/* 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_H | |

#define SHELL_MATH_H 1 | |

PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN | |

#if ENABLE_SH_MATH_SUPPORT_64 | |

typedef long long arith_t; | |

#define arith_t_fmt "%lld" | |

#define strto_arith_t strtoll | |

#else | |

typedef long arith_t; | |

#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*); | |

POP_SAVED_FUNCTION_VISIBILITY | |

#endif |