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Expression parser
Collaboration diagram for Expression parser:

Data Structures

struct  ap_expr_info_t
 
struct  ap_expr_eval_ctx_t
 
struct  ap_expr_lookup_parms
 

Macros

#define AP_EXPR_FLAG_SSL_EXPR_COMPAT   1
 
#define AP_EXPR_FLAG_DONT_VARY   2
 
#define AP_EXPR_FLAG_RESTRICTED   4
 
#define AP_EXPR_FLAG_STRING_RESULT   8
 
#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)
 

Typedefs

typedef struct ap_expr_node ap_expr_t
 
typedef int ap_expr_op_unary_t (ap_expr_eval_ctx_t *ctx, const void *data, const char *arg)
 
typedef int ap_expr_op_binary_t (ap_expr_eval_ctx_t *ctx, const void *data, const char *arg1, const char *arg2)
 
typedef const char *( ap_expr_string_func_t )(ap_expr_eval_ctx_t *ctx, const void *data, const char *arg)
 
typedef const char *( ap_expr_string_list_func_t )(ap_expr_eval_ctx_t *ctx, const void *data, const apr_array_header_t *args)
 
typedef apr_array_header_t *( ap_expr_list_func_t )(ap_expr_eval_ctx_t *ctx, const void *data, const char *arg)
 
typedef const char *( ap_expr_var_func_t )(ap_expr_eval_ctx_t *ctx, const void *data)
 
typedef intap_expr_lookup_fn_t )(ap_expr_lookup_parms *parms)
 

Functions

int ap_expr_exec (request_rec *r, const ap_expr_info_t *expr, const char **err)
 
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)
 
int ap_expr_exec_ctx (ap_expr_eval_ctx_t *ctx)
 
const char * ap_expr_str_exec (request_rec *r, const ap_expr_info_t *expr, const char **err)
 
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)
 
int ap_expr_lookup_default (ap_expr_lookup_parms *parms)
 
int expr_lookup (ap_expr_lookup_parms *parms)
 
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)
 
ap_expr_info_tap_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)
 
void ap_expr_init (apr_pool_t *pool)
 

Detailed Description

Macro Definition Documentation

#define AP_EXPR_FLAG_DONT_VARY   2

Don't add siginificant request headers to the Vary response header

#define AP_EXPR_FLAG_RESTRICTED   4

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_SSL_EXPR_COMPAT   1

Use ssl_expr compatibility mode (changes the meaning of the comparison operators)

#define AP_EXPR_FLAG_STRING_RESULT   8

Expression evaluates to a string, not to a bool

#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)

Convenience wrapper for ap_expr_parse_cmd_mi() that sets module_index = APLOG_MODULE_INDEX

Typedef Documentation

typedef apr_array_header_t*( ap_expr_list_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.

Parameters
ctxThe evaluation context
dataAn opaque context provided by the lookup hook function
argThe argument
Returns
The functions result list of strings, may be NULL for 'empty array'
typedef int( ap_expr_lookup_fn_t)(ap_expr_lookup_parms *parms)

Function for looking up the provider function for a variable, operator or function in an expression.

Parameters
parmsThe parameter struct, also determins where the result is stored.
Returns
OK on success, !OK on failure, DECLINED if the requested name is not handled by this function
typedef int ap_expr_op_binary_t(ap_expr_eval_ctx_t *ctx, const void *data, const char *arg1, const char *arg2)

Binary operator, takes two string arguments and returns a bool value. The name must have the form '-cmp' (at least two letters).

Parameters
ctxThe evaluation context
dataAn opaque context provided by the lookup hook function
arg1The left operand
arg2The right operand
Returns
0 or 1
typedef int ap_expr_op_unary_t(ap_expr_eval_ctx_t *ctx, const void *data, const char *arg)

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).

Parameters
ctxThe evaluation context
dataAn opaque context provided by the lookup hook function
argThe (right) operand
Returns
0 or 1
typedef const char*( ap_expr_string_func_t)(ap_expr_eval_ctx_t *ctx, const void *data, const char *arg)

String valued function, takes a string argument and returns a string

Parameters
ctxThe evaluation context
dataAn opaque context provided by the lookup hook function
argThe argument
Returns
The functions result string, may be NULL for 'empty string'
typedef const char*( ap_expr_string_list_func_t)(ap_expr_eval_ctx_t *ctx, const void *data, const apr_array_header_t *args)

String valued function, takes a list argument and returns a string

Parameters
ctxThe evaluation context
dataAn opaque context provided by the lookup hook function
argsThe list of string arguments
Returns
The functions result string, may be NULL for 'empty string'
typedef struct ap_expr_node ap_expr_t

A node in the expression parse tree

typedef const char*( ap_expr_var_func_t)(ap_expr_eval_ctx_t *ctx, const void *data)

Variable lookup function, takes no argument and returns a string

Parameters
ctxThe evaluation context
dataAn opaque context provided by the lookup hook function
Returns
The expanded variable

Function Documentation

int ap_expr_exec ( request_rec r,
const ap_expr_info_t expr,
const char **  err 
)

Evaluate a parse tree, simple interface

Parameters
rThe current request
exprThe expression to be evaluated
errWhere an error message should be stored
Returns
> 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
request headers used during evaluation will be added to the Vary: response header, unless AP_EXPR_FLAG_DONT_VARY is set.
int ap_expr_exec_ctx ( ap_expr_eval_ctx_t ctx)

Evaluate a parse tree, full featured version

Parameters
ctxThe evaluation context with all data filled in
Returns
> 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
request headers used during evaluation will be added to the Vary: response header if ctx->vary_this is set.
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 
)

Evaluate a parse tree, with access to regexp backreference

Parameters
rThe current request
exprThe expression to be evaluated
nmatchsize of the regex match vector pmatch
pmatchinformation about regex matches
sourcethe string that pmatch applies to
errWhere an error message should be stored
Returns
> 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
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.
request headers used during evaluation will be added to the Vary: response header, unless AP_EXPR_FLAG_DONT_VARY is set.
void ap_expr_init ( apr_pool_t pool)

Internal initialisation of ap_expr (for httpd internal use)

int ap_expr_lookup_default ( 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.

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 
)

Parse an expression into a parse tree

Parameters
poolPool
ptemptemp pool
infoThe ap_expr_info_t struct (with values filled in)
exprThe expression string to parse
lookup_fnThe lookup function to use, NULL for default
Returns
NULL on success, error message on error. A pointer to the resulting parse tree will be stored in info->root_node.
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 
)

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.

Parameters
cmdThe cmd_parms struct
exprThe expression string to parse
flagsThe flags to use, see AP_EXPR_FLAG_*
errSet to NULL on success, error message on error
lookup_fnThe lookup function used to lookup vars, functions, and operators
module_indexThe module_index to set for the expression
Returns
The parsed expression
Note
Usually ap_expr_parse_cmd() should be used
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

Parameters
rThe current request
exprThe expression to be evaluated
errWhere an error message should be stored
Returns
The result string, NULL on error
Note
err will be set to NULL on success, or to an error message on error
request headers used during evaluation will be added to the Vary: response header, unless AP_EXPR_FLAG_DONT_VARY is set.
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 
)

Evaluate a parse tree of a string valued expression

Parameters
rThe current request
exprThe expression to be evaluated
nmatchsize of the regex match vector pmatch
pmatchinformation about regex matches
sourcethe string that pmatch applies to
errWhere an error message should be stored
Returns
The result string, NULL on error
Note
err will be set to NULL on success, or to an error message on error
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.
request headers used during evaluation will be added to the Vary: response header, unless AP_EXPR_FLAG_DONT_VARY is set.
int expr_lookup ( ap_expr_lookup_parms parms)