comparison osx/include/capnp/compat/json.h @ 62:0994c39f1e94

Cap'n Proto v0.6 + build for OSX

+// Copyright (c) 2015 Sandstorm Development Group, Inc. and contributors
+// Licensed under the MIT License:
+//
+// 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.
+
+#ifndef CAPNP_COMPAT_JSON_H_
+#define CAPNP_COMPAT_JSON_H_
+
+#include <capnp/schema.h>
+#include <capnp/dynamic.h>
+#include <capnp/compat/json.capnp.h>
+
+namespace capnp {
+
+class JsonCodec {
+  // Flexible class for encoding Cap'n Proto types as JSON, and decoding JSON back to Cap'n Proto.
+  //
+  // Typical usage:
+  //
+  //     JsonCodec json;
+  //
+  //     // encode
+  //     kj::String encoded = json.encode(someStructReader);
+  //
+  //     // decode
+  //     json.decode(encoded, someStructBuilder);
+  //
+  // Advanced users can do fancy things like override the way certain types or fields are
+  // represented in JSON by registering handlers. See the unit test for an example.
+  //
+  // Notes:
+  // - When encoding, all primitive fields are always encoded, even if default-valued. Pointer
+  //   fields are only encoded if they are non-null.
+  // - 64-bit integers are encoded as strings, since JSON "numbers" are double-precision floating
+  //   points which cannot store a 64-bit integer without losing data.
+  // - NaNs and infinite floating point numbers are not allowed by the JSON spec, and so are encoded
+  //   as null. This matches the behavior of `JSON.stringify` in at least Firefox and Chrome.
+  // - Data is encoded as an array of numbers in the range [0,255]. You probably want to register
+  //   a handler that does something better, like maybe base64 encoding, but there are a zillion
+  //   different ways people do this.
+  // - Encoding/decoding capabilities and AnyPointers requires registering a Handler, since there's
+  //   no obvious default behavior.
+  // - When decoding, unrecognized field names are ignored. Note: This means that JSON is NOT a
+  //   good format for receiving input from a human. Consider `capnp eval` or the SchemaParser
+  //   library for human input.
+
+public:
+  JsonCodec();
+  ~JsonCodec() noexcept(false);
+
+  // ---------------------------------------------------------------------------
+  // standard API
+
+  void setPrettyPrint(bool enabled);
+  // Enable to insert newlines, indentation, and other extra spacing into the output. The default
+  // is to use minimal whitespace.
+
+  void setMaxNestingDepth(size_t maxNestingDepth);
+  // Set maximum nesting depth when decoding JSON to prevent highly nested input from overflowing
+  // the call stack. The default is 64.
+
+  template <typename T>
+  kj::String encode(T&& value);
+  // Encode any Cap'n Proto value to JSON, including primitives and
+  // Dynamic{Enum,Struct,List,Capability}, but not DynamicValue (see below).
+
+  kj::String encode(DynamicValue::Reader value, Type type) const;
+  // Encode a DynamicValue to JSON. `type` is needed because `DynamicValue` itself does
+  // not distinguish between e.g. int32 and int64, which in JSON are handled differently. Most
+  // of the time, though, you can use the single-argument templated version of `encode()` instead.
+
+  void decode(kj::ArrayPtr<const char> input, DynamicStruct::Builder output) const;
+  // Decode JSON text directly into a struct builder. This only works for structs since lists
+  // need to be allocated with the correct size in advance.
+  //
+  // (Remember that any Cap'n Proto struct reader type can be implicitly cast to
+  // DynamicStruct::Reader.)
+
+  template <typename T>
+  Orphan<T> decode(kj::ArrayPtr<const char> input, Orphanage orphanage) const;
+  // Decode JSON text to any Cap'n Proto object (pointer value), allocated using the given
+  // orphanage. T must be specified explicitly and cannot be dynamic, e.g.:
+  //
+  //     Orphan<MyType> orphan = json.decode<MyType>(text, orphanage);
+
+  template <typename T>
+  ReaderFor<T> decode(kj::ArrayPtr<const char> input) const;
+  // Decode JSON text into a primitive or capability value. T must be specified explicitly and
+  // cannot be dynamic, e.g.:
+  //
+  //     uint32_t n = json.decode<uint32_t>(text);
+
+  Orphan<DynamicValue> decode(kj::ArrayPtr<const char> input, Type type, Orphanage orphanage) const;
+  Orphan<DynamicList> decode(
+      kj::ArrayPtr<const char> input, ListSchema type, Orphanage orphanage) const;
+  Orphan<DynamicStruct> decode(
+      kj::ArrayPtr<const char> input, StructSchema type, Orphanage orphanage) const;
+  DynamicCapability::Client decode(kj::ArrayPtr<const char> input, InterfaceSchema type) const;
+  DynamicEnum decode(kj::ArrayPtr<const char> input, EnumSchema type) const;
+  // Decode to a dynamic value, specifying the type schema.
+
+  // ---------------------------------------------------------------------------
+  // layered API
+  //
+  // You can separate text <-> JsonValue from JsonValue <-> T. These are particularly useful
+  // for calling from Handler implementations.
+
+  kj::String encodeRaw(JsonValue::Reader value) const;
+  void decodeRaw(kj::ArrayPtr<const char> input, JsonValue::Builder output) const;
+  // Translate JsonValue <-> text.
+
+  template <typename T>
+  void encode(T&& value, JsonValue::Builder output);
+  void encode(DynamicValue::Reader input, Type type, JsonValue::Builder output) const;
+  void decode(JsonValue::Reader input, DynamicStruct::Builder output) const;
+  template <typename T>
+  Orphan<T> decode(JsonValue::Reader input, Orphanage orphanage) const;
+  template <typename T>
+  ReaderFor<T> decode(JsonValue::Reader input) const;
+
+  Orphan<DynamicValue> decode(JsonValue::Reader input, Type type, Orphanage orphanage) const;
+  Orphan<DynamicList> decode(JsonValue::Reader input, ListSchema type, Orphanage orphanage) const;
+  Orphan<DynamicStruct> decode(
+      JsonValue::Reader input, StructSchema type, Orphanage orphanage) const;
+  DynamicCapability::Client decode(JsonValue::Reader input, InterfaceSchema type) const;
+  DynamicEnum decode(JsonValue::Reader input, EnumSchema type) const;
+
+  // ---------------------------------------------------------------------------
+  // specializing particular types
+
+  template <typename T, Style s = style<T>()>
+  class Handler;
+  // Implement this interface to specify a special encoding for a particular type or field.
+  //
+  // The templates are a bit ugly, but subclasses of this type essentially implement two methods,
+  // one to encode values of this type and one to decode values of this type. `encode()` is simple:
+  //
+  //   void encode(const JsonCodec& codec, ReaderFor<T> input, JsonValue::Builder output) const;
+  //
+  // `decode()` is a bit trickier. When T is a struct (including DynamicStruct), it is:
+  //
+  //   void decode(const JsonCodec& codec, JsonValue::Reader input, BuilderFor<T> output) const;
+  //
+  // However, when T is a primitive, decode() is:
+  //
+  //   T decode(const JsonCodec& codec, JsonValue::Reader input) const;
+  //
+  // Or when T is any non-struct object (list, blob), decode() is:
+  //
+  //   Orphan<T> decode(const JsonCodec& codec, JsonValue::Reader input, Orphanage orphanage) const;
+  //
+  // Or when T is an interface:
+  //
+  //   T::Client decode(const JsonCodec& codec, JsonValue::Reader input) const;
+  //
+  // Additionally, when T is a struct you can *optionally* also implement the orphan-returning form
+  // of decode(), but it will only be called when the struct would be allocated as an individual
+  // object, not as part of a list. This allows you to return "nullptr" in these cases to say that
+  // the pointer value should be null. This does not apply to list elements because struct list
+  // elements cannot ever be null (since Cap'n Proto encodes struct lists as a flat list rather
+  // than list-of-pointers).
+
+  template <typename T>
+  void addTypeHandler(Handler<T>& handler);
+  void addTypeHandler(Type type, Handler<DynamicValue>& handler);
+  void addTypeHandler(EnumSchema type, Handler<DynamicEnum>& handler);
+  void addTypeHandler(StructSchema type, Handler<DynamicStruct>& handler);
+  void addTypeHandler(ListSchema type, Handler<DynamicList>& handler);
+  void addTypeHandler(InterfaceSchema type, Handler<DynamicCapability>& handler);
+  // Arrange that whenever the type T appears in the message, your handler will be used to
+  // encode/decode it.
+  //
+  // Note that if you register a handler for a capability type, it will also apply to subtypes.
+  // Thus Handler<Capability> handles all capabilities.
+
+  template <typename T>
+  void addFieldHandler(StructSchema::Field field, Handler<T>& handler);
+  // Matches only the specific field. T can be a dynamic type. T must match the field's type.
+
+private:
+  class HandlerBase;
+  struct Impl;
+
+  kj::Own<Impl> impl;
+
+  void encodeField(StructSchema::Field field, DynamicValue::Reader input,
+                   JsonValue::Builder output) const;
+  void decodeArray(List<JsonValue>::Reader input, DynamicList::Builder output) const;
+  void decodeObject(List<JsonValue::Field>::Reader input, DynamicStruct::Builder output) const;
+  void addTypeHandlerImpl(Type type, HandlerBase& handler);
+  void addFieldHandlerImpl(StructSchema::Field field, Type type, HandlerBase& handler);
+};
+
+// =======================================================================================
+// inline implementation details
+
+template <typename T>
+kj::String JsonCodec::encode(T&& value) {
+  typedef FromAny<kj::Decay<T>> Base;
+  return encode(DynamicValue::Reader(ReaderFor<Base>(kj::fwd<T>(value))), Type::from<Base>());
+}
+
+template <typename T>
+inline Orphan<T> JsonCodec::decode(kj::ArrayPtr<const char> input, Orphanage orphanage) const {
+  return decode(input, Type::from<T>(), orphanage).template releaseAs<T>();
+}
+
+template <typename T>
+inline ReaderFor<T> JsonCodec::decode(kj::ArrayPtr<const char> input) const {
+  static_assert(style<T>() == Style::PRIMITIVE || style<T>() == Style::CAPABILITY,
+                "must specify an orphanage to decode an object type");
+  return decode(input, Type::from<T>(), Orphanage()).getReader().template as<T>();
+}
+
+inline Orphan<DynamicList> JsonCodec::decode(
+    kj::ArrayPtr<const char> input, ListSchema type, Orphanage orphanage) const {
+  return decode(input, Type(type), orphanage).releaseAs<DynamicList>();
+}
+inline Orphan<DynamicStruct> JsonCodec::decode(
+    kj::ArrayPtr<const char> input, StructSchema type, Orphanage orphanage) const {
+  return decode(input, Type(type), orphanage).releaseAs<DynamicStruct>();
+}
+inline DynamicCapability::Client JsonCodec::decode(
+    kj::ArrayPtr<const char> input, InterfaceSchema type) const {
+  return decode(input, Type(type), Orphanage()).getReader().as<DynamicCapability>();
+}
+inline DynamicEnum JsonCodec::decode(kj::ArrayPtr<const char> input, EnumSchema type) const {
+  return decode(input, Type(type), Orphanage()).getReader().as<DynamicEnum>();
+}
+
+// -----------------------------------------------------------------------------
+
+template <typename T>
+void JsonCodec::encode(T&& value, JsonValue::Builder output) {
+  typedef FromAny<kj::Decay<T>> Base;
+  encode(DynamicValue::Reader(ReaderFor<Base>(kj::fwd<T>(value))), Type::from<Base>(), output);
+}
+
+template <typename T>
+inline Orphan<T> JsonCodec::decode(JsonValue::Reader input, Orphanage orphanage) const {
+  return decode(input, Type::from<T>(), orphanage).template releaseAs<T>();
+}
+
+template <typename T>
+inline ReaderFor<T> JsonCodec::decode(JsonValue::Reader input) const {
+  static_assert(style<T>() == Style::PRIMITIVE || style<T>() == Style::CAPABILITY,
+                "must specify an orphanage to decode an object type");
+  return decode(input, Type::from<T>(), Orphanage()).getReader().template as<T>();
+}
+
+inline Orphan<DynamicList> JsonCodec::decode(
+    JsonValue::Reader input, ListSchema type, Orphanage orphanage) const {
+  return decode(input, Type(type), orphanage).releaseAs<DynamicList>();
+}
+inline Orphan<DynamicStruct> JsonCodec::decode(
+    JsonValue::Reader input, StructSchema type, Orphanage orphanage) const {
+  return decode(input, Type(type), orphanage).releaseAs<DynamicStruct>();
+}
+inline DynamicCapability::Client JsonCodec::decode(
+    JsonValue::Reader input, InterfaceSchema type) const {
+  return decode(input, Type(type), Orphanage()).getReader().as<DynamicCapability>();
+}
+inline DynamicEnum JsonCodec::decode(JsonValue::Reader input, EnumSchema type) const {
+  return decode(input, Type(type), Orphanage()).getReader().as<DynamicEnum>();
+}
+
+// -----------------------------------------------------------------------------
+
+class JsonCodec::HandlerBase {
+  // Internal helper; ignore.
+public:
+  virtual void encodeBase(const JsonCodec& codec, DynamicValue::Reader input,
+                          JsonValue::Builder output) const = 0;
+  virtual Orphan<DynamicValue> decodeBase(const JsonCodec& codec, JsonValue::Reader input,
+                                          Type type, Orphanage orphanage) const;
+  virtual void decodeStructBase(const JsonCodec& codec, JsonValue::Reader input,
+                                DynamicStruct::Builder output) const;
+};
+
+template <typename T>
+class JsonCodec::Handler<T, Style::POINTER>: private JsonCodec::HandlerBase {
+public:
+  virtual void encode(const JsonCodec& codec, ReaderFor<T> input,
+                      JsonValue::Builder output) const = 0;
+  virtual Orphan<T> decode(const JsonCodec& codec, JsonValue::Reader input,
+                           Orphanage orphanage) const = 0;
+
+private:
+  void encodeBase(const JsonCodec& codec, DynamicValue::Reader input,
+                  JsonValue::Builder output) const override final {
+    encode(codec, input.as<T>(), output);
+  }
+  Orphan<DynamicValue> decodeBase(const JsonCodec& codec, JsonValue::Reader input,
+                                  Type type, Orphanage orphanage) const override final {
+    return decode(codec, input, orphanage);
+  }
+  friend class JsonCodec;
+};
+
+template <typename T>
+class JsonCodec::Handler<T, Style::STRUCT>: private JsonCodec::HandlerBase {
+public:
+  virtual void encode(const JsonCodec& codec, ReaderFor<T> input,
+                      JsonValue::Builder output) const = 0;
+  virtual void decode(const JsonCodec& codec, JsonValue::Reader input,
+                      BuilderFor<T> output) const = 0;
+  virtual Orphan<T> decode(const JsonCodec& codec, JsonValue::Reader input,
+                           Orphanage orphanage) const {
+    // If subclass does not override, fall back to regular version.
+    auto result = orphanage.newOrphan<T>();
+    decode(codec, input, result.get());
+    return result;
+  }
+
+private:
+  void encodeBase(const JsonCodec& codec, DynamicValue::Reader input,
+                  JsonValue::Builder output) const override final {
+    encode(codec, input.as<T>(), output);
+  }
+  Orphan<DynamicValue> decodeBase(const JsonCodec& codec, JsonValue::Reader input,
+                                  Type type, Orphanage orphanage) const override final {
+    return decode(codec, input, orphanage);
+  }
+  void decodeStructBase(const JsonCodec& codec, JsonValue::Reader input,
+                        DynamicStruct::Builder output) const override final {
+    decode(codec, input, output.as<T>());
+  }
+  friend class JsonCodec;
+};
+
+template <>
+class JsonCodec::Handler<DynamicStruct>: private JsonCodec::HandlerBase {
+  // Almost identical to Style::STRUCT except that we pass the struct type to decode().
+
+public:
+  virtual void encode(const JsonCodec& codec, DynamicStruct::Reader input,
+                      JsonValue::Builder output) const = 0;
+  virtual void decode(const JsonCodec& codec, JsonValue::Reader input,
+                      DynamicStruct::Builder output) const = 0;
+  virtual Orphan<DynamicStruct> decode(const JsonCodec& codec, JsonValue::Reader input,
+                                       StructSchema type, Orphanage orphanage) const {
+    // If subclass does not override, fall back to regular version.
+    auto result = orphanage.newOrphan(type);
+    decode(codec, input, result.get());
+    return result;
+  }
+
+private:
+  void encodeBase(const JsonCodec& codec, DynamicValue::Reader input,
+                  JsonValue::Builder output) const override final {
+    encode(codec, input.as<DynamicStruct>(), output);
+  }
+  Orphan<DynamicValue> decodeBase(const JsonCodec& codec, JsonValue::Reader input,
+                                  Type type, Orphanage orphanage) const override final {
+    return decode(codec, input, type.asStruct(), orphanage);
+  }
+  void decodeStructBase(const JsonCodec& codec, JsonValue::Reader input,
+                        DynamicStruct::Builder output) const override final {
+    decode(codec, input, output.as<DynamicStruct>());
+  }
+  friend class JsonCodec;
+};
+
+template <typename T>
+class JsonCodec::Handler<T, Style::PRIMITIVE>: private JsonCodec::HandlerBase {
+public:
+  virtual void encode(const JsonCodec& codec, T input, JsonValue::Builder output) const = 0;
+  virtual T decode(const JsonCodec& codec, JsonValue::Reader input) const = 0;
+
+private:
+  void encodeBase(const JsonCodec& codec, DynamicValue::Reader input,
+                  JsonValue::Builder output) const override final {
+    encode(codec, input.as<T>(), output);
+  }
+  Orphan<DynamicValue> decodeBase(const JsonCodec& codec, JsonValue::Reader input,
+                                  Type type, Orphanage orphanage) const override final {
+    return decode(codec, input);
+  }
+  friend class JsonCodec;
+};
+
+template <typename T>
+class JsonCodec::Handler<T, Style::CAPABILITY>: private JsonCodec::HandlerBase {
+public:
+  virtual void encode(const JsonCodec& codec, typename T::Client input,
+                      JsonValue::Builder output) const = 0;
+  virtual typename T::Client decode(const JsonCodec& codec, JsonValue::Reader input) const = 0;
+
+private:
+  void encodeBase(const JsonCodec& codec, DynamicValue::Reader input,
+                  JsonValue::Builder output) const override final {
+    encode(codec, input.as<T>(), output);
+  }
+  Orphan<DynamicValue> decodeBase(const JsonCodec& codec, JsonValue::Reader input,
+                                  Type type, Orphanage orphanage) const override final {
+    return orphanage.newOrphanCopy(decode(codec, input));
+  }
+  friend class JsonCodec;
+};
+
+template <typename T>
+inline void JsonCodec::addTypeHandler(Handler<T>& handler) {
+  addTypeHandlerImpl(Type::from<T>(), handler);
+}
+inline void JsonCodec::addTypeHandler(Type type, Handler<DynamicValue>& handler) {
+  addTypeHandlerImpl(type, handler);
+}
+inline void JsonCodec::addTypeHandler(EnumSchema type, Handler<DynamicEnum>& handler) {
+  addTypeHandlerImpl(type, handler);
+}
+inline void JsonCodec::addTypeHandler(StructSchema type, Handler<DynamicStruct>& handler) {
+  addTypeHandlerImpl(type, handler);
+}
+inline void JsonCodec::addTypeHandler(ListSchema type, Handler<DynamicList>& handler) {
+  addTypeHandlerImpl(type, handler);
+}
+inline void JsonCodec::addTypeHandler(InterfaceSchema type, Handler<DynamicCapability>& handler) {
+  addTypeHandlerImpl(type, handler);
+}
+
+template <typename T>
+inline void JsonCodec::addFieldHandler(StructSchema::Field field, Handler<T>& handler) {
+  addFieldHandlerImpl(field, Type::from<T>(), handler);
+}
+
+template <> void JsonCodec::addTypeHandler(Handler<DynamicValue>& handler)
+    KJ_UNAVAILABLE("JSON handlers for type sets (e.g. all structs, all lists) not implemented; "
+                   "try specifying a specific type schema as the first parameter");
+template <> void JsonCodec::addTypeHandler(Handler<DynamicEnum>& handler)
+    KJ_UNAVAILABLE("JSON handlers for type sets (e.g. all structs, all lists) not implemented; "
+                   "try specifying a specific type schema as the first parameter");
+template <> void JsonCodec::addTypeHandler(Handler<DynamicStruct>& handler)
+    KJ_UNAVAILABLE("JSON handlers for type sets (e.g. all structs, all lists) not implemented; "
+                   "try specifying a specific type schema as the first parameter");
+template <> void JsonCodec::addTypeHandler(Handler<DynamicList>& handler)
+    KJ_UNAVAILABLE("JSON handlers for type sets (e.g. all structs, all lists) not implemented; "
+                   "try specifying a specific type schema as the first parameter");
+template <> void JsonCodec::addTypeHandler(Handler<DynamicCapability>& handler)
+    KJ_UNAVAILABLE("JSON handlers for type sets (e.g. all structs, all lists) not implemented; "
+                   "try specifying a specific type schema as the first parameter");
+// TODO(someday): Implement support for registering handlers that cover thinsg like "all structs"
+//   or "all lists". Currently you can only target a specific struct or list type.
+
+} // namespace capnp
+
+#endif // CAPNP_COMPAT_JSON_H_