query.h

   1 /* Copyright (C) 2010 Red Hat, Inc.
   2
   3    This program is free software: you can redistribute it and/or modify
   4    it under the terms of the GNU General Public License as published by
   5    the Free Software Foundation, either version 3 of the License, or
   6    (at your option) any later version.
   7
   8    This program is distributed in the hope that it will be useful,
   9    but WITHOUT ANY WARRANTY; without even the implied warranty of
  10    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11    GNU General Public License for more details.
  12
  13    You should have received a copy of the GNU General Public License
  14    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  15
  16 #ifndef _QUERY_H
  17 #define _QUERY_H 1
  18
  19 #if defined(__CPLUSPLUS__) || defined(__cplusplus)
  20 extern "C" {
  21 #endif
  22
  23 #include "iwhd-qparser.h"
  24
  25 /*
  26  * Comparisons are all the same type to the parser, but when it comes to
  27  * evaluation we need to know the difference so we use these subtypes.
  28  */
  29 typedef enum {
  30         C_LESSTHAN,     C_LESSOREQ,
  31         C_EQUAL,        C_DIFFERENT,
  32         C_GREATEROREQ,  C_GREATERTHAN
  33 } comp_t;
  34
  35 /* The actual values are generated by the parser. */
  36 typedef enum yytokentype type_t;
  37
  38 /*
  39  * Universal AST object.  T_NUMBER uses as_num, and some day T_DATE might as
  40  * well.  Several types (T_STRING, T_ID, T_*FIELD) all use as_str.  The rest
  41  * use as_tree, but there's a caveat.  In most cases as_tree.right really is
  42  * a value_t, but for T_LINK it's a bare string.
  43  * TBD: use a separate as_link union member for T_LINK.
  44  */
  45 typedef struct value_t {
  46         type_t type;
  47         union {
  48                 long long as_num;
  49                 char *as_str;
  50                 struct {
  51                         comp_t op;
  52                         struct value_t *left;
  53                         struct value_t *right;
  54                 } as_tree;
  55         };
  56         const char *resolved;   /* saved result for T_OFIELD/T_SFIELD/T_LINK */
  57 } value_t;
  58
  59 /*
  60  * In a higher-level language, this would be a method pointer.  It's just
  61  * a pointer to a function plus a little piece of the caller's context (in
  62  * the replication-policy case it's the current bucket and key) so that we
  63  * can do concurrent evaluations with separate contexts.
  64  */
  65 typedef struct {
  66         const char      *(*func)        (void *, const char *);
  67         void            *ctx;
  68 } getter_t;
  69 #define CALL_GETTER(g,x)        g->func(g->ctx,x)
  70
  71 /*
  72  * In the normal case a caller would invoke parse once, eval multiple times,
  73  * and free_value once.  print_value is just for debugging/testing.
  74  * TBD: make parse reentrant (eval already is, free_value doesn't need to be.
  75  * Unfortunately, a quick scan of generated code and information on the web
  76  * seems to indicate that even a "reentrant" bison parser only encapsulates
  77  * user state and still relies quite a bit on internal globals.  That might
  78  * mean that we just have to put a lock around it instead.
  79  */
  80 int      eval           (const value_t *expr,
  81                          const getter_t *oget, const getter_t *sget);
  82 void     free_value     (value_t *);
  83 void     print_value    (const value_t *);
  84
  85 value_t *parse (const char *text);
  86
  87 #if defined(__CPLUSPLUS__) || defined(__cplusplus)
  88 }
  89 #endif
  90
  91 #endif