jsonapi.h

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/*-------------------------------------------------------------------------
 *
 * jsonapi.h
 *    Declarations for JSON API support.
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/utils/jsonapi.h
 *
 *-------------------------------------------------------------------------
 */

#ifndef JSONAPI_H
#define JSONAPI_H

#include "lib/stringinfo.h"

typedef enum
{
    JSON_TOKEN_INVALID,
    JSON_TOKEN_STRING,
    JSON_TOKEN_NUMBER,
    JSON_TOKEN_OBJECT_START,
    JSON_TOKEN_OBJECT_END,
    JSON_TOKEN_ARRAY_START,
    JSON_TOKEN_ARRAY_END,
    JSON_TOKEN_COMMA,
    JSON_TOKEN_COLON,
    JSON_TOKEN_TRUE,
    JSON_TOKEN_FALSE,
    JSON_TOKEN_NULL,
    JSON_TOKEN_END,
}   JsonTokenType;


/*
 * All the fields in this structure should be treated as read-only.
 *
 * If strval is not null, then it should contain the de-escaped value
 * of the lexeme if it's a string. Otherwise most of these field names
 * should be self-explanatory.
 *
 * line_number and line_start are principally for use by the parser's
 * error reporting routines.
 * token_terminator and prev_token_terminator point to the character
 * AFTER the end of the token, i.e. where there would be a nul byte
 * if we were using nul-terminated strings.
 */
typedef struct JsonLexContext
{
    char       *input;
    int         input_length;
    char       *token_start;
    char       *token_terminator;
    char       *prev_token_terminator;
    JsonTokenType token_type;
    int         lex_level;
    int         line_number;
    char       *line_start;
    StringInfo  strval;
} JsonLexContext;

typedef void (*json_struct_action) (void *state);
typedef void (*json_ofield_action) (void *state, char *fname, bool isnull);
typedef void (*json_aelem_action) (void *state, bool isnull);
typedef void (*json_scalar_action) (void *state, char *token, JsonTokenType tokentype);


/*
 * Semantic Action structure for use in parsing json.
 * Any of these actions can be NULL, in which case nothing is done at that
 * point, Likewise, semstate can be NULL. Using an all-NULL structure amounts
 * to doing a pure parse with no side-effects, and is therefore exactly
 * what the json input routines do.
 */
typedef struct jsonSemAction
{
    void       *semstate;
    json_struct_action object_start;
    json_struct_action object_end;
    json_struct_action array_start;
    json_struct_action array_end;
    json_ofield_action object_field_start;
    json_ofield_action object_field_end;
    json_aelem_action array_element_start;
    json_aelem_action array_element_end;
    json_scalar_action scalar;
}   jsonSemAction, *JsonSemAction;

/*
 * parse_json will parse the string in the lex calling the
 * action functions in sem at the appropriate points. It is
 * up to them to keep what state they need  in semstate. If they
 * need access to the state of the lexer, then its pointer
 * should be passed to them as a member of whatever semstate
 * points to. If the action pointers are NULL the parser
 * does nothing and just continues.
 */
extern void pg_parse_json(JsonLexContext *lex, JsonSemAction sem);

/*
 * constructor for JsonLexContext, with or without strval element.
 * If supplied, the strval element will contain a de-escaped version of
 * the lexeme. However, doing this imposes a performance penalty, so
 * it should be avoided if the de-escaped lexeme is not required.
 */
extern JsonLexContext *makeJsonLexContext(text *json, bool need_escapes);

#endif   /* JSONAPI_H */