zephyr/data/json.h

/*
 * Copyright (c) 2017 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#ifndef ZEPHYR_INCLUDE_DATA_JSON_H_
#define ZEPHYR_INCLUDE_DATA_JSON_H_

#include <zephyr/sys/util.h>
#include <stddef.h>
#include <zephyr/toolchain.h>
#include <zephyr/types.h>
#include <sys/types.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @defgroup json JSON
 * @ingroup utilities
 * @{
 */

enum json_tokens {
	/* Before changing this enum, ensure that its maximum
	 * value is still within 7 bits. See comment next to the
	 * declaration of `type` in struct json_obj_descr.
	 */

	JSON_TOK_NONE = '_',
	JSON_TOK_OBJECT_START = '{',
	JSON_TOK_OBJECT_END = '}',
	JSON_TOK_ARRAY_START = '[',
	JSON_TOK_ARRAY_END = ']',
	JSON_TOK_STRING = '"',
	JSON_TOK_STRING_BUF = 's',
	JSON_TOK_COLON = ':',
	JSON_TOK_COMMA = ',',
	JSON_TOK_NUMBER = '0',
	JSON_TOK_FLOAT = '1',
	JSON_TOK_OPAQUE = '2',
	JSON_TOK_OBJ_ARRAY = '3',
	JSON_TOK_ENCODED_OBJ = '4',
	JSON_TOK_INT64 = '5',
	JSON_TOK_UINT64 = '6',
	JSON_TOK_FLOAT_FP = '7',
	JSON_TOK_DOUBLE_FP = '8',
	JSON_TOK_INT = 'i',
	JSON_TOK_UINT = 'u',
	JSON_TOK_TRUE = 't',
	JSON_TOK_FALSE = 'f',
	JSON_TOK_MIXED_ARRAY = 'm',
	JSON_TOK_NULL = 'n',
	JSON_TOK_ERROR = '!',
	JSON_TOK_EOF = '\0',
};

struct json_token {
	enum json_tokens type;
	char *start;
	char *end;
};

struct json_lexer {
	void *(*state)(struct json_lexer *lex);
	char *start;
	char *pos;
	char *end;
	struct json_token tok;
};

struct json_obj {
	struct json_lexer lex;
};

struct json_obj_token {
	char *start;
	size_t length;
};


struct json_obj_descr {
	const char *field_name;

	/* Alignment can be 1, 2, 4, or 8.  The macros to create
	 * a struct json_obj_descr will store the alignment's
	 * power of 2 in order to keep this value in the 0-3 range
	 * and thus use only 2 bits.
	 */
	uint32_t align_shift : 2;

	/* 127 characters is more than enough for a field name. */
	uint32_t field_name_len : 7;

	/* Valid values here (enum json_tokens): JSON_TOK_STRING,
	 * JSON_TOK_NUMBER, JSON_TOK_TRUE, JSON_TOK_FALSE,
	 * JSON_TOK_OBJECT_START, JSON_TOK_ARRAY_START.  (All others
	 * ignored.) Maximum value is '}' (125), so this has to be 7 bits
	 * long.
	 */
	uint32_t type : 7;

	/* 65535 bytes is more than enough for many JSON payloads. */
	uint32_t offset : 16;

	union {
		struct {
			const struct json_obj_descr *sub_descr;
			size_t sub_descr_len;
		} object;
		struct {
			const struct json_obj_descr *element_descr;
			size_t n_elements;
		} array;
		struct {
			size_t size;
		} field;
	};
};

/**
 * @brief Function pointer type to append bytes to a buffer while
 * encoding JSON data.
 *
 * @param bytes Contents to write to the output
 * @param len Number of bytes to append to output
 * @param data User-provided pointer
 *
 * @return This callback function should return a negative number on
 * error (which will be propagated to the return value of
 * json_obj_encode()), or 0 on success.
 */
typedef int (*json_append_bytes_t)(const char *bytes, size_t len,
				   void *data);

#define Z_ALIGN_SHIFT(type)	(__alignof__(type) == 1 ? 0 : \
				 __alignof__(type) == 2 ? 1 : \
				 __alignof__(type) == 4 ? 2 : 3)

/**
 * @brief Helper macro to declare a descriptor for supported primitive
 * values.
 *
 * @param struct_ Struct packing the values
 * @param field_name_ Field name in the struct
 * @param type_ Token type for JSON value corresponding to a primitive
 * type. Must be one of: JSON_TOK_STRING for strings, JSON_TOK_NUMBER
 * for numbers, JSON_TOK_TRUE (or JSON_TOK_FALSE) for booleans.
 *
 * Here's an example of use:
 *
 *     struct foo {
 *         int32_t some_int;
 *     };
 *
 *     struct json_obj_descr foo[] = {
 *         JSON_OBJ_DESCR_PRIM(struct foo, some_int, JSON_TOK_NUMBER),
 *     };
 */
#define JSON_OBJ_DESCR_PRIM(struct_, field_name_, type_) \
	{ \
		.field_name = (#field_name_), \
		.align_shift = Z_ALIGN_SHIFT(struct_), \
		.field_name_len = sizeof(#field_name_) - 1, \
		.type = type_, \
		.offset = offsetof(struct_, field_name_), \
		.field = { \
			.size = SIZEOF_FIELD(struct_, field_name_) \
		}, \
	}

/**
 * @brief Helper macro to declare a descriptor for an object value
 *
 * @param struct_ Struct packing the values
 * @param field_name_ Field name in the struct
 * @param sub_descr_ Array of json_obj_descr describing the subobject
 *
 * Here's an example of use:
 *
 *      struct nested {
 *          int32_t foo;
 *          struct {
 *             int32_t baz;
 *          } bar;
 *      };
 *
 *      struct json_obj_descr nested_bar[] = {
 *          { ... declare bar.baz descriptor ... },
 *      };
 *      struct json_obj_descr nested[] = {
 *          { ... declare foo descriptor ... },
 *          JSON_OBJ_DESCR_OBJECT(struct nested, bar, nested_bar),
 *      };
 */
#define JSON_OBJ_DESCR_OBJECT(struct_, field_name_, sub_descr_) \
	{ \
		.field_name = (#field_name_), \
		.align_shift = Z_ALIGN_SHIFT(struct_), \
		.field_name_len = (sizeof(#field_name_) - 1), \
		.type = JSON_TOK_OBJECT_START, \
		.offset = offsetof(struct_, field_name_), \
		.object = { \
			.sub_descr = sub_descr_, \
			.sub_descr_len = ARRAY_SIZE(sub_descr_), \
		}, \
	}

/**
 * @internal @brief Helper macro to declare an element descriptor
 *
 * @param struct_ Struct packing the values
 * @param len_field_ Field name in the struct for the number of elements
 * in the array
 * @param elem_type_ Element type, must be a primitive type
 * @param union_ Optional macro argument containing array or object descriptor
 */
#define Z_JSON_ELEMENT_DESCR(struct_, len_field_, elem_type_, union_) \
	(const struct json_obj_descr[]) \
	{ \
		{ \
			.align_shift = Z_ALIGN_SHIFT(struct_), \
			.type = elem_type_, \
			.offset = offsetof(struct_, len_field_), \
			union_ \
		} \
	}

/**
 * @internal @brief Helper macro to declare an array descriptor
 *
 * @param elem_descr_ Element descriptor, pointer to a descriptor array
 * @param elem_descr_len_ Number of elements in elem_descr_
 */
#define Z_JSON_DESCR_ARRAY(elem_descr_, elem_descr_len_) \
	{ \
		.array = { \
			.element_descr = elem_descr_, \
			.n_elements = elem_descr_len_, \
		}, \
	}

/**
 * @internal @brief Helper macro to declare an object descriptor
 *
 * @param elem_descr_ Element descriptor, pointer to a descriptor array
 * @param elem_descr_len_ Number of elements in elem_descr_
 */
#define Z_JSON_DESCR_OBJ(elem_descr_, elem_descr_len_) \
		.object = { \
			.sub_descr = elem_descr_, \
			.sub_descr_len = elem_descr_len_, \
		}, \

/**
 * @internal @brief Helper macro to declare a field descriptor
 *
 * @param struct_ Struct packing the values
 * @param field_name_ Field name in the struct
 */
#define Z_JSON_DESCR_FIELD(struct_, field_name_) \
	{ \
		.field = { \
			.size = SIZEOF_FIELD(struct_, field_name_), \
		}, \
	}

/**
 * @brief Helper macro to declare a descriptor for an array of primitives
 *
 * @param struct_ Struct packing the values
 * @param field_name_ Field name in the struct
 * @param max_len_ Maximum number of elements in array
 * @param len_field_ Field name in the struct for the number of elements
 * in the array
 * @param elem_type_ Element type, must be a primitive type
 *
 * Here's an example of use:
 *
 *      struct example {
 *          int32_t foo[10];
 *          size_t foo_len;
 *      };
 *
 *      struct json_obj_descr array[] = {
 *           JSON_OBJ_DESCR_ARRAY(struct example, foo, 10, foo_len,
 *                                JSON_TOK_NUMBER)
 *      };
 */
#define JSON_OBJ_DESCR_ARRAY(struct_, field_name_, max_len_, \
			     len_field_, elem_type_) \
	{ \
		.field_name = (#field_name_), \
		.align_shift = Z_ALIGN_SHIFT(struct_), \
		.field_name_len = sizeof(#field_name_) - 1, \
		.type = JSON_TOK_ARRAY_START, \
		.offset = offsetof(struct_, field_name_), \
		.array = { \
			.element_descr = Z_JSON_ELEMENT_DESCR(struct_, len_field_, \
				elem_type_, \
				Z_JSON_DESCR_FIELD(struct_, field_name_[0])), \
			.n_elements = (max_len_), \
		}, \
	}

/**
 * @brief Helper macro to declare a descriptor for an array of objects
 *
 * @param struct_ Struct packing the values
 * @param field_name_ Field name in the struct containing the array
 * @param max_len_ Maximum number of elements in the array
 * @param len_field_ Field name in the struct for the number of elements
 * in the array
 * @param elem_descr_ Element descriptor, pointer to a descriptor array
 * @param elem_descr_len_ Number of elements in elem_descr_
 *
 * Here's an example of use:
 *
 *      struct person_height {
 *          const char *name;
 *          int32_t height;
 *      };
 *
 *      struct people_heights {
 *          struct person_height heights[10];
 *          size_t heights_len;
 *      };
 *
 *      struct json_obj_descr person_height_descr[] = {
 *           JSON_OBJ_DESCR_PRIM(struct person_height, name, JSON_TOK_STRING),
 *           JSON_OBJ_DESCR_PRIM(struct person_height, height, JSON_TOK_NUMBER),
 *      };
 *
 *      struct json_obj_descr array[] = {
 *           JSON_OBJ_DESCR_OBJ_ARRAY(struct people_heights, heights, 10,
 *                                    heights_len, person_height_descr,
 *                                    ARRAY_SIZE(person_height_descr)),
 *      };
 */
#define JSON_OBJ_DESCR_OBJ_ARRAY(struct_, field_name_, max_len_, \
				 len_field_, elem_descr_, elem_descr_len_) \
	{ \
		.field_name = (#field_name_), \
		.align_shift = Z_ALIGN_SHIFT(struct_), \
		.field_name_len = sizeof(#field_name_) - 1, \
		.type = JSON_TOK_ARRAY_START, \
		.offset = offsetof(struct_, field_name_), \
		.array = { \
			.element_descr = Z_JSON_ELEMENT_DESCR(struct_, len_field_, \
				JSON_TOK_OBJECT_START, \
				Z_JSON_DESCR_OBJ(elem_descr_, elem_descr_len_)), \
			.n_elements = (max_len_), \
		}, \
	}

/**
 * @brief Helper macro to declare a descriptor for an array of array
 *
 * @param struct_ Struct packing the values
 * @param field_name_ Field name in the struct containing the array
 * @param max_len_ Maximum number of elements in the array
 * @param len_field_ Field name in the struct for the number of elements
 * in the array
 * @param elem_descr_ Element descriptor, pointer to a descriptor array
 * @param elem_descr_len_ Number of elements in elem_descr_
 *
 * Here's an example of use:
 *
 *      struct person_height {
 *          const char *name;
 *          int32_t height;
 *      };
 *
 *      struct person_heights_array {
 *          struct person_height heights;
 *      }
 *
 *      struct people_heights {
 *          struct person_height_array heights[10];
 *          size_t heights_len;
 *      };
 *
 *      struct json_obj_descr person_height_descr[] = {
 *          JSON_OBJ_DESCR_PRIM(struct person_height, name, JSON_TOK_STRING),
 *          JSON_OBJ_DESCR_PRIM(struct person_height, height, JSON_TOK_NUMBER),
 *      };
 *
 *      struct json_obj_descr person_height_array_descr[] = {
 *          JSON_OBJ_DESCR_OBJECT(struct person_heights_array,
 *                                heights, person_height_descr),
 *      };
 *
 *      struct json_obj_descr array_array[] = {
 *           JSON_OBJ_DESCR_ARRAY_ARRAY(struct people_heights, heights, 10,
 *                                      heights_len, person_height_array_descr,
 *                                      ARRAY_SIZE(person_height_array_descr)),
 *      };
 */
#define JSON_OBJ_DESCR_ARRAY_ARRAY(struct_, field_name_, max_len_, len_field_, \
				   elem_descr_, elem_descr_len_) \
	{ \
		.field_name = (#field_name_), \
		.align_shift = Z_ALIGN_SHIFT(struct_), \
		.field_name_len = sizeof(#field_name_) - 1, \
		.type = JSON_TOK_ARRAY_START, \
		.offset = offsetof(struct_, field_name_), \
		.array = { \
			.element_descr = Z_JSON_ELEMENT_DESCR( \
				struct_, len_field_, JSON_TOK_ARRAY_START, \
				Z_JSON_DESCR_ARRAY( \
					elem_descr_, \
					1 + ZERO_OR_COMPILE_ERROR(elem_descr_len_ == 1))), \
			.n_elements = (max_len_), \
		}, \
	}

/**
 * @brief Variant of JSON_OBJ_DESCR_ARRAY_ARRAY that can be used when the
 *        structure and JSON field names differ.
 *
 * This is useful when the JSON field is not a valid C identifier.
 *
 * @param struct_ Struct packing the values
 * @param json_field_name_ String, field name in JSON strings
 * @param struct_field_name_ Field name in the struct containing the array
 * @param max_len_ Maximum number of elements in the array
 * @param len_field_ Field name in the struct for the number of elements
 * in the array
 * @param elem_descr_ Element descriptor, pointer to a descriptor array
 * @param elem_descr_len_ Number of elements in elem_descr_
 *
 * @see JSON_OBJ_DESCR_ARRAY_ARRAY
 */
#define JSON_OBJ_DESCR_ARRAY_ARRAY_NAMED(struct_, json_field_name_, struct_field_name_, \
					 max_len_, len_field_, elem_descr_, elem_descr_len_) \
	{ \
		.field_name = (#json_field_name_), \
		.align_shift = Z_ALIGN_SHIFT(struct_), \
		.field_name_len = sizeof(#json_field_name_) - 1, \
		.type = JSON_TOK_ARRAY_START, \
		.offset = offsetof(struct_, struct_field_name_), \
		.array = { \
			.element_descr = Z_JSON_ELEMENT_DESCR( \
				struct_, len_field_, JSON_TOK_ARRAY_START, \
				Z_JSON_DESCR_ARRAY( \
					elem_descr_, \
					1 + ZERO_OR_COMPILE_ERROR(elem_descr_len_ == 1))), \
			.n_elements = (max_len_), \
		}, \
	}

/**
 * @brief Variant of JSON_OBJ_DESCR_PRIM that can be used when the
 *        structure and JSON field names differ.
 *
 * This is useful when the JSON field is not a valid C identifier.
 *
 * @param struct_ Struct packing the values.
 * @param json_field_name_ String, field name in JSON strings
 * @param struct_field_name_ Field name in the struct
 * @param type_ Token type for JSON value corresponding to a primitive
 * type.
 *
 * @see JSON_OBJ_DESCR_PRIM
 */
#define JSON_OBJ_DESCR_PRIM_NAMED(struct_, json_field_name_, \
				  struct_field_name_, type_) \
	{ \
		.field_name = (json_field_name_), \
		.align_shift = Z_ALIGN_SHIFT(struct_), \
		.field_name_len = sizeof(json_field_name_) - 1, \
		.type = type_, \
		.offset = offsetof(struct_, struct_field_name_), \
		.field = { \
			.size = SIZEOF_FIELD(struct_, struct_field_name_) \
		}, \
	}

/**
 * @brief Variant of JSON_OBJ_DESCR_OBJECT that can be used when the
 *        structure and JSON field names differ.
 *
 * This is useful when the JSON field is not a valid C identifier.
 *
 * @param struct_ Struct packing the values
 * @param json_field_name_ String, field name in JSON strings
 * @param struct_field_name_ Field name in the struct
 * @param sub_descr_ Array of json_obj_descr describing the subobject
 *
 * @see JSON_OBJ_DESCR_OBJECT
 */
#define JSON_OBJ_DESCR_OBJECT_NAMED(struct_, json_field_name_, \
				    struct_field_name_, sub_descr_) \
	{ \
		.field_name = (json_field_name_), \
		.align_shift = Z_ALIGN_SHIFT(struct_), \
		.field_name_len = (sizeof(json_field_name_) - 1), \
		.type = JSON_TOK_OBJECT_START, \
		.offset = offsetof(struct_, struct_field_name_), \
		.object = { \
			.sub_descr = sub_descr_, \
			.sub_descr_len = ARRAY_SIZE(sub_descr_), \
		}, \
	}

/**
 * @brief Variant of JSON_OBJ_DESCR_ARRAY that can be used when the
 *        structure and JSON field names differ.
 *
 * This is useful when the JSON field is not a valid C identifier.
 *
 * @param struct_ Struct packing the values
 * @param json_field_name_ String, field name in JSON strings
 * @param struct_field_name_ Field name in the struct
 * @param max_len_ Maximum number of elements in array
 * @param len_field_ Field name in the struct for the number of elements
 * in the array
 * @param elem_type_ Element type, must be a primitive type
 *
 * @see JSON_OBJ_DESCR_ARRAY
 */
#define JSON_OBJ_DESCR_ARRAY_NAMED(struct_, json_field_name_,\
				   struct_field_name_, max_len_, len_field_, \
				   elem_type_) \
	{ \
		.field_name = (json_field_name_), \
		.align_shift = Z_ALIGN_SHIFT(struct_), \
		.field_name_len = sizeof(json_field_name_) - 1, \
		.type = JSON_TOK_ARRAY_START, \
		.offset = offsetof(struct_, struct_field_name_), \
		.array = { \
			.element_descr = Z_JSON_ELEMENT_DESCR(struct_, len_field_, \
				elem_type_, \
				Z_JSON_DESCR_FIELD(struct_, struct_field_name_[0])), \
			.n_elements = (max_len_), \
		}, \
	}

/**
 * @brief Variant of JSON_OBJ_DESCR_OBJ_ARRAY that can be used when
 *        the structure and JSON field names differ.
 *
 * This is useful when the JSON field is not a valid C identifier.
 *
 * @param struct_ Struct packing the values
 * @param json_field_name_ String, field name of the array in JSON strings
 * @param struct_field_name_ Field name in the struct containing the array
 * @param max_len_ Maximum number of elements in the array
 * @param len_field_ Field name in the struct for the number of elements
 * in the array
 * @param elem_descr_ Element descriptor, pointer to a descriptor array
 * @param elem_descr_len_ Number of elements in elem_descr_
 *
 * Here's an example of use:
 *
 *      struct person_height {
 *          const char *name;
 *          int32_t height;
 *      };
 *
 *      struct people_heights {
 *          struct person_height heights[10];
 *          size_t heights_len;
 *      };
 *
 *      struct json_obj_descr person_height_descr[] = {
 *           JSON_OBJ_DESCR_PRIM(struct person_height, name, JSON_TOK_STRING),
 *           JSON_OBJ_DESCR_PRIM(struct person_height, height, JSON_TOK_NUMBER),
 *      };
 *
 *      struct json_obj_descr array[] = {
 *           JSON_OBJ_DESCR_OBJ_ARRAY_NAMED(struct people_heights,
 *                                          "people-heights", heights,
 *                                          10, heights_len,
 *                                          person_height_descr,
 *                                          ARRAY_SIZE(person_height_descr)),
 *      };
 */
#define JSON_OBJ_DESCR_OBJ_ARRAY_NAMED(struct_, json_field_name_, \
				       struct_field_name_, max_len_, \
				       len_field_, elem_descr_, \
				       elem_descr_len_) \
	{ \
		.field_name = json_field_name_, \
		.align_shift = Z_ALIGN_SHIFT(struct_), \
		.field_name_len = sizeof(json_field_name_) - 1, \
		.type = JSON_TOK_ARRAY_START, \
		.offset = offsetof(struct_, struct_field_name_), \
		.array = { \
			.element_descr = Z_JSON_ELEMENT_DESCR(struct_, len_field_, \
				JSON_TOK_OBJECT_START, \
				Z_JSON_DESCR_OBJ(elem_descr_, elem_descr_len_)), \
			.n_elements = (max_len_), \
		}, \
	}

/**
 * @brief Parses the JSON-encoded object pointed to by @a json, with
 * size @a len, according to the descriptor pointed to by @a descr.
 * Values are stored in a struct pointed to by @a val.  Set up the
 * descriptor like this:
 *
 *    struct s { int32_t foo; char *bar; }
 *    struct json_obj_descr descr[] = {
 *       JSON_OBJ_DESCR_PRIM(struct s, foo, JSON_TOK_NUMBER),
 *       JSON_OBJ_DESCR_PRIM(struct s, bar, JSON_TOK_STRING),
 *    };
 *
 * Since this parser is designed for machine-to-machine communications, some
 * liberties were taken to simplify the design:
 * (1) strings are not unescaped (but only valid escape sequences are
 * accepted);
 * (2) no UTF-8 validation is performed; and
 * (3) only integer numbers are supported (no strtod() in the minimal libc).
 *
 * @param json Pointer to JSON-encoded value to be parsed
 * @param len Length of JSON-encoded value
 * @param descr Pointer to the descriptor array
 * @param descr_len Number of elements in the descriptor array. Must be less
 * than 63 due to implementation detail reasons (if more fields are
 * necessary, use two descriptors)
 * @param val Pointer to the struct to hold the decoded values
 *
 * @return < 0 if error, bitmap of decoded fields on success (bit 0
 * is set if first field in the descriptor has been properly decoded, etc).
 */
int64_t json_obj_parse(char *json, size_t len,
	const struct json_obj_descr *descr, size_t descr_len,
	void *val);

/**
 * @brief Parses the JSON-encoded array pointed to by @a json, with
 * size @a len, according to the descriptor pointed to by @a descr.
 * Values are stored in a struct pointed to by @a val.  Set up the
 * descriptor like this:
 *
 *    struct s { int32_t foo; char *bar; }
 *    struct json_obj_descr descr[] = {
 *       JSON_OBJ_DESCR_PRIM(struct s, foo, JSON_TOK_NUMBER),
 *       JSON_OBJ_DESCR_PRIM(struct s, bar, JSON_TOK_STRING),
 *    };
 *    struct a { struct s baz[10]; size_t count; }
 *    struct json_obj_descr array[] = {
 *       JSON_OBJ_DESCR_OBJ_ARRAY(struct a, baz, 10, count,
 *                                descr, ARRAY_SIZE(descr)),
 *    };
 *
 * Since this parser is designed for machine-to-machine communications, some
 * liberties were taken to simplify the design:
 * (1) strings are not unescaped (but only valid escape sequences are
 * accepted);
 * (2) no UTF-8 validation is performed; and
 * (3) only integer numbers are supported (no strtod() in the minimal libc).
 *
 * @param json Pointer to JSON-encoded array to be parsed
 * @param len Length of JSON-encoded array
 * @param descr Pointer to the descriptor array
 * @param val Pointer to the struct to hold the decoded values
 *
 * @return 0 if array has been successfully parsed. A negative value
 * indicates an error (as defined on errno.h).
 */
int json_arr_parse(char *json, size_t len,
	const struct json_obj_descr *descr, void *val);

/**
 * @brief Initialize single-object array parsing
 *
 * JSON-encoded array data is going to be parsed one object at a time. Data is provided by
 * @a payload with the size of @a len bytes.
 *
 * Function validate that Json Array start is detected and initialize @a json object for
 * Json object parsing separately.
 *
 * @param json Provide storage for parser states. To be used when parsing the array.
 * @param payload Pointer to JSON-encoded array to be parsed
 * @param len Length of JSON-encoded array
 *
 * @return 0 if array start is detected and initialization is successful or negative error
 * code in case of failure.
 */
int json_arr_separate_object_parse_init(struct json_obj *json, char *payload, size_t len);

/**
 * @brief Parse a single object from array.
 *
 * Parses the JSON-encoded object pointed to by @a json object array, with
 * size @a len, according to the descriptor pointed to by @a descr.
 *
 * @param json Pointer to JSON-object message state
 * @param descr Pointer to the descriptor array
 * @param descr_len Number of elements in the descriptor array. Must be less than 31.
 * @param val Pointer to the struct to hold the decoded values
 *
 * @return < 0 if error, 0 for end of message, bitmap of decoded fields on success (bit 0
 * is set if first field in the descriptor has been properly decoded, etc).
 */
int json_arr_separate_parse_object(struct json_obj *json, const struct json_obj_descr *descr,
				   size_t descr_len, void *val);

/**
 * @brief Escapes the string so it can be used to encode JSON objects
 *
 * @param str The string to escape; the escape string is stored the
 * buffer pointed to by this parameter
 * @param len Points to a size_t containing the size before and after
 * the escaping process
 * @param buf_size The size of buffer str points to
 *
 * @return 0 if string has been escaped properly, or -ENOMEM if there
 * was not enough space to escape the buffer
 */
ssize_t json_escape(char *str, size_t *len, size_t buf_size);

/**
 * @brief Calculates the JSON-escaped string length
 *
 * @param str The string to analyze
 * @param len String size
 *
 * @return The length str would have if it were escaped
 */
size_t json_calc_escaped_len(const char *str, size_t len);

/**
 * @brief Calculates the string length to fully encode an object
 *
 * @param descr Pointer to the descriptor array
 * @param descr_len Number of elements in the descriptor array
 * @param val Struct holding the values
 *
 * @return Number of bytes necessary to encode the values if >0,
 * an error code is returned.
 */
ssize_t json_calc_encoded_len(const struct json_obj_descr *descr,
			      size_t descr_len, const void *val);

/**
 * @brief Calculates the string length to fully encode an array
 *
 * @param descr Pointer to the descriptor array
 * @param val Struct holding the values
 *
 * @return Number of bytes necessary to encode the values if >0,
 * an error code is returned.
 */
ssize_t json_calc_encoded_arr_len(const struct json_obj_descr *descr,
				  const void *val);

/**
 * @brief Encodes an object in a contiguous memory location
 *
 * @param descr Pointer to the descriptor array
 * @param descr_len Number of elements in the descriptor array
 * @param val Struct holding the values
 * @param buffer Buffer to store the JSON data
 * @param buf_size Size of buffer, in bytes, with space for the terminating
 * NUL character
 *
 * @return 0 if object has been successfully encoded. A negative value
 * indicates an error (as defined on errno.h).
 */
int json_obj_encode_buf(const struct json_obj_descr *descr, size_t descr_len,
			const void *val, char *buffer, size_t buf_size);

/**
 * @brief Encodes an array in a contiguous memory location
 *
 * @param descr Pointer to the descriptor array
 * @param val Struct holding the values
 * @param buffer Buffer to store the JSON data
 * @param buf_size Size of buffer, in bytes, with space for the terminating
 * NUL character
 *
 * @return 0 if object has been successfully encoded. A negative value
 * indicates an error (as defined on errno.h).
 */
int json_arr_encode_buf(const struct json_obj_descr *descr, const void *val,
			char *buffer, size_t buf_size);

/**
 * @brief Encodes an object using an arbitrary writer function
 *
 * @param descr Pointer to the descriptor array
 * @param descr_len Number of elements in the descriptor array
 * @param val Struct holding the values
 * @param append_bytes Function to append bytes to the output
 * @param data Data pointer to be passed to the append_bytes callback
 * function.
 *
 * @return 0 if object has been successfully encoded. A negative value
 * indicates an error.
 */
int json_obj_encode(const struct json_obj_descr *descr, size_t descr_len,
		    const void *val, json_append_bytes_t append_bytes,
		    void *data);

/**
 * @brief Encodes an array using an arbitrary writer function
 *
 * @param descr Pointer to the descriptor array
 * @param val Struct holding the values
 * @param append_bytes Function to append bytes to the output
 * @param data Data pointer to be passed to the append_bytes callback
 * function.
 *
 * @return 0 if object has been successfully encoded. A negative value
 * indicates an error.
 */
int json_arr_encode(const struct json_obj_descr *descr, const void *val,
		    json_append_bytes_t append_bytes, void *data);

/**
 * @brief Descriptor for a mixed-type JSON array.
 *
 * This structure describes a top-level JSON array whose elements may be
 * of different types (primitives, objects, arrays, or nested mixed arrays).
 * Each element in the array is described by an entry in a descriptor array.
 *
 * Mixed arrays are useful for parsing and encoding JSON arrays that do not
 * have a homogeneous element type, such as:
 *
 *   [ "string", 42, { "foo": 1 }, [1,2,3], true ]
 *
 * @note This structure and its associated macros are intended for use with
 *       the mixed array parsing and encoding APIs (see json_mixed_arr_parse()).
 */
struct json_mixed_arr_descr {
	uint32_t type : 7;
	size_t count_offset;

	union {
		struct {
			size_t offset;
			size_t size;
		} primitive;

		struct {
			const struct json_obj_descr *sub_descr;
			size_t sub_descr_len;
			size_t offset;
		} object;

		struct {
			const struct json_obj_descr *element_descr;
			size_t n_elements;
			size_t offset;
		} array;

		struct {
			const struct json_mixed_arr_descr *sub_descr;
			size_t sub_descr_len;
			size_t offset;
		} mixed_array;
	};
};

/**
 * @brief Helper macro to declare a mixed array primitive element descriptor.
 *
 * @param struct_		Struct containing the value.
 * @param field_name_	Field name in the struct.
 * @param type_		Token type for the JSON value (see enum json_tokens).
 * @param count_field_	Field name in the struct for the number of elements.
 *
 * Example:
 *	struct foo { int x; size_t x_count; };
 *	const struct json_mixed_arr_descr foo_descr[] = {
 *		JSON_MIXED_ARR_DESCR_PRIM(struct foo, x, JSON_TOK_NUMBER, x_count),
 *	};
 */
#define JSON_MIXED_ARR_DESCR_PRIM(struct_, field_name_, type_, count_field_) \
{ \
	.type = type_, \
	.count_offset = offsetof(struct_, count_field_), \
	.primitive = { \
	    .offset = offsetof(struct_, field_name_), \
	    .size = SIZEOF_FIELD(struct_, field_name_) \
	} \
}

/**
 * @brief Helper macro to declare a mixed array object element descriptor.
 *
 * @param struct_		Struct containing the object.
 * @param field_name_	Field name in the struct.
 * @param sub_descr_	Array of json_obj_descr describing the object fields.
 * @param count_field_	Field name in the struct for the number of elements.
 *
 * Example:
 *	struct bar { int y; };
 *	struct foo { struct bar b; size_t b_count; };
 *	const struct json_obj_descr bar_descr[] = { ... };
 *	const struct json_mixed_arr_descr foo_descr[] = {
 *		JSON_MIXED_ARR_DESCR_OBJECT(struct foo, b, bar_descr, b_count),
 *	};
 */
#define JSON_MIXED_ARR_DESCR_OBJECT(struct_, field_name_, sub_descr_, count_field_) \
{ \
	.type = JSON_TOK_OBJECT_START, \
	.count_offset = offsetof(struct_, count_field_), \
	.object = { \
		.sub_descr = sub_descr_, \
		.sub_descr_len = ARRAY_SIZE(sub_descr_), \
		.offset = offsetof(struct_, field_name_) \
	} \
}

/**
 * @brief Helper macro to declare a mixed array homogeneous array element descriptor.
 *
 * @param struct_		Struct containing the array.
 * @param field_name_	Field name in the struct.
 * @param max_len_		Maximum number of elements in the array.
 * @param elem_descr_	Element descriptor (pointer to json_obj_descr array).
 * @param count_field_	Field name in the struct for the number of elements.
 *
 * Example:
 *	struct foo {
 *		int arr[4];
 *		size_t arr_count;
 *	};
 *	const struct json_obj_descr arr_elem_descr[] = {
 *		JSON_OBJ_DESCR_ARRAY(struct foo, arr, 4, arr_count, JSON_TOK_NUMBER),
 *	};
 *	const struct json_mixed_arr_descr foo_descr[] = {
 *		JSON_MIXED_ARR_DESCR_ARRAY(struct foo, arr, 4, arr_elem_descr, arr_count),
 *	};
 */
#define JSON_MIXED_ARR_DESCR_ARRAY(struct_, field_name_, max_len_, elem_descr_, count_field_) \
{ \
	.type = JSON_TOK_ARRAY_START, \
	.count_offset = offsetof(struct_, count_field_), \
	.array = { \
		.element_descr = elem_descr_, \
		.n_elements = (max_len_), \
		.offset = offsetof(struct_, field_name_) \
	} \
}

/**
 * @brief Helper macro to declare a nested mixed array element descriptor.
 *
 * @param struct_		Struct containing the nested mixed array.
 * @param field_name_	Field name in the struct.
 * @param sub_descr_	Mixed array descriptor for the nested array.
 * @param count_field_	Field name in the struct for the number of elements.
 *
 * Example:
 *	struct foo { ...; size_t nested_count; };
 *	const struct json_mixed_arr_descr nested_descr[] = { ... };
 *	const struct json_mixed_arr_descr foo_descr[] = {
 *		JSON_MIXED_ARR_DESCR_MIXED_ARRAY(struct foo, nested, nested_descr, nested_count),
 *	};
 */
#define JSON_MIXED_ARR_DESCR_MIXED_ARRAY(struct_, field_name_, sub_descr_, count_field_) \
{ \
	.type = JSON_TOK_MIXED_ARRAY, \
	.count_offset = offsetof(struct_, count_field_), \
	.mixed_array = { \
		.sub_descr = sub_descr_, \
		.sub_descr_len = ARRAY_SIZE(sub_descr_), \
		.offset = offsetof(struct_, field_name_) \
	} \
}

/**
 * @brief Parse a JSON mixed array into a C structure.
 *
 * This function parses a JSON array (which may contain elements of varying types)
 * according to the provided mixed array descriptor and stores the result in the
 * user-supplied structure.
 *
 * @param json		Pointer to the input JSON string.
 * @param len		Length of the input JSON string.
 * @param descr		Descriptor array describing the structure of the mixed array.
 * @param descr_len	Number of elements in the descriptor array.
 * @param val		Pointer to the structure to populate with parsed data.
 *
 * @return < 0 if error, number of elements parsed on success.
 */
int json_mixed_arr_parse(char *json, size_t len,
			 const struct json_mixed_arr_descr *descr,
			 size_t descr_len, void *val);

/**
 * @brief Encode a C structure as a JSON mixed array.
 *
 * This function encodes a C structure, described by the mixed array descriptor,
 * as a JSON array.
 *
 * @param descr		Descriptor array describing the structure of the mixed array.
 * @param descr_len	Number of elements in the descriptor array.
 * @param val		Pointer to the structure to encode.
 * @param append_bytes Function to append bytes to the output
 * @param data Data pointer to be passed to the append_bytes callback
 * function.
 *
 * @return 0 if mixed array has been successfully encoded. Negative error code on failure.
 */
int json_mixed_arr_encode(const struct json_mixed_arr_descr *descr,
			  size_t descr_len, void *val,
			  json_append_bytes_t append_bytes,
			  void *data);

/**
 * @brief Encode a C structure as a JSON mixed array into a buffer.
 *
 * This function encodes a C structure, described by the mixed array descriptor,
 * as a JSON array and writes the result into the provided buffer.
 *
 * @param descr		Descriptor array describing the structure of the mixed array.
 * @param descr_len	Number of elements in the descriptor array.
 * @param val		Pointer to the structure to encode.
 * @param buffer	Output buffer to write the JSON string.
 * @param buf_size	Size of the output buffer.
 *
 * @return 0 if mixed array has been successfully encoded. Negative error code on failure.
 */
int json_mixed_arr_encode_buf(const struct json_mixed_arr_descr *descr,
			      size_t descr_len, void *val,
			      char *buffer, size_t buf_size);

/**
 * @brief Calculate the length of the encoded JSON mixed array.
 *
 * This function calculates the number of bytes required to encode the given
 * structure as a JSON mixed array, according to the provided descriptor.
 *
 * @param descr		Descriptor array describing the structure of the mixed array.
 * @param descr_len	Number of elements in the descriptor array.
 * @param val		Pointer to the structure to encode.
 *
 * @return		Number of bytes required for encoding, or negative error code.
 */
ssize_t json_calc_mixed_arr_len(const struct json_mixed_arr_descr *descr,
				size_t descr_len, void *val);

#ifdef __cplusplus
}
#endif

/**
 * @}
 */
#endif /* ZEPHYR_INCLUDE_DATA_JSON_H_ */