LXR 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
  64PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN
  65
  66#if ENABLE_FEATURE_SH_MATH_64
  67typedef long long arith_t;
  68# define ARITH_FMT "%lld"
  69#else
  70typedef long arith_t;
  71# define ARITH_FMT "%ld"
  72#endif
  73
  74typedef const char* FAST_FUNC (*arith_var_lookup_t)(const char *name);
  75typedef void        FAST_FUNC (*arith_var_set_t)(const char *name, const char *val);
  76//typedef const char* FAST_FUNC (*arith_var_endofname_t)(const char *name);
  77
  78typedef struct arith_state_t {
  79        const char           *errmsg;
  80        arith_var_lookup_t    lookupvar;
  81        arith_var_set_t       setvar;
  82//      arith_var_endofname_t endofname;
  83        void                 *list_of_recursed_names;
  84} arith_state_t;
  85
  86arith_t FAST_FUNC arith(arith_state_t *state, const char *expr);
  87
  88POP_SAVED_FUNCTION_VISIBILITY
  89
  90#endif
  91