bdlb_bitmaskutil.h

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/// @file bdlb_bitmaskutil.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlb_bitmaskutil.h                                                 -*-C++-*-
#ifndef INCLUDED_BDLB_BITMASKUTIL
#define INCLUDED_BDLB_BITMASKUTIL
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlb_bitmaskutil bdlb_bitmaskutil
/// @brief  Provide simple mask values of `uint32_t` and `uint64_t` types.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlb
/// @{
/// @addtogroup bdlb_bitmaskutil
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlb_bitmaskutil-purpose"> Purpose</a>
/// * <a href="#bdlb_bitmaskutil-classes"> Classes </a>
/// * <a href="#bdlb_bitmaskutil-description"> Description </a>
///   * <a href="#bdlb_bitmaskutil-usage"> Usage </a>
///     * <a href="#bdlb_bitmaskutil-example-1-creation-of-simple-bit-masks"> Example 1: Creation of Simple Bit Masks </a>
///
/// # Purpose {#bdlb_bitmaskutil-purpose}
/// Provide simple mask values of `uint32_t` and `uint64_t` types.
///
/// # Classes {#bdlb_bitmaskutil-classes}
///
/// -  bdlb::BitMaskUtil: namespace for bit-level mask operations
///
/// # Description {#bdlb_bitmaskutil-description}
/// This component provides a utility `struct`,
/// `bdlb::BitMaskUtil`, that serves as a namespace for a collection of
/// functions that provide simple binary masks.
///
/// ## Usage {#bdlb_bitmaskutil-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Creation of Simple Bit Masks {#bdlb_bitmaskutil-example-1-creation-of-simple-bit-masks}
///
///
/// The following usage examples illustrate how some of the methods provided by
/// this component are used.  Note that, in all of these examples, the low-order
/// bit is considered bit 0 and resides on the right edge of the bit string.
///
/// First, the `ge` function takes a single argument, `index`, and returns a bit
/// mask with all bits below the specified `index` cleared and all bits at or
/// above the `index` set:
/// @code
/// +-------------------------------------------------------------------------+
/// | 'bdlb::BitMaskUtil::ge(16)' in binary:                                  |
/// |                                                                         |
/// | 'index': bit 16:                                      *                 |
/// | All bits at and above bit 16 are set:  11111111111111110000000000000000 |
/// +-------------------------------------------------------------------------+
///
/// const uint32_t expGe = 0xffff0000;
/// assert(expGe == bdlb::BitMaskUtil::ge(16));
/// @endcode
/// Next, the `lt` function returns a bit mask with all bits at or above the
/// specified `index` cleared, and all bits below `index` set.  `lt` and `ge`
/// return the complement of each other if passed the same `index`:
/// @code
/// +-------------------------------------------------------------------------+
/// | 'bdlb::BitMaskUtil::lt(16)' in binary:                                  |
/// |                                                                         |
/// | 'index': bit 16:                                      *                 |
/// | All bits below bit 16 are set:         00000000000000001111111111111111 |
/// +-------------------------------------------------------------------------+
///
/// const uint32_t expLt = 0x0000ffff;
/// assert(expLt == bdlb::BitMaskUtil::lt(16));
///
/// assert(expGe == ~expLt);
/// @endcode
/// Then, the `eq` function returns a bit mask with only the bit at the
/// specified `index` set:
/// @code
/// +-------------------------------------------------------------------------+
/// | 'bdlb::BitMaskUtil::eq(23)' in binary:                                  |
/// |                                                                         |
/// | 'index': bit 23:                               *                        |
/// | Only bit 23 is set:                    00000000100000000000000000000000 |
/// +-------------------------------------------------------------------------+
///
/// const uint32_t expEq = 0x00800000;
/// assert(expEq == bdlb::BitMaskUtil::eq(23));
/// @endcode
/// Now, the `ne` function returns a bit mask with only the bit at the specified
/// `index` cleared.  `ne` and `eq` return the complement of each other for a
/// given `index`:
/// @code
/// +-------------------------------------------------------------------------+
/// | 'bdlb::BitMaskUtil::ne(23)' in binary:                                  |
/// |                                                                         |
/// | 'index': bit 23:                               *                        |
/// | All bits other than bit 16 are set:    11111111011111111111111111111111 |
/// +-------------------------------------------------------------------------+
///
/// const uint32_t expNe = 0xff7fffff;
/// assert(expNe == bdlb::BitMaskUtil::ne(23));
///
/// assert(expEq == ~expNe);
/// @endcode
/// Finally, `one` and `zero` return a bit mask with all bits within a specified
/// range starting from a specified `index` either set or cleared, respectively.
/// For the same arguments, `one` and `zero` return the complement of each
/// other:
/// @code
/// +-------------------------------------------------------------------------+
/// | 'bdlb::BitMaskUtil::one(16, 4)' in binary:                              |
/// |                                                                         |
/// | bit 16:                                               *                 |
/// | 4 bits starting at bit 16:                         ****                 |
/// | Result: only those bits set:           00000000000011110000000000000000 |
/// +-------------------------------------------------------------------------+
///
/// const uint32_t expOne = 0x000f0000;
/// assert(expOne == bdlb::BitMaskUtil::one(16, 4));
///
/// +-------------------------------------------------------------------------+
/// | 'bdlb::BitMaskUtil::zero(16, 4)' in binary:                             |
/// |                                                                         |
/// | bit 16:                                               *                 |
/// | 4 bits starting at bit 16:                         ****                 |
/// | Result: only those bits cleared:       11111111111100001111111111111111 |
/// +-------------------------------------------------------------------------+
///
/// const uint32_t expZero = 0xfff0ffff;
/// assert(expZero == bdlb::BitMaskUtil::zero(16, 4));
///
/// assert(expZero == ~expOne);
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlb
 * @{
 */
/** @addtogroup bdlb_bitmaskutil
 * @{
 */
 
#include <bdlscm_version.h>
 
#include <bdlb_bitutil.h>
 
#include <bsls_assert.h>
#include <bsls_performancehint.h>
#include <bsls_review.h>
 
#include <bsl_cstdint.h>
 
 
namespace bdlb {
 
                               // ==================
                               // struct BitMaskUtil
                               // ==================
 
/// This utility `struct` provides a namespace for a set of bit-level,
/// stateless functions that take one or two `int` arguments and return
/// masks of the built-in 32- and 64-bit integer types `uint32_t` and
/// `uint64_t`, respectively.
struct BitMaskUtil {
 
    // PUBLIC TYPES
    enum {
        k_BITS_PER_UINT32 = 32,  // number of bits in type 'uint32_t'
 
        k_BITS_PER_UINT64 = 64   // number of bits in type 'uint64_t'
    };
 
    // CLASS METHODS
    static bsl::uint32_t eq(int   index);
 
    /// Return the unsigned integral value having the bit at the specified
    /// `index` position set to 1, and all other bits set to 0.  The
    /// behavior is undefined unless `0 <= index <= # of bits in result`.
    static bsl::uint64_t eq64(int index);
 
    static bsl::uint32_t ge(int   index);
 
    /// Return the unsigned integral value having all bits at positions
    /// greater than or equal to the specified `index` set to 1, and all
    /// other bits set to 0.  The behavior is undefined unless
    /// `0 <= index <= # of bits in result`.
    static bsl::uint64_t ge64(int index);
 
    static bsl::uint32_t gt(int   index);
 
    /// Return the unsigned integral value having all bits at positions
    /// greater than the specified `index` set to 1, and all other bits set
    /// to 0.  The behavior is undefined unless
    /// `0 <= index <= # of bits in result`.
    static bsl::uint64_t gt64(int index);
 
    static bsl::uint32_t le(int   index);
 
    /// Return the unsigned integral value having all bits at positions less
    /// than or equal to the specified `index` set to 1, and all other bits
    /// set to 0.  The behavior is undefined unless
    /// `0 <= index <= # of bits in result`.
    static bsl::uint64_t le64(int index);
 
    static bsl::uint32_t lt(int   index);
 
    /// Return the unsigned integral value having all bits at positions less
    /// than the specified `index` set to 1, and all other bits set to 0.
    /// The behavior is undefined unless
    /// `0 <= index <= # of bits in result`.
    static bsl::uint64_t lt64(int index);
 
    static bsl::uint32_t ne(int   index);
 
    /// Return the unsigned integral value having the bit at the specified
    /// `index` position set to 0, and all other bits set to 1.  The
    /// behavior is undefined unless `0 <= index <= # of bits in result`.
    static bsl::uint64_t ne64(int index);
 
    static bsl::uint32_t one(int   index, int numBits);
 
    /// Return the unsigned integral value having the specified `numBits`
    /// starting at the specified `index` set to 1, and all other bits set
    /// to 0.  The behavior is undefined unless `0 <= index`,
    /// `0 <= numBits`, and `index + numBits <= # of bits in result`.
    static bsl::uint64_t one64(int index, int numBits);
 
    static bsl::uint32_t zero(int   index, int numBits);
 
    /// Return the unsigned integral value having the specified `numBits`
    /// starting at the specified `index` set to 0, and all other bits set
    /// to 1.  The behavior is undefined unless `0 <= index`,
    /// `0 <= numBits`, and `index + numBits <= # of bits in result`.
    static bsl::uint64_t zero64(int index, int numBits);
};
 
// ============================================================================
//                              INLINE DEFINITIONS
// ============================================================================
 
                               // ------------------
                               // struct BitMaskUtil
                               // ------------------
 
// CLASS METHODS
inline
bsl::uint32_t BitMaskUtil::eq(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT32));
 
    return BSLS_PERFORMANCEHINT_PREDICT_LIKELY(
                                   index < static_cast<int>(k_BITS_PER_UINT32))
           ? 1u << index
           : 0;
}
 
inline
bsl::uint64_t BitMaskUtil::eq64(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT64));
 
    return BSLS_PERFORMANCEHINT_PREDICT_LIKELY(
                                   index < static_cast<int>(k_BITS_PER_UINT64))
           ? 1LL << index
           : 0;
}
 
inline
bsl::uint32_t BitMaskUtil::ge(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT32));
 
    return BSLS_PERFORMANCEHINT_PREDICT_LIKELY(
                                   index < static_cast<int>(k_BITS_PER_UINT32))
           ? ~0U << index
           : 0;
}
 
inline
bsl::uint64_t BitMaskUtil::ge64(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT64));
 
    return BSLS_PERFORMANCEHINT_PREDICT_LIKELY(
                                   index < static_cast<int>(k_BITS_PER_UINT64))
           ? ~0ULL << index
           : 0;
}
 
inline
bsl::uint32_t BitMaskUtil::gt(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT32));
 
    ++index;
    return BSLS_PERFORMANCEHINT_PREDICT_LIKELY(
                                   index < static_cast<int>(k_BITS_PER_UINT32))
           ? ~0U << index
           : 0;
}
 
inline
bsl::uint64_t BitMaskUtil::gt64(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT64));
 
    ++index;
    return BSLS_PERFORMANCEHINT_PREDICT_LIKELY(
                                   index < static_cast<int>(k_BITS_PER_UINT64))
           ? ~0ULL << index
           : 0;
}
 
inline
bsl::uint32_t BitMaskUtil::le(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT32));
 
    ++index;
    return BSLS_PERFORMANCEHINT_PREDICT_LIKELY(
                                   index < static_cast<int>(k_BITS_PER_UINT32))
           ? ~(~0U << index)
           : -1;
}
 
inline
bsl::uint64_t BitMaskUtil::le64(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT64));
 
    ++index;
    return BSLS_PERFORMANCEHINT_PREDICT_LIKELY(
                                   index < static_cast<int>(k_BITS_PER_UINT64))
           ? ~(~0ULL << index)
           : -1LL;
}
 
inline
bsl::uint32_t BitMaskUtil::lt(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT32));
 
    return BSLS_PERFORMANCEHINT_PREDICT_UNLIKELY(
                                   index < static_cast<int>(k_BITS_PER_UINT32))
           ? ~(~0U << index)
           : -1;
}
 
inline
bsl::uint64_t BitMaskUtil::lt64(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT64));
 
    return BSLS_PERFORMANCEHINT_PREDICT_UNLIKELY(
                                   index < static_cast<int>(k_BITS_PER_UINT64))
           ? ~(~0ULL << index)
           : -1LL;
}
 
inline
bsl::uint32_t BitMaskUtil::ne(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT32));
 
    return BSLS_PERFORMANCEHINT_PREDICT_UNLIKELY(
                                  index >= static_cast<int>(k_BITS_PER_UINT32))
           ? -1
           : ~(1u << index);
}
 
inline
bsl::uint64_t BitMaskUtil::ne64(int index)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(     index <= static_cast<int>(k_BITS_PER_UINT64));
 
    return BSLS_PERFORMANCEHINT_PREDICT_UNLIKELY(
                                  index >= static_cast<int>(k_BITS_PER_UINT64))
           ? -1LL
           : ~(1LL << index);
}
 
inline
bsl::uint32_t BitMaskUtil::one(int index, int numBits)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(0 <= numBits);
    BSLS_ASSERT(index + numBits <= static_cast<int>(k_BITS_PER_UINT32));
 
    return lt(index + numBits) & ge(index);
}
 
inline
bsl::uint64_t BitMaskUtil::one64(int index, int numBits)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(0 <= numBits);
    BSLS_ASSERT(index + numBits <= static_cast<int>(k_BITS_PER_UINT64));
 
    return lt64(index + numBits) & ge64(index);
}
 
inline
bsl::uint32_t BitMaskUtil::zero(int index, int numBits)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(0 <= numBits);
    BSLS_ASSERT(index + numBits <= static_cast<int>(k_BITS_PER_UINT32));
 
    return lt(index) | ge(index + numBits);
}
 
inline
bsl::uint64_t BitMaskUtil::zero64(int index, int numBits)
{
    BSLS_ASSERT(0 <= index);
    BSLS_ASSERT(0 <= numBits);
    BSLS_ASSERT(index + numBits <= static_cast<int>(k_BITS_PER_UINT64));
 
    return lt64(index) | ge64(index + numBits);
}
 
}  // close package namespace
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2015 Bloomberg Finance L.P.
//
// 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.
// ----------------------------- END-OF-FILE ----------------------------------
 
/** @} */
/** @} */
/** @} */