busybox/shell/math.h
Denys Vlasenko 0b8835861b Make it possible to select "sh" and "bash" aliases without selecting ash or hush
The same can be done for msh, but we are probably better off just deleting it
in a next versio or two.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2016-12-23 16:56:43 +01:00

93 lines
3.0 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(arith_state_t *state, const char *expr);
*
* The expr argument is the math string to parse. All normal expansions must
* be done already. i.e. no dollar symbols should be present.
*
* The state argument is a pointer to a struct of hooks for your shell (see below),
* and an error message string (NULL if no error).
*
* 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]*
*/
#ifndef SHELL_MATH_H
#define SHELL_MATH_H 1
PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN
#if ENABLE_FEATURE_SH_MATH_64
typedef long long arith_t;
#define ARITH_FMT "%lld"
#define strto_arith_t strtoull
#else
typedef long arith_t;
#define ARITH_FMT "%ld"
#define strto_arith_t strtoul
#endif
typedef const char* FAST_FUNC (*arith_var_lookup_t)(const char *name);
typedef void FAST_FUNC (*arith_var_set_t)(const char *name, const char *val);
//typedef const char* FAST_FUNC (*arith_var_endofname_t)(const char *name);
typedef struct arith_state_t {
const char *errmsg;
arith_var_lookup_t lookupvar;
arith_var_set_t setvar;
// arith_var_endofname_t endofname;
void *list_of_recursed_names;
} arith_state_t;
arith_t FAST_FUNC arith(arith_state_t *state, const char *expr);
POP_SAVED_FUNCTION_VISIBILITY
#endif