102 lines
3.5 KiB
C
102 lines
3.5 KiB
C
/* math.h - interface to shell math "library" -- this allows shells to share
|
|
* the implementation of arithmetic $((...)) expansions.
|
|
*
|
|
* This aims to be a POSIX shell math library as documented here:
|
|
* http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_04
|
|
*
|
|
* See math.c for internal documentation.
|
|
*/
|
|
|
|
/* The math library has just one function:
|
|
*
|
|
* arith_t arith(const char *expr, int *perrcode, arith_eval_hooks_t *hooks);
|
|
*
|
|
* The first argument is the math string to parse. All normal expansions must
|
|
* be done already. i.e. no dollar symbols should be present.
|
|
*
|
|
* The second argument is a semi-detailed error description in case something
|
|
* goes wrong in the parsing steps. Currently, those values are (for
|
|
* compatibility, you should assume all negative values are errors):
|
|
* 0 - no errors (yay!)
|
|
* -1 - unspecified problem
|
|
* -2 - divide by zero
|
|
* -3 - exponent less than 0
|
|
* -5 - expression recursion loop detected
|
|
*
|
|
* The third argument is a struct pointer of hooks for your shell (see below).
|
|
*
|
|
* The function returns the answer to the expression. So if you called it
|
|
* with the expression:
|
|
* "1 + 2 + 3"
|
|
* You would obviously get back 6.
|
|
*/
|
|
|
|
/* To add support to a shell, you need to implement three functions:
|
|
*
|
|
* lookupvar() - look up and return the value of a variable
|
|
*
|
|
* If the shell does:
|
|
* foo=123
|
|
* Then the code:
|
|
* const char *val = lookupvar("foo");
|
|
* Will result in val pointing to "123"
|
|
*
|
|
* setvar() - set a variable to some value
|
|
*
|
|
* If the arithmetic expansion does something like:
|
|
* $(( i = 1))
|
|
* Then the math code will make a call like so:
|
|
* setvar("i", "1", 0);
|
|
* The storage for the first two parameters are not allocated, so your
|
|
* shell implementation will most likely need to strdup() them to save.
|
|
*
|
|
* endofname() - return the end of a variable name from input
|
|
*
|
|
* The arithmetic code does not know about variable naming conventions.
|
|
* So when it is given an experession, it knows something is not numeric,
|
|
* but it is up to the shell to dictate what is a valid identifiers.
|
|
* So when it encounters something like:
|
|
* $(( some_var + 123 ))
|
|
* It will make a call like so:
|
|
* end = endofname("some_var + 123");
|
|
* So the shell needs to scan the input string and return a pointer to the
|
|
* first non-identifier string. In this case, it should return the input
|
|
* pointer with an offset pointing to the first space. The typical
|
|
* implementation will return the offset of first char that does not match
|
|
* the regex (in C locale): ^[a-zA-Z_][a-zA-Z_0-9]*
|
|
*/
|
|
|
|
/* To make your life easier when dealing with optional 64bit math support,
|
|
* rather than assume that the type is "signed long" and you can always
|
|
* use "%ld" to scan/print the value, use the arith_t helper defines. See
|
|
* below for the exact things that are available.
|
|
*/
|
|
|
|
#ifndef _SHELL_MATH_
|
|
#define _SHELL_MATH_
|
|
|
|
#if ENABLE_SH_MATH_SUPPORT_64
|
|
typedef int64_t arith_t;
|
|
#define arith_t_type long long
|
|
#define arith_t_fmt "%lld"
|
|
#define strto_arith_t strtoll
|
|
#else
|
|
typedef long arith_t;
|
|
#define arith_t_type long
|
|
#define arith_t_fmt "%ld"
|
|
#define strto_arith_t strtol
|
|
#endif
|
|
|
|
typedef const char *(*arith_var_lookup_t)(const char *name);
|
|
typedef void (*arith_var_set_t)(const char *name, const char *val, int flags);
|
|
typedef char *(*arith_var_endofname_t)(const char *name);
|
|
typedef struct arith_eval_hooks {
|
|
arith_var_lookup_t lookupvar;
|
|
arith_var_set_t setvar;
|
|
arith_var_endofname_t endofname;
|
|
} arith_eval_hooks_t;
|
|
|
|
arith_t arith(const char *expr, int *perrcode, arith_eval_hooks_t*);
|
|
|
|
#endif
|