diff options
Diffstat (limited to 'src/s6-portable-utils/s6-expr.c')
| -rw-r--r-- | src/s6-portable-utils/s6-expr.c | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/src/s6-portable-utils/s6-expr.c b/src/s6-portable-utils/s6-expr.c new file mode 100644 index 0000000..91be041 --- /dev/null +++ b/src/s6-portable-utils/s6-expr.c @@ -0,0 +1,205 @@ +/* ISC license. */ + +#include <string.h> +#include <skalibs/allreadwrite.h> +#include <skalibs/types.h> +#include <skalibs/strerr.h> + +#define USAGE "s6-expr arithmetic expression" +#define bail() strerr_dief1x(2, "invalid expression") + +enum expr_opnum_e +{ + T_DATA, + T_AND, + T_OR, + T_LEFTP, + T_RIGHTP, + T_EQUAL, + T_NEQUAL, + T_GREATER, + T_GREATERE, + T_LESSER, + T_LESSERE, + T_PLUS, + T_MINUS, + T_TIMES, + T_DIV, + T_MOD +} ; + +struct expr_token_s +{ + char const *string ; + enum expr_opnum_e op ; + unsigned int type ; +} ; + +struct expr_node_s +{ + enum expr_opnum_e op ; + unsigned int type ; + unsigned int arg1 ; + unsigned int arg2 ; + long data ; +} ; + +static unsigned int expr_lex (struct expr_node_s *tree, char const *const *argv) +{ + static struct expr_token_s const tokens[16] = + { + { "+", T_PLUS, 3 }, + { "-", T_MINUS, 3 }, + { "*", T_TIMES, 2 }, + { "/", T_DIV, 2 }, + { "%", T_MOD, 2 }, + { "(", T_LEFTP, 7 }, + { ")", T_RIGHTP, 8 }, + { "=", T_EQUAL, 4 }, + { "!=", T_NEQUAL, 4 }, + { "<", T_LESSER, 4 }, + { "<=", T_LESSERE, 4 }, + { ">", T_GREATER, 4 }, + { ">=", T_GREATERE, 4 }, + { "|", T_OR, 6 }, + { "&", T_AND, 5 }, + { 0, 0, 0 } + } ; + unsigned int pos = 0 ; + + for (; argv[pos] ; pos++) + { + unsigned int i = 0 ; + for (i = 0 ; tokens[i].string ; i++) + if (!strcmp(argv[pos], tokens[i].string)) + { + tree[pos].op = tokens[i].op ; + tree[pos].type = tokens[i].type ; + break ; + } + if (!tokens[i].string) + { + tree[pos].op = T_DATA ; + tree[pos].type = 0 ; + if (!long_scan(argv[pos], &tree[pos].data)) bail() ; + } + } + return pos ; +} + +static void expr_reduce (struct expr_node_s *tree, unsigned int *stack, unsigned int *sp, unsigned int type) +{ + if (tree[stack[*sp-1]].type == type) + { + tree[stack[*sp-1]].arg1 = stack[*sp-2] ; + tree[stack[*sp-1]].arg2 = stack[*sp] ; + stack[*sp-2] = stack[*sp-1] ; + *sp -= 2 ; + } + tree[stack[*sp]].type = type + 7 ; +} + +static unsigned int expr_parse (struct expr_node_s *tree, unsigned int n) +{ + static char const table[9][15] = + { + "xsssssssxzzzzzz", + "xxxxxxxx!zzzzzz", + "mxxxxxxxMszzzzz", + "mxxxxxxxMaszzzz", + "mxxxxxxxMacszzz", + "mxxxxxxxMacAszz", + "mxxxxxxxMacAOsz", + "xsssssssxzzzzzz", + "mxxxxxxxMacAOEs" + } ; + unsigned int stack[n] ; + unsigned int sp = 0, pos = 0 ; + char cont = 1 ; + stack[0] = n + 1 ; + tree[n].type = 8 ; /* add ) for the final reduce */ + tree[n+1].type = 1 ; /* add EOF */ + while (cont) + { + switch (table[tree[pos].type][tree[stack[sp]].type]) + { + case 'x' : bail() ; + case '!' : cont = 0 ; break ; + case 's' : stack[++sp] = pos++ ; break ; + case 'M' : + if (tree[stack[sp-2]].type != 7) bail() ; + stack[sp-2] = stack[sp-1] ; + sp -= 2 ; + case 'm' : expr_reduce(tree, stack, &sp, 2) ; break ; + case 'a' : expr_reduce(tree, stack, &sp, 3) ; break ; + case 'c' : expr_reduce(tree, stack, &sp, 4) ; break ; + case 'A' : expr_reduce(tree, stack, &sp, 5) ; break ; + case 'O' : expr_reduce(tree, stack, &sp, 6) ; break ; + case 'E' : tree[stack[sp]].type = 14 ; break ; + case 'z' : + default : strerr_dief1x(101, "internal error in parse, please submit a bug-report.") ; /* can't happen */ + } + } + if (sp != 2) bail() ; + return stack[1] ; +} + +static long expr_run (struct expr_node_s const *tree, unsigned int root) +{ + switch (tree[root].op) + { + case T_DATA : + return tree[root].data ; + case T_OR : + { + long r = expr_run(tree, tree[root].arg1) ; + return r ? r : expr_run(tree, tree[root].arg2) ; + } + case T_AND : + { + long r = expr_run(tree, tree[root].arg1) ; + return r ? expr_run(tree, tree[root].arg2) ? r : 0 : 0 ; + } + case T_EQUAL : + return expr_run(tree, tree[root].arg1) == expr_run(tree, tree[root].arg2) ; + case T_NEQUAL : + return expr_run(tree, tree[root].arg1) != expr_run(tree, tree[root].arg2) ; + case T_GREATER : + return expr_run(tree, tree[root].arg1) > expr_run(tree, tree[root].arg2) ; + case T_GREATERE : + return expr_run(tree, tree[root].arg1) >= expr_run(tree, tree[root].arg2) ; + case T_LESSER : + return expr_run(tree, tree[root].arg1) < expr_run(tree, tree[root].arg2) ; + case T_LESSERE : + return expr_run(tree, tree[root].arg1) <= expr_run(tree, tree[root].arg2) ; + case T_PLUS : + return expr_run(tree, tree[root].arg1) + expr_run(tree, tree[root].arg2) ; + case T_MINUS : + return expr_run(tree, tree[root].arg1) - expr_run(tree, tree[root].arg2) ; + case T_TIMES : + return expr_run(tree, tree[root].arg1) * expr_run(tree, tree[root].arg2) ; + case T_DIV : + return expr_run(tree, tree[root].arg1) / expr_run(tree, tree[root].arg2) ; + case T_MOD : + return expr_run(tree, tree[root].arg1) % expr_run(tree, tree[root].arg2) ; + default : strerr_dief1x(101, "internal error in expr_run, please submit a bug-report") ; + } +} + +int main (int argc, char const *const *argv) +{ + char fmt[LONG_FMT] ; + long val ; + size_t len ; + PROG = "s6-expr" ; + if (argc <= 1) return 2 ; + { + struct expr_node_s tree[argc + 1] ; + val = expr_run(tree, expr_parse(tree, expr_lex(tree, argv+1))) ; + } + len = long_fmt(fmt, val) ; + fmt[len++] = '\n' ; + if (allwrite(1, fmt, len) < len) + strerr_diefu1sys(111, "write to stdout") ; + return !val ; +} |