296 lines
8.2 KiB
C
296 lines
8.2 KiB
C
/*
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* Copyright (c) 2017 Intel Corporation
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef __JSON_H
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#define __JSON_H
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#include <misc/util.h>
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#include <stddef.h>
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#include <zephyr/types.h>
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#include <sys/types.h>
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enum json_tokens {
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JSON_TOK_NONE = '_',
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JSON_TOK_OBJECT_START = '{',
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JSON_TOK_OBJECT_END = '}',
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JSON_TOK_LIST_START = '[',
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JSON_TOK_LIST_END = ']',
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JSON_TOK_STRING = '"',
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JSON_TOK_COLON = ':',
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JSON_TOK_COMMA = ',',
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JSON_TOK_NUMBER = '0',
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JSON_TOK_TRUE = 't',
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JSON_TOK_FALSE = 'f',
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JSON_TOK_NULL = 'n',
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JSON_TOK_ERROR = '!',
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JSON_TOK_EOF = '\0',
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};
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struct json_obj_descr {
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const char *field_name;
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size_t field_name_len;
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size_t offset;
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/* Valid values here: JSON_TOK_STRING, JSON_TOK_NUMBER,
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* JSON_TOK_TRUE, JSON_TOK_FALSE, JSON_TOK_OBJECT_START,
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* JSON_TOK_LIST_START. (All others ignored.)
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*/
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enum json_tokens type;
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union {
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struct {
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const struct json_obj_descr *sub_descr;
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size_t sub_descr_len;
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};
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struct {
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const struct json_obj_descr *element_descr;
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size_t n_elements;
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};
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};
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};
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/**
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* @brief Function pointer type to append bytes to a buffer while
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* encoding JSON data.
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*
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* @param bytes Contents to write to the output
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* @param len Number of bytes in @param bytes to append to output
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* @param data User-provided pointer
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*
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* @return This callback function should return a negative number on
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* error (which will be propagated to the return value of
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* json_obj_encode()), or 0 on success.
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*/
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typedef int (*json_append_bytes_t)(const u8_t *bytes, size_t len,
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void *data);
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/**
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* @brief Helper macro to declare a descriptor for supported primitive
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* values.
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*
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* @param struct_ Struct packing the values
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*
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* @param field_name_ Field name in the struct
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*
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* @param type_ Token type for JSON value corresponding to a primitive
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* type. Must be one of: JSON_TOK_STRING for strings, JSON_TOK_NUMBER
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* for numbers, JSON_TOK_TRUE (or JSON_TOK_FALSE) for booleans.
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*
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* Here's an example of use:
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*
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* struct foo {
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* int some_int;
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* };
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*
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* struct json_obj_descr foo[] = {
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* JSON_OBJ_DESCR_PRIM(struct foo, some_int, JSON_TOK_NUMBER),
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* };
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*/
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#define JSON_OBJ_DESCR_PRIM(struct_, field_name_, type_) \
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{ \
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.field_name = (#field_name_), \
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.field_name_len = sizeof(#field_name_) - 1, \
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.offset = offsetof(struct_, field_name_), \
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.type = type_, \
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}
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/**
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* @brief Helper macro to declare a descriptor for an object value
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*
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* @param struct_ Struct packing the values
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*
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* @param field_name_ Field name in the struct
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*
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* @param sub_descr_ Array of json_obj_descr describing the subobject
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*
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* Here's an example of use:
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* struct nested {
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* int foo;
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* struct {
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* int baz;
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* } bar;
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* };
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*
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* struct json_obj_descr nested_bar[] = {
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* { ... declare bar.baz descriptor ... },
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* };
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* struct json_obj_descr nested[] = {
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* { ... declare foo descriptor ... },
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* JSON_OBJ_DESCR_OBJECT(struct nested, bar, nested_bar),
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* };
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*/
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#define JSON_OBJ_DESCR_OBJECT(struct_, field_name_, sub_descr_) \
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{ \
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.field_name = (#field_name_), \
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.field_name_len = (sizeof(#field_name_) - 1), \
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.offset = offsetof(struct_, field_name_), \
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.type = JSON_TOK_OBJECT_START, \
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.sub_descr = sub_descr_, \
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.sub_descr_len = ARRAY_SIZE(sub_descr_) \
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}
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/**
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* @brief Helper macro to declare a descriptor for an array value
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*
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* @param struct_ Struct packing the values
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*
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* @param field_name_ Field name in the struct
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*
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* @param max_len_ Maximum number of elements in array
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*
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* @param len_field_ Field name in the struct for the number of elements
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* in the array
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*
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* @param elem_type_ Element type
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*
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* Here's an example of use:
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* struct example {
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* int foo[10];
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* size_t foo_len;
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* };
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*
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* struct json_obj_descr array[] = {
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* JSON_OBJ_DESCR_ARRAY(struct example, foo, JSON_TOK_NUMBER)
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* };
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*/
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#define JSON_OBJ_DESCR_ARRAY(struct_, field_name_, max_len_, \
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len_field_, elem_type_) \
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{ \
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.field_name = (#field_name_), \
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.field_name_len = sizeof(#field_name_) - 1, \
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.offset = offsetof(struct_, field_name_), \
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.type = JSON_TOK_LIST_START, \
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.element_descr = &(struct json_obj_descr) { \
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.type = elem_type_, \
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.offset = offsetof(struct_, len_field_), \
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}, \
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.n_elements = (max_len_), \
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}
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/**
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* @brief Parses the JSON-encoded object pointer to by @param json, with
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* size @param len, according to the descriptor pointed to by @param descr.
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* Values are stored in a struct pointed to by @param val. Set up the
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* descriptor like this:
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*
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* struct s { int foo; char *bar; }
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* struct json_obj_descr descr[] = {
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* JSON_OBJ_DESCR_PRIM(struct s, foo, JSON_TOK_NUMBER),
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* JSON_OBJ_DESCR_PRIM(struct s, bar, JSON_TOK_STRING),
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* };
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*
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* Since this parser is designed for machine-to-machine communications, some
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* liberties were taken to simplify the design:
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* (1) strings are not unescaped (but only valid escape sequences are
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* accepted);
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* (2) no UTF-8 validation is performed; and
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* (3) only integer numbers are supported (no strtod() in the minimal libc).
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*
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* @param json Pointer to JSON-encoded value to be parsed
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*
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* @param len Length of JSON-encoded value
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*
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* @param descr Pointer to the descriptor array
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*
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* @param descr_len Number of elements in the descriptor array. Must be less
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* than 31 due to implementation detail reasons (if more fields are
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* necessary, use two descriptors)
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*
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* @param val Pointer to the struct to hold the decoded values
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*
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* @return < 0 if error, bitmap of decoded fields on success (bit 0
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* is set if first field in the descriptor has been properly decoded, etc).
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*/
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int json_obj_parse(char *json, size_t len,
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const struct json_obj_descr *descr, size_t descr_len,
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void *val);
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/**
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* @brief Escapes the string so it can be used to encode JSON objects
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*
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* @param str The string to escape; the escape string is stored the
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* buffer pointed to by this parameter
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*
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* @param len Points to a size_t containing the size before and after
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* the escaping process
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*
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* @param buf_size The size of buffer str points to
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*
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* @return 0 if string has been escaped properly, or -ENOMEM if there
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* was not enough space to escape the buffer
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*/
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ssize_t json_escape(char *str, size_t *len, size_t buf_size);
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/**
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* @brief Calculates the JSON-escaped string length
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*
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* @param str The string to analyze
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*
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* @param len String size
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*
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* @return The length str would have if it were escaped
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*/
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size_t json_calc_escaped_len(const char *str, size_t len);
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/**
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* @brief Calculates the string length to fully encode an object
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*
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* @param descr Pointer to the descriptor array
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*
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* @param descr_len Number of elements in the descriptor array
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*
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* @param val Struct holding the values
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*
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* @return Number of bytes necessary to encode the values if >0,
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* an error code is returned.
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*/
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ssize_t json_calc_encoded_len(const struct json_obj_descr *descr,
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size_t descr_len, const void *val);
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/**
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* @brief Encodes an object in a contiguous memory location
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*
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* @param descr Pointer to the descriptor array
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*
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* @param descr_len Number of elements in the descriptor array
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*
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* @param val Struct holding the values
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*
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* @param buffer Buffer to store the JSON data
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*
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* @param buf_size Size of buffer, in bytes, with space for the terminating
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* NUL character
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*
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* @return 0 if object has been successfully encoded. A negative value
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* indicates an error (as defined on errno.h).
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*/
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int json_obj_encode_buf(const struct json_obj_descr *descr, size_t descr_len,
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const void *val, char *buffer, size_t buf_size);
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/**
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* @brief Encodes an object using an arbitrary writer function
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*
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* @param descr Pointer to the descriptor array
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*
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* @param descr_len Number of elements in the descriptor array
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*
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* @param val Struct holding the values
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*
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* @param append_bytes Function to append bytes to the output
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*
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* @param data Data pointer to be passed to the append_bytes callback
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* function.
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*
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* @return 0 if object has been successfully encoded. A negative value
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* indicates an error.
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*/
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int json_obj_encode(const struct json_obj_descr *descr, size_t descr_len,
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const void *val, json_append_bytes_t append_bytes,
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void *data);
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#endif /* __JSON_H */
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