shell/math.h

   1 /* math.h - interface to shell math "library" -- this allows shells to share
   2  *          the implementation of arithmetic $((...)) expansions.
   3  *
   4  * This aims to be a POSIX shell math library as documented here:
   5  *      http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_04
   6  *
   7  * See math.c for internal documentation.
   8  */
   9 /* The math library has just one function:
  10  *
  11  * arith_t arith(arith_state_t *state, const char *expr);
  12  *
  13  * The expr argument is the math string to parse.  All normal expansions must
  14  * be done already.  i.e. no dollar symbols should be present.
  15  *
  16  * The state argument is a pointer to a struct of hooks for your shell (see below),
  17  * and an error message string (NULL if no error).
  18  *
  19  * The function returns the answer to the expression.  So if you called it
  20  * with the expression:
  21  * "1 + 2 + 3"
  22  * you would obviously get back 6.
  23  */
  24 /* To add support to a shell, you need to implement three functions:
  25  *
  26  * lookupvar() - look up and return the value of a variable
  27  *
  28  *      If the shell does:
  29  *              foo=123
  30  *      Then the code:
  31  *              const char *val = lookupvar("foo");
  32  *      will result in val pointing to "123"
  33  *
  34  * setvar() - set a variable to some value
  35  *
  36  *      If the arithmetic expansion does something like:
  37  *              $((i = 1))
  38  *      then the math code will make a call like so:
  39  *              setvar("i", "1");
  40  *      The storage for the first two parameters are not allocated, so your
  41  *      shell implementation will most likely need to strdup() them to save.
  42  */
  43 #ifndef SHELL_MATH_H
  44 #define SHELL_MATH_H 1
  45
  46 PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN
  47
  48 #if ENABLE_FEATURE_SH_MATH_64
  49 typedef long long arith_t;
  50 # define ARITH_FMT "%lld"
  51 #else
  52 typedef long arith_t;
  53 # define ARITH_FMT "%ld"
  54 #endif
  55
  56 typedef const char* FAST_FUNC (*arith_var_lookup_t)(const char *name);
  57 typedef void        FAST_FUNC (*arith_var_set_t)(const char *name, const char *val);
  58
  59 typedef struct arith_state_t {
  60         unsigned              evaluation_disabled;
  61         const char           *errmsg;
  62         void                 *list_of_recursed_names;
  63         arith_var_lookup_t    lookupvar;
  64         arith_var_set_t       setvar;
  65 } arith_state_t;
  66
  67 arith_t FAST_FUNC arith(arith_state_t *state, const char *expr);
  68
  69 POP_SAVED_FUNCTION_VISIBILITY
  70
  71 #endif