IDX(end_bit - 1)) {
>> + uint64_t word;
>> + int word_ffs;
>> +
>> + word = bitset[word_idx];
>> + if (find_clear)
>> + word = ~word;
>> +
>> + word >>= offset;
>> +
>> + word_ffs = __builtin_ffsll(word);
>> +
>> + if (word_ffs != 0) {
>> + ssize_t ffs = start_bit + word_ffs - 1;
>> +
>> + /*
>> + * Check if set bit were among the last,
>> + * unused bits, in the last word.
>> + */
>> + if (unlikely(ffs >= (ssize_t)end_bit))
>> + return -1;
>> +
>> + return ffs;
>> + }
>> +
>> + start_bit += (RTE_BITSET_WORD_BITS - offset);
>> + word_idx++;
>> + offset = 0;
>> + }
>> +
>> + return -1;
>> +
>> +}
>> +
