ap_expr.h revision d95a7ac0fe7a06495c3aab5d684b4174f9ab282c
/* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* @file ap_expr.h
* @brief Expression parser
*
* @defgroup AP_EXPR ap_expr
* @ingroup APACHE_CORE
* @{
*/
#ifndef AP_EXPR_H
#define AP_EXPR_H
#include "httpd.h"
#include "http_config.h"
#include "ap_regex.h"
#ifdef __cplusplus
extern "C" {
#endif
/** A node in the expression parse tree */
typedef struct ap_expr_node ap_expr_t;
/** Struct describing a parsed expression */
typedef struct {
/** The root of the actual expression parse tree */
ap_expr_t *root_node;
/** The filename where the expression has been defined (for logging).
* May be NULL
*/
const char *filename;
/** The line number where the expression has been defined (for logging). */
unsigned int line_number;
/** Flags relevant for the expression, see AP_EXPR_FLAG_* */
unsigned int flags;
/** The module that is used for loglevel configuration */
int module_index;
} ap_expr_info_t;
/** Use ssl_expr compatibility mode (changes the meaning of the comparison
* operators)
*/
#define AP_EXPR_FLAG_SSL_EXPR_COMPAT 1
/** Don't add siginificant request headers to the Vary response header */
#define AP_EXPR_FLAG_DONT_VARY 2
/** Don't allow functions/vars that bypass the current request's access
* restrictions or would otherwise leak confidential information.
* Used by e.g. mod_include.
*/
#define AP_EXPR_FLAG_RESTRICTED 4
/** Expression evaluates to a string, not to a bool */
#define AP_EXPR_FLAG_STRING_RESULT 8
/**
* Evaluate a parse tree, simple interface
* @param r The current request
* @param expr The expression to be evaluated
* @param err Where an error message should be stored
* @return > 0 if expression evaluates to true, == 0 if false, < 0 on error
* @note err will be set to NULL on success, or to an error message on error
* @note request headers used during evaluation will be added to the Vary:
* response header, unless ::AP_EXPR_FLAG_DONT_VARY is set.
*/
AP_DECLARE(int) ap_expr_exec(request_rec *r, const ap_expr_info_t *expr,
const char **err);
/**
* Evaluate a parse tree, with access to regexp backreference
* @param r The current request
* @param expr The expression to be evaluated
* @param nmatch size of the regex match vector pmatch
* @param pmatch information about regex matches
* @param source the string that pmatch applies to
* @param err Where an error message should be stored
* @return > 0 if expression evaluates to true, == 0 if false, < 0 on error
* @note err will be set to NULL on success, or to an error message on error
* @note nmatch/pmatch/source can be used both to make previous matches
* available to ap_expr_exec_re and to use ap_expr_exec_re's matches
* later on.
* @note request headers used during evaluation will be added to the Vary:
* response header, unless ::AP_EXPR_FLAG_DONT_VARY is set.
*/
AP_DECLARE(int) ap_expr_exec_re(request_rec *r, const ap_expr_info_t *expr,
apr_size_t nmatch, ap_regmatch_t *pmatch,
const char **source, const char **err);
/** Context used during evaluation of a parse tree, created by ap_expr_exec */
typedef struct {
/** the current request */
request_rec *r;
/** the current connection */
conn_rec *c;
/** the current connection */
server_rec *s;
/** the pool to use */
apr_pool_t *p;
/** where to store the error string */
const char **err;
/** ap_expr_info_t for the expression */
const ap_expr_info_t *info;
/** regex match information for back references */
ap_regmatch_t *re_pmatch;
/** size of the vector pointed to by re_pmatch */
apr_size_t re_nmatch;
/** the string corresponding to the re_pmatch */
const char **re_source;
/** A string where the comma separated names of headers are stored
* to be later added to the Vary: header. If NULL, the caller is not
* interested in this information.
*/
const char **vary_this;
/** where to store the result string */
const char **result_string;
/** Arbitrary context data provided by the caller for custom functions */
void *data;
} ap_expr_eval_ctx_t;
/**
* Evaluate a parse tree, full featured version
* @param ctx The evaluation context with all data filled in
* @return > 0 if expression evaluates to true, == 0 if false, < 0 on error
* @note *ctx->err will be set to NULL on success, or to an error message on
* error
* @note request headers used during evaluation will be added to the Vary:
* response header if ctx->vary_this is set.
*/
AP_DECLARE(int) ap_expr_exec_ctx(ap_expr_eval_ctx_t *ctx);
/**
* Evaluate a parse tree of a string valued expression
* @param r The current request
* @param expr The expression to be evaluated
* @param err Where an error message should be stored
* @return The result string, NULL on error
* @note err will be set to NULL on success, or to an error message on error
* @note request headers used during evaluation will be added to the Vary:
* response header, unless ::AP_EXPR_FLAG_DONT_VARY is set.
*/
AP_DECLARE(const char *) ap_expr_str_exec(request_rec *r,
const ap_expr_info_t *expr,
const char **err);
/**
* Evaluate a parse tree of a string valued expression
* @param r The current request
* @param expr The expression to be evaluated
* @param nmatch size of the regex match vector pmatch
* @param pmatch information about regex matches
* @param source the string that pmatch applies to
* @param err Where an error message should be stored
* @return The result string, NULL on error
* @note err will be set to NULL on success, or to an error message on error
* @note nmatch/pmatch/source can be used both to make previous matches
* available to ap_expr_exec_re and to use ap_expr_exec_re's matches
* later on.
* @note request headers used during evaluation will be added to the Vary:
* response header, unless ::AP_EXPR_FLAG_DONT_VARY is set.
*/
AP_DECLARE(const char *) ap_expr_str_exec_re(request_rec *r,
const ap_expr_info_t *expr,
apr_size_t nmatch,
ap_regmatch_t *pmatch,
const char **source,
const char **err);
/**
* The parser can be extended with variable lookup, functions, and
* and operators.
*
* During parsing, the parser calls the lookup function to resolve a
* name into a function pointer and an opaque context for the function.
* If the argument to a function or operator is constant, the lookup function
* may also parse that argument and store the parsed data in the context.
*
* The default lookup function is the hook ::ap_expr_lookup_default which just
* calls ap_run_expr_lookup. Modules can use it to make functions and
* variables generally available.
*
* An ap_expr consumer can also provide its own custom lookup function to
* modify the set of variables and functions that are available. The custom
* lookup function can in turn call 'ap_run_expr_lookup'.
*/
/** Unary operator, takes one string argument and returns a bool value.
* The name must have the form '-z' (one letter only).
* @param ctx The evaluation context
* @param data An opaque context provided by the lookup hook function
* @param arg The (right) operand
* @return 0 or 1
*/
typedef int ap_expr_op_unary_t(ap_expr_eval_ctx_t *ctx, const void *data,
const char *arg);
/** Binary operator, takes two string arguments and returns a bool value.
* The name must have the form '-cmp' (at least two letters).
* @param ctx The evaluation context
* @param data An opaque context provided by the lookup hook function
* @param arg1 The left operand
* @param arg2 The right operand
* @return 0 or 1
*/
typedef int ap_expr_op_binary_t(ap_expr_eval_ctx_t *ctx, const void *data,
const char *arg1, const char *arg2);
/** String valued function, takes a string argument and returns a string
* @param ctx The evaluation context
* @param data An opaque context provided by the lookup hook function
* @param arg The argument
* @return The functions result string, may be NULL for 'empty string'
*/
typedef const char *(ap_expr_string_func_t)(ap_expr_eval_ctx_t *ctx,
const void *data,
const char *arg);
/** List valued function, takes a string argument and returns a list of strings
* Can currently only be called following the builtin '-in' operator.
* @param ctx The evaluation context
* @param data An opaque context provided by the lookup hook function
* @param arg The argument
* @return The functions result list of strings, may be NULL for 'empty array'
*/
typedef apr_array_header_t *(ap_expr_list_func_t)(ap_expr_eval_ctx_t *ctx,
const void *data,
const char *arg);
/** Variable lookup function, takes no argument and returns a string
* @param ctx The evaluation context
* @param data An opaque context provided by the lookup hook function
* @return The expanded variable
*/
typedef const char *(ap_expr_var_func_t)(ap_expr_eval_ctx_t *ctx,
const void *data);
/** parameter struct passed to the lookup hook functions */
typedef struct {
/** type of the looked up object */
int type;
#define AP_EXPR_FUNC_VAR 0
#define AP_EXPR_FUNC_STRING 1
#define AP_EXPR_FUNC_LIST 2
#define AP_EXPR_FUNC_OP_UNARY 3
#define AP_EXPR_FUNC_OP_BINARY 4
/** name of the looked up object */
const char *name;
int flags;
apr_pool_t *pool;
apr_pool_t *ptemp;
/** where to store the function pointer */
const void **func;
/** where to store the function's context */
const void **data;
/** where to store the error message (if any) */
const char **err;
/** arg for pre-parsing (only if a simple string).
* For binary ops, this is the right argument. */
const char *arg;
} ap_expr_lookup_parms;
/** Function for looking up the provider function for a variable, operator
* or function in an expression.
* @param parms The parameter struct, also determins where the result is
* stored.
* @return OK on success,
* !OK on failure,
* DECLINED if the requested name is not handled by this function
*/
typedef int (ap_expr_lookup_fn_t)(ap_expr_lookup_parms *parms);
/** Default lookup function which just calls ap_run_expr_lookup().
* ap_run_expr_lookup cannot be used directly because it has the wrong
* calling convention under Windows.
*/
AP_DECLARE_NONSTD(int) ap_expr_lookup_default(ap_expr_lookup_parms *parms);
AP_DECLARE_HOOK(int, expr_lookup, (ap_expr_lookup_parms *parms))
/**
* Parse an expression into a parse tree
* @param pool Pool
* @param ptemp temp pool
* @param info The ap_expr_info_t struct (with values filled in)
* @param expr The expression string to parse
* @param lookup_fn The lookup function to use, NULL for default
* @return NULL on success, error message on error.
* A pointer to the resulting parse tree will be stored in
* info->root_node.
*/
AP_DECLARE(const char *) ap_expr_parse(apr_pool_t *pool, apr_pool_t *ptemp,
ap_expr_info_t *info, const char *expr,
ap_expr_lookup_fn_t *lookup_fn);
/**
* High level interface to ap_expr_parse that also creates ap_expr_info_t and
* uses info from cmd_parms to fill in most of it.
* @param cmd The cmd_parms struct
* @param expr The expression string to parse
* @param flags The flags to use, see AP_EXPR_FLAG_*
* @param err Set to NULL on success, error message on error
* @param lookup_fn The lookup function used to lookup vars, functions, and
* operators
* @param module_index The module_index to set for the expression
* @return The parsed expression
* @note Usually ap_expr_parse_cmd() should be used
*/
AP_DECLARE(ap_expr_info_t *) ap_expr_parse_cmd_mi(const cmd_parms *cmd,
const char *expr,
unsigned int flags,
const char **err,
ap_expr_lookup_fn_t *lookup_fn,
int module_index);
/**
* Convenience wrapper for ap_expr_parse_cmd_mi() that sets
* module_index = APLOG_MODULE_INDEX
*/
#define ap_expr_parse_cmd(cmd, expr, flags, err, lookup_fn) \
ap_expr_parse_cmd_mi(cmd, expr, flags, err, lookup_fn, APLOG_MODULE_INDEX)
/**
* Internal initialisation of ap_expr (for httpd internal use)
*/
void ap_expr_init(apr_pool_t *pool);
#ifdef __cplusplus
}
#endif
#endif /* AP_EXPR_H */
/** @} */