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Rearrange sources (#4997)
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John Freeman
John Freeman
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260
include/xrpl/json/Writer.h
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260
include/xrpl/json/Writer.h
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//------------------------------------------------------------------------------
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/*
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This file is part of rippled: https://github.com/ripple/rippled
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Copyright (c) 2012, 2013 Ripple Labs Inc.
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Permission to use, copy, modify, and/or distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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ANY SPECIAL , DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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//==============================================================================
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#ifndef RIPPLE_JSON_WRITER_H_INCLUDED
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#define RIPPLE_JSON_WRITER_H_INCLUDED
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#include <ripple/basics/ToString.h>
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#include <ripple/basics/contract.h>
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#include <ripple/json/Output.h>
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#include <ripple/json/json_value.h>
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#include <memory>
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namespace Json {
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/**
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* Writer implements an O(1)-space, O(1)-granular output JSON writer.
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*
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* O(1)-space means that it uses a fixed amount of memory, and that there are
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* no heap allocations at each step of the way.
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*
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* O(1)-granular output means the writer only outputs in small segments of a
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* bounded size, using a bounded number of CPU cycles in doing so. This is
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* very helpful in scheduling long jobs.
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*
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* The tradeoff is that you have to fill items in the JSON tree as you go,
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* and you can never go backward.
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*
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* Writer can write single JSON tokens, but the typical use is to write out an
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* entire JSON object. For example:
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*
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* {
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* Writer w (out);
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*
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* w.startObject (); // Start the root object.
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* w.set ("hello", "world");
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* w.set ("goodbye", 23);
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* w.finishObject (); // Finish the root object.
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* }
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*
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* which outputs the string
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*
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* {"hello":"world","goodbye":23}
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*
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* There can be an object inside an object:
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*
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* {
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* Writer w (out);
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*
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* w.startObject (); // Start the root object.
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* w.set ("hello", "world");
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*
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* w.startObjectSet ("subobject"); // Start a sub-object.
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* w.set ("goodbye", 23); // Add a key, value assignment.
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* w.finishObject (); // Finish the sub-object.
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*
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* w.finishObject (); // Finish the root-object.
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* }
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*
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* which outputs the string
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*
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* {"hello":"world","subobject":{"goodbye":23}}.
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*
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* Arrays work similarly
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*
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* {
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* Writer w (out);
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* w.startObject (); // Start the root object.
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*
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* w.startArraySet ("hello"); // Start an array.
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* w.append (23) // Append some items.
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* w.append ("skidoo")
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* w.finishArray (); // Finish the array.
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*
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* w.finishObject (); // Finish the root object.
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* }
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*
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* which outputs the string
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*
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* {"hello":[23,"skidoo"]}.
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*
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*
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* If you've reached the end of a long object, you can just use finishAll()
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* which finishes all arrays and objects that you have started.
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*
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* {
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* Writer w (out);
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* w.startObject (); // Start the root object.
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*
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* w.startArraySet ("hello"); // Start an array.
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* w.append (23) // Append an item.
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*
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* w.startArrayAppend () // Start a sub-array.
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* w.append ("one");
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* w.append ("two");
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*
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* w.startObjectAppend (); // Append a sub-object.
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* w.finishAll (); // Finish everything.
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* }
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*
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* which outputs the string
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*
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* {"hello":[23,["one","two",{}]]}.
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*
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* For convenience, the destructor of Writer calls w.finishAll() which makes
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* sure that all arrays and objects are closed. This means that you can throw
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* an exception, or have a coroutine simply clean up the stack, and be sure
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* that you do in fact generate a complete JSON object.
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*/
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class Writer
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{
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public:
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enum CollectionType { array, object };
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explicit Writer(Output const& output);
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Writer(Writer&&) noexcept;
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Writer&
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operator=(Writer&&) noexcept;
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~Writer();
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/** Start a new collection at the root level. */
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void startRoot(CollectionType);
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/** Start a new collection inside an array. */
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void startAppend(CollectionType);
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/** Start a new collection inside an object. */
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void
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startSet(CollectionType, std::string const& key);
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/** Finish the collection most recently started. */
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void
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finish();
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/** Finish all objects and arrays. After finishArray() has been called, no
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* more operations can be performed. */
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void
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finishAll();
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/** Append a value to an array.
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*
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* Scalar must be a scalar - that is, a number, boolean, string, string
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* literal, nullptr or Json::Value
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*/
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template <typename Scalar>
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void
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append(Scalar t)
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{
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rawAppend();
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output(t);
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}
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/** Add a comma before this next item if not the first item in an array.
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Useful if you are writing the actual array yourself. */
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void
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rawAppend();
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/** Add a key, value assignment to an object.
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*
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* Scalar must be a scalar - that is, a number, boolean, string, string
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* literal, or nullptr.
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*
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* While the JSON spec doesn't explicitly disallow this, you should avoid
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* calling this method twice with the same tag for the same object.
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*
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* If CHECK_JSON_WRITER is defined, this function throws an exception if if
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* the tag you use has already been used in this object.
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*/
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template <typename Type>
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void
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set(std::string const& tag, Type t)
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{
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rawSet(tag);
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output(t);
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}
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/** Emit just "tag": as part of an object. Useful if you are writing the
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actual value data yourself. */
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void
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rawSet(std::string const& key);
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// You won't need to call anything below here until you are writing single
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// items (numbers, strings, bools, null) to a JSON stream.
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/*** Output a string. */
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void
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output(std::string const&);
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/*** Output a literal constant or C string. */
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void
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output(char const*);
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/*** Output a Json::Value. */
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void
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output(Json::Value const&);
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/** Output a null. */
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void output(std::nullptr_t);
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/** Output a float. */
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void
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output(float);
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/** Output a double. */
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void
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output(double);
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/** Output a bool. */
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void
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output(bool);
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/** Output numbers or booleans. */
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template <typename Type>
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void
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output(Type t)
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{
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implOutput(std::to_string(t));
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}
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void
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output(Json::StaticString const& t)
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{
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output(t.c_str());
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}
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private:
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class Impl;
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std::unique_ptr<Impl> impl_;
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void
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implOutput(std::string const&);
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};
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inline void
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check(bool condition, std::string const& message)
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{
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if (!condition)
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ripple::Throw<std::logic_error>(message);
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}
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} // namespace Json
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#endif
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