release/src/router/busybox/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
  10 /* The math library has just one function:
  11  *
  12  * arith_t arith(arith_state_t *state, const char *expr);
  13  *
  14  * The expr argument is the math string to parse.  All normal expansions must
  15  * be done already.  i.e. no dollar symbols should be present.
  16  *
  17  * The state argument is a pointer to a struct of hooks for your shell (see below),
  18  * and an error message string (NULL if no error).
  19  *
  20  * The function returns the answer to the expression.  So if you called it
  21  * with the expression:
  22  * "1 + 2 + 3"
  23  * you would obviously get back 6.
  24  */
  25
  26 /* To add support to a shell, you need to implement three functions:
  27  *
  28  * lookupvar() - look up and return the value of a variable
  29  *
  30  *      If the shell does:
  31  *              foo=123
  32  *      Then the code:
  33  *              const char *val = lookupvar("foo");
  34  *      will result in val pointing to "123"
  35  *
  36  * setvar() - set a variable to some value
  37  *
  38  *      If the arithmetic expansion does something like:
  39  *              $(( i = 1))
  40  *      then the math code will make a call like so:
  41  *              setvar("i", "1", 0);
  42  *      The storage for the first two parameters are not allocated, so your
  43  *      shell implementation will most likely need to strdup() them to save.
  44  *
  45  * endofname() - return the end of a variable name from input
  46  *
  47  *      The arithmetic code does not know about variable naming conventions.
  48  *      So when it is given an experession, it knows something is not numeric,
  49  *      but it is up to the shell to dictate what is a valid identifiers.
  50  *      So when it encounters something like:
  51  *              $(( some_var + 123 ))
  52  *      It will make a call like so:
  53  *              end = endofname("some_var + 123");
  54  *      So the shell needs to scan the input string and return a pointer to the
  55  *      first non-identifier string.  In this case, it should return the input
  56  *      pointer with an offset pointing to the first space.  The typical
  57  *      implementation will return the offset of first char that does not match
  58  *      the regex (in C locale): ^[a-zA-Z_][a-zA-Z_0-9]*
  59  */
  60
  61 #ifndef SHELL_MATH_H
  62 #define SHELL_MATH_H 1
  63
  64 PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN
  65
  66 #if ENABLE_SH_MATH_SUPPORT_64
  67 typedef long long arith_t;
  68 #define ARITH_FMT "%lld"
  69 #define strto_arith_t strtoull
  70 #else
  71 typedef long arith_t;
  72 #define ARITH_FMT "%ld"
  73 #define strto_arith_t strtoul
  74 #endif
  75
  76 typedef const char* FAST_FUNC (*arith_var_lookup_t)(const char *name);
  77 typedef void        FAST_FUNC (*arith_var_set_t)(const char *name, const char *val);
  78 //typedef const char* FAST_FUNC (*arith_var_endofname_t)(const char *name);
  79
  80 typedef struct arith_state_t {
  81         const char           *errmsg;
  82         arith_var_lookup_t    lookupvar;
  83         arith_var_set_t       setvar;
  84 //      arith_var_endofname_t endofname;
  85         void                 *list_of_recursed_names;
  86 } arith_state_t;
  87
  88 arith_t FAST_FUNC arith(arith_state_t *state, const char *expr);
  89
  90 POP_SAVED_FUNCTION_VISIBILITY
  91
  92 #endif