protobuf-c.h 32.8 KB
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/*
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 * Copyright (c) 2008-2018, Dave Benson and the protobuf-c authors.
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 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*! \file
 * \mainpage Introduction
 *
 * This is [protobuf-c], a C implementation of [Protocol Buffers].
 *
 * This file defines the public API for the `libprotobuf-c` support library.
 * This API includes interfaces that can be used directly by client code as well
 * as the interfaces used by the code generated by the `protoc-c` compiler.
 *
 * The `libprotobuf-c` support library performs the actual serialization and
 * deserialization of Protocol Buffers messages. It interacts with structures,
 * definitions, and metadata generated by the `protoc-c` compiler from .proto
 * files.
 *
 * \authors Dave Benson and the `protobuf-c` authors.
 *
 * \copyright 2008-2014. Licensed under the terms of the [BSD-2-Clause] license.
 *
 * [protobuf-c]:       https://github.com/protobuf-c/protobuf-c
 * [Protocol Buffers]: https://developers.google.com/protocol-buffers/
 * [BSD-2-Clause]:     http://opensource.org/licenses/BSD-2-Clause
 *
 * \page gencode Generated Code
 *
 * For each enum, we generate a C enum. For each message, we generate a C
 * structure which can be cast to a `ProtobufCMessage`.
 *
 * For each enum and message, we generate a descriptor object that allows us to
 * implement a kind of reflection on the structures.
 *
 * First, some naming conventions:
 *
 * - The name of the type for enums and messages and services is camel case
 *   (meaning WordsAreCrammedTogether) except that double underscores are used
 *   to delimit scopes. For example, the following `.proto` file:
 *
~~~{.proto}
        package foo.bar;
        message BazBah {
            optional int32 val = 1;
        }
~~~
 *
 * would generate a C type `Foo__Bar__BazBah`.
 *
 * - Identifiers for functions and globals are all lowercase, with camel case
 *   words separated by single underscores. For example, one of the function
 *   prototypes generated by `protoc-c` for the above example:
 *
~~~{.c}
Foo__Bar__BazBah *
       foo__bar__baz_bah__unpack
                     (ProtobufCAllocator  *allocator,
                      size_t               len,
                      const uint8_t       *data);
~~~
 *
 * - Identifiers for enum values contain an uppercase prefix which embeds the
 *   package name and the enum type name.
 *
 * - A double underscore is used to separate further components of identifier
 *   names.
 *
 * For example, in the name of the unpack function above, the package name
 * `foo.bar` has become `foo__bar`, the message name BazBah has become
 * `baz_bah`, and the method name is `unpack`. These are all joined with double
 * underscores to form the C identifier `foo__bar__baz_bah__unpack`.
 *
 * We also generate descriptor objects for messages and enums. These are
 * declared in the `.pb-c.h` files:
 *
~~~{.c}
extern const ProtobufCMessageDescriptor foo__bar__baz_bah__descriptor;
~~~
 *
 * The message structures all begin with `ProtobufCMessageDescriptor *` which is
 * sufficient to allow them to be cast to `ProtobufCMessage`.
 *
 * For each message defined in a `.proto` file, we generate a number of
 * functions and macros. Each function name contains a prefix based on the
 * package name and message name in order to make it a unique C identifier.
 *
 * - `INIT`. Statically initializes a message object, initializing its
 *   descriptor and setting its fields to default values. Uninitialized
 *   messages cannot be processed by the protobuf-c library.
 *
~~~{.c}
#define FOO__BAR__BAZ_BAH__INIT \
 { PROTOBUF_C_MESSAGE_INIT (&foo__bar__baz_bah__descriptor), 0 }
~~~
 * - `init()`. Initializes a message object, initializing its descriptor and
 *   setting its fields to default values. Uninitialized messages cannot be
 *   processed by the protobuf-c library.
 *
~~~{.c}
void foo__bar__baz_bah__init
                     (Foo__Bar__BazBah *message);
~~~
 * - `unpack()`. Unpacks data for a particular message format. Note that the
 *   `allocator` parameter is usually `NULL` to indicate that the system's
 *   `malloc()` and `free()` functions should be used for dynamically allocating
 *   memory.
 *
~~~{.c}
Foo__Bar__BazBah *
       foo__bar__baz_bah__unpack
                     (ProtobufCAllocator  *allocator,
                      size_t               len,
                      const uint8_t       *data);
~~~
 *
 * - `free_unpacked()`. Frees a message object obtained with the `unpack()`
 *   method. Freeing `NULL` is allowed (the same as with `free()`).
 *
~~~{.c}
void   foo__bar__baz_bah__free_unpacked
                     (Foo__Bar__BazBah *message,
                      ProtobufCAllocator *allocator);
~~~
 *
 * - `get_packed_size()`. Calculates the length in bytes of the serialized
 *   representation of the message object.
 *
~~~{.c}
size_t foo__bar__baz_bah__get_packed_size
                     (const Foo__Bar__BazBah   *message);
~~~
 *
 * - `pack()`. Pack a message object into a preallocated buffer. Assumes that
 *   the buffer is large enough. (Use `get_packed_size()` first.)
 *
~~~{.c}
size_t foo__bar__baz_bah__pack
                     (const Foo__Bar__BazBah   *message,
                      uint8_t             *out);
~~~
 *
 * - `pack_to_buffer()`. Packs a message into a "virtual buffer". This is an
 *   object which defines an "append bytes" callback to consume data as it is
 *   serialized.
 *
~~~{.c}
size_t foo__bar__baz_bah__pack_to_buffer
                     (const Foo__Bar__BazBah   *message,
                      ProtobufCBuffer     *buffer);
~~~
 *
 * \page pack Packing and unpacking messages
 *
 * To pack a message, first compute the packed size of the message with
 * protobuf_c_message_get_packed_size(), then allocate a buffer of at least
 * that size, then call protobuf_c_message_pack().
 *
 * Alternatively, a message can be serialized without calculating the final size
 * first. Use the protobuf_c_message_pack_to_buffer() function and provide a
 * ProtobufCBuffer object which implements an "append" method that consumes
 * data.
 *
 * To unpack a message, call the protobuf_c_message_unpack() function. The
 * result can be cast to an object of the type that matches the descriptor for
 * the message.
 *
 * The result of unpacking a message should be freed with
 * protobuf_c_message_free_unpacked().
 */

#ifndef PROTOBUF_C_H
#define PROTOBUF_C_H

#include <assert.h>
#include <limits.h>
#include <stddef.h>
#include <stdint.h>

#ifdef __cplusplus
# define PROTOBUF_C__BEGIN_DECLS	extern "C" {
# define PROTOBUF_C__END_DECLS		}
#else
# define PROTOBUF_C__BEGIN_DECLS
# define PROTOBUF_C__END_DECLS
#endif

PROTOBUF_C__BEGIN_DECLS

#if defined(_WIN32) && defined(PROTOBUF_C_USE_SHARED_LIB)
# ifdef PROTOBUF_C_EXPORT
#  define PROTOBUF_C__API __declspec(dllexport)
# else
#  define PROTOBUF_C__API __declspec(dllimport)
# endif
#else
# define PROTOBUF_C__API
#endif

#if !defined(PROTOBUF_C__NO_DEPRECATED) && \
	((__GNUC__ > 3) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
# define PROTOBUF_C__DEPRECATED __attribute__((__deprecated__))
#else
# define PROTOBUF_C__DEPRECATED
#endif

#ifndef PROTOBUF_C__FORCE_ENUM_TO_BE_INT_SIZE
 #define PROTOBUF_C__FORCE_ENUM_TO_BE_INT_SIZE(enum_name) \
  , _##enum_name##_IS_INT_SIZE = INT_MAX
#endif

#define PROTOBUF_C__SERVICE_DESCRIPTOR_MAGIC    0x14159bc3
#define PROTOBUF_C__MESSAGE_DESCRIPTOR_MAGIC    0x28aaeef9
#define PROTOBUF_C__ENUM_DESCRIPTOR_MAGIC       0x114315af

/* Empty string used for initializers */
extern const char protobuf_c_empty_string[];

/**
 * \defgroup api Public API
 *
 * This is the public API for `libprotobuf-c`. These interfaces are stable and
 * subject to Semantic Versioning guarantees.
 *
 * @{
 */

/**
 * Values for the `flags` word in `ProtobufCFieldDescriptor`.
 */
typedef enum {
	/** Set if the field is repeated and marked with the `packed` option. */
	PROTOBUF_C_FIELD_FLAG_PACKED		= (1 << 0),

	/** Set if the field is marked with the `deprecated` option. */
	PROTOBUF_C_FIELD_FLAG_DEPRECATED	= (1 << 1),

	/** Set if the field is a member of a oneof (union). */
	PROTOBUF_C_FIELD_FLAG_ONEOF		= (1 << 2),
} ProtobufCFieldFlag;

/**
 * Message field rules.
 *
 * \see [Defining A Message Type] in the Protocol Buffers documentation.
 *
 * [Defining A Message Type]:
 *      https://developers.google.com/protocol-buffers/docs/proto#simple
 */
typedef enum {
	/** A well-formed message must have exactly one of this field. */
	PROTOBUF_C_LABEL_REQUIRED,

	/**
	 * A well-formed message can have zero or one of this field (but not
	 * more than one).
	 */
	PROTOBUF_C_LABEL_OPTIONAL,

	/**
	 * This field can be repeated any number of times (including zero) in a
	 * well-formed message. The order of the repeated values will be
	 * preserved.
	 */
	PROTOBUF_C_LABEL_REPEATED,

	/**
	 * This field has no label. This is valid only in proto3 and is
	 * equivalent to OPTIONAL but no "has" quantifier will be consulted.
	 */
	PROTOBUF_C_LABEL_NONE,
} ProtobufCLabel;

/**
 * Field value types.
 *
 * \see [Scalar Value Types] in the Protocol Buffers documentation.
 *
 * [Scalar Value Types]:
 *      https://developers.google.com/protocol-buffers/docs/proto#scalar
 */
typedef enum {
	PROTOBUF_C_TYPE_INT32,      /**< int32 */
	PROTOBUF_C_TYPE_SINT32,     /**< signed int32 */
	PROTOBUF_C_TYPE_SFIXED32,   /**< signed int32 (4 bytes) */
	PROTOBUF_C_TYPE_INT64,      /**< int64 */
	PROTOBUF_C_TYPE_SINT64,     /**< signed int64 */
	PROTOBUF_C_TYPE_SFIXED64,   /**< signed int64 (8 bytes) */
	PROTOBUF_C_TYPE_UINT32,     /**< unsigned int32 */
	PROTOBUF_C_TYPE_FIXED32,    /**< unsigned int32 (4 bytes) */
	PROTOBUF_C_TYPE_UINT64,     /**< unsigned int64 */
	PROTOBUF_C_TYPE_FIXED64,    /**< unsigned int64 (8 bytes) */
	PROTOBUF_C_TYPE_FLOAT,      /**< float */
	PROTOBUF_C_TYPE_DOUBLE,     /**< double */
	PROTOBUF_C_TYPE_BOOL,       /**< boolean */
	PROTOBUF_C_TYPE_ENUM,       /**< enumerated type */
	PROTOBUF_C_TYPE_STRING,     /**< UTF-8 or ASCII string */
	PROTOBUF_C_TYPE_BYTES,      /**< arbitrary byte sequence */
	PROTOBUF_C_TYPE_MESSAGE,    /**< nested message */
} ProtobufCType;

/**
 * Field wire types.
 *
 * \see [Message Structure] in the Protocol Buffers documentation.
 *
 * [Message Structure]:
 *      https://developers.google.com/protocol-buffers/docs/encoding#structure
 */
typedef enum {
	PROTOBUF_C_WIRE_TYPE_VARINT = 0,
	PROTOBUF_C_WIRE_TYPE_64BIT = 1,
	PROTOBUF_C_WIRE_TYPE_LENGTH_PREFIXED = 2,
	/* "Start group" and "end group" wire types are unsupported. */
	PROTOBUF_C_WIRE_TYPE_32BIT = 5,
} ProtobufCWireType;

struct ProtobufCAllocator;
struct ProtobufCBinaryData;
struct ProtobufCBuffer;
struct ProtobufCBufferSimple;
struct ProtobufCEnumDescriptor;
struct ProtobufCEnumValue;
struct ProtobufCEnumValueIndex;
struct ProtobufCFieldDescriptor;
struct ProtobufCIntRange;
struct ProtobufCMessage;
struct ProtobufCMessageDescriptor;
struct ProtobufCMessageUnknownField;
struct ProtobufCMethodDescriptor;
struct ProtobufCService;
struct ProtobufCServiceDescriptor;

typedef struct ProtobufCAllocator ProtobufCAllocator;
typedef struct ProtobufCBinaryData ProtobufCBinaryData;
typedef struct ProtobufCBuffer ProtobufCBuffer;
typedef struct ProtobufCBufferSimple ProtobufCBufferSimple;
typedef struct ProtobufCEnumDescriptor ProtobufCEnumDescriptor;
typedef struct ProtobufCEnumValue ProtobufCEnumValue;
typedef struct ProtobufCEnumValueIndex ProtobufCEnumValueIndex;
typedef struct ProtobufCFieldDescriptor ProtobufCFieldDescriptor;
typedef struct ProtobufCIntRange ProtobufCIntRange;
typedef struct ProtobufCMessage ProtobufCMessage;
typedef struct ProtobufCMessageDescriptor ProtobufCMessageDescriptor;
typedef struct ProtobufCMessageUnknownField ProtobufCMessageUnknownField;
typedef struct ProtobufCMethodDescriptor ProtobufCMethodDescriptor;
typedef struct ProtobufCService ProtobufCService;
typedef struct ProtobufCServiceDescriptor ProtobufCServiceDescriptor;

/** Boolean type. */
typedef int protobuf_c_boolean;

typedef void (*ProtobufCClosure)(const ProtobufCMessage *, void *closure_data);
typedef void (*ProtobufCMessageInit)(ProtobufCMessage *);
typedef void (*ProtobufCServiceDestroy)(ProtobufCService *);

/**
 * Structure for defining a custom memory allocator.
 */
struct ProtobufCAllocator {
	/** Function to allocate memory. */
	void		*(*alloc)(void *allocator_data, size_t size);

	/** Function to free memory. */
	void		(*free)(void *allocator_data, void *pointer);

	/** Opaque pointer passed to `alloc` and `free` functions. */
	void		*allocator_data;
};

/**
 * Structure for the protobuf `bytes` scalar type.
 *
 * The data contained in a `ProtobufCBinaryData` is an arbitrary sequence of
 * bytes. It may contain embedded `NUL` characters and is not required to be
 * `NUL`-terminated.
 */
struct ProtobufCBinaryData {
	size_t	len;        /**< Number of bytes in the `data` field. */
	uint8_t	*data;      /**< Data bytes. */
};

/**
 * Structure for defining a virtual append-only buffer. Used by
 * protobuf_c_message_pack_to_buffer() to abstract the consumption of serialized
 * bytes.
 *
 * `ProtobufCBuffer` "subclasses" may be defined on the stack. For example, to
 * write to a `FILE` object:
 *
~~~{.c}
typedef struct {
        ProtobufCBuffer base;
        FILE *fp;
} BufferAppendToFile;

static void
my_buffer_file_append(ProtobufCBuffer *buffer,
                      size_t len,
                      const uint8_t *data)
{
        BufferAppendToFile *file_buf = (BufferAppendToFile *) buffer;
        fwrite(data, len, 1, file_buf->fp); // XXX: No error handling!
}
~~~
 *
 * To use this new type of ProtobufCBuffer, it could be called as follows:
 *
~~~{.c}
...
BufferAppendToFile tmp = {0};
tmp.base.append = my_buffer_file_append;
tmp.fp = fp;
protobuf_c_message_pack_to_buffer(&message, &tmp);
...
~~~
 */
struct ProtobufCBuffer {
	/** Append function. Consumes the `len` bytes stored at `data`. */
	void		(*append)(ProtobufCBuffer *buffer,
				  size_t len,
				  const uint8_t *data);
};

/**
 * Simple buffer "subclass" of `ProtobufCBuffer`.
 *
 * A `ProtobufCBufferSimple` object is declared on the stack and uses a
 * scratch buffer provided by the user for the initial allocation. It performs
 * exponential resizing, using dynamically allocated memory. A
 * `ProtobufCBufferSimple` object can be created and used as follows:
 *
~~~{.c}
uint8_t pad[128];
ProtobufCBufferSimple simple = PROTOBUF_C_BUFFER_SIMPLE_INIT(pad);
ProtobufCBuffer *buffer = (ProtobufCBuffer *) &simple;
~~~
 *
 * `buffer` can now be used with `protobuf_c_message_pack_to_buffer()`. Once a
 * message has been serialized to a `ProtobufCBufferSimple` object, the
 * serialized data bytes can be accessed from the `.data` field.
 *
 * To free the memory allocated by a `ProtobufCBufferSimple` object, if any,
 * call PROTOBUF_C_BUFFER_SIMPLE_CLEAR() on the object, for example:
 *
~~~{.c}
PROTOBUF_C_BUFFER_SIMPLE_CLEAR(&simple);
~~~
 *
 * \see PROTOBUF_C_BUFFER_SIMPLE_INIT
 * \see PROTOBUF_C_BUFFER_SIMPLE_CLEAR
 */
struct ProtobufCBufferSimple {
	/** "Base class". */
	ProtobufCBuffer		base;
	/** Number of bytes allocated in `data`. */
	size_t			alloced;
	/** Number of bytes currently stored in `data`. */
	size_t			len;
	/** Data bytes. */
	uint8_t			*data;
	/** Whether `data` must be freed. */
	protobuf_c_boolean	must_free_data;
	/** Allocator to use. May be NULL to indicate the system allocator. */
	ProtobufCAllocator	*allocator;
};

/**
 * Describes an enumeration as a whole, with all of its values.
 */
struct ProtobufCEnumDescriptor {
	/** Magic value checked to ensure that the API is used correctly. */
	uint32_t			magic;

	/** The qualified name (e.g., "namespace.Type"). */
	const char			*name;
	/** The unqualified name as given in the .proto file (e.g., "Type"). */
	const char			*short_name;
	/** Identifier used in generated C code. */
	const char			*c_name;
	/** The dot-separated namespace. */
	const char			*package_name;

	/** Number elements in `values`. */
	unsigned			n_values;
	/** Array of distinct values, sorted by numeric value. */
	const ProtobufCEnumValue	*values;

	/** Number of elements in `values_by_name`. */
	unsigned			n_value_names;
	/** Array of named values, including aliases, sorted by name. */
	const ProtobufCEnumValueIndex	*values_by_name;

	/** Number of elements in `value_ranges`. */
	unsigned			n_value_ranges;
	/** Value ranges, for faster lookups by numeric value. */
	const ProtobufCIntRange		*value_ranges;

	/** Reserved for future use. */
	void				*reserved1;
	/** Reserved for future use. */
	void				*reserved2;
	/** Reserved for future use. */
	void				*reserved3;
	/** Reserved for future use. */
	void				*reserved4;
};

/**
 * Represents a single value of an enumeration.
 */
struct ProtobufCEnumValue {
	/** The string identifying this value in the .proto file. */
	const char	*name;

	/** The string identifying this value in generated C code. */
	const char	*c_name;

	/** The numeric value assigned in the .proto file. */
	int		value;
};

/**
 * Used by `ProtobufCEnumDescriptor` to look up enum values.
 */
struct ProtobufCEnumValueIndex {
	/** Name of the enum value. */
	const char      *name;
	/** Index into values[] array. */
	unsigned        index;
};

/**
 * Describes a single field in a message.
 */
struct ProtobufCFieldDescriptor {
	/** Name of the field as given in the .proto file. */
	const char		*name;

	/** Tag value of the field as given in the .proto file. */
	uint32_t		id;

	/** Whether the field is `REQUIRED`, `OPTIONAL`, or `REPEATED`. */
	ProtobufCLabel		label;

	/** The type of the field. */
	ProtobufCType		type;

	/**
	 * The offset in bytes of the message's C structure's quantifier field
	 * (the `has_MEMBER` field for optional members or the `n_MEMBER` field
	 * for repeated members or the case enum for oneofs).
	 */
	unsigned		quantifier_offset;

	/**
	 * The offset in bytes into the message's C structure for the member
	 * itself.
	 */
	unsigned		offset;

	/**
	 * A type-specific descriptor.
	 *
	 * If `type` is `PROTOBUF_C_TYPE_ENUM`, then `descriptor` points to the
	 * corresponding `ProtobufCEnumDescriptor`.
	 *
	 * If `type` is `PROTOBUF_C_TYPE_MESSAGE`, then `descriptor` points to
	 * the corresponding `ProtobufCMessageDescriptor`.
	 *
	 * Otherwise this field is NULL.
	 */
	const void		*descriptor; /* for MESSAGE and ENUM types */

	/** The default value for this field, if defined. May be NULL. */
	const void		*default_value;

	/**
	 * A flag word. Zero or more of the bits defined in the
	 * `ProtobufCFieldFlag` enum may be set.
	 */
	uint32_t		flags;

	/** Reserved for future use. */
	unsigned		reserved_flags;
	/** Reserved for future use. */
	void			*reserved2;
	/** Reserved for future use. */
	void			*reserved3;
};

/**
 * Helper structure for optimizing int => index lookups in the case
 * where the keys are mostly consecutive values, as they presumably are for
 * enums and fields.
 *
 * The data structures requires that the values in the original array are
 * sorted.
 */
struct ProtobufCIntRange {
	int             start_value;
	unsigned        orig_index;
	/*
	 * NOTE: the number of values in the range can be inferred by looking
	 * at the next element's orig_index. A dummy element is added to make
	 * this simple.
	 */
};

/**
 * An instance of a message.
 *
 * `ProtobufCMessage` is a light-weight "base class" for all messages.
 *
 * In particular, `ProtobufCMessage` doesn't have any allocation policy
 * associated with it. That's because it's common to create `ProtobufCMessage`
 * objects on the stack. In fact, that's what we recommend for sending messages.
 * If the object is allocated from the stack, you can't really have a memory
 * leak.
 *
 * This means that calls to functions like protobuf_c_message_unpack() which
 * return a `ProtobufCMessage` must be paired with a call to a free function,
 * like protobuf_c_message_free_unpacked().
 */
struct ProtobufCMessage {
	/** The descriptor for this message type. */
	const ProtobufCMessageDescriptor	*descriptor;
	/** The number of elements in `unknown_fields`. */
	unsigned				n_unknown_fields;
	/** The fields that weren't recognized by the parser. */
	ProtobufCMessageUnknownField		*unknown_fields;
};

/**
 * Describes a message.
 */
struct ProtobufCMessageDescriptor {
	/** Magic value checked to ensure that the API is used correctly. */
	uint32_t			magic;

	/** The qualified name (e.g., "namespace.Type"). */
	const char			*name;
	/** The unqualified name as given in the .proto file (e.g., "Type"). */
	const char			*short_name;
	/** Identifier used in generated C code. */
	const char			*c_name;
	/** The dot-separated namespace. */
	const char			*package_name;

	/**
	 * Size in bytes of the C structure representing an instance of this
	 * type of message.
	 */
	size_t				sizeof_message;

	/** Number of elements in `fields`. */
	unsigned			n_fields;
	/** Field descriptors, sorted by tag number. */
	const ProtobufCFieldDescriptor	*fields;
	/** Used for looking up fields by name. */
	const unsigned			*fields_sorted_by_name;

	/** Number of elements in `field_ranges`. */
	unsigned			n_field_ranges;
	/** Used for looking up fields by id. */
	const ProtobufCIntRange		*field_ranges;

	/** Message initialisation function. */
	ProtobufCMessageInit		message_init;

	/** Reserved for future use. */
	void				*reserved1;
	/** Reserved for future use. */
	void				*reserved2;
	/** Reserved for future use. */
	void				*reserved3;
};

/**
 * An unknown message field.
 */
struct ProtobufCMessageUnknownField {
	/** The tag number. */
	uint32_t		tag;
	/** The wire type of the field. */
	ProtobufCWireType	wire_type;
	/** Number of bytes in `data`. */
	size_t			len;
	/** Field data. */
	uint8_t			*data;
};

/**
 * Method descriptor.
 */
struct ProtobufCMethodDescriptor {
	/** Method name. */
	const char				*name;
	/** Input message descriptor. */
	const ProtobufCMessageDescriptor	*input;
	/** Output message descriptor. */
	const ProtobufCMessageDescriptor	*output;
};

/**
 * Service.
 */
struct ProtobufCService {
	/** Service descriptor. */
	const ProtobufCServiceDescriptor *descriptor;
	/** Function to invoke the service. */
	void (*invoke)(ProtobufCService *service,
		       unsigned method_index,
		       const ProtobufCMessage *input,
		       ProtobufCClosure closure,
		       void *closure_data);
	/** Function to destroy the service. */
	void (*destroy)(ProtobufCService *service);
};

/**
 * Service descriptor.
 */
struct ProtobufCServiceDescriptor {
	/** Magic value checked to ensure that the API is used correctly. */
	uint32_t			magic;

	/** Service name. */
	const char			*name;
	/** Short version of service name. */
	const char			*short_name;
	/** C identifier for the service name. */
	const char			*c_name;
	/** Package name. */
	const char			*package;
	/** Number of elements in `methods`. */
	unsigned			n_methods;
	/** Method descriptors, in the order defined in the .proto file. */
	const ProtobufCMethodDescriptor	*methods;
	/** Sort index of methods. */
	const unsigned			*method_indices_by_name;
};

/**
 * Get the version of the protobuf-c library. Note that this is the version of
 * the library linked against, not the version of the headers compiled against.
 *
 * \return A string containing the version number of protobuf-c.
 */
PROTOBUF_C__API
const char *
protobuf_c_version(void);

/**
 * Get the version of the protobuf-c library. Note that this is the version of
 * the library linked against, not the version of the headers compiled against.
 *
 * \return A 32 bit unsigned integer containing the version number of
 *      protobuf-c, represented in base-10 as (MAJOR*1E6) + (MINOR*1E3) + PATCH.
 */
PROTOBUF_C__API
uint32_t
protobuf_c_version_number(void);

/**
 * The version of the protobuf-c headers, represented as a string using the same
 * format as protobuf_c_version().
 */
793
#define PROTOBUF_C_VERSION		"1.3.1"
794 795 796 797 798

/**
 * The version of the protobuf-c headers, represented as an integer using the
 * same format as protobuf_c_version_number().
 */
799
#define PROTOBUF_C_VERSION_NUMBER	1003001
800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106

/**
 * The minimum protoc-c version which works with the current version of the
 * protobuf-c headers.
 */
#define PROTOBUF_C_MIN_COMPILER_VERSION	1000000

/**
 * Look up a `ProtobufCEnumValue` from a `ProtobufCEnumDescriptor` by name.
 *
 * \param desc
 *      The `ProtobufCEnumDescriptor` object.
 * \param name
 *      The `name` field from the corresponding `ProtobufCEnumValue` object to
 *      match.
 * \return
 *      A `ProtobufCEnumValue` object.
 * \retval NULL
 *      If not found or if the optimize_for = CODE_SIZE option was set.
 */
PROTOBUF_C__API
const ProtobufCEnumValue *
protobuf_c_enum_descriptor_get_value_by_name(
	const ProtobufCEnumDescriptor *desc,
	const char *name);

/**
 * Look up a `ProtobufCEnumValue` from a `ProtobufCEnumDescriptor` by numeric
 * value.
 *
 * \param desc
 *      The `ProtobufCEnumDescriptor` object.
 * \param value
 *      The `value` field from the corresponding `ProtobufCEnumValue` object to
 *      match.
 *
 * \return
 *      A `ProtobufCEnumValue` object.
 * \retval NULL
 *      If not found.
 */
PROTOBUF_C__API
const ProtobufCEnumValue *
protobuf_c_enum_descriptor_get_value(
	const ProtobufCEnumDescriptor *desc,
	int value);

/**
 * Look up a `ProtobufCFieldDescriptor` from a `ProtobufCMessageDescriptor` by
 * the name of the field.
 *
 * \param desc
 *      The `ProtobufCMessageDescriptor` object.
 * \param name
 *      The name of the field.
 * \return
 *      A `ProtobufCFieldDescriptor` object.
 * \retval NULL
 *      If not found or if the optimize_for = CODE_SIZE option was set.
 */
PROTOBUF_C__API
const ProtobufCFieldDescriptor *
protobuf_c_message_descriptor_get_field_by_name(
	const ProtobufCMessageDescriptor *desc,
	const char *name);

/**
 * Look up a `ProtobufCFieldDescriptor` from a `ProtobufCMessageDescriptor` by
 * the tag value of the field.
 *
 * \param desc
 *      The `ProtobufCMessageDescriptor` object.
 * \param value
 *      The tag value of the field.
 * \return
 *      A `ProtobufCFieldDescriptor` object.
 * \retval NULL
 *      If not found.
 */
PROTOBUF_C__API
const ProtobufCFieldDescriptor *
protobuf_c_message_descriptor_get_field(
	const ProtobufCMessageDescriptor *desc,
	unsigned value);

/**
 * Determine the number of bytes required to store the serialised message.
 *
 * \param message
 *      The message object to serialise.
 * \return
 *      Number of bytes.
 */
PROTOBUF_C__API
size_t
protobuf_c_message_get_packed_size(const ProtobufCMessage *message);

/**
 * Serialise a message from its in-memory representation.
 *
 * This function stores the serialised bytes of the message in a pre-allocated
 * buffer.
 *
 * \param message
 *      The message object to serialise.
 * \param[out] out
 *      Buffer to store the bytes of the serialised message. This buffer must
 *      have enough space to store the packed message. Use
 *      protobuf_c_message_get_packed_size() to determine the number of bytes
 *      required.
 * \return
 *      Number of bytes stored in `out`.
 */
PROTOBUF_C__API
size_t
protobuf_c_message_pack(const ProtobufCMessage *message, uint8_t *out);

/**
 * Serialise a message from its in-memory representation to a virtual buffer.
 *
 * This function calls the `append` method of a `ProtobufCBuffer` object to
 * consume the bytes generated by the serialiser.
 *
 * \param message
 *      The message object to serialise.
 * \param buffer
 *      The virtual buffer object.
 * \return
 *      Number of bytes passed to the virtual buffer.
 */
PROTOBUF_C__API
size_t
protobuf_c_message_pack_to_buffer(
	const ProtobufCMessage *message,
	ProtobufCBuffer *buffer);

/**
 * Unpack a serialised message into an in-memory representation.
 *
 * \param descriptor
 *      The message descriptor.
 * \param allocator
 *      `ProtobufCAllocator` to use for memory allocation. May be NULL to
 *      specify the default allocator.
 * \param len
 *      Length in bytes of the serialised message.
 * \param data
 *      Pointer to the serialised message.
 * \return
 *      An unpacked message object.
 * \retval NULL
 *      If an error occurred during unpacking.
 */
PROTOBUF_C__API
ProtobufCMessage *
protobuf_c_message_unpack(
	const ProtobufCMessageDescriptor *descriptor,
	ProtobufCAllocator *allocator,
	size_t len,
	const uint8_t *data);

/**
 * Free an unpacked message object.
 *
 * This function should be used to deallocate the memory used by a call to
 * protobuf_c_message_unpack().
 *
 * \param message
 *      The message object to free. May be NULL.
 * \param allocator
 *      `ProtobufCAllocator` to use for memory deallocation. May be NULL to
 *      specify the default allocator.
 */
PROTOBUF_C__API
void
protobuf_c_message_free_unpacked(
	ProtobufCMessage *message,
	ProtobufCAllocator *allocator);

/**
 * Check the validity of a message object.
 *
 * Makes sure all required fields (`PROTOBUF_C_LABEL_REQUIRED`) are present.
 * Recursively checks nested messages.
 *
 * \retval TRUE
 *      Message is valid.
 * \retval FALSE
 *      Message is invalid.
 */
PROTOBUF_C__API
protobuf_c_boolean
protobuf_c_message_check(const ProtobufCMessage *);

/** Message initialiser. */
#define PROTOBUF_C_MESSAGE_INIT(descriptor) { descriptor, 0, NULL }

/**
 * Initialise a message object from a message descriptor.
 *
 * \param descriptor
 *      Message descriptor.
 * \param message
 *      Allocated block of memory of size `descriptor->sizeof_message`.
 */
PROTOBUF_C__API
void
protobuf_c_message_init(
	const ProtobufCMessageDescriptor *descriptor,
	void *message);

/**
 * Free a service.
 *
 * \param service
 *      The service object to free.
 */
PROTOBUF_C__API
void
protobuf_c_service_destroy(ProtobufCService *service);

/**
 * Look up a `ProtobufCMethodDescriptor` by name.
 *
 * \param desc
 *      Service descriptor.
 * \param name
 *      Name of the method.
 *
 * \return
 *      A `ProtobufCMethodDescriptor` object.
 * \retval NULL
 *      If not found or if the optimize_for = CODE_SIZE option was set.
 */
PROTOBUF_C__API
const ProtobufCMethodDescriptor *
protobuf_c_service_descriptor_get_method_by_name(
	const ProtobufCServiceDescriptor *desc,
	const char *name);

/**
 * Initialise a `ProtobufCBufferSimple` object.
 */
#define PROTOBUF_C_BUFFER_SIMPLE_INIT(array_of_bytes)                   \
{                                                                       \
	{ protobuf_c_buffer_simple_append },                            \
	sizeof(array_of_bytes),                                         \
	0,                                                              \
	(array_of_bytes),                                               \
	0,                                                              \
	NULL                                                            \
}

/**
 * Clear a `ProtobufCBufferSimple` object, freeing any allocated memory.
 */
#define PROTOBUF_C_BUFFER_SIMPLE_CLEAR(simp_buf)                        \
do {                                                                    \
	if ((simp_buf)->must_free_data) {                               \
		if ((simp_buf)->allocator != NULL)                      \
			(simp_buf)->allocator->free(                    \
				(simp_buf)->allocator,                  \
				(simp_buf)->data);			\
		else                                                    \
			free((simp_buf)->data);                         \
	}                                                               \
} while (0)

/**
 * The `append` method for `ProtobufCBufferSimple`.
 *
 * \param buffer
 *      The buffer object to append to. Must actually be a
 *      `ProtobufCBufferSimple` object.
 * \param len
 *      Number of bytes in `data`.
 * \param data
 *      Data to append.
 */
PROTOBUF_C__API
void
protobuf_c_buffer_simple_append(
	ProtobufCBuffer *buffer,
	size_t len,
	const unsigned char *data);

PROTOBUF_C__API
void
protobuf_c_service_generated_init(
	ProtobufCService *service,
	const ProtobufCServiceDescriptor *descriptor,
	ProtobufCServiceDestroy destroy);

PROTOBUF_C__API
void
protobuf_c_service_invoke_internal(
	ProtobufCService *service,
	unsigned method_index,
	const ProtobufCMessage *input,
	ProtobufCClosure closure,
	void *closure_data);

/**@}*/

PROTOBUF_C__END_DECLS

#endif /* PROTOBUF_C_H */