1 files changed, 197 insertions, 0 deletions
diff --git a/src/locale/pleval.c b/src/locale/pleval.c
new file mode 100644
index 00000000..47aefc34
--- /dev/null
+++ b/src/locale/pleval.c
@@ -0,0 +1,197 @@
+#include <stdlib.h>
+#include <ctype.h>
+
+/*
+grammar:
+
+Start = Expr ';'
+Expr  = Or | Or '?' Expr ':' Expr
+Or    = And | Or '||' And
+And   = Eq | And '&&' Eq
+Eq    = Rel | Eq '==' Rel | Eq '!=' Rel
+Rel   = Add | Rel '<=' Add | Rel '>=' Add | Rel '<' Add | Rel '>' Add
+Add   = Mul | Add '+' Mul | Add '-' Mul
+Mul   = Term | Mul '*' Term | Mul '/' Term | Mul '%' Term
+Term  = '(' Expr ')' | '!' Term | decimal | 'n'
+
+internals:
+
+recursive descent expression evaluator with stack depth limit.
+eval* functions return the value of the subexpression and set
+the current string pointer to the next non-space char.
+*/
+
+struct st {
+	const char *s;
+	unsigned long n;
+	int err;
+};
+
+static const char *skipspace(const char *s)
+{
+	while (isspace(*s)) s++;
+	return s;
+}
+
+static unsigned long evalconst(struct st *st)
+{
+	char *e;
+	unsigned long n;
+	n = strtoul(st->s, &e, 10);
+	if (!isdigit(*st->s) || e == st->s || n == -1)
+		st->err = 1;
+	st->s = skipspace(e);
+	return n;
+}
+
+static unsigned long evalexpr(struct st *st, int d);
+
+static unsigned long evalterm(struct st *st, int d)
+{
+	unsigned long a;
+	if (d <= 0) {
+		st->err = 1;
+		return 0;
+	}
+	st->s = skipspace(st->s);
+	if (*st->s == '!') {
+		st->s++;
+		return !evalterm(st, d-1);
+	}
+	if (*st->s == '(') {
+		st->s++;
+		a = evalexpr(st, d-1);
+		if (*st->s != ')') {
+			st->err = 1;
+			return 0;
+		}
+		st->s = skipspace(st->s + 1);
+		return a;
+	}
+	if (*st->s == 'n') {
+		st->s = skipspace(st->s + 1);
+		return st->n;
+	}
+	return evalconst(st);
+}
+
+static unsigned long evalmul(struct st *st, int d)
+{
+	unsigned long b, a = evalterm(st, d-1);
+	int op;
+	for (;;) {
+		op = *st->s;
+		if (op != '*' && op != '/' && op != '%')
+			return a;
+		st->s++;
+		b = evalterm(st, d-1);
+		if (op == '*') {
+			a *= b;
+		} else if (!b) {
+			st->err = 1;
+			return 0;
+		} else if (op == '%') {
+			a %= b;
+		} else {
+			a /= b;
+		}
+	}
+}
+
+static unsigned long evaladd(struct st *st, int d)
+{
+	unsigned long a = 0;
+	int add = 1;
+	for (;;) {
+		a += (add?1:-1) * evalmul(st, d-1);
+		if (*st->s != '+' && *st->s != '-')
+			return a;
+		add = *st->s == '+';
+		st->s++;
+	}
+}
+
+static unsigned long evalrel(struct st *st, int d)
+{
+	unsigned long b, a = evaladd(st, d-1);
+	int less, eq;
+	for (;;) {
+		if (*st->s != '<' && *st->s != '>')
+			return a;
+		less = st->s[0] == '<';
+		eq = st->s[1] == '=';
+		st->s += 1 + eq;
+		b = evaladd(st, d-1);
+		a = (less ? a < b : a > b) || (eq && a == b);
+	}
+}
+
+static unsigned long evaleq(struct st *st, int d)
+{
+	unsigned long a = evalrel(st, d-1);
+	int neg;
+	for (;;) {
+		if ((st->s[0] != '=' && st->s[0] != '!') || st->s[1] != '=')
+			return a;
+		neg = st->s[0] == '!';
+		st->s += 2;
+		a = evalrel(st, d-1) == a;
+		a ^= neg;
+	}
+}
+
+static unsigned long evaland(struct st *st, int d)
+{
+	unsigned long a = evaleq(st, d-1);
+	for (;;) {
+		if (st->s[0] != '&' || st->s[1] != '&')
+			return a;
+		st->s += 2;
+		a = evaleq(st, d-1) && a;
+	}
+}
+
+static unsigned long evalor(struct st *st, int d)
+{
+	unsigned long a = evaland(st, d-1);
+	for (;;) {
+		if (st->s[0] != '|' || st->s[1] != '|')
+			return a;
+		st->s += 2;
+		a = evaland(st, d-1) || a;
+	}
+}
+
+static unsigned long evalexpr(struct st *st, int d)
+{
+	unsigned long a1, a2, a3;
+	if (d <= 0) {
+		st->err = 1;
+		return 0;
+	}
+	a1 = evalor(st, d-1);
+	if (*st->s != '?')
+		return a1;
+	st->s++;
+	a2 = evalexpr(st, d-1);
+	if (*st->s != ':') {
+		st->err = 1;
+		return 0;
+	}
+	st->s++;
+	a3 = evalexpr(st, d-1);
+	return a1 ? a2 : a3;
+}
+
+unsigned long __pleval(const char *s, unsigned long n)
+{
+	unsigned long a;
+	struct st st;
+	st.s = s;
+	st.n = n;
+	st.err = 0;
+	a = evalexpr(&st, 100);
+	if (st.err || *st.s != ';')
+		return -1;
+	return a;
+}