fb192c5da0
This is a minimal JSON parser (and string encoder helper). This has been originally written for the NATS client sample project, but since it's a generic bit of code, it's also being provided as a library outside the NATS application source. It's limited (no support for arrays, nested objects, only integer numbers, etc), but it is sufficient for the NATS protocol to work. Jira: ZEP-1012 Change-Id: Ibfe64aa1884e8763576ec5862f77e81b4fd54b69 Signed-off-by: Leandro Pereira <leandro.pereira@intel.com>
110 lines
3.1 KiB
C
110 lines
3.1 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 <stddef.h>
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#include <stdint.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_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. (All others ignored.)
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*/
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enum json_tokens type;
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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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* { .field_name = "foo",
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* .field_name_len = 3,
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* .offset = offsetof(struct s, foo),
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* .type = JSON_TOK_NUMBER },
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* { .field_name = "bar",
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* .field_name_len = 3,
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* .offset = offsetof(struct s, bar),
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* .type = 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,
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* some liberties were taken to simplify the design: (1) strings are not
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* unescaped; (2) no UTF-8 validation is performed; (3) only integer
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* numbers are supported; (4) nested objects are not supported, including
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* arrays and objects within objects.
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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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#endif /* __JSON_H */
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