From 425ef692da7e74112f88f0b368f3286dba84f846 Mon Sep 17 00:00:00 2001
From: Nicholas Noll <nbnoll@eml.cc>
Date: Thu, 18 Jun 2020 19:45:40 -0700
Subject: feat: working parser for rc shell language

---
 sys/cmd/rc/var.c | 108 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 sys/cmd/rc/var.c

(limited to 'sys/cmd/rc/var.c')

diff --git a/sys/cmd/rc/var.c b/sys/cmd/rc/var.c
new file mode 100644
index 0000000..dbe7c14
--- /dev/null
+++ b/sys/cmd/rc/var.c
@@ -0,0 +1,108 @@
+#include "rc.h"
+
+Var *globals[1021] = { 0 };
+
+struct Keyword {
+    ushort type;
+    char  *name;
+    struct Keyword *link;
+} *keywords[41];
+
+// -----------------------------------------------------------------------
+// utility
+
+static
+int
+hash(char *s, int n)
+{
+    int i = 1, h = 0;
+    while (*s)
+        h += *s++*i++;
+    h %= n;
+    return (h<0)?h+n:h;
+}
+
+// -----------------------------------------------------------------------
+// keywords
+
+static
+void
+putkw(int type, char *name)
+{
+    struct Keyword *kw;
+    int h = hash(name, arrlen(keywords));
+
+    alloc(kw);
+    kw->type = type;
+    kw->name = name;
+    kw->link = keywords[h];
+
+    keywords[h] = kw;
+}
+
+void
+initkw(void)
+{
+    putkw(Kfor, "for");
+    putkw(Kin, "in");
+    putkw(Kwhile, "while");
+    putkw(Kif, "if");
+    putkw(Kelse, "else");
+    putkw(Kswitch, "switch");
+    putkw(Kcase, "case");
+    putkw(Kfunc, "func");
+}
+
+int
+kwlookup(char *name)
+{
+    int t;
+    struct Keyword *it;
+    for(t=-1,it = keywords[hash(name, arrlen(keywords))];it;it = it->link)
+        if(!strcmp(it->name, name))
+            t = it->type;
+    return t;
+}
+
+// -----------------------------------------------------------------------
+// variables 
+
+Var *
+newvar(char *name, Var *link)
+{
+    Var *v;
+
+    alloc(v);
+    v->name = name;
+    v->val  = 0;
+    v->func = nil;
+    v->link = link;
+
+    return v;
+}
+
+/* only global lookup */
+
+Var *
+gvlookup(char *name)
+{
+    Var *v;
+    int h = hash(name, arrlen(globals));
+    for (v = globals[h]; v; v = v->link)
+        if (!strcmp(v->name, name))
+            return v;
+
+    return globals[h] = newvar(strdup(name), globals[h]);
+}
+
+/* local + global lookup */
+Var *
+vlookup(char *name)
+{
+    Var *v;
+    if (shell)
+        for (v = shell->local; v; v = v->link)
+            if (!strcmp(v->name, name))
+                return v;
+    return gvlookup(name);
+}
-- 
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