baljsn_formatter.h

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/// @file baljsn_formatter.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// baljsn_formatter.h                                                 -*-C++-*-
#ifndef INCLUDED_BALJSN_FORMATTER
#define INCLUDED_BALJSN_FORMATTER
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup baljsn_formatter baljsn_formatter
/// @brief  Provide a formatter for encoding data in the JSON format.
/// @addtogroup bal
/// @{
/// @addtogroup baljsn
/// @{
/// @addtogroup baljsn_formatter
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#baljsn_formatter-purpose"> Purpose</a>
/// * <a href="#baljsn_formatter-classes"> Classes </a>
/// * <a href="#baljsn_formatter-description"> Description </a>
///   * <a href="#baljsn_formatter-valid-sequence-of-operations"> Valid sequence of operations </a>
///   * <a href="#baljsn_formatter-usage"> Usage </a>
///     * <a href="#baljsn_formatter-example-1-encoding-a-stock-portfolio-in-json"> Example 1: Encoding a Stock Portfolio in JSON </a>
///
/// # Purpose {#baljsn_formatter-purpose}
/// Provide a formatter for encoding data in the JSON format.
///
/// # Classes {#baljsn_formatter-classes}
///
/// - baljsn::Formatter: JSON formatter
///
/// @see  baljsn_encoder, baljsn_printutil, baljsn_simpleformatter
///
/// # Description {#baljsn_formatter-description}
/// This component provides a class, `baljsn::Formatter`, for
/// formatting JSON objects, arrays, and name-value pairs in the JSON encoding
/// format to a specified output stream.
///
/// The JSON encoding format (see http://json.org or ECMA-404 standard for more
/// information) specifies a self-describing and simple syntax that is built on
/// two structures:
///
/// * Objects: JSON objects are represented as collections of name value
///   pairs.  The `Formatter` `class` allows encoding objects by providing the
///   `openObject` and `closeObject` methods to open and close an object and
///   the `openMember`, `closeMember`, and `putValue` methods to add members
///   and values to an object.
/// * Arrays: JSON arrays are specified as an ordered list of values.  The
///   `Formatter` `class` provides the `openArray` and `closeArray` method to
///   open and close an array.  Additionally the `Formatter` `class` allows of
///   separation of array items by a comma via the `addArrayElementSeparator`
///   method.
///
/// The `Formatter` `class` also provides the ability to specify formatting
/// options at construction.  The options that can be provided include the
/// encoding style (compact or pretty), the initial indentation level and spaces
/// per level if encoding in the pretty format.
///
/// ## Valid sequence of operations {#baljsn_formatter-valid-sequence-of-operations}
///
///
/// The `Formatter` `class` does only minimal checking to verify that the
/// sequence of operations called on its object result in a valid JSON
/// document.  It is the user's responsibility to ensure that the methods
/// provided by this component are called in the right order.
///
/// ## Usage {#baljsn_formatter-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Encoding a Stock Portfolio in JSON {#baljsn_formatter-example-1-encoding-a-stock-portfolio-in-json}
///
///
/// Let us say that we have to encode a JSON document with the following
/// information about stocks that we are interested in.  For brevity we just
/// show and encode a part of the complete document.
/// @code
/// {
///   "Stocks" : [
///     {
///       "Name" : "International Business Machines Corp",
///       "Ticker" : "IBM US Equity",
///       "Last Price" : 149.3,
///       "Dividend Yield" : 3.95
///     },
///     {
///       "Name" : "Apple Inc",
///       "Ticker" : "AAPL US Equity",
///       "Last Price" : 205.8,
///       "Dividend Yield" : 1.4
///     }
///   ]
/// }
/// @endcode
/// First, we specify the result that we are expecting to get:
/// @code
/// const bsl::string EXPECTED =
///     "{\n"
///     "  \"Stocks\" : [\n"
///     "    {\n"
///     "      \"Name\" : \"International Business Machines Corp\",\n"
///     "      \"Ticker\" : \"IBM US Equity\",\n"
///     "      \"Last Price\" : 149.3,\n"
///     "      \"Dividend Yield\" : 3.95\n"
///     "    },\n"
///     "    {\n"
///     "      \"Name\" : \"Apple Inc\",\n"
///     "      \"Ticker\" : \"AAPL US Equity\",\n"
///     "      \"Last Price\" : 205.8,\n"
///     "      \"Dividend Yield\" : 1.4\n"
///     "    }\n"
///     "  ]\n"
///     "}";
/// @endcode
/// Then, to encode this JSON document we create a `baljsn::Formatter` object.
/// Since we want the document to be written in a pretty, easy to understand
/// format we will specify the `true` for the `usePrettyStyle` option and
/// provide an appropriate initial indent level and spaces per level values:
/// @code
/// bsl::ostringstream os;
/// baljsn::Formatter formatter(os, true, 0, 2);
/// @endcode
/// Next, we start calling the sequence of methods requires to produce this
/// document.  We start with the top level object and add an element named
/// `Stocks` to it:
/// @code
/// formatter.openObject();
/// formatter.openMember("Stocks");
/// @endcode
/// Then, we see that `Stocks` is an array element so we specify the start of
/// the array:
/// @code
/// formatter.openArray();
/// @endcode
/// Next, each element within `Stocks` is an object that contains the
/// information for an individual stock.  So we have to output an object here:
/// @code
/// formatter.openObject();
/// @endcode
/// We now encode the other elements in the stock object.  The `closeMember`
/// terminates the element by adding a `,` at the end.  For the last element in
/// an object do not call the `closeMember` method.
/// @code
/// formatter.openMember("Name");
/// formatter.putValue("International Business Machines Corp");
/// formatter.closeMember();
///
/// formatter.openMember("Ticker");
/// formatter.putValue("IBM US Equity");
/// formatter.closeMember();
///
/// formatter.openMember("Last Price");
/// formatter.putValue(149.3);
/// formatter.closeMember();
///
/// formatter.openMember("Dividend Yield");
/// formatter.putValue(3.95);
/// // Note no call to 'closeMember' for the last element
/// @endcode
/// Then, close the first stock object and separate it from the second one using
/// the `addArrayElementSeparator` method.
/// @code
/// formatter.closeObject();
/// formatter.addArrayElementSeparator();
/// @endcode
/// Next, we add another stock object.  But we don't need to separate it as it
/// is the last one.
/// @code
/// formatter.openObject();
///
/// formatter.openMember("Name");
/// formatter.putValue("Apple Inc");
/// formatter.closeMember();
///
/// formatter.openMember("Ticker");
/// formatter.putValue("AAPL US Equity");
/// formatter.closeMember();
///
/// formatter.openMember("Last Price");
/// formatter.putValue(205.8);
/// formatter.closeMember();
///
/// formatter.openMember("Dividend Yield");
/// formatter.putValue(1.4);
///
/// formatter.closeObject();
/// @endcode
/// Similarly, we can continue to format the rest of the document.  For the
/// purpose of this usage example we will complete this document.
/// @code
/// formatter.closeArray();
/// formatter.closeObject();
/// @endcode
/// Once the formatting is complete the written data can be viewed from the
/// stream passed to the formatter at construction.
/// @code
/// if (verbose)
///     bsl::cout << os.str() << bsl::endl;
/// @endcode
/// Finally, verify the received result:
/// @code
/// assert(EXPECTED == os.str());
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bal
 * @{
 */
/** @addtogroup baljsn
 * @{
 */
/** @addtogroup baljsn_formatter
 * @{
 */
 
#include <balscm_version.h>
 
#include <baljsn_printutil.h>
 
#include <bdlb_print.h>
 
#include <bdlc_bitarray.h>
 
#include <bsl_ostream.h>
 
#include <bsls_assert.h>
#include <bsls_review.h>
 
#include <bsl_string.h>
#include <bsl_string_view.h>
 
 
namespace baljsn {
 
class EncoderOptions;
 
                          // ===============
                          // class Formatter
                          // ===============
 
/// This class implements a formatter providing operations for rendering JSON
/// text elements to an output stream (supplied at construction) according to a
/// set of formatting options (also supplied at construction).
///
/// See @ref baljsn_formatter 
class Formatter {
 
    // DATA
    bsl::ostream&     d_outputStream;        // stream for output (held, not
                                             // owned)
 
    bool              d_usePrettyStyle;      // encoding style
 
    int               d_indentLevel;         // current indentation level
 
    int               d_spacesPerLevel;      // spaces per indentation level
 
    bdlc::BitArray    d_callSequence;        // array specifying the sequence
                                             // in which the 'openObject' and
                                             // 'openArray' methods were
                                             // called.  An 'openObject' call
                                             // is represented by 'false' and
                                             // an 'openArray' call by 'true'.
 
    // PRIVATE MANIPULATORS
 
    /// Unconditionally print onto the stream supplied at construction the
    /// sequence of whitespace characters for the proper indentation of an
    /// element at the current indentation level.  Note that this method does
    /// not check that `d_usePrettyStyle` is `true` before indenting.
    void indent();
 
    // PRIVATE ACCESSORS
 
    /// Return `true` if the value being encoded is an element of an array, and
    /// `false` otherwise.  A value is identified as an element of an array if
    /// `openArray` was called on this object and was not subsequently followed
    /// by either an `openObject` or `closeArray` call.
    bool isArrayElement() const;
 
  public:
    // CREATORS
 
    /// Create a `Formatter` object using the specified `stream`.  Optionally
    /// specify `usePrettyStyle` to inform the formatter whether the pretty
    /// encoding style should be used when writing data.  If `usePrettyStyle`
    /// is not specified then the data is written in a compact style.  If
    /// `usePrettyStyle` is specified, additionally specify
    /// `initialIndentLevel` and `spacesPerLevel` to provide the initial
    /// indentation level and spaces per level at which the data should be
    /// formatted.  If `initialIndentLevel` or `spacesPerLevel` is not
    /// specified then an initial value of `0` is used for both parameters.  If
    /// `usePrettyStyle` is `false` then `initialIndentLevel` and
    /// `spacesPerLevel` are both ignored.  Optionally specify a
    /// `basicAllocator` used to supply memory.  If `basicAllocator` is 0, the
    /// currently installed default allocator is used.
    Formatter(bsl::ostream&     stream,
              bool              usePrettyStyle     = false,
              int               initialIndentLevel = 0,
              int               spacesPerLevel     = 0,
              bslma::Allocator *basicAllocator     = 0);
 
    /// Destroy this object.
     ~Formatter() = default;
 
    // MANIPULATORS
 
    /// Print onto the stream supplied at construction the sequence of
    /// characters designating the start of an object (referred to as an
    /// "object" in JSON).
    void openObject();
 
    /// Print onto the stream supplied at construction the sequence of
    /// characters designating the end of an object (referred to as an "object"
    /// in JSON).  The behavior is undefined unless this `Formatter` is
    /// currently formatting an object.
    void closeObject();
 
    /// Print onto the stream supplied at construction the sequence of
    /// characters designating the start of an array (referred to as an "array"
    /// in JSON).  Optionally specify `formatAsEmptyArray` denoting if the
    /// array being opened should be formatted as an empty array.  If
    /// `formatAsEmptyArray` is not specified then the array being opened is
    /// formatted as an array having elements.  Note that the formatting (and
    /// as a consequence the `formatAsEmptyArray`) is relevant only if this
    /// formatter encodes in the pretty style and is ignored otherwise.
    void openArray(bool formatAsEmptyArray = false);
 
    /// Print onto the stream supplied at construction the sequence of
    /// characters designating the end of an array (referred to as an "array"
    /// in JSON).  Optionally specify `formatAsEmptyArray` denoting if the
    /// array being closed should be formatted as an empty array.  If
    /// `formatAsEmptyArray` is not specified then the array being closed is
    /// formatted as an array having elements.  The behavior is undefined
    /// unless this `Formatter` is currently formatting an array.  Note that
    /// the formatting (and as a consequence the `formatAsEmptyArray`) is
    /// relevant only if this formatter encodes in the pretty style and is
    /// ignored otherwise.
    void closeArray(bool formatAsEmptyArray = false);
 
    /// Print onto the stream supplied at construction the sequence of
    /// characters designating the start of a member (referred to as a
    /// "name/value pair" in JSON) having the specified `name`.  Return 0 on
    /// success and a non-zero value otherwise.
    int openMember(const bsl::string_view& name);
 
    /// Print onto the stream supplied at construction the value corresponding
    /// to a null element.
    void putNullValue();
 
    /// Print onto the stream supplied at construction the specified `value`.
    /// Optionally specify `options` according which `value` should be encoded.
    /// Return 0 on success and a non-zero value otherwise.
    template <class TYPE>
    int putValue(const TYPE& value, const EncoderOptions *options = 0);
 
    /// Print onto the stream supplied at construction the sequence of
    /// characters designating the end of an member (referred to as a
    /// "name/value pair" in JSON).  The behavior is undefined unless this
    /// `Formatter` is currently formatting a member.
    void closeMember();
 
    /// Print onto the stream supplied at construction the sequence of
    /// characters designating an array element separator (i.e., `,`).  The
    /// behavior is undefined unless this `Formatter` is currently formatting a
    /// member.
    void addArrayElementSeparator();
 
    // ACCESSORS
 
    /// Return the number of currently open nested objects or arrays.
    int nestingDepth() const;
};
 
// ============================================================================
//                            INLINE DEFINITIONS
// ============================================================================
 
                        // ---------------
                        // class Formatter
                        // ---------------
 
// PRIVATE MANIPULATORS
inline
void Formatter::indent()
{
    bdlb::Print::indent(d_outputStream, d_indentLevel, d_spacesPerLevel);
}
 
// PRIVATE ACCESSORS
inline
bool Formatter::isArrayElement() const
{
    BSLS_ASSERT(d_callSequence.length() >= 1);
 
    return d_callSequence[d_callSequence.length() - 1];
}
 
// MANIPULATORS
inline
void Formatter::putNullValue()
{
    if (d_usePrettyStyle && isArrayElement()) {
        indent();
    }
    d_outputStream << "null";
}
 
template <class TYPE>
int Formatter::putValue(const TYPE& value, const EncoderOptions *options)
{
    if (d_usePrettyStyle && isArrayElement()) {
        indent();
    }
    return baljsn::PrintUtil::printValue(d_outputStream, value, options);
}
 
// ACCESSORS
inline
int Formatter::nestingDepth() const
{
    // The call sequence contains a "dummy" initial element, so subtract one
    // from the length.
    return static_cast<int>(d_callSequence.length()) - 1;
}
 
}  // close package namespace
 
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2017 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */