blob: 32e1ffe350cbe00157e54a347e9d1463db8f66a5
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_FEATURE_SH_MATH_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 |
93 |