comparison vamp-json/VampJson.h @ 75:81e1c48e97f9

Rearrange and rename to Piper C++ structure

+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    Piper C++
+
+    Centre for Digital Music, Queen Mary, University of London.
+    Copyright 2015-2016 QMUL.
+  
+    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 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.
+
+    Except as contained in this notice, the names of the Centre for
+    Digital Music; Queen Mary, University of London; and Chris Cannam
+    shall not be used in advertising or otherwise to promote the sale,
+    use or other dealings in this Software without prior written
+    authorization.
+*/
+
+#ifndef PIPER_VAMP_JSON_H
+#define PIPER_VAMP_JSON_H
+
+#include <vector>
+#include <string>
+#include <sstream>
+
+#include <json11/json11.hpp>
+#include <base-n/include/basen.hpp>
+
+#include <vamp-hostsdk/Plugin.h>
+#include <vamp-hostsdk/PluginLoader.h>
+
+#include "vamp-support/PluginHandleMapper.h"
+#include "vamp-support/PluginOutputIdMapper.h"
+#include "vamp-support/RequestResponseType.h"
+
+namespace piper {
+
+/**
+ * Convert the structures laid out in the Vamp SDK classes into JSON
+ * (and back again) following the schema in the vamp-json-schema
+ * project repo.
+ *
+ * Functions with names starting "from" convert from a Vamp SDK object
+ * to JSON output. Most of them return a json11::Json object, with a
+ * few exceptions for low-level utilities that return a string. These
+ * functions succeed all of the time.
+ *
+ * Functions with names starting "to" convert to a Vamp SDK object
+ * from JSON input. These functions all accept a json11::Json object
+ * as first argument, with a few exceptions for low-level utilities
+ * that accept a string. These functions all accept a string reference
+ * as a final argument and return an error string through it if the
+ * conversion fails. If conversion fails the return value is
+ * undefined, and any returned object may be incomplete or
+ * invalid. Callers should check for an empty error string (indicating
+ * success) before using the returned value.
+ */
+
+class VampJson
+{
+public:
+    /** Serialisation format for arrays of floats (process input and
+     *  feature values). Wherever such an array appears, it may
+     *  alternatively be replaced by a single string containing a
+     *  base-64 encoding of the IEEE float buffer. When parsing, if a
+     *  string is found instead of an array in this case, it will be
+     *  interpreted as a base-64 encoded buffer. Only array or base-64
+     *  encoding may be provided, not both.
+     */
+    enum class BufferSerialisation {
+
+        /** Default JSON serialisation of values in array form. This
+         *  is relatively slow to parse and serialise, and can take a
+         *  lot of space.
+         */
+        Array,
+
+        /** Base64-encoded string of the raw data as packed
+         *  little-endian IEEE 32-bit floats. Faster and more compact
+         *  than the text encoding but more complicated to
+         *  provide. Note that Base64 serialisations produced by this
+         *  library do not including padding characters and so are not
+         *  necessarily multiples of 4 characters long. You will need
+         *  to pad them yourself if concatenating them or supplying to
+         *  a consumer that expects padding.
+         */
+        Base64
+    };
+    
+    static bool failed(const std::string &err) {
+        return err != "";
+    }
+    
+    template <typename T>
+    static json11::Json
+    fromBasicDescriptor(const T &t) {
+        return json11::Json::object { 
+            { "identifier", t.identifier },
+            { "name", t.name },
+            { "description", t.description }
+        };
+    }
+
+    template <typename T>
+    static void
+    toBasicDescriptor(json11::Json j, T &t, std::string &err) {
+        if (!j.is_object()) {
+            err = "object expected for basic descriptor content";
+            return;
+        }
+        if (!j["identifier"].is_string()) {
+            err = "string expected for identifier";
+            return;
+        }
+        t.identifier = j["identifier"].string_value();
+        t.name = j["name"].string_value();
+        t.description = j["description"].string_value();
+    }
+
+    template <typename T>
+    static json11::Json
+    fromValueExtents(const T &t) {
+        return json11::Json::object {
+            { "min", t.minValue },
+            { "max", t.maxValue }
+        };
+    }
+
+    template <typename T>
+    static bool
+    toValueExtents(json11::Json j, T &t, std::string &err) {
+        if (j["extents"].is_null()) {
+            return false;
+        } else if (j["extents"].is_object()) {
+            if (j["extents"]["min"].is_number() &&
+                j["extents"]["max"].is_number()) {
+                t.minValue = j["extents"]["min"].number_value();
+                t.maxValue = j["extents"]["max"].number_value();
+                return true;
+            } else {
+                err = "numbers expected for min and max";
+                return false;
+            }
+        } else {
+            err = "object expected for extents (if present)";
+            return false;
+        }
+    }
+
+    static json11::Json
+    fromRealTime(const Vamp::RealTime &r) {
+        return json11::Json::object {
+            { "s", r.sec },
+            { "n", r.nsec }
+        };
+    }
+
+    static Vamp::RealTime
+    toRealTime(json11::Json j, std::string &err) {
+        json11::Json sec = j["s"];
+        json11::Json nsec = j["n"];
+        if (!sec.is_number() || !nsec.is_number()) {
+            err = "invalid Vamp::RealTime object " + j.dump();
+            return {};
+        }
+        return Vamp::RealTime(sec.int_value(), nsec.int_value());
+    }
+
+    static std::string
+    fromSampleType(Vamp::Plugin::OutputDescriptor::SampleType type) {
+        switch (type) {
+        case Vamp::Plugin::OutputDescriptor::OneSamplePerStep:
+            return "OneSamplePerStep";
+        case Vamp::Plugin::OutputDescriptor::FixedSampleRate:
+            return "FixedSampleRate";
+        case Vamp::Plugin::OutputDescriptor::VariableSampleRate:
+            return "VariableSampleRate";
+        }
+        return "";
+    }
+
+    static Vamp::Plugin::OutputDescriptor::SampleType
+    toSampleType(std::string text, std::string &err) {
+        if (text == "OneSamplePerStep") {
+            return Vamp::Plugin::OutputDescriptor::OneSamplePerStep;
+        } else if (text == "FixedSampleRate") {
+            return Vamp::Plugin::OutputDescriptor::FixedSampleRate;
+        } else if (text == "VariableSampleRate") {
+            return Vamp::Plugin::OutputDescriptor::VariableSampleRate;
+        } else {
+            err = "invalid sample type string: " + text;
+            return Vamp::Plugin::OutputDescriptor::OneSamplePerStep;
+        }
+    }
+
+    static json11::Json
+    fromConfiguredOutputDescriptor(const Vamp::Plugin::OutputDescriptor &desc) {
+        json11::Json::object jo {
+            { "unit", desc.unit },
+            { "sampleType", fromSampleType(desc.sampleType) },
+            { "sampleRate", desc.sampleRate },
+            { "hasDuration", desc.hasDuration }
+        };
+        if (desc.hasFixedBinCount) {
+            jo["binCount"] = int(desc.binCount);
+            jo["binNames"] = json11::Json::array
+                (desc.binNames.begin(), desc.binNames.end());
+        }
+        if (desc.hasKnownExtents) {
+            jo["extents"] = fromValueExtents(desc);
+        }
+        if (desc.isQuantized) {
+            jo["quantizeStep"] = desc.quantizeStep;
+        }
+        return json11::Json(jo);
+    }
+    
+    static json11::Json
+    fromOutputDescriptor(const Vamp::Plugin::OutputDescriptor &desc) {
+        json11::Json::object jo {
+            { "basic", fromBasicDescriptor(desc) },
+            { "configured", fromConfiguredOutputDescriptor(desc) }
+        };
+        return json11::Json(jo);
+    }
+    
+    static Vamp::Plugin::OutputDescriptor
+    toConfiguredOutputDescriptor(json11::Json j, std::string &err) {
+
+        Vamp::Plugin::OutputDescriptor od;
+        if (!j.is_object()) {
+            err = "object expected for output descriptor";
+            return {};
+        }
+    
+        od.unit = j["unit"].string_value();
+
+        od.sampleType = toSampleType(j["sampleType"].string_value(), err);
+        if (failed(err)) return {};
+
+        if (!j["sampleRate"].is_number()) {
+            err = "number expected for sample rate";
+            return {};
+        }
+        od.sampleRate = j["sampleRate"].number_value();
+        od.hasDuration = j["hasDuration"].bool_value();
+
+        if (j["binCount"].is_number() && j["binCount"].int_value() > 0) {
+            od.hasFixedBinCount = true;
+            od.binCount = j["binCount"].int_value();
+            for (auto &n: j["binNames"].array_items()) {
+                if (!n.is_string()) {
+                    err = "string expected for bin name";
+                    return {};
+                }
+                od.binNames.push_back(n.string_value());
+            }
+        } else {
+            od.hasFixedBinCount = false;
+        }
+
+        bool extentsPresent = toValueExtents(j, od, err);
+        if (failed(err)) return {};
+        
+        od.hasKnownExtents = extentsPresent;
+
+        if (j["quantizeStep"].is_number()) {
+            od.isQuantized = true;
+            od.quantizeStep = j["quantizeStep"].number_value();
+        } else {
+            od.isQuantized = false;
+        }
+
+        return od;
+    }
+    
+    static Vamp::Plugin::OutputDescriptor
+    toOutputDescriptor(json11::Json j, std::string &err) {
+
+        Vamp::Plugin::OutputDescriptor od;
+        if (!j.is_object()) {
+            err = "object expected for output descriptor";
+            return {};
+        }
+
+        od = toConfiguredOutputDescriptor(j, err);
+        if (failed(err)) return {};
+    
+        toBasicDescriptor(j["basic"], od, err);
+        if (failed(err)) return {};
+
+        return od;
+    }
+
+    static json11::Json
+    fromParameterDescriptor(const Vamp::PluginBase::ParameterDescriptor &desc) {
+
+        json11::Json::object jo {
+            { "basic", fromBasicDescriptor(desc) },
+            { "unit", desc.unit },
+            { "extents", fromValueExtents(desc) },
+            { "defaultValue", desc.defaultValue },
+            { "valueNames", json11::Json::array
+                    (desc.valueNames.begin(), desc.valueNames.end()) }
+        };
+        if (desc.isQuantized) {
+            jo["quantizeStep"] = desc.quantizeStep;
+        }
+        return json11::Json(jo);
+    }
+
+    static Vamp::PluginBase::ParameterDescriptor
+    toParameterDescriptor(json11::Json j, std::string &err) {
+
+        Vamp::PluginBase::ParameterDescriptor pd;
+        if (!j.is_object()) {
+            err = "object expected for parameter descriptor";
+            return {};
+        }
+    
+        toBasicDescriptor(j["basic"], pd, err);
+        if (failed(err)) return {};
+
+        pd.unit = j["unit"].string_value();
+
+        bool extentsPresent = toValueExtents(j, pd, err);
+        if (failed(err)) return {};
+        if (!extentsPresent) {
+            err = "extents must be present in parameter descriptor";
+            return {};
+        }
+    
+        if (!j["defaultValue"].is_number()) {
+            err = "number expected for default value";
+            return {};
+        }
+    
+        pd.defaultValue = j["defaultValue"].number_value();
+
+        pd.valueNames.clear();
+        for (auto &n: j["valueNames"].array_items()) {
+            if (!n.is_string()) {
+                err = "string expected for value name";
+                return {};
+            }
+            pd.valueNames.push_back(n.string_value());
+        }
+
+        if (j["quantizeStep"].is_number()) {
+            pd.isQuantized = true;
+            pd.quantizeStep = j["quantizeStep"].number_value();
+        } else {
+            pd.isQuantized = false;
+        }
+
+        return pd;
+    }
+
+    static std::string
+    fromFloatBuffer(const float *buffer, size_t nfloats) {
+        // must use char pointers, otherwise the converter will only
+        // encode every 4th byte (as it will count up in float* steps)
+        const char *start = reinterpret_cast<const char *>(buffer);
+        const char *end = reinterpret_cast<const char *>(buffer + nfloats);
+        std::string encoded;
+        bn::encode_b64(start, end, back_inserter(encoded));
+        return encoded;
+    }
+
+    static std::vector<float>
+    toFloatBuffer(std::string encoded, std::string & /* err */) {
+        std::string decoded;
+        bn::decode_b64(encoded.begin(), encoded.end(), back_inserter(decoded));
+        const float *buffer = reinterpret_cast<const float *>(decoded.c_str());
+        size_t n = decoded.size() / sizeof(float);
+        return std::vector<float>(buffer, buffer + n);
+    }
+
+    static json11::Json
+    fromFeature(const Vamp::Plugin::Feature &f,
+                BufferSerialisation serialisation) {
+
+        json11::Json::object jo;
+        if (f.values.size() > 0) {
+            if (serialisation == BufferSerialisation::Array) {
+                jo["featureValues"] = json11::Json::array(f.values.begin(),
+                                                          f.values.end());
+            } else {
+                jo["featureValues"] = fromFloatBuffer(f.values.data(),
+                                                      f.values.size());
+            }
+        }
+        if (f.label != "") {
+            jo["label"] = f.label;
+        }
+        if (f.hasTimestamp) {
+            jo["timestamp"] = fromRealTime(f.timestamp);
+        }
+        if (f.hasDuration) {
+            jo["duration"] = fromRealTime(f.duration);
+        }
+        return json11::Json(jo);
+    }
+
+    static Vamp::Plugin::Feature
+    toFeature(json11::Json j, BufferSerialisation &serialisation, std::string &err) {
+
+        Vamp::Plugin::Feature f;
+        if (!j.is_object()) {
+            err = "object expected for feature";
+            return {};
+        }
+        if (j["timestamp"].is_object()) {
+            f.timestamp = toRealTime(j["timestamp"], err);
+            if (failed(err)) return {};
+            f.hasTimestamp = true;
+        }
+        if (j["duration"].is_object()) {
+            f.duration = toRealTime(j["duration"], err);
+            if (failed(err)) return {};
+            f.hasDuration = true;
+        }
+        if (j["featureValues"].is_string()) {
+            f.values = toFloatBuffer(j["featureValues"].string_value(), err);
+            if (failed(err)) return {};
+            serialisation = BufferSerialisation::Base64;
+        } else if (j["featureValues"].is_array()) {
+            for (auto v : j["featureValues"].array_items()) {
+                f.values.push_back(v.number_value());
+            }
+            serialisation = BufferSerialisation::Array;
+        }
+        f.label = j["label"].string_value();
+        return f;
+    }
+
+    static json11::Json
+    fromFeatureSet(const Vamp::Plugin::FeatureSet &fs,
+                   const PluginOutputIdMapper &omapper,
+                   BufferSerialisation serialisation) {
+
+        json11::Json::object jo;
+        for (const auto &fsi : fs) {
+            std::vector<json11::Json> fj;
+            for (const Vamp::Plugin::Feature &f: fsi.second) {
+                fj.push_back(fromFeature(f, serialisation));
+            }
+            jo[omapper.indexToId(fsi.first)] = fj;
+        }
+        return json11::Json(jo);
+    }
+
+    static Vamp::Plugin::FeatureList
+    toFeatureList(json11::Json j,
+                  BufferSerialisation &serialisation, std::string &err) {
+
+        Vamp::Plugin::FeatureList fl;
+        if (!j.is_array()) {
+            err = "array expected for feature list";
+            return {};
+        }
+        for (const json11::Json &fj : j.array_items()) {
+            fl.push_back(toFeature(fj, serialisation, err));
+            if (failed(err)) return {};
+        }
+        return fl;
+    }
+
+    static Vamp::Plugin::FeatureSet
+    toFeatureSet(json11::Json j,
+                 const PluginOutputIdMapper &omapper,
+                 BufferSerialisation &serialisation,
+                 std::string &err) {
+
+        Vamp::Plugin::FeatureSet fs;
+        if (!j.is_object()) {
+            err = "object expected for feature set";
+            return {};
+        }
+        for (auto &entry : j.object_items()) {
+            int n = omapper.idToIndex(entry.first);
+            if (fs.find(n) != fs.end()) {
+                err = "duplicate numerical index for output";
+                return {};
+            }
+            fs[n] = toFeatureList(entry.second, serialisation, err);
+            if (failed(err)) return {};
+        }
+        return fs;
+    }
+
+    static std::string
+    fromInputDomain(Vamp::Plugin::InputDomain domain) {
+
+        switch (domain) {
+        case Vamp::Plugin::TimeDomain:
+            return "TimeDomain";
+        case Vamp::Plugin::FrequencyDomain:
+            return "FrequencyDomain";
+        }
+        return "";
+    }
+
+    static Vamp::Plugin::InputDomain
+    toInputDomain(std::string text, std::string &err) {
+
+        if (text == "TimeDomain") {
+            return Vamp::Plugin::TimeDomain;
+        } else if (text == "FrequencyDomain") {
+            return Vamp::Plugin::FrequencyDomain;
+        } else {
+            err = "invalid input domain string: " + text;
+            return {};
+        }
+    }
+
+    static json11::Json
+    fromPluginStaticData(const Vamp::HostExt::PluginStaticData &d) {
+
+        json11::Json::object jo;
+        jo["key"] = d.pluginKey;
+        jo["basic"] = fromBasicDescriptor(d.basic);
+        jo["maker"] = d.maker;
+        jo["copyright"] = d.copyright;
+        jo["version"] = d.pluginVersion;
+
+        json11::Json::array cat;
+        for (const std::string &c: d.category) cat.push_back(c);
+        jo["category"] = cat;
+
+        jo["minChannelCount"] = d.minChannelCount;
+        jo["maxChannelCount"] = d.maxChannelCount;
+
+        json11::Json::array params;
+        Vamp::PluginBase::ParameterList vparams = d.parameters;
+        for (auto &p: vparams) params.push_back(fromParameterDescriptor(p));
+        jo["parameters"] = params;
+
+        json11::Json::array progs;
+        Vamp::PluginBase::ProgramList vprogs = d.programs;
+        for (auto &p: vprogs) progs.push_back(p);
+        jo["programs"] = progs;
+
+        jo["inputDomain"] = fromInputDomain(d.inputDomain);
+
+        json11::Json::array outinfo;
+        auto vouts = d.basicOutputInfo;
+        for (auto &o: vouts) outinfo.push_back(fromBasicDescriptor(o));
+        jo["basicOutputInfo"] = outinfo;
+    
+        return json11::Json(jo);
+    }
+
+    static Vamp::HostExt::PluginStaticData
+    toPluginStaticData(json11::Json j, std::string &err) {
+
+        if (!j.has_shape({
+                    { "key", json11::Json::STRING },
+                    { "version", json11::Json::NUMBER },
+                    { "minChannelCount", json11::Json::NUMBER },
+                    { "maxChannelCount", json11::Json::NUMBER },
+                    { "inputDomain", json11::Json::STRING }}, err)) {
+
+            err = "malformed plugin static data: " + err;
+
+        } else if (!j["basicOutputInfo"].is_array()) {
+
+            err = "array expected for basic output info";
+
+        } else if (!j["maker"].is_null() &&
+                   !j["maker"].is_string()) {
+
+            err = "string expected for maker";
+
+        } else if (!j["copyright"].is_null() &&
+                   !j["copyright"].is_string()) {
+            err = "string expected for copyright";
+
+        } else if (!j["category"].is_null() &&
+                   !j["category"].is_array()) {
+
+            err = "array expected for category";
+
+        } else if (!j["parameters"].is_null() &&
+                   !j["parameters"].is_array()) {
+
+            err = "array expected for parameters";
+
+        } else if (!j["programs"].is_null() &&
+                   !j["programs"].is_array()) {
+
+            err = "array expected for programs";
+
+        } else if (!j["inputDomain"].is_null() &&
+                   !j["inputDomain"].is_string()) {
+
+            err = "string expected for inputDomain";
+
+        } else if (!j["basicOutputInfo"].is_null() &&
+                   !j["basicOutputInfo"].is_array()) {
+            
+            err = "array expected for basicOutputInfo";
+
+        } else {
+
+            Vamp::HostExt::PluginStaticData psd;
+
+            psd.pluginKey = j["key"].string_value();
+
+            toBasicDescriptor(j["basic"], psd.basic, err);
+            if (failed(err)) return {};
+
+            psd.maker = j["maker"].string_value();
+            psd.copyright = j["copyright"].string_value();
+            psd.pluginVersion = j["version"].int_value();
+
+            for (const auto &c : j["category"].array_items()) {
+                if (!c.is_string()) {
+                    err = "strings expected in category array";
+                    return {};
+                }
+                psd.category.push_back(c.string_value());
+            }
+
+            psd.minChannelCount = j["minChannelCount"].int_value();
+            psd.maxChannelCount = j["maxChannelCount"].int_value();
+
+            for (const auto &p : j["parameters"].array_items()) {
+                auto pd = toParameterDescriptor(p, err);
+                if (failed(err)) return {};
+                psd.parameters.push_back(pd);
+            }
+
+            for (const auto &p : j["programs"].array_items()) {
+                if (!p.is_string()) {
+                    err = "strings expected in programs array";
+                    return {};
+                }
+                psd.programs.push_back(p.string_value());
+            }
+
+            psd.inputDomain = toInputDomain(j["inputDomain"].string_value(), err);
+            if (failed(err)) return {};
+
+            for (const auto &bo : j["basicOutputInfo"].array_items()) {
+                Vamp::HostExt::PluginStaticData::Basic b;
+                toBasicDescriptor(bo, b, err);
+                if (failed(err)) return {};
+                psd.basicOutputInfo.push_back(b);
+            }
+            
+            return psd;
+        }
+
+        // fallthrough error case
+        return {};
+    }
+
+    static json11::Json
+    fromPluginConfiguration(const Vamp::HostExt::PluginConfiguration &c) {
+
+        json11::Json::object jo;
+
+        json11::Json::object paramValues;
+        for (auto &vp: c.parameterValues) {
+            paramValues[vp.first] = vp.second;
+        }
+        jo["parameterValues"] = paramValues;
+
+        if (c.currentProgram != "") {
+            jo["currentProgram"] = c.currentProgram;
+        }
+
+        jo["channelCount"] = c.channelCount;
+        jo["stepSize"] = c.stepSize;
+        jo["blockSize"] = c.blockSize;
+    
+        return json11::Json(jo);
+    }
+
+    static Vamp::HostExt::PluginConfiguration
+    toPluginConfiguration(json11::Json j, std::string &err) {
+        
+        if (!j.has_shape({
+                    { "channelCount", json11::Json::NUMBER },
+                    { "stepSize", json11::Json::NUMBER },
+                    { "blockSize", json11::Json::NUMBER } }, err)) {
+            err = "malformed plugin configuration: " + err;
+            return {};
+        }
+
+        if (!j["parameterValues"].is_null() &&
+            !j["parameterValues"].is_object()) {
+            err = "object expected for parameter values";
+            return {};
+        }
+
+        for (auto &pv : j["parameterValues"].object_items()) {
+            if (!pv.second.is_number()) {
+                err = "number expected for parameter value";
+                return {};
+            }
+        }
+    
+        if (!j["currentProgram"].is_null() &&
+            !j["currentProgram"].is_string()) {
+            err = "string expected for program name";
+            return {};
+        }
+
+        Vamp::HostExt::PluginConfiguration config;
+
+        config.channelCount = j["channelCount"].number_value();
+        config.stepSize = j["stepSize"].number_value();
+        config.blockSize = j["blockSize"].number_value();
+        
+        for (auto &pv : j["parameterValues"].object_items()) {
+            config.parameterValues[pv.first] = pv.second.number_value();
+        }
+
+        if (j["currentProgram"].is_string()) {
+            config.currentProgram = j["currentProgram"].string_value();
+        }
+
+        return config;
+    }
+
+    static json11::Json
+    fromAdapterFlags(int flags) {
+
+        json11::Json::array arr;
+
+        if (flags & Vamp::HostExt::PluginLoader::ADAPT_INPUT_DOMAIN) {
+            arr.push_back("AdaptInputDomain");
+        }
+        if (flags & Vamp::HostExt::PluginLoader::ADAPT_CHANNEL_COUNT) {
+            arr.push_back("AdaptChannelCount");
+        }
+        if (flags & Vamp::HostExt::PluginLoader::ADAPT_BUFFER_SIZE) {
+            arr.push_back("AdaptBufferSize");
+        }
+
+        return json11::Json(arr);
+    }
+
+    static Vamp::HostExt::PluginLoader::AdapterFlags
+    toAdapterFlags(json11::Json j, std::string &err) {
+
+        int flags = 0x0;
+
+        if (!j.is_array()) {
+
+            err = "array expected for adapter flags";
+
+        } else {
+
+            for (auto &jj: j.array_items()) {
+                if (!jj.is_string()) {
+                    err = "string expected for adapter flag";
+                    break;
+                }
+                std::string text = jj.string_value();
+                if (text == "AdaptInputDomain") {
+                    flags |= Vamp::HostExt::PluginLoader::ADAPT_INPUT_DOMAIN;
+                } else if (text == "AdaptChannelCount") {
+                    flags |= Vamp::HostExt::PluginLoader::ADAPT_CHANNEL_COUNT;
+                } else if (text == "AdaptBufferSize") {
+                    flags |= Vamp::HostExt::PluginLoader::ADAPT_BUFFER_SIZE;
+                } else if (text == "AdaptAllSafe") {
+                    flags |= Vamp::HostExt::PluginLoader::ADAPT_ALL_SAFE;
+                } else if (text == "AdaptAll") {
+                    flags |= Vamp::HostExt::PluginLoader::ADAPT_ALL;
+                } else {
+                    err = "invalid adapter flag string: " + text;
+                    break;
+                }
+            }
+        }
+
+        return Vamp::HostExt::PluginLoader::AdapterFlags(flags);
+    }
+
+    static json11::Json
+    fromLoadRequest(const Vamp::HostExt::LoadRequest &req) {
+
+        json11::Json::object jo;
+        jo["key"] = req.pluginKey;
+        jo["inputSampleRate"] = req.inputSampleRate;
+        jo["adapterFlags"] = fromAdapterFlags(req.adapterFlags);
+        return json11::Json(jo);
+    }
+
+    static Vamp::HostExt::LoadRequest
+    toLoadRequest(json11::Json j, std::string &err) {
+        
+        if (!j.has_shape({
+                    { "key", json11::Json::STRING },
+                    { "inputSampleRate", json11::Json::NUMBER } }, err)) {
+            err = "malformed load request: " + err;
+            return {};
+        }
+    
+        Vamp::HostExt::LoadRequest req;
+        req.pluginKey = j["key"].string_value();
+        req.inputSampleRate = j["inputSampleRate"].number_value();
+        if (!j["adapterFlags"].is_null()) {
+            req.adapterFlags = toAdapterFlags(j["adapterFlags"], err);
+            if (failed(err)) return {};
+        }
+        return req;
+    }
+
+    static json11::Json
+    fromLoadResponse(const Vamp::HostExt::LoadResponse &resp,
+                     const PluginHandleMapper &pmapper) {
+
+        json11::Json::object jo;
+        jo["handle"] = double(pmapper.pluginToHandle(resp.plugin));
+        jo["staticData"] = fromPluginStaticData(resp.staticData);
+        jo["defaultConfiguration"] =
+            fromPluginConfiguration(resp.defaultConfiguration);
+        return json11::Json(jo);
+    }
+
+    static Vamp::HostExt::LoadResponse
+    toLoadResponse(json11::Json j,
+                   const PluginHandleMapper &pmapper, std::string &err) {
+
+        if (!j.has_shape({
+                    { "handle", json11::Json::NUMBER },
+                    { "staticData", json11::Json::OBJECT },
+                    { "defaultConfiguration", json11::Json::OBJECT } }, err)) {
+            err = "malformed load response: " + err;
+            return {};
+        }
+
+        Vamp::HostExt::LoadResponse resp;
+        resp.plugin = pmapper.handleToPlugin(j["handle"].int_value());
+        resp.staticData = toPluginStaticData(j["staticData"], err);
+        if (failed(err)) return {};
+        resp.defaultConfiguration = toPluginConfiguration(j["defaultConfiguration"],
+                                                          err);
+        if (failed(err)) return {};
+        return resp;
+    }
+
+    static json11::Json
+    fromConfigurationRequest(const Vamp::HostExt::ConfigurationRequest &cr,
+                             const PluginHandleMapper &pmapper) {
+
+        json11::Json::object jo;
+
+        jo["handle"] = pmapper.pluginToHandle(cr.plugin);
+        jo["configuration"] = fromPluginConfiguration(cr.configuration);
+        
+        return json11::Json(jo);
+    }
+
+    static Vamp::HostExt::ConfigurationRequest
+    toConfigurationRequest(json11::Json j,
+                           const PluginHandleMapper &pmapper, std::string &err) {
+
+        if (!j.has_shape({
+                    { "handle", json11::Json::NUMBER },
+                    { "configuration", json11::Json::OBJECT } }, err)) {
+            err = "malformed configuration request: " + err;
+            return {};
+        }
+
+        Vamp::HostExt::ConfigurationRequest cr;
+        cr.plugin = pmapper.handleToPlugin(j["handle"].int_value());
+        cr.configuration = toPluginConfiguration(j["configuration"], err);
+        if (failed(err)) return {};
+        return cr;
+    }
+
+    static json11::Json
+    fromConfigurationResponse(const Vamp::HostExt::ConfigurationResponse &cr,
+                              const PluginHandleMapper &pmapper) {
+
+        json11::Json::object jo;
+
+        jo["handle"] = pmapper.pluginToHandle(cr.plugin);
+        
+        json11::Json::array outs;
+        for (auto &d: cr.outputs) {
+            outs.push_back(fromOutputDescriptor(d));
+        }
+        jo["outputList"] = outs;
+        
+        return json11::Json(jo);
+    }
+
+    static Vamp::HostExt::ConfigurationResponse
+    toConfigurationResponse(json11::Json j,
+                            const PluginHandleMapper &pmapper, std::string &err) {
+        
+        Vamp::HostExt::ConfigurationResponse cr;
+
+        cr.plugin = pmapper.handleToPlugin(j["handle"].int_value());
+        
+        if (!j["outputList"].is_array()) {
+            err = "array expected for output list";
+            return {};
+        }
+
+        for (const auto &o: j["outputList"].array_items()) {
+            cr.outputs.push_back(toOutputDescriptor(o, err));
+            if (failed(err)) return {};
+        }
+
+        return cr;
+    }
+
+    static json11::Json
+    fromProcessRequest(const Vamp::HostExt::ProcessRequest &r,
+                       const PluginHandleMapper &pmapper,
+                       BufferSerialisation serialisation) {
+
+        json11::Json::object jo;
+        jo["handle"] = pmapper.pluginToHandle(r.plugin);
+
+        json11::Json::object io;
+        io["timestamp"] = fromRealTime(r.timestamp);
+
+        json11::Json::array chans;
+        for (size_t i = 0; i < r.inputBuffers.size(); ++i) {
+            if (serialisation == BufferSerialisation::Array) {
+                chans.push_back(json11::Json::array(r.inputBuffers[i].begin(),
+                                                    r.inputBuffers[i].end()));
+            } else {
+                chans.push_back(fromFloatBuffer(r.inputBuffers[i].data(),
+                                                r.inputBuffers[i].size()));
+            }
+        }
+        io["inputBuffers"] = chans;
+        
+        jo["processInput"] = io;
+        return json11::Json(jo);
+    }
+
+    static Vamp::HostExt::ProcessRequest
+    toProcessRequest(json11::Json j,
+                     const PluginHandleMapper &pmapper,
+                     BufferSerialisation &serialisation, std::string &err) {
+
+        if (!j.has_shape({
+                    { "handle", json11::Json::NUMBER },
+                    { "processInput", json11::Json::OBJECT } }, err)) {
+            err = "malformed process request: " + err;
+            return {};
+        }
+
+        auto input = j["processInput"];
+
+        if (!input.has_shape({
+                    { "timestamp", json11::Json::OBJECT },
+                    { "inputBuffers", json11::Json::ARRAY } }, err)) {
+            err = "malformed process request: " + err;
+            return {};
+        }
+
+        Vamp::HostExt::ProcessRequest r;
+        r.plugin = pmapper.handleToPlugin(j["handle"].int_value());
+
+        r.timestamp = toRealTime(input["timestamp"], err);
+        if (failed(err)) return {};
+
+        for (const auto &a: input["inputBuffers"].array_items()) {
+
+            if (a.is_string()) {
+                std::vector<float> buf = toFloatBuffer(a.string_value(),
+                                                       err);
+                if (failed(err)) return {};
+                r.inputBuffers.push_back(buf);
+                serialisation = BufferSerialisation::Base64;
+
+            } else if (a.is_array()) {
+                std::vector<float> buf;
+                for (auto v : a.array_items()) {
+                    buf.push_back(v.number_value());
+                }
+                r.inputBuffers.push_back(buf);
+                serialisation = BufferSerialisation::Array;
+
+            } else {
+                err = "expected arrays or strings in inputBuffers array";
+                return {};
+            }
+        }
+
+        return r;
+    }
+    
+private: // go private briefly for a couple of helper functions
+    
+    static void
+    checkTypeField(json11::Json j, std::string expected, std::string &err) {
+        if (!j["method"].is_string()) {
+            err = "string expected for method";
+            return;
+        }
+        if (j["method"].string_value() != expected) {
+            err = "expected value \"" + expected + "\" for type";
+            return;
+        }
+    }
+
+    static bool
+    successful(json11::Json j, std::string &err) {
+        if (!j["success"].is_bool()) {
+            err = "bool expected for success";
+            return false;
+        }
+        return j["success"].bool_value();
+    }
+
+    static void
+    markRPC(json11::Json::object &jo) {
+        jo["jsonrpc"] = "2.0";
+    }
+
+    static void
+    addId(json11::Json::object &jo, const json11::Json &id) {
+        if (!id.is_null()) {
+            jo["id"] = id;
+        }
+    }
+    
+public:
+
+    static json11::Json
+    fromRpcRequest_List(const json11::Json &id) {
+
+        json11::Json::object jo;
+        markRPC(jo);
+
+        jo["method"] = "list";
+        addId(jo, id);
+        return json11::Json(jo);
+    }
+
+    static json11::Json
+    fromRpcResponse_List(const Vamp::HostExt::ListResponse &resp,
+                         const json11::Json &id) {
+
+        json11::Json::object jo;
+        markRPC(jo);
+
+        json11::Json::array arr;
+        for (const auto &a: resp.available) {
+            arr.push_back(fromPluginStaticData(a));
+        }
+        json11::Json::object po;
+        po["available"] = arr;
+
+        jo["method"] = "list";
+        jo["result"] = po;
+        addId(jo, id);
+        return json11::Json(jo);
+    }
+    
+    static json11::Json
+    fromRpcRequest_Load(const Vamp::HostExt::LoadRequest &req,
+                        const json11::Json &id) {
+
+        json11::Json::object jo;
+        markRPC(jo);
+
+        jo["method"] = "load";
+        jo["params"] = fromLoadRequest(req);
+        addId(jo, id);
+        return json11::Json(jo);
+    }    
+
+    static json11::Json
+    fromRpcResponse_Load(const Vamp::HostExt::LoadResponse &resp,
+                         const PluginHandleMapper &pmapper,
+                         const json11::Json &id) {
+
+        if (resp.plugin) {
+
+            json11::Json::object jo;
+            markRPC(jo);
+
+            jo["method"] = "load";
+            jo["result"] = fromLoadResponse(resp, pmapper);
+            addId(jo, id);
+            return json11::Json(jo);
+            
+        } else {
+            return fromError("Failed to load plugin", RRType::Load, id);
+        }
+    }
+
+    static json11::Json
+    fromRpcRequest_Configure(const Vamp::HostExt::ConfigurationRequest &req,
+                             const PluginHandleMapper &pmapper,
+                             const json11::Json &id) {
+
+        json11::Json::object jo;
+        markRPC(jo);
+
+        jo["method"] = "configure";
+        jo["params"] = fromConfigurationRequest(req, pmapper);
+        addId(jo, id);
+        return json11::Json(jo);
+    }    
+
+    static json11::Json
+    fromRpcResponse_Configure(const Vamp::HostExt::ConfigurationResponse &resp,
+                              const PluginHandleMapper &pmapper,
+                              const json11::Json &id) {
+
+        if (!resp.outputs.empty()) {
+        
+            json11::Json::object jo;
+            markRPC(jo);
+
+            jo["method"] = "configure";
+            jo["result"] = fromConfigurationResponse(resp, pmapper);
+            addId(jo, id);
+            return json11::Json(jo);
+
+        } else {
+            return fromError("Failed to configure plugin", RRType::Configure, id);
+        }
+    }
+    
+    static json11::Json
+    fromRpcRequest_Process(const Vamp::HostExt::ProcessRequest &req,
+                           const PluginHandleMapper &pmapper,
+                           BufferSerialisation serialisation,
+                           const json11::Json &id) {
+
+        json11::Json::object jo;
+        markRPC(jo);
+
+        jo["method"] = "process";
+        jo["params"] = fromProcessRequest(req, pmapper, serialisation);
+        addId(jo, id);
+        return json11::Json(jo);
+    }    
+
+    static json11::Json
+    fromRpcResponse_Process(const Vamp::HostExt::ProcessResponse &resp,
+                            const PluginHandleMapper &pmapper,
+                            BufferSerialisation serialisation,
+                            const json11::Json &id) {
+        
+        json11::Json::object jo;
+        markRPC(jo);
+
+        json11::Json::object po;
+        po["handle"] = pmapper.pluginToHandle(resp.plugin);
+        po["features"] = fromFeatureSet(resp.features,
+                                        *pmapper.pluginToOutputIdMapper(resp.plugin),
+                                        serialisation);
+        jo["method"] = "process";
+        jo["result"] = po;
+        addId(jo, id);
+        return json11::Json(jo);
+    }
+    
+    static json11::Json
+    fromRpcRequest_Finish(const Vamp::HostExt::FinishRequest &req,
+                          const PluginHandleMapper &pmapper,
+                          const json11::Json &id) {
+
+        json11::Json::object jo;
+        markRPC(jo);
+
+        json11::Json::object fo;
+        fo["handle"] = pmapper.pluginToHandle(req.plugin);
+
+        jo["method"] = "finish";
+        jo["params"] = fo;
+        addId(jo, id);
+        return json11::Json(jo);
+    }    
+    
+    static json11::Json
+    fromRpcResponse_Finish(const Vamp::HostExt::ProcessResponse &resp,
+                           const PluginHandleMapper &pmapper,
+                           BufferSerialisation serialisation,
+                           const json11::Json &id) {
+
+        json11::Json::object jo;
+        markRPC(jo);
+
+        json11::Json::object po;
+        po["handle"] = pmapper.pluginToHandle(resp.plugin);
+        po["features"] = fromFeatureSet(resp.features,
+                                        *pmapper.pluginToOutputIdMapper(resp.plugin),
+                                        serialisation);
+        jo["method"] = "finish";
+        jo["result"] = po;
+        addId(jo, id);
+        return json11::Json(jo);
+    }
+
+    static json11::Json
+    fromError(std::string errorText,
+              RRType responseType,
+              const json11::Json &id) {
+
+        json11::Json::object jo;
+        markRPC(jo);
+
+        std::string type;
+
+        if (responseType == RRType::List) type = "list";
+        else if (responseType == RRType::Load) type = "load";
+        else if (responseType == RRType::Configure) type = "configure";
+        else if (responseType == RRType::Process) type = "process";
+        else if (responseType == RRType::Finish) type = "finish";
+        else type = "invalid";
+
+        json11::Json::object eo;
+        eo["code"] = 0;
+        eo["message"] = 
+            std::string("error in ") + type + " request: " + errorText;
+
+        jo["method"] = type;
+        jo["error"] = eo;
+        addId(jo, id);
+        return json11::Json(jo);
+    }
+
+    static RRType
+    getRequestResponseType(json11::Json j, std::string &err) {
+
+        if (!j["method"].is_string()) {
+            err = "string expected for method";
+            return RRType::NotValid;
+        }
+        
+        std::string type = j["method"].string_value();
+
+	if (type == "list") return RRType::List;
+	else if (type == "load") return RRType::Load;
+	else if (type == "configure") return RRType::Configure;
+	else if (type == "process") return RRType::Process;
+	else if (type == "finish") return RRType::Finish;
+        else if (type == "invalid") return RRType::NotValid;
+	else {
+	    err = "unknown or unexpected request/response type \"" + type + "\"";
+            return RRType::NotValid;
+	}
+    }
+
+    static void
+    toRpcRequest_List(json11::Json j, std::string &err) {
+        checkTypeField(j, "list", err);
+    }
+
+    static Vamp::HostExt::ListResponse
+    toRpcResponse_List(json11::Json j, std::string &err) {
+
+        Vamp::HostExt::ListResponse resp;
+        if (successful(j, err) && !failed(err)) {
+            for (const auto &a: j["result"]["available"].array_items()) {
+                resp.available.push_back(toPluginStaticData(a, err));
+                if (failed(err)) return {};
+            }
+        }
+        
+        return resp;
+    }
+
+    static Vamp::HostExt::LoadRequest
+    toRpcRequest_Load(json11::Json j, std::string &err) {
+        
+        checkTypeField(j, "load", err);
+        if (failed(err)) return {};
+        return toLoadRequest(j["params"], err);
+    }
+    
+    static Vamp::HostExt::LoadResponse
+    toRpcResponse_Load(json11::Json j,
+                        const PluginHandleMapper &pmapper,
+                        std::string &err) {
+        
+        Vamp::HostExt::LoadResponse resp;
+        if (successful(j, err) && !failed(err)) {
+            resp = toLoadResponse(j["result"], pmapper, err);
+        }
+        return resp;
+    }
+    
+    static Vamp::HostExt::ConfigurationRequest
+    toRpcRequest_Configure(json11::Json j,
+                            const PluginHandleMapper &pmapper,
+                            std::string &err) {
+        
+        checkTypeField(j, "configure", err);
+        if (failed(err)) return {};
+        return toConfigurationRequest(j["params"], pmapper, err);
+    }
+    
+    static Vamp::HostExt::ConfigurationResponse
+    toRpcResponse_Configure(json11::Json j,
+                             const PluginHandleMapper &pmapper,
+                             std::string &err) {
+        
+        Vamp::HostExt::ConfigurationResponse resp;
+        if (successful(j, err) && !failed(err)) {
+            resp = toConfigurationResponse(j["result"], pmapper, err);
+        }
+        return resp;
+    }
+    
+    static Vamp::HostExt::ProcessRequest
+    toRpcRequest_Process(json11::Json j, const PluginHandleMapper &pmapper,
+                          BufferSerialisation &serialisation, std::string &err) {
+        
+        checkTypeField(j, "process", err);
+        if (failed(err)) return {};
+        return toProcessRequest(j["params"], pmapper, serialisation, err);
+    }
+    
+    static Vamp::HostExt::ProcessResponse
+    toRpcResponse_Process(json11::Json j,
+                           const PluginHandleMapper &pmapper,
+                           BufferSerialisation &serialisation, std::string &err) {
+        
+        Vamp::HostExt::ProcessResponse resp;
+        if (successful(j, err) && !failed(err)) {
+            auto jc = j["result"];
+            auto h = jc["handle"].int_value();
+            resp.plugin = pmapper.handleToPlugin(h);
+            resp.features = toFeatureSet(jc["features"],
+                                         *pmapper.handleToOutputIdMapper(h),
+                                         serialisation, err);
+        }
+        return resp;
+    }
+    
+    static Vamp::HostExt::FinishRequest
+    toRpcRequest_Finish(json11::Json j, const PluginHandleMapper &pmapper,
+                         std::string &err) {
+        
+        checkTypeField(j, "finish", err);
+        if (failed(err)) return {};
+        Vamp::HostExt::FinishRequest req;
+        req.plugin = pmapper.handleToPlugin
+            (j["params"]["handle"].int_value());
+        return req;
+    }
+    
+    static Vamp::HostExt::ProcessResponse
+    toRpcResponse_Finish(json11::Json j,
+                          const PluginHandleMapper &pmapper,
+                          BufferSerialisation &serialisation, std::string &err) {
+        
+        Vamp::HostExt::ProcessResponse resp;
+        if (successful(j, err) && !failed(err)) {
+            auto jc = j["result"];
+            auto h = jc["handle"].int_value();
+            resp.plugin = pmapper.handleToPlugin(h);
+            resp.features = toFeatureSet(jc["features"],
+                                         *pmapper.handleToOutputIdMapper(h),
+                                         serialisation, err);
+        }
+        return resp;
+    }
+};
+
+}
+
+#endif