A compact, field-agnostic query language for filtering records. More...

Typedefs
typedef const char (	N_QUERY_GET) (const char field, void user_data)
	Field-value getter: return the value of `field` for the record being evaluated (NUL-terminated, borrowed), or NULL when the field is unknown/empty.

Functions
N_QUERY *	n_query_compile (const char expr, char errbuf, size_t errlen)
	Compile an expression into a query.

int	n_query_eval (const N_QUERY query, N_QUERY_GET get, void user_data)
	Evaluate a compiled query against one record via `get`.

void	n_query_free (N_QUERY **query)
	Free a compiled query and set the pointer to NULL.

Detailed Description

A compact, field-agnostic query language for filtering records.

The grammar is:

query := or or := and ( "OR" and )* and := not ( "AND" not )* not := "NOT" not | primary primary := "(" or ")" | comparison comparison := FIELD OP VALUE

FIELD is an identifier (letters, digits, '_' and '.', e.g. "host" or "req.path"). VALUE is a bareword (run of non-space, non-operator, non-paren characters) or a double-quoted string. The operators are:

= case-insensitive string equality != case-insensitive string inequality ~ case-insensitive substring contains !~ does not contain =~ regex match (PCRE via n_pcre) !~~ regex does not match

‍ < >= <= numeric comparison (both sides parsed as numbers)

AND/OR/NOT are case-insensitive keywords. Evaluation pulls each field's value through a caller-supplied getter, so the language is independent of any record type: the caller maps field names to its own data.

Typedef Documentation

◆ N_QUERY_GET

typedef const char *(* N_QUERY_GET) (const char *field, void *user_data)

Field-value getter: return the value of field for the record being evaluated (NUL-terminated, borrowed), or NULL when the field is unknown/empty.

Definition at line 71 of file n_query.h.

Function Documentation

◆ n_query_compile()

N_QUERY * n_query_compile	(	const char *	expr,
		char *	errbuf,
		size_t	errlen
	)

Compile an expression into a query.

On error returns NULL and, when errbuf is non-NULL, writes a short message into it. Free with n_query_free. An empty/whitespace expression compiles to a match-all query.

Definition at line 375 of file n_query.c.

References PARSER::err, lex_next(), node_free(), PARSER::p, parse_or(), root, TK_END, PARSER::tok, and PARSER::tval.

Referenced by expect_parse_error(), and run().

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