Merge pull request #2145 from FrancoisChabot/1813-user-input

Fix Issue#1813: user defined input adapters

README.md

@@ -416,7 +416,7 @@ Please note that setting the exception bit for `failbit` is inappropriate for th
 
 #### Read from iterator range
 
-You can also parse JSON from an iterator range; that is, from any container accessible by iterators whose content is stored as contiguous byte sequence, for instance a `std::vector<std::uint8_t>`:
+You can also parse JSON from an iterator range; that is, from any container accessible by iterators whose `value_type` is an integral type of 1, 2 or 4 bytes, which will be interpreted as UTF-8, UTF-16 and UTF-32 respectively. For instance, a `std::vector<std::uint8_t>`, or a `std::list<std::uint16_t>`:
 
 ```cpp
 std::vector<std::uint8_t> v = {'t', 'r', 'u', 'e'};
@@ -430,6 +430,53 @@ std::vector<std::uint8_t> v = {'t', 'r', 'u', 'e'};
 json j = json::parse(v);
 ```
 
+#### Custom data source
+
+Since the parse function accepts arbitrary iterator ranges, you can provide your own data sources by implementing the `LegacyInputIterator` concept.
+
+```cpp
+struct MyContainer {
+  void advance();
+  const char& get_current();
+};
+
+struct MyIterator {
+    using difference_type = std::ptrdiff_t;
+    using value_type = char;
+    using pointer = const char*;
+    using reference = const char&;
+    using iterator_category = std::input_iterator_tag;
+
+    MyIterator& operator++() {
+        MyContainer.advance();
+        return *this;
+    }
+
+    bool operator!=(const MyIterator& rhs) const {
+        return rhs.target != target;
+    }
+
+    reference operator*() const {
+        return target.get_current();
+    }
+
+    MyContainer* target = nullptr;
+};
+
+MyIterator begin(MyContainer& tgt) {
+    return MyIterator{&tgt};
+}
+
+MyIterator end(const MyContainer&) {
+    return {}; 
+}
+
+void foo() {
+    MyContainer c;
+    json j = json::parse(c);
+}
+```
+
 #### SAX interface
 
 The library uses a SAX-like interface with the following functions:

test/CMakeLists.txt

@@ -133,6 +133,7 @@ set(files
     src/unit-ubjson.cpp
     src/unit-udt.cpp
     src/unit-unicode.cpp
+    src/unit-user_defined_input.cpp
     src/unit-wstring.cpp)
 
 foreach(file ${files})

test/Makefile

@@ -44,6 +44,7 @@ SOURCES = src/unit.cpp \
           src/unit-testsuites.cpp \
           src/unit-ubjson.cpp \
           src/unit-unicode.cpp \
+          src/unit-user_defined_input.cpp \
           src/unit-wstring.cpp
 
 OBJECTS = $(SOURCES:.cpp=.o)

test/src/unit-user_defined_input.cpp

+/*
+    __ _____ _____ _____
+ __|  |   __|     |   | |  JSON for Modern C++ (test suite)
+|  |  |__   |  |  | | | |  version 3.7.3
+|_____|_____|_____|_|___|  https://github.com/nlohmann/json
+
+Licensed under the MIT License <http://opensource.org/licenses/MIT>.
+SPDX-License-Identifier: MIT
+Copyright (c) 2013-2019 Niels Lohmann <http://nlohmann.me>.
+
+Permission is hereby  granted, free of charge, to any  person obtaining a copy
+of this software and associated  documentation files (the "Software"), to deal
+in the Software  without restriction, including without  limitation the rights
+to  use, copy,  modify, merge,  publish, distribute,  sublicense, and/or  sell
+copies  of  the Software,  and  to  permit persons  to  whom  the Software  is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE  IS PROVIDED "AS  IS", WITHOUT WARRANTY  OF ANY KIND,  EXPRESS OR
+IMPLIED,  INCLUDING BUT  NOT  LIMITED TO  THE  WARRANTIES OF  MERCHANTABILITY,
+FITNESS FOR  A PARTICULAR PURPOSE AND  NONINFRINGEMENT. IN NO EVENT  SHALL THE
+AUTHORS  OR COPYRIGHT  HOLDERS  BE  LIABLE FOR  ANY  CLAIM,  DAMAGES OR  OTHER
+LIABILITY, WHETHER IN AN ACTION OF  CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE  OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+#include "doctest_compatibility.h"
+
+#include <nlohmann/json.hpp>
+using nlohmann::json;
+
+#include <list>
+
+namespace
+{
+TEST_CASE("Use arbitrary stdlib container")
+{
+    std::string raw_data = "[1,2,3,4]";
+    std::list<char> data(raw_data.begin(), raw_data.end());
+
+    json as_json = json::parse(data.begin(), data.end());
+    CHECK(as_json.at(0) == 1);
+    CHECK(as_json.at(1) == 2);
+    CHECK(as_json.at(2) == 3);
+    CHECK(as_json.at(3) == 4);
+}
+
+struct MyContainer
+{
+    const char* data;
+};
+
+const char* begin(const MyContainer& c)
+{
+    return c.data;
+}
+
+const char* end(const MyContainer& c)
+{
+    return c.data + strlen(c.data);
+}
+
+TEST_CASE("Custom container")
+{
+
+    MyContainer data{"[1,2,3,4]"};
+    json as_json = json::parse(data);
+    CHECK(as_json.at(0) == 1);
+    CHECK(as_json.at(1) == 2);
+    CHECK(as_json.at(2) == 3);
+    CHECK(as_json.at(3) == 4);
+
+}
+
+TEST_CASE("Custom iterator")
+{
+    const char* raw_data = "[1,2,3,4]";
+
+    struct MyIterator
+    {
+        using difference_type = std::size_t;
+        using value_type = char;
+        using pointer = const char*;
+        using reference = const char&;
+        using iterator_category = std::input_iterator_tag;
+
+
+        MyIterator& operator++()
+        {
+            ++ptr;
+            return *this;
+        }
+
+        reference operator*() const
+        {
+            return *ptr;
+        }
+
+        bool operator!=(const MyIterator& rhs) const
+        {
+            return ptr != rhs.ptr;
+        }
+
+        const char* ptr;
+    };
+
+    MyIterator begin{raw_data};
+    MyIterator end{raw_data + strlen(raw_data)};
+
+    json as_json = json::parse(begin, end);
+    CHECK(as_json.at(0) == 1);
+    CHECK(as_json.at(1) == 2);
+    CHECK(as_json.at(2) == 3);
+    CHECK(as_json.at(3) == 4);
+}
+
+
+
+}
\ No newline at end of file