From 094d3c76925cf6c05a8bfcc112849627d16279b8 Mon Sep 17 00:00:00 2001
From: Nicholas Noll <nbnoll@eml.cc>
Date: Tue, 26 Oct 2021 09:44:47 -0700
Subject: feat(rc): added index operations

---
 sys/cmd/rc/exec.c | 149 +++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 113 insertions(+), 36 deletions(-)

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

diff --git a/sys/cmd/rc/exec.c b/sys/cmd/rc/exec.c
index e8d59c1..fbcfb9b 100644
--- a/sys/cmd/rc/exec.c
+++ b/sys/cmd/rc/exec.c
@@ -702,6 +702,119 @@ Xconcatenate(void)
     runner->args->word = w;
 }
 
+void
+Xdollar(void)
+{
+    int n;
+    char *s, *t;
+    Word *a, *star;
+
+    if(count(runner->args->word)!=1){
+        Xerror("variable name not singleton!\n");
+        return;
+    }
+    s = runner->args->word->str;
+    // deglob(s);
+    n = 0;
+
+    for(t = s;'0'<=*t && *t<='9';t++) 
+        n = n*10+*t-'0';
+
+    a = runner->args->link->word;
+
+    if(n==0 || *t)
+        a = copywords(var(s)->val, a);
+    else{
+        star = var("*")->val;
+        if(star && 1<=n && n<=count(star)){
+            while(--n)
+                star = star->link;
+
+            a = makeword(star->str, a);
+        }
+    }
+
+    poplist();
+    runner->args->word = a;
+}
+
+static
+Word*
+cpwords(Word *array, Word *tail, int n)
+{
+    Word *cp, **end;
+
+    cp = nil, end = &cp;
+    while(n-- > 0){
+        *end = makeword(array->str, nil);
+        end = &(*end)->link;
+        array = array->link;
+    }
+    *end = tail;
+
+    return cp;
+}
+
+
+static
+Word*
+getindex(Word *array, int len, Word *index, Word *tail)
+{
+    char *s;
+    int n, m;
+    if(!index)
+        return tail;
+
+    tail = getindex(array, len, index->link, tail);
+
+    s = index->str;
+    //deglob(s)
+
+    m = 0, n = 0;
+    while('0' <= *s && *s <= '9')
+        n = 10*n + (*s++ - '0');
+    if(*s == '-'){
+        if(*++s == 0)
+            m = len - n;
+        else{
+            while('0' <= *s && *s <= '9')
+                m = 10*m + (*s++ - '0');
+            m -= n;
+        }
+    }
+
+    if(n<1 || n > len || m < 0)
+        return tail;
+    if(n+m > len)
+        m = len-n;
+    while(--n > 0)
+        array = array->link;
+    return cpwords(array, tail, m+1);
+}
+
+void
+Xindex(void)
+{
+    char *s;
+    Word *val, *ret;
+
+    if(count(runner->args->word) != 1){
+        Xerror("variable name not a singleton");
+        return;
+    }
+    s = runner->args->word->str;
+    //deglob(s)
+    val = var(s)->val;
+    poplist();
+
+    ret = runner->args->link->word; // pointer to next stack frame
+    ret = getindex(val, count(val), runner->args->word, ret);
+    poplist();
+
+    // push result back on stack
+    runner->args->word = ret;
+}
+
 void
 Xjoin(void)
 {
@@ -743,42 +856,6 @@ Xjoin(void)
     efree(s);
 }
 
-void
-Xdollar(void)
-{
-    int n;
-    char *s, *t;
-    Word *a, *star;
-
-    if(count(runner->args->word)!=1){
-        Xerror("variable name not singleton!\n");
-        return;
-    }
-    s = runner->args->word->str;
-    // deglob(s);
-    n = 0;
-
-    for(t = s;'0'<=*t && *t<='9';t++) 
-        n = n*10+*t-'0';
-
-    a = runner->args->link->word;
-
-    if(n==0 || *t)
-        a = copywords(var(s)->val, a);
-    else{
-        star = var("*")->val;
-        if(star && 1<=n && n<=count(star)){
-            while(--n)
-                star = star->link;
-
-            a = makeword(star->str, a);
-        }
-    }
-
-    poplist();
-    runner->args->word = a;
-}
-
 void
 Xassign(void)
 {
-- 
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