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/**
* @file xpath.h
* @author Michal Vasko <mvasko@cesnet.cz>
* @brief YANG XPath evaluation functions header
*
* Copyright (c) 2015 - 2020 CESNET, z.s.p.o.
*
* This source code is licensed under BSD 3-Clause License (the "License").
* You may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://opensource.org/licenses/BSD-3-Clause
*/
#ifndef LY_XPATH_H
#define LY_XPATH_H
#include <stdint.h>
#include <stddef.h>
#include "compat.h"
#include "log.h"
#include "plugins_types.h"
#include "tree_schema.h"
struct ly_ctx;
/*
* XPath evaluator fully compliant with http://www.w3.org/TR/1999/REC-xpath-19991116/
* except the following restrictions in the grammar.
*
* PARSED GRAMMAR
*
* Full axes are not supported, abbreviated forms must be used,
* variables are not supported, "id()" function is not supported,
* and processing instruction and comment nodes are not supported,
* which is also reflected in the grammar. Undefined rules and
* constants are tokens.
*
* Modified full grammar:
*
* [1] Expr ::= OrExpr // just an alias
*
* [2] LocationPath ::= RelativeLocationPath | AbsoluteLocationPath
* [3] AbsoluteLocationPath ::= '/' RelativeLocationPath? | '//' RelativeLocationPath
* [4] RelativeLocationPath ::= Step | RelativeLocationPath '/' Step | RelativeLocationPath '//' Step
* [5] Step ::= '@'? NodeTest Predicate* | '.' | '..'
* [6] NodeTest ::= NameTest | NodeType '(' ')'
* [7] NameTest ::= '*' | NCName ':' '*' | QName
* [8] NodeType ::= 'text' | 'node'
* [9] Predicate ::= '[' Expr ']'
* [10] PrimaryExpr ::= '(' Expr ')' | Literal | Number | FunctionCall
* [11] FunctionCall ::= FunctionName '(' ( Expr ( ',' Expr )* )? ')'
* [12] PathExpr ::= LocationPath | PrimaryExpr Predicate*
* | PrimaryExpr Predicate* '/' RelativeLocationPath
* | PrimaryExpr Predicate* '//' RelativeLocationPath
* [13] OrExpr ::= AndExpr | OrExpr 'or' AndExpr
* [14] AndExpr ::= EqualityExpr | AndExpr 'and' EqualityExpr
* [15] EqualityExpr ::= RelationalExpr | EqualityExpr '=' RelationalExpr
* | EqualityExpr '!=' RelationalExpr
* [16] RelationalExpr ::= AdditiveExpr
* | RelationalExpr '<' AdditiveExpr
* | RelationalExpr '>' AdditiveExpr
* | RelationalExpr '<=' AdditiveExpr
* | RelationalExpr '>=' AdditiveExpr
* [17] AdditiveExpr ::= MultiplicativeExpr
* | AdditiveExpr '+' MultiplicativeExpr
* | AdditiveExpr '-' MultiplicativeExpr
* [18] MultiplicativeExpr ::= UnaryExpr
* | MultiplicativeExpr '*' UnaryExpr
* | MultiplicativeExpr 'div' UnaryExpr
* | MultiplicativeExpr 'mod' UnaryExpr
* [19] UnaryExpr ::= UnionExpr | '-' UnaryExpr
* [20] UnionExpr ::= PathExpr | UnionExpr '|' PathExpr
*/
/* expression tokens allocation */
#define LYXP_EXPR_SIZE_START 10
#define LYXP_EXPR_SIZE_STEP 5
/* XPath matches allocation */
#define LYXP_SET_SIZE_START 2
#define LYXP_SET_SIZE_STEP 2
/* building string when casting */
#define LYXP_STRING_CAST_SIZE_START 64
#define LYXP_STRING_CAST_SIZE_STEP 16
/**
* @brief Tokens that can be in an XPath expression.
*/
enum lyxp_token {
LYXP_TOKEN_NONE = 0,
LYXP_TOKEN_PAR1, /* '(' */
LYXP_TOKEN_PAR2, /* ')' */
LYXP_TOKEN_BRACK1, /* '[' */
LYXP_TOKEN_BRACK2, /* ']' */
LYXP_TOKEN_DOT, /* '.' */
LYXP_TOKEN_DDOT, /* '..' */
LYXP_TOKEN_AT, /* '@' */
LYXP_TOKEN_COMMA, /* ',' */
/* LYXP_TOKEN_DCOLON, * '::' * axes not supported */
LYXP_TOKEN_NAMETEST, /* NameTest */
LYXP_TOKEN_NODETYPE, /* NodeType */
LYXP_TOKEN_FUNCNAME, /* FunctionName */
LYXP_TOKEN_OPER_LOG, /* Operator 'and', 'or' */
LYXP_TOKEN_OPER_EQUAL, /* Operator '=' */
LYXP_TOKEN_OPER_NEQUAL, /* Operator '!=' */
LYXP_TOKEN_OPER_COMP, /* Operator '<', '<=', '>', '>=' */
LYXP_TOKEN_OPER_MATH, /* Operator '+', '-', '*', 'div', 'mod', '-' (unary) */
LYXP_TOKEN_OPER_UNI, /* Operator '|' */
LYXP_TOKEN_OPER_PATH, /* Operator '/' */
LYXP_TOKEN_OPER_RPATH, /* Operator '//' (recursive path) */
/* LYXP_TOKEN_AXISNAME, * AxisName * axes not supported */
LYXP_TOKEN_LITERAL, /* Literal - with either single or double quote */
LYXP_TOKEN_NUMBER /* Number */
};
/**
* @brief XPath (sub)expressions that can be repeated.
*/
enum lyxp_expr_type {
LYXP_EXPR_NONE = 0,
LYXP_EXPR_OR,
LYXP_EXPR_AND,
LYXP_EXPR_EQUALITY,
LYXP_EXPR_RELATIONAL,
LYXP_EXPR_ADDITIVE,
LYXP_EXPR_MULTIPLICATIVE,
LYXP_EXPR_UNARY,
LYXP_EXPR_UNION,
};
/**
* @brief Types of context nodes, #LYXP_NODE_ROOT_CONFIG used only in when or must conditions.
*/
enum lyxp_node_type {
LYXP_NODE_NONE, /* invalid node type */
/* XML document roots */
LYXP_NODE_ROOT, /* access to all the data (node value first top-level node) */
LYXP_NODE_ROOT_CONFIG, /* <running> data context, no state data (node value first top-level node) */
/* XML elements */
LYXP_NODE_ELEM, /* YANG data element (most common) */
LYXP_NODE_TEXT, /* YANG data text element (extremely specific use, unlikely to be ever needed) */
LYXP_NODE_META /* YANG metadata (do not use for the context node) */
};
/**
* @brief Structure holding a parsed XPath expression.
*/
struct lyxp_expr {
enum lyxp_token *tokens; /* array of tokens */
uint16_t *tok_pos; /* array of the token offsets in expr */
uint16_t *tok_len; /* array of token lengths in expr */
enum lyxp_expr_type **repeat; /* array of expression types that this token begins and is repeated ended with 0,
more in the comment after this declaration */
uint16_t used; /* used array items */
uint16_t size; /* allocated array items */
const char *expr; /* the original XPath expression */
};
/*
* lyxp_expr repeat
*
* This value is NULL for all the tokens that do not begin an
* expression which can be repeated. Otherwise it is an array
* of expression types that this token begins. These values
* are used during evaluation to know whether we need to
* duplicate the current context or not and to decide what
* the current expression is (for example, if we are only
* starting the parsing and the first token has no repeat,
* we do not parse it as an OrExpr but directly as PathExpr).
* Examples:
*
* Expression: "/ *[key1 and key2 or key1 < key2]"
* Tokens: '/', '*', '[', NameTest, 'and', NameTest, 'or', NameTest, '<', NameTest, ']'
* Repeat: NULL, NULL, NULL, [AndExpr, NULL, NULL, NULL, [RelationalExpr, NULL, NULL, NULL
* OrExpr, 0],
* 0],
*
* Expression: "//node[key and node2]/key | /cont"
* Tokens: '//', 'NameTest', '[', 'NameTest', 'and', 'NameTest', ']', '/', 'NameTest', '|', '/', 'NameTest'
* Repeat: [UnionExpr, NULL, NULL, [AndExpr, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
* 0], 0],
*
* Operators between expressions which this concerns:
* 'or', 'and', '=', '!=', '<', '>', '<=', '>=', '+', '-', '*', 'div', 'mod', '|'
*/
/**
* @brief Supported types of (partial) XPath results.
*/
enum lyxp_set_type {
LYXP_SET_NODE_SET = 0,
LYXP_SET_SCNODE_SET,
LYXP_SET_BOOLEAN,
LYXP_SET_NUMBER,
LYXP_SET_STRING
};
/**
* @brief Item stored in an XPath set hash table.
*/
struct lyxp_set_hash_node {
struct lyd_node *node;
enum lyxp_node_type type;
} _PACKED;
/**
* @brief XPath set - (partial) result.
*/
struct lyxp_set {
enum lyxp_set_type type;
union {
struct lyxp_set_node {
struct lyd_node *node;
enum lyxp_node_type type;
uint32_t pos;
} *nodes;
struct lyxp_set_scnode {
struct lysc_node *scnode;
enum lyxp_node_type type;
/* -2 - scnode not traversed, currently (the only node) in context;
* -1 - scnode not traversed except for the eval start, not currently in the context;
* 0 - scnode was traversed, but not currently in the context;
* 1 - scnode currently in context;
* 2 - scnode in context and just added, so skip it for the current operation;
* >=3 - scnode is not in context because we are in a predicate and this scnode was used/will be used later */
int32_t in_ctx;
} *scnodes;
struct lyxp_set_meta {
struct lyd_meta *meta;
enum lyxp_node_type type;
uint32_t pos; /* if node_type is LYXP_SET_NODE_META, it is the parent node position */
} *meta;
char *str;
long double num;
int bln;
} val;
/* this is valid only for type LYXP_SET_NODE_SET and LYXP_SET_SCNODE_SET */
uint32_t used;
uint32_t size;
struct hash_table *ht;
/* XPath context information, this is valid only for type LYXP_SET_NODE_SET */
uint32_t ctx_pos;
uint32_t ctx_size;
/* general context */
struct ly_ctx *ctx;
union {
const struct lyd_node *ctx_node;
const struct lysc_node *ctx_scnode;
};
enum lyxp_node_type root_type;
const struct lysc_node *context_op;
const struct lys_module *local_mod;
const struct lyd_node *tree;
LY_PREFIX_FORMAT format;
};
/**
* @brief Print an XPath token \p tok type.
*
* @param[in] tok Token to print.
* @return Token type string.
*/
const char *lyxp_print_token(enum lyxp_token tok);
/**
* @brief Evaluate an XPath expression on data. Be careful when using this function, the result can often
* be confusing without thorough understanding of XPath evaluation rules defined in RFC 7950.
*
* @param[in] exp Parsed XPath expression to be evaluated.
* @param[in] format Format of the XPath expression (more specifcally, of any used prefixes).
* @param[in] local_mod Local module relative to the @p expr.
* @param[in] ctx_node Current (context) data node. In case of a root node, set @p ctx_node_type correctly,
* but @p ctx_node must also be set to any node from the root node module - it will be used for resolving
* unqualified names.
* @param[in] ctx_node_type Current (context) data node type.
* @param[in] tree Data tree on which to perform the evaluation, it must include all the available data (including
* the tree of @p ctx_node).
* @param[out] set Result set.
* @param[in] options Whether to apply some evaluation restrictions.
* @return LY_EVALID for invalid argument types/count,
* @return LY_EINCOMPLETE for unresolved when,
* @return LY_EINVAL, LY_EMEM, LY_EINT for other errors.
*/
LY_ERR lyxp_eval(struct lyxp_expr *exp, LY_PREFIX_FORMAT format, const struct lys_module *local_mod,
const struct lyd_node *ctx_node, enum lyxp_node_type ctx_node_type, const struct lyd_node *tree,
struct lyxp_set *set, int options);
#define LYXP_SCHEMA 0x01 /**< Apply data node access restrictions defined for 'when' and 'must' evaluation. */
/**
* @brief Get all the partial XPath nodes (atoms) that are required for @p exp to be evaluated.
*
* @param[in] exp Parsed XPath expression to be evaluated.
* @param[in] format Format of the XPath expression (more specifcally, of any used prefixes).
* @param[in] local_mod Local module relative to the @p exp.
* @param[in] ctx_scnode Current (context) schema node. In case of a root node, set @p ctx_scnode_type correctly,
* but @p ctx_scnode must also be set to any node from the root node module - it will be used for resolving
* unqualified names.
* @param[in] ctx_scnode_type Current (context) schema node type.
* @param[out] set Result set.
* @param[in] options Whether to apply some evaluation restrictions, one flag must always be used.
* @return LY_ERR (same as lyxp_eval()).
*/
LY_ERR lyxp_atomize(struct lyxp_expr *exp, LY_PREFIX_FORMAT format, const struct lys_module *local_mod,
const struct lysc_node *ctx_scnode, enum lyxp_node_type ctx_scnode_type, struct lyxp_set *set,
int options);
/* used only internally */
#define LYXP_SCNODE_ALL 0x0E
/**
* @brief Cast XPath set to another type.
* Indirectly context position aware.
*
* @param[in] set Set to cast.
* @param[in] target Target type to cast \p set into.
* @return LY_ERR
*/
LY_ERR lyxp_set_cast(struct lyxp_set *set, enum lyxp_set_type target);
/**
* @brief Free dynamic content of a set.
*
* @param[in] set Set to modify.
*/
void lyxp_set_free_content(struct lyxp_set *set);
/**
* @brief Insert schema node into set.
*
* @param[in] set Set to insert into.
* @param[in] node Node to insert.
* @param[in] node_type Node type of @p node.
* @return Index of the inserted node in set.
*/
int lyxp_set_scnode_insert_node(struct lyxp_set *set, const struct lysc_node *node, enum lyxp_node_type node_type);
/**
* @brief Check for duplicates in a schema node set.
*
* @param[in] set Set to check.
* @param[in] node Node to look for in @p set.
* @param[in] node_type Type of @p node.
* @param[in] skip_idx Index from @p set to skip.
* @return Index of the found node, -1 if not found.
*/
int lyxp_set_scnode_dup_node_check(struct lyxp_set *set, const struct lysc_node *node, enum lyxp_node_type node_type,
int skip_idx);
/**
* @brief Merge 2 schema node sets.
*
* @param[in] set1 Set to merge into.
* @param[in] set2 Set to merge. Its content is freed.
*/
void lyxp_set_scnode_merge(struct lyxp_set *set1, struct lyxp_set *set2);
/**
* @brief Parse an XPath expression into a structure of tokens.
* Logs directly.
*
* https://www.w3.org/TR/1999/REC-xpath-19991116/#exprlex
*
* @param[in] ctx Context for errors.
* @param[in] expr XPath expression to parse. It is duplicated.
* @param[in] expr_len Length of @p expr, can be 0 if @p expr is 0-terminated.
* @param[in] reparse Whether to re-parse the expression to finalize full XPath parsing and fill
* information about expressions and their operators (fill repeat).
* @return Filled expression structure or NULL on error.
*/
struct lyxp_expr *lyxp_expr_parse(const struct ly_ctx *ctx, const char *expr, size_t expr_len, int reparse);
/**
* @brief Duplicate parsed XPath expression.
*
* @param[in] ctx Context with a dictionary.
* @param[in] exp Parsed expression.
* @return Duplicated structure, NULL on error.
*/
struct lyxp_expr *lyxp_expr_dup(const struct ly_ctx *ctx, const struct lyxp_expr *exp);
/**
* @brief Look at the next token and check its kind.
*
* @param[in] ctx Context for logging, not logged if NULL.
* @param[in] exp Expression to use.
* @param[in] tok_idx Token index in the expression \p exp.
* @param[in] want_tok Expected token.
* @return LY_EINCOMPLETE on EOF,
* @return LY_ENOT on non-matching token,
* @return LY_SUCCESS on success.
*/
LY_ERR lyxp_check_token(const struct ly_ctx *ctx, const struct lyxp_expr *exp, uint16_t tok_idx, enum lyxp_token want_tok);
/**
* @brief Look at the next token and skip it if it matches the expected one.
*
* @param[in] ctx Context for logging, not logged if NULL.
* @param[in] exp Expression to use.
* @param[in,out] tok_idx Token index in the expression \p exp, is updated.
* @param[in] want_tok Expected token.
* @return LY_EINCOMPLETE on EOF,
* @return LY_ENOT on non-matching token,
* @return LY_SUCCESS on success.
*/
LY_ERR lyxp_next_token(const struct ly_ctx *ctx, const struct lyxp_expr *exp, uint16_t *tok_idx, enum lyxp_token want_tok);
/**
* @brief Frees a parsed XPath expression. @p expr should not be used afterwards.
*
* @param[in] ctx libyang context of the expression.
* @param[in] expr Expression to free.
*/
void lyxp_expr_free(const struct ly_ctx *ctx, struct lyxp_expr *expr);
#endif /* LY_XPATH_H */