bdlb_indexspanutil.h

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/// @file bdlb_indexspanutil.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlb_indexspanutil.h                                               -*-C++-*-
#ifndef INCLUDED_BDLB_INDEXSPANUTIL
#define INCLUDED_BDLB_INDEXSPANUTIL
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlb_indexspanutil bdlb_indexspanutil
/// @brief  Provide functions that operate on `IndexSpan` objects.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlb
/// @{
/// @addtogroup bdlb_indexspanutil
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlb_indexspanutil-purpose"> Purpose</a>
/// * <a href="#bdlb_indexspanutil-classes"> Classes </a>
/// * <a href="#bdlb_indexspanutil-description"> Description </a>
///   * <a href="#bdlb_indexspanutil-usage"> Usage </a>
///     * <a href="#bdlb_indexspanutil-example1-taking-a-ipv6-address-out-of-a-uri"> Example1: Taking a IPv6 address out of a URI </a>
///
/// # Purpose {#bdlb_indexspanutil-purpose}
/// Provide functions that operate on `IndexSpan` objects.
///
/// # Classes {#bdlb_indexspanutil-classes}
///
/// -  bdlb::IndexSpanUtil: namespace for functions that operate on `IndexSpan`
///
/// @see  bdlb_indexspan
///
/// # Description {#bdlb_indexspanutil-description}
/// This component provides a struct, `IndexSpanUtil`, that serves
/// as a namespace for utility functions that operate on `IndexSpan` objects.
/// At the moment the only function provided is `shrink`, and it creates a new
/// `IndexSpan` that represents a (possibly) smaller span than the argument.
///
/// ## Usage {#bdlb_indexspanutil-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example1: Taking a IPv6 address out of a URI {#bdlb_indexspanutil-example1-taking-a-ipv6-address-out-of-a-uri}
///
///
/// Suppose we have a class that stores a parsed URL using a string to store the
/// full URL and `IndexSpan` objects to describe the individual parts of the
/// URL, and we want to add accessors that handle the case when the host part of
/// the URL is an IPv6 address, such as "http://[ff:fe:9]/index.html".  As
/// observed, an IPv6 address is indicated by the `[` and `]` characters (the
/// URL is ill formed if the closing `]` is not present).  We want to implement
/// two methods, one to query if the host part of the URL is IPv6 (`isIPv6Host`)
/// and another to get the IPv6 address (the part without the square brackets)
/// if the host is actually an IPv6 address (`getIPv6Host`).
///
/// First, let us create a `ParsedUrl` class.  For brevity, the class has only
/// those parts that are needed to implement `isIPv6Host` and `getIPv6Host`.
/// @code
/// class ParsedUrl {
///   private:
///     // DATA
///     bsl::string     d_url;
///     bdlb::IndexSpan d_host;
///
///   public:
///     // CREATORS
///
///     /// Create a `ParsedUrl` from the specified `url`, and `host`.
///     ParsedUrl(const bslstl::StringRef& url, bdlb::IndexSpan host)
///     : d_url(url)
///     , d_host(host)
///     {
///     }
///
///     // ACCESSORS
///
///     /// Return `true` if the host part represents an IPv6 address and
///     /// `false` otherwise.
///     bool isIPv6Host() const;
///
///     /// Return a string reference to the IPv6 address in the host part
///     /// of this URL.  The behavior is undefined unless
///     /// `isIPv6Host() == true` for this object.
///     bslstl::StringRef getIPv6Host() const;
/// };
/// @endcode
/// Next, we implement `isIPv6Host`.
/// @code
/// bool ParsedUrl::isIPv6Host() const
/// {
///     return !d_host.isEmpty() && '[' == d_url[d_host.position()];
/// }
/// @endcode
///  Then, to make the accessors simple (and readable), we implement a helper
///  function that creates a `StringRef` from a `StringRef` and an `IndexSpan`.
///  (Don't do this in real code, use `IndexSpanStringUtil::bind` that is
///  levelized above this component - so we cannot use it here.)
/// @code
/// /// Return a string reference to the substring of the specified `full`
/// /// thing defined by the specified `part`.
/// bslstl::StringRef bindSpan(const bslstl::StringRef& full,
///                            const bdlb::IndexSpan&   part)
/// {
///     BSLS_ASSERT(part.position() <= full.length());
///     BSLS_ASSERT(part.position() + part.length() <= full.length());
///
///     return bslstl::StringRef(full.data() + part.position(), part.length());
/// }
/// @endcode
/// Next, we implement `getIPv6Host` using `bdlb::IndexSpanUtil::shrink`.
/// @code
/// bslstl::StringRef ParsedUrl::getIPv6Host() const
/// {
///     BSLS_ASSERT(isIPv6Host());
///
///     return bindSpan(d_url, bdlb::IndexSpanUtil::shrink(d_host, 1, 1));
/// }
/// @endcode
/// Finally, we verify the two methods with URLs.
/// @code
/// ParsedUrl pu1("https://host/path/", bdlb::IndexSpan(8, 4));
/// assert(false == pu1.isIPv6Host());
///
/// ParsedUrl pu2("https://[12:3:fe:9]/path/", bdlb::IndexSpan(8, 11));
/// assert(true == pu2.isIPv6Host());
/// assert("12:3:fe:9" == pu2.getIPv6Host());
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlb
 * @{
 */
/** @addtogroup bdlb_indexspanutil
 * @{
 */
 
#include <bdlscm_version.h>
 
#include <bdlb_indexspan.h>
 
#include <bsls_assert.h>
 
 
namespace bdlb {
 
                        // ====================
                        // struct IndexSpanUtil
                        // ====================
 
/// This struct serves as a namespace for utility functions that operate on
/// `IndexSpan` objects.
///
/// See @ref bdlb_indexspanutil 
struct IndexSpanUtil {
  public:
    // CLASS METHODS
 
    /// Return an `IndexSpan` object transformed from the specified
    /// `original` using the specified `shrinkBegin` and `shrinkEnd` so that
    /// its position is `original.position() + shrinkBegin` and whose length
    /// is `original.length() - (shrinkBegin + shrinkEnd)`.  
    /// 
    /// \pre The behavior is undefined   unless `shrinkBegin + shrinkEnd <= original.length()`.
    static IndexSpan shrink(const IndexSpan&     original,
                            IndexSpan::size_type shrinkBegin,
                            IndexSpan::size_type shrinkEnd);
};
 
// ============================================================================
//                             INLINE DEFINITIONS
// ============================================================================
 
                        // --------------------
                        // struct IndexSpanUtil
                        // --------------------
 
// CLASS METHODS
inline
IndexSpan IndexSpanUtil::shrink(const IndexSpan&     original,
                                IndexSpan::size_type shrinkBegin,
                                IndexSpan::size_type shrinkEnd)
{
    BSLS_ASSERT(shrinkBegin + shrinkEnd <= original.length());
 
    return IndexSpan(original.position() + shrinkBegin,
                     original.length() - (shrinkBegin + shrinkEnd));
}
 
}  // close package namespace
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2018 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */