include/ap_expr.h

   1 /* Licensed to the Apache Software Foundation (ASF) under one or more
   2  * contributor license agreements.  See the NOTICE file distributed with
   3  * this work for additional information regarding copyright ownership.
   4  * The ASF licenses this file to You under the Apache License, Version 2.0
   5  * (the "License"); you may not use this file except in compliance with
   6  * the License.  You may obtain a copy of the License at
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 /**
  18  * @file ap_expr.h
  19  * @brief Expression parser
  20  */
  21
  22 #ifndef AP_EXPR_H
  23 #define AP_EXPR_H
  24
  25 #include "httpd.h"
  26 #include "ap_regex.h"
  27
  28 #ifdef __cplusplus
  29 extern "C" {
  30 #endif
  31
  32 /* conditional expression parser stuff */
  33 typedef enum {
  34     TOKEN_STRING,
  35     TOKEN_RE,
  36     TOKEN_AND,
  37     TOKEN_OR,
  38     TOKEN_NOT,
  39     TOKEN_EQ,
  40     TOKEN_NE,
  41     TOKEN_RBRACE,
  42     TOKEN_LBRACE,
  43     TOKEN_GROUP,
  44     TOKEN_GE,
  45     TOKEN_LE,
  46     TOKEN_GT,
  47     TOKEN_LT,
  48     TOKEN_ACCESS
  49 } token_type_t;
  50
  51 typedef struct {
  52     token_type_t  type;
  53     const char   *value;
  54 #ifdef DEBUG_INCLUDE
  55     const char   *s;
  56 #endif
  57 } token_t;
  58
  59 typedef struct parse_node {
  60     struct parse_node *parent;
  61     struct parse_node *left;
  62     struct parse_node *right;
  63     token_t token;
  64     int value;
  65     int done;
  66 #ifdef DEBUG_INCLUDE
  67     int dump_done;
  68 #endif
  69 } ap_parse_node_t;
  70
  71 typedef struct {
  72     const char *source;
  73     const char *rexp;
  74     apr_size_t  nsub;
  75     ap_regmatch_t match[AP_MAX_REG_MATCH];
  76 } backref_t;
  77
  78 typedef const char *(*string_func_t)(request_rec*, const char*);
  79 typedef int (*opt_func_t)(request_rec*, ap_parse_node_t*, string_func_t);
  80
  81 /**
  82  * Parse an expression into a parse tree
  83  * @param pool Pool
  84  * @param expr The expression to parse
  85  * @param was_error On return, set to zero if parse successful, nonzero on error
  86  * @return The parse tree
  87  */
  88 AP_DECLARE(ap_parse_node_t*) ap_expr_parse(apr_pool_t *pool, const char *expr,
  89                                            int *was_error);
  90 /**
  91  * Evaluate a parse tree
  92  * @param r The current request
  93  * @param root The root node of the parse tree
  94  * @param was_error On return, set to zero if parse successful, nonzero on error
  95  * @param reptr Regular expression memory for backreferencing if a regexp was parsed
  96  * @param string_func String parser function - perform variable substitutions
  97  *                    Use ap_expr_string where applicable
  98  * @param eval_func Option evaluation function (e.g. -A filename)
  99  * @return the value the expression parsed to
 100  */
 101 AP_DECLARE(int) ap_expr_eval(request_rec *r, ap_parse_node_t *root,
 102                              int *was_error, backref_t **reptr,
 103                              string_func_t string_func, opt_func_t eval_func);
 104 /**
 105  * Evaluate an expression.  This is functionally equivalent to
 106  * ap_expr_parse followed by ap_expr_eval, but faster and more efficient
 107  * when an expression only needs to be parsed once and discarded.
 108  * @param r The current request
 109  * @param expr The expression to parse
 110  * @param was_error On return, set to zero if parse successful, nonzero on error
 111  * @param reptr Regular expression memory for backreferencing if a regexp was parsed
 112  * @param string_func String parser function - perform variable substitutions
 113  *                    Use ap_expr_string where applicable
 114  * @param eval_func Option evaluation function (e.g. -A filename)
 115  * @return the value the expression parsed to
 116  */
 117 AP_DECLARE(int) ap_expr_evalstring(request_rec *r, const char *expr,
 118                                    int *was_error, backref_t **reptr,
 119                                    string_func_t string_func,
 120                                    opt_func_t eval_func);
 121
 122 /**
 123  * Internal initialisation of ap_expr (for httpd)
 124  * @param pool Pool
 125  * @return APR_SUCCESS or error
 126  */
 127 AP_DECLARE(apr_status_t) ap_expr_init(apr_pool_t *pool);
 128
 129 /**
 130  * Default string evaluation function for passing to ap_expr_eval and
 131  * ap_expr_evalstring.  Use this (and update as necessary) to offer
 132  * a consistent expression syntax across different modules.
 133  * Supports the following:
 134  *     $req{foo}     - request header "foo"
 135  *     $resp{foo}    - response header "foo"
 136  *     $env{foo}     - environment variable "foo"
 137  *     $handler      - r->handler
 138  *     $content-type - r->content_type
 139  * Other strings are returned unmodified.
 140  * @param r The current request
 141  * @param str The string to evaluate
 142  * @return The evaluated string
 143  */
 144 AP_DECLARE_NONSTD(const char*) ap_expr_string(request_rec *r,
 145                                               const char *str);
 146
 147 #ifdef __cplusplus
 148 }
 149 #endif
 150
 151 #endif /* AP_EXPR_H */