bslim_fuzzutil.h

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/// @file bslim_fuzzutil.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslim_fuzzutil.h                                                   -*-C++-*-
#ifndef INCLUDED_BSLIM_FUZZUTIL
#define INCLUDED_BSLIM_FUZZUTIL
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslim_fuzzutil bslim_fuzzutil
/// @brief  Provide fuzz test utilities for basic types.
/// @addtogroup bsl
/// @{
/// @addtogroup bslim
/// @{
/// @addtogroup bslim_fuzzutil
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslim_fuzzutil-purpose"> Purpose</a>
/// * <a href="#bslim_fuzzutil-classes"> Classes </a>
/// * <a href="#bslim_fuzzutil-description"> Description </a>
///   * <a href="#bslim_fuzzutil-usage"> Usage </a>
///     * <a href="#bslim_fuzzutil-example-1-consuming-integers-in-a-range-to-pass-to-an-interface"> Example 1: Consuming Integers in a Range to Pass to an Interface </a>
///
/// # Purpose {#bslim_fuzzutil-purpose}
/// Provide fuzz test utilities for basic types.
///
/// # Classes {#bslim_fuzzutil-classes}
///
/// - bslim::FuzzUtil: functions to create basic types from fuzz data
///
/// @see  bslim_fuzzdataview
///
/// # Description {#bslim_fuzzutil-description}
/// This component provides a namespace, `bslim::FuzzUtil`,
/// containing functions that create fundamental and standard library types from
/// fuzz data provided by a fuzz harness (e.g., `libFuzzer`).
///
/// See {http://bburl/BDEFuzzTesting} for details on how to build and run with
/// fuzz testing enabled.
///
/// ## Usage {#bslim_fuzzutil-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Consuming Integers in a Range to Pass to an Interface {#bslim_fuzzutil-example-1-consuming-integers-in-a-range-to-pass-to-an-interface}
///
///
/// Suppose we wish to fuzz test a function with preconditions.
///
/// First, we define the `TradingInterfaceUnderTest` `struct`:
/// @code
/// struct TradingInterfaceUnderTest {
///     // This utility class provides sample functionality to demonstrate how
///     // fuzz data might be used.
///
///     // CLASS METHODS
///     static int numEarningsAnnouncements(int year, int month)
///         // Return a value containing the number of earnings announcements
///         // in the specified 'year' and 'month'.  The behavior is undefined
///         // unless '1950 < year < 2030' and 'month' is in '[1 .. 12]'.  Note
///         // that the values here are arbitrary, and in the real-world this
///         // data would be obtained from a database or an API.
///     {
///         BSLS_ASSERT(1950 <  year  && year  < 2030);
///         BSLS_ASSERT(   1 <= month && month <=  12);
///
///         if (2020 < year && 6 < month) {
///             return 11;                                            // RETURN
///         }
///         return 6;
///     }
/// };
/// @endcode
/// Then, we need a block of raw bytes.  This would normally come from a fuzz
/// harness (e.g., the `LLVMFuzzerTestOneInput` entry point function from
/// `libFuzzer`).  Since `libFuzzer` is not available here, we initialize a
/// `myFuzzData` array that we will use instead.
/// @code
/// const bsl::uint8_t  myFuzzData[] = {0x43, 0x19, 0x0D, 0x44, 0x37, 0x0D,
///                                     0x38, 0x5E, 0x9B, 0xAA, 0xF3, 0xDA};
/// @endcode
/// Next, we create a `FuzzDataView` to wrap the raw bytes.
/// @code
/// bslim::FuzzDataView fdv(myFuzzData, sizeof myFuzzData);
/// @endcode
/// Now, we pass this `FuzzDataView` to `FuzzUtil` to generate values within the
/// permissible range of the function under test:
/// @code
/// int month = bslim::FuzzUtil::consumeNumberInRange<int>(&fdv,    1,   12);
/// int year  = bslim::FuzzUtil::consumeNumberInRange<int>(&fdv, 1951, 2029);
/// assert(   1 <= month && month <=   12);
/// assert(1951 <= year  && year  <= 2029);
/// @endcode
/// Finally, we can use these `int` values to pass to a function that returns
/// the number of earnings announcements scheduled in a given month.
/// @code
/// int numEarnings =
///     TradingInterfaceUnderTest::numEarningsAnnouncements(year, month);
/// (void) numEarnings;
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslim
 * @{
 */
/** @addtogroup bslim_fuzzutil
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslim_fuzzdataview.h>
 
#include <bslmf_assert.h>
 
#include <bsls_assert.h>
#include <bsls_libraryfeatures.h>
#include <bsls_types.h>           // 'bsls::Types::Uint64'
 
#include <bsl_cmath.h>            // 'bsl::isfinite'
#include <bsl_cstdint.h>          // 'bsl::uint8_t'
#include <bsl_limits.h>           // 'bsl::numeric_limits'
#include <bsl_string.h>
#include <bsl_type_traits.h>      // 'bsl::is_same'
#include <bsl_vector.h>
 
#include <string>
#include <vector>
 
 
namespace bslim {
 
                              // ===============
                              // struct FuzzUtil
                              // ===============
 
/// This utility `struct` provides a namespace for a suite of functions
/// operating on objects of type `FuzzDataView`and providing the consumption
/// of fuzz data bytes into fundamental and standard library types.
struct FuzzUtil {
 
    // CLASS METHODS
 
    /// Return a `bool` value based upon consuming a single byte from the
    /// specified `fuzzDataView`.  If `fuzzDataView->length()` is 0, return
    /// `false`.
    static bool consumeBool(FuzzDataView *fuzzDataView);
 
    template <class TYPE>
    static typename bsl::enable_if<bsl::is_integral<TYPE>::value, TYPE>::type
    consumeNumber(FuzzDataView *fuzzDataView);
 
    /// Return a value of (template parameter) `TYPE` in the range
    /// [min .. max] -- where `min` and `max` are the minimum and maximum
    /// values representable by the `TYPE` -- based on at most the next
    /// `sizeof(TYPE) + 1` bytes from the specified `fuzzDataView`, and
    /// update `fuzzDataView` to reflect the bytes consumed.  If
    /// `0 == fuzzDataView->length()`, return the minimum value of `TYPE`.
    /// This function does not participate in overload resolution unless
    /// either `bsl::is_integral<TYPE>::value` or
    /// `bsl::is_floating_point<TYPE>::value` is `true`.  The behavior is
    /// undefined if `bsl::is_same<TYPE, bool>::value` or
    /// `bsl::is_same<TYPE, long double>` is `true`.
    template <class TYPE>
    static typename
    bsl::enable_if<bsl::is_floating_point<TYPE>::value, TYPE>::type
    consumeNumber(FuzzDataView *fuzzDataView);
 
    /// Return a value of (template parameter) `TYPE` in the specified range
    /// [min .. max] based on at most the next `sizeof(TYPE) + 1` bytes from
    /// the specified `fuzzDataView`, and update `fuzzDataView` to reflect
    /// the bytes consumed.  If `0 == fuzzDataView->length()`, return the
    /// specified `min`.  This function does not participate in overload
    /// resolution unless either `bsl::is_integral<TYPE>::value` or
    /// `bsl::is_floating_point<TYPE>::value` is `true`.  The behavior is
    /// undefined if `min > max`, `min` or `max` is not finite, or either
    /// `bsl::is_same<TYPE, bool>::value` or
    /// `bsl::is_same<TYPE, long double>` is `true`.
    template <class TYPE>
    static typename
    bsl::enable_if<bsl::is_integral<TYPE>::value, TYPE>::type
    consumeNumberInRange(FuzzDataView                *fuzzDataView,
                         TYPE                         min,
                         TYPE                         max);
    template <class TYPE>
    static typename
    bsl::enable_if<bsl::is_floating_point<TYPE>::value, TYPE>::type
    consumeNumberInRange(FuzzDataView *fuzzDataView, TYPE min, TYPE max);
 
    static void consumeRandomLengthChars(bsl::vector<char> *output,
                                         FuzzDataView      *fuzzDataView,
                                         bsl::size_t        maxLength);
    static void consumeRandomLengthChars(std::vector<char> *output,
                                         FuzzDataView      *fuzzDataView,
                                         bsl::size_t        maxLength);
#ifdef BSLS_LIBRARYFEATURES_HAS_CPP17_PMR
    static void consumeRandomLengthChars(std::pmr::vector<char> *output,
                                         FuzzDataView           *fuzzDataView,
                                         bsl::size_t             maxLength);
#endif
    // Load into the specified 'output' a sequence of characters of length from
    // 0 to the specified 'maxLength'.  If the specified 'fuzzDataView' has
    // fewer bytes than 'maxLength', load at most 'fuzzDataView->length()'
    // bytes into 'output'.  If the buffer in 'fuzzDataView' contains two
    // successive backslash characters, then in 'output' they will be converted
    // to a single backslash ('\\') character; if a single backslash character
    // is encountered, the consumption of bytes is terminated.  Note that
    // because double backslashes are mapped to single backslashes, more than
    // 'maxLength' bytes may be consumed from the buffer to produce the
    // 'output'.  Also note that the purpose of this function is to enable the
    // creation of a non-zero-terminated @ref string_view , which is not possible
    // with the 'string' counterpart.
 
    static void consumeRandomLengthString(bsl::string      *output,
                                          FuzzDataView     *fuzzDataView,
                                          bsl::size_t       maxLength);
    static void consumeRandomLengthString(std::string      *output,
                                          FuzzDataView     *fuzzDataView,
                                          bsl::size_t       maxLength);
#ifdef BSLS_LIBRARYFEATURES_HAS_CPP17_PMR_STRING
    static void consumeRandomLengthString(std::pmr::string *output,
                                          FuzzDataView     *fuzzDataView,
                                          bsl::size_t       maxLength);
#endif
        // Load into the specified 'output' a string of length from 0 to the
        // specified 'maxLength'.  If the specified 'fuzzDataView' has fewer
        // bytes than 'maxLength', load at most 'fuzzDataView->length()' bytes
        // into 'output'.  If the buffer in 'fuzzDataView' contains two
        // successive backslash characters, then in 'output' they will be
        // converted to a single backslash ('\\') character; if a single
        // backslash character is encountered, the consumption of bytes is
        // terminated.  Note that because double backslashes are mapped to
        // single backslashes, more than 'maxLength' bytes may be consumed
        // from the buffer to produce the 'output'.
};
 
// ============================================================================
//                            INLINE DEFINITIONS
// ============================================================================
 
                              // ---------------
                              // struct FuzzUtil
                              // ---------------
 
// CLASS METHODS
inline
bool FuzzUtil::consumeBool(FuzzDataView *fuzzDataView)
{
    return 1 & consumeNumber<bsl::uint8_t>(fuzzDataView);
}
 
template <class TYPE>
typename bsl::enable_if<bsl::is_integral<TYPE>::value, TYPE>::type
FuzzUtil::consumeNumber(FuzzDataView *fuzzDataView)
{
    return consumeNumberInRange(fuzzDataView,
                                bsl::numeric_limits<TYPE>::min(),
                                bsl::numeric_limits<TYPE>::max());
}
 
template <class TYPE>
typename
bsl::enable_if<bsl::is_floating_point<TYPE>::value, TYPE>::type
FuzzUtil::consumeNumber(FuzzDataView *fuzzDataView)
{
    return consumeNumberInRange(fuzzDataView,
                                -bsl::numeric_limits<TYPE>::max(),
                                bsl::numeric_limits<TYPE>::max());
}
 
template <class TYPE>
typename bsl::enable_if<bsl::is_integral<TYPE>::value, TYPE>::type
FuzzUtil::consumeNumberInRange(FuzzDataView *fuzzDataView, TYPE min, TYPE max)
{
    BSLMF_ASSERT(bsl::is_integral<TYPE>::value);
    BSLMF_ASSERT((!bsl::is_same<TYPE, bool>::value));
    BSLMF_ASSERT(sizeof(TYPE) <= sizeof(bsls::Types::Uint64));
    BSLS_ASSERT(min <= max);
 
    bsls::Types::Uint64 range = static_cast<bsls::Types::Uint64>(max) - min;
 
    int numBytes = 0;
 
    for (bsls::Types::Uint64 rangeCpy = range; 0 != rangeCpy;
         rangeCpy >>= 8, ++numBytes) {
    }
 
    bsls::Types::Uint64 addend = 0;
 
    FuzzDataView prefix = fuzzDataView->removePrefix(numBytes);
 
    for (const bsl::uint8_t *it = prefix.begin(); it != prefix.end(); it++) {
        addend = (addend << 8) | *it;
    }
 
    if (bsl::numeric_limits<bsls::Types::Uint64>::max() != range) {
        addend %= (range + 1);
    }
 
    return static_cast<TYPE>(min + addend);
}
 
template <class TYPE>
typename bsl::enable_if<bsl::is_floating_point<TYPE>::value, TYPE>::type
FuzzUtil::consumeNumberInRange(FuzzDataView *fuzzDataView, TYPE min, TYPE max)
{
    BSLMF_ASSERT((!bsl::is_same<TYPE, long double>::value));
    BSLMF_ASSERT(bsl::numeric_limits<TYPE>::has_infinity);
 
    BSLS_ASSERT(min <= max);
 
    BSLS_ASSERT(min == min && max == max);
    BSLS_ASSERT(bsl::numeric_limits<TYPE>::infinity() != max &&
                -bsl::numeric_limits<TYPE>::infinity() != min);
 
    TYPE       addend = min;
    TYPE       range  = 0;
    const TYPE k_HALF = 0.5;
 
    if (max > min + bsl::numeric_limits<TYPE>::max()) {
        range = max * k_HALF - min * k_HALF;
        if (consumeBool(fuzzDataView)) {
            addend = min + range;
        }
    }
    else {
        range = max - min;
    }
 
    typedef typename bsl::conditional<(sizeof(TYPE) <= sizeof(bsl::uint32_t)),
                                      bsl::uint32_t,
                                      bsls::Types::Uint64>::type IntegralType;
 
    TYPE factor =
        static_cast<TYPE>(consumeNumber<IntegralType>(fuzzDataView)) /
        static_cast<TYPE>(
            bsl::numeric_limits<IntegralType>::max());  // between 0-1
 
    return addend + range * factor;
}
 
}  // close package namespace
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2021 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */