liw-modules-0_3.tar.gz_字符串处理

/* * expr_compile.c -- compile expression given in string form * * Part of publib. See man page for more information * "@(#)publib-expr:expr_compile.c,v 1.1.1.1 1993/11/20 15:57:29 liw Exp" */ #include <assert.h> #include <string.h> #include <stdlib.h> #include <ctype.h> #include <errno.h> #include "publib/expr.h" #include "publib/errormsg.h" #define UNGOT_MAX 8 static struct expr_instr ungot_tokens[UNGOT_MAX]; static int ungot_count = 0; static int get_token(const char **s, struct expr_instr *in); static void unget_token(struct expr_instr *in); static int assignment(const char **s, Expr *e); static int expr(const char **s, Expr *e); static int factor(const char **s, Expr *e); static int term(const char **s, Expr *e); static int simple_expr(const char **s, Expr *e); static int arg_list(struct expr_instr *syminstr, const char **s, Expr *e); static int push(Expr *e, struct expr_instr *); Expr *expr_compile(const char *string) { Expr *e; e = (Expr *) malloc(sizeof(Expr)); if (e == NULL) { __publib_error("malloc failed"); return NULL; } e->prg = NULL; e->size = 0; e->allocated = 0; if (assignment(&string, e) == -1) { expr_free(e); return NULL; } if (*string != '\0') { __publib_error("syntax error: " "expression continues unexpectedly"); expr_free(e); return NULL; } return e; } static int assignment(const char **s, Expr *e) { struct expr_instr in, in2; if (get_token(s, &in) == -1) return -1; if (in.op != op_sym || get_token(s, &in2) == -1) { unget_token(&in); return expr(s, e); } if (in2.op != op_ass) { unget_token(&in2); unget_token(&in); return expr(s, e); } in2.val.sym = in.val.sym; if (expr(s, e) == -1 || push(e, &in2) == -1) return -1; return 0; } static int expr(const char **s, Expr *e) { struct expr_instr in; if (term(s, e) == -1) return -1; while (get_token(s, &in) != -1) { if (in.op != op_add && in.op != op_sub) { unget_token(&in); return 0; } if (term(s, e) == -1 || push(e, &in) == -1) return -1; } return 0; } static int term(const char **s, Expr *e) { struct expr_instr in; if (factor(s, e) == -1) return -1; while (get_token(s, &in) != -1) { if (in.op != op_mul && in.op != op_div && in.op != op_rem) { unget_token(&in); return 0; } if (factor(s, e) == -1 || push(e, &in) == -1) return -1; } return 0; } static int factor(const char **s, Expr *e) { struct expr_instr in; if (get_token(s, &in) == -1) return -1; if (in.op == op_sub || in.op == op_add) { if (get_token(s, &in) == -1) return -1; if (in.op != op_num) { __publib_error("syntax error: " "unary + or - not followed by number"); return -1; } in.op = op_num; if (in.op == op_sub) in.val.num = -in.val.num; else in.val.num = in.val.num; return 0; } unget_token(&in); return simple_expr(s, e); } static int simple_expr(const char **s, Expr *e) { struct expr_instr in; if (get_token(s, &in) == -1) return -1; switch (in.op) { case op_num: if (push(e, &in) == -1) return -1; return 0; case op_left: if (expr(s, e) == -1) return -1; if (get_token(s, &in) == -1) return -1; if (in.op != op_right) { __publib_error("syntax error: unbalanced ("); return -1; } return 0; case op_sym: if (arg_list(&in, s, e) == -1) return -1; if (push(e, &in) == -1) return -1; return 0; default: __publib_error("syntax error: unexpected token"); return -1; } } static int arg_list(struct expr_instr *syminstr, const char **s, Expr *e) { struct expr_instr in; if (get_token(s, &in) == -1) return 0; if (in.op != op_left) { unget_token(&in); return 0; } syminstr->op = op_fun; syminstr->val.fun.name = syminstr->val.sym; syminstr->val.fun.nargs = 0; do { if (expr(s, e) == -1) return -1; if (get_token(s, &in) == -1) return -1; if (in.op != op_right && in.op != op_comma) { __publib_error("syntax error: expression not " "followed by , or ) in argument list"); return -1; } ++syminstr->val.fun.nargs; } while (in.op == op_comma); return 0; } static void unget_token(struct expr_instr *in) { ungot_tokens[ungot_count] = *in; if (ungot_count < UNGOT_MAX) ++ungot_count; } static int get_token(const char **s, struct expr_instr *in) { int off = 1; if (ungot_count > 0) { --ungot_count; *in = ungot_tokens[ungot_count]; return 0; } while (isspace(**s)) ++(*s); switch (**s) { case '+': in->op = op_add; break; case '-': in->op = op_sub; break; case '*': in->op = op_mul; break; case '/': in->op = op_div; break; case '%': in->op = op_rem; break; case '(': in->op = op_left; break; case ')': in->op = op_right; break; case ',': in->op = op_comma; break; case '=': in->op = op_ass; break; case '\0': return -1; default: if (isalpha(**s) || **s == '_') { char *sym; const char *p = *s; size_t len; while (isalnum(**s) || **s == '_') ++(*s); len = *s - p + 1; sym = (char *) malloc(len); if (sym == NULL) { __publib_error("malloc failed"); return -1; } memcpy(sym, p, len-1); sym[len-1] = '\0'; in->op = op_sym; in->val.sym = sym; off = 0; break; } if (!isdigit(**s)) { __publib_error("syntax error: unexpected character"); return -1; } in->op = op_num; in->val.num = strtod(*s, (char **)s); off = 0; break; } *s += off; return 0; } static int push(Expr *e, struct expr_instr *in) { struct expr_instr *p; size_t n; if (e->size >= e->allocated) { n = e->allocated + 64; if (e->prg == NULL) p = (struct expr_instr *)malloc(n*sizeof(*p)); else p = (struct expr_instr *)realloc(e->prg, n*sizeof(*p)); if (p == NULL) { __publib_error("realloc failed"); return -1; } e->allocated = n; e->prg = p; } e->prg[e->size] = *in; ++e->size; return 0; }