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Diffstat (limited to 'include/json_lib.h')
| -rw-r--r-- | include/json_lib.h | 356 |
1 files changed, 356 insertions, 0 deletions
diff --git a/include/json_lib.h b/include/json_lib.h new file mode 100644 index 00000000000..d9e3bb7c624 --- /dev/null +++ b/include/json_lib.h @@ -0,0 +1,356 @@ +#ifndef JSON_LIB_INCLUDED +#define JSON_LIB_INCLUDED + +#ifdef __cplusplus +extern "C" { +#endif + +#define JSON_DEPTH_LIMIT 32 + +/* + When error happens, the c_next of the JSON engine contains the + character that caused the error, and the c_str is the position + in string where the error occurs. +*/ +enum json_errors { + JE_BAD_CHR= -1, /* Invalid character, charset handler cannot read it. */ + + JE_NOT_JSON_CHR= -2, /* Character met not used in JSON. */ + /* ASCII 00-08 for instance. */ + + JE_EOS= -3, /* Unexpected end of string. */ + + JE_SYN= -4, /* The next character breaks the JSON syntax. */ + + JE_STRING_CONST= -5, /* Character disallowed in string constant. */ + + JE_ESCAPING= -6, /* Error in the escaping. */ + + JE_DEPTH= -7, /* The limit on the JSON depth was overrun. */ +}; + + +typedef struct st_json_string_t +{ + const uchar *c_str; /* Current position in JSON string */ + const uchar *str_end; /* The end on the string. */ + my_wc_t c_next; /* UNICODE of the last read character */ + int error; /* error code. */ + + CHARSET_INFO *cs; /* Character set of the JSON string. */ + + my_charset_conv_mb_wc wc; /* UNICODE conversion function. */ + /* It's taken out of the cs just to speed calls. */ +} json_string_t; + + +void json_string_set_cs(json_string_t *s, CHARSET_INFO *i_cs); +void json_string_set_str(json_string_t *s, + const uchar *str, const uchar *end); +#define json_next_char(j) \ + (j)->wc((j)->cs, &(j)->c_next, (j)->c_str, (j)->str_end) +#define json_eos(j) ((j)->c_str >= (j)->str_end) +/* + read_string_const_chr() reads the next character of the string constant + and saves it to the js->c_next. + It takes into account possible escapings, so if for instance + the string is '\b', the read_string_const_chr() sets 8. +*/ +int json_read_string_const_chr(json_string_t *js); + + +/* + Various JSON-related operations expect JSON path as a parameter. + The path is a string like this "$.keyA[2].*" + The path itself is a number of steps specifying either a key or a position + in an array. Some of them can be wildcards. + So the representation of the JSON path is the json_path_t class + containing an array of json_path_step_t objects. +*/ + + +enum json_path_step_types +{ + JSON_PATH_KEY=0, + JSON_PATH_ARRAY=1 +}; + + +typedef struct st_json_path_step_t +{ + enum json_path_step_types type; /* The type of the step - KEY or ARRAY */ + int wild; /* If the step is a wildcard */ + const uchar *key; /* Pointer to the beginning of the key. */ + const uchar *key_end; /* Pointer to the end of the key. */ + uint n_item; /* Item number in an array. No meaning for the key step. */ +} json_path_step_t; + + +typedef struct st_json_path_t +{ + json_string_t s; /* The string to be parsed. */ + json_path_step_t steps[JSON_DEPTH_LIMIT]; /* Steps of the path. */ + json_path_step_t *last_step; /* Points to the last step. */ + + int mode_strict; /* TRUE if the path specified as 'strict' */ +} json_path_t; + + +int json_path_setup(json_path_t *p, + CHARSET_INFO *i_cs, const uchar *str, const uchar *end); + + +/* + The set of functions and structures below provides interface + to the JSON text parser. + Running the parser normally goes like this: + + json_engine_t j_eng; // structure keeps parser's data + json_scan_start(j_eng) // begin the parsing + + do + { + // The parser has read next piece of JSON + // and set fields of j_eng structure accordingly. + // So let's see what we have: + switch (j_eng.state) + { + case JST_KEY: + // Handle key name. See the json_read_keyname_chr() + // Probably compare it with the keyname we're looking for + case JST_VALUE: + // Handle value. It is either value of the key or an array item. + // see the json_read_value() + case JST_OBJ_START: + // parser found an object (the '{' in JSON) + case JST_OBJ_END: + // parser found the end of the object (the '}' in JSON) + case JST_ARRAY_START: + // parser found an array (the '[' in JSON) + case JST_ARRAY_END: + // parser found the end of the array (the ']' in JSON) + + }; + } while (json_scan_next() == 0); // parse next structure + + + if (j_eng.s.error) // we need to check why the loop ended. + // Did we get to the end of JSON, or came upon error. + { + signal_error_in_JSON() + } + + + Parts of JSON can be quickly skipped. If we are not interested + in a particular key, we can just skip it with json_skip_key() call. + Similarly json_skip_level() goes right to the end of an object + or an array. +*/ + + +/* These are JSON parser states that user can expect and handle. */ +enum json_states { + JST_VALUE, /* value found */ + JST_KEY, /* key found */ + JST_OBJ_START, /* object */ + JST_OBJ_END, /* object ended */ + JST_ARRAY_START, /* array */ + JST_ARRAY_END, /* array ended */ + NR_JSON_USER_STATES +}; + + +enum json_value_types +{ + JSON_VALUE_OBJECT=0, + JSON_VALUE_ARRAY=1, + JSON_VALUE_STRING, + JSON_VALUE_NUMBER, + JSON_VALUE_TRUE, + JSON_VALUE_FALSE, + JSON_VALUE_NULL +}; + + +typedef struct st_json_engine_t +{ + json_string_t s; /* String to parse. */ + int sav_c_len; /* Length of the current character. + Can be more than 1 for multibyte charsets */ + + int state; /* The state of the parser. One of 'enum json_states'. + It tells us what construction of JSON we've just read. */ + + /* These values are only set after the json_read_value() call. */ + enum json_value_types value_type; /* type of the value.*/ + const uchar *value; /* Points to the value. */ + const uchar *value_begin;/* Points to where the value starts in the JSON. */ + + /* + In most cases the 'value' and 'value_begin' are equal. + They only differ if the value is a string constants. Then 'value_begin' + points to the starting quotation mark, while the 'value' - to + the first character of the string. + */ + + const uchar *value_end; /* Points to the next character after the value. */ + int value_len; /* The length of the value. Does not count quotations for */ + /* string constants. */ + + int stack[JSON_DEPTH_LIMIT]; /* Keeps the stack of nested JSON structures. */ + int *stack_p; /* The 'stack' pointer. */ +} json_engine_t; + + +int json_scan_start(json_engine_t *je, + CHARSET_INFO *i_cs, const uchar *str, const uchar *end); +int json_scan_next(json_engine_t *j); + + +/* + json_read_keyname_chr() function assists parsing the name of an JSON key. + It only can be called when the json_engine is in JST_KEY. + The json_read_keyname_chr() reads one character of the name of the key, + and puts it in j_eng.s.next_c. + Typical usage is like this: + + if (j_eng.state == JST_KEY) + { + while (json_read_keyname_chr(&j) == 0) + { + //handle next character i.e. match it against the pattern + } + } +*/ + +int json_read_keyname_chr(json_engine_t *j); + + +/* + json_read_value() function parses the JSON value syntax, + so that we can handle the value of a key or an array item. + It only returns meaningful result when the engine is in + the JST_VALUE state. + + Typical usage is like this: + + if (j_eng.state == JST_VALUE) + { + json_read_value(&j_eng); + switch(j_eng.value_type) + { + case JSON_VALUE_STRING: + // get the string + str= j_eng.value; + str_length= j_eng.value_len; + case JSON_VALUE_NUMBER: + // get the number + ... etc + } +*/ +int json_read_value(json_engine_t *j); + + +/* + json_skip_key() makes parser skip the content of the current + JSON key quickly. + It can be called only when the json_engine state is JST_KEY. + Typical usage is: + + if (j_eng.state == JST_KEY) + { + if (key_does_not_match(j_eng)) + json_skip_key(j_eng); + } +*/ + +int json_skip_key(json_engine_t *j); + + +/* + json_skip_level() makes parser quickly skip the JSON content + to the end of the current object or array. + It is used when we're not interested in the rest of an array + or the rest of the keys of an object. +*/ +int json_skip_level(json_engine_t *j); + + +#define json_skip_array_item json_skip_key + +/* + Checks if the current value is of scalar type - + not an OBJECT nor ARRAY. +*/ +#define json_value_scalar(je) ((je)->value_type > JSON_VALUE_ARRAY) + +/* + Look for the JSON PATH in the json string. + Function can be called several times with same JSON/PATH to + find multiple matches. + On the first call, the json_engine_t parameter should be + initialized with the JSON string, and the json_path_t with the JSON path + appropriately. The 'p_cur_step' should point at the first + step of the path. + The 'array_counters' is the array of JSON_DEPTH_LIMIT size. + It stores the array counters of the parsed JSON. + If function returns 0, it means it found the match. The position of + the match is je->s.c_str. Then we can call the json_find_path() + with same engine/path/p_cur_step to get the next match. + Non-zero return means no matches found. + Check je->s.error to see if there was an error in JSON. +*/ +int json_find_path(json_engine_t *je, + json_path_t *p, json_path_step_t **p_cur_step, + uint *array_counters); + + +typedef struct st_json_find_paths_t +{ + uint n_paths; + json_path_t *paths; + uint cur_depth; + uint *path_depths; + uint array_counters[JSON_DEPTH_LIMIT]; +} json_find_paths_t; + + +int json_find_paths_first(json_engine_t *je, json_find_paths_t *state, + uint n_paths, json_path_t *paths, uint *path_depths); +int json_find_paths_next(json_engine_t *je, json_find_paths_t *state); + + +/* + Converst JSON string constant into ordinary string constant + which can involve unpacking json escapes and changing character set. + Returns negative integer in the case of an error, + the length of the result otherwise. +*/ +int json_unescape(CHARSET_INFO *json_cs, + const uchar *json_str, const uchar *json_end, + CHARSET_INFO *res_cs, + uchar *res, uchar *res_end); + +/* + Converst ordinary string constant into JSON string constant. + which can involve appropriate escaping and changing character set. + Returns negative integer in the case of an error, + the length of the result otherwise. +*/ +int json_escape(CHARSET_INFO *str_cs, const uchar *str, const uchar *str_end, + CHARSET_INFO *json_cs, uchar *json, uchar *json_end); + + +/* + Appends the ASCII string to the json with the charset conversion. +*/ +int json_append_ascii(CHARSET_INFO *json_cs, + uchar *json, uchar *json_end, + const uchar *ascii, const uchar *ascii_end); + +#ifdef __cplusplus +} +#endif + +#endif /* JSON_LIB_INCLUDED */ + |