| /** |
| * @file xpath.h |
| * @author Michal Vasko <mvasko@cesnet.cz> |
| * @brief YANG XPath evaluation functions header |
| * |
| * Copyright (c) 2015 - 2019 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 _XPATH_H |
| #define _XPATH_H |
| |
| #include <stdint.h> |
| |
| #include "log.h" |
| |
| struct ly_ctx; |
| struct lysc_node; |
| |
| /* |
| * 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] Predicate ::= '[' Expr ']' |
| * [8] PrimaryExpr ::= '(' Expr ')' | Literal | Number | FunctionCall |
| * [9] FunctionCall ::= FunctionName '(' ( Expr ( ',' Expr )* )? ')' |
| * [10] PathExpr ::= LocationPath | PrimaryExpr Predicate* |
| * | PrimaryExpr Predicate* '/' RelativeLocationPath |
| * | PrimaryExpr Predicate* '//' RelativeLocationPath |
| * [11] OrExpr ::= AndExpr | OrExpr 'or' AndExpr |
| * [12] AndExpr ::= EqualityExpr | AndExpr 'and' EqualityExpr |
| * [13] EqualityExpr ::= RelationalExpr | EqualityExpr '=' RelationalExpr |
| * | EqualityExpr '!=' RelationalExpr |
| * [14] RelationalExpr ::= AdditiveExpr |
| * | RelationalExpr '<' AdditiveExpr |
| * | RelationalExpr '>' AdditiveExpr |
| * | RelationalExpr '<=' AdditiveExpr |
| * | RelationalExpr '>=' AdditiveExpr |
| * [15] AdditiveExpr ::= MultiplicativeExpr |
| * | AdditiveExpr '+' MultiplicativeExpr |
| * | AdditiveExpr '-' MultiplicativeExpr |
| * [16] MultiplicativeExpr ::= UnaryExpr |
| * | MultiplicativeExpr '*' UnaryExpr |
| * | MultiplicativeExpr 'div' UnaryExpr |
| * | MultiplicativeExpr 'mod' UnaryExpr |
| * [17] UnaryExpr ::= UnionExpr | '-' UnaryExpr |
| * [18] 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_OPERATOR_LOG, /* Operator 'and', 'or' */ |
| LYXP_TOKEN_OPERATOR_COMP, /* Operator '=', '!=', '<', '<=', '>', '>=' */ |
| LYXP_TOKEN_OPERATOR_MATH, /* Operator '+', '-', '*', 'div', 'mod', '-' (unary) */ |
| LYXP_TOKEN_OPERATOR_UNI, /* Operator '|' */ |
| LYXP_TOKEN_OPERATOR_PATH, /* Operator '/', '//' */ |
| /* 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 { |
| /* 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, /* XML element (most common) */ |
| LYXP_NODE_TEXT, /* XML text element (extremely specific use, unlikely to be ever needed) */ |
| LYXP_NODE_ATTR /* XML attribute (in YANG cannot happen, 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_EMPTY = 0, |
| LYXP_SET_NODE_SET, |
| 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; |
| /* 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 */ |
| uint32_t in_ctx; |
| } *scnodes; |
| struct lyxp_set_attr { |
| struct lyd_attr *attr; |
| enum lyxp_node_type type; |
| uint32_t pos; /* if node_type is LYXP_SET_NODE_ATTR, it is the parent node position */ |
| } *attrs; |
| char *str; |
| long double num; |
| int bool; |
| } 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 lys_module *local_mod; |
| const struct lyd_node **trees; |
| LYD_FORMAT format; |
| }; |
| |
| /** |
| * @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] expr XPath expression to evaluate. |
| * @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, NULL for root node. |
| * @param[in] ctx_node_type Current (context) data node type. For every standard case use #LYXP_NODE_ELEM. But there are |
| * cases when the context node @p ctx_node is actually supposed to be the XML root, there is no such data node. So, in |
| * this case just pass NULL for @p ctx_node and use an enum value for this kind of root (#LYXP_NODE_ROOT_CONFIG if |
| * @p ctx_node has config true, otherwise #LYXP_NODE_ROOT). #LYXP_NODE_TEXT and #LYXP_NODE_ATTR can also be used, |
| * but there are no use-cases in YANG. |
| * @param[in] trees Data trees on which to perform the evaluation, they must include all the available tree (including |
| * the tree of @p ctx_node). |
| * @param[out] set Result set. Must be valid and in the same libyang context as @p ctx_node. |
| * To be safe, always either zero or cast the @p set to empty. After done using, either cast |
| * the @p set to empty (if allocated statically) or free it (if allocated dynamically) to |
| * prevent memory leaks. |
| * @param[in] options Whether to apply some evaluation restrictions. |
| * @return LY_ERR |
| */ |
| LY_ERR lyxp_eval(const char *expr, LYD_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 **trees, 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. |
| * |
| * If any LYXP_SCNODE* options is set, only fatal errors are printed, otherwise they are downgraded |
| * to warnings. |
| * |
| * @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, NULL for root node. |
| * @param[in] ctx_scnode_type Current (context) schema node type. |
| * @param[out] set Result set. Must be valid and in the same libyang context as @p ctx_scnode. |
| * To be safe, always either zero or cast the @p set to empty. After done using, either cast |
| * the @p set to empty (if allocated statically) or free it (if allocated dynamically) to |
| * prevent memory leaks. |
| * @param[in] options Whether to apply some evaluation restrictions, one flag must always be used. |
| * @return LY_ERR |
| */ |
| LY_ERR lyxp_atomize(struct lyxp_expr *exp, LYD_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); |
| |
| /* these are used only internally */ |
| #define LYXP_SCNODE 0x02 /**< No special data tree access modifiers. */ |
| #define LYXP_SCNODE_SCHEMA 0x04 /**< Apply schema node access restrictions defined for 'when' and 'must' evaluation. */ |
| #define LYXP_SCNODE_OUTPUT 0x08 /**< Search RPC/action output instead of input. */ |
| |
| #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 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. |
| * @return Filled expression structure or NULL on error. |
| */ |
| struct lyxp_expr *lyxp_expr_parse(struct ly_ctx *ctx, const char *expr); |
| |
| /** |
| * @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(struct ly_ctx *ctx, struct lyxp_expr *expr); |
| |
| #endif /* _XPATH_H */ |