From 6f2cac23a7e759c464ef52103fac929e1eeb6b10 Mon Sep 17 00:00:00 2001
From: Nicholas Noll <nbnoll@eml.cc>
Date: Sat, 9 Oct 2021 10:30:50 -0700
Subject: feat(rc): added shell

---
 sys/cmd/rc/code.dep | 166 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 166 insertions(+)
 create mode 100644 sys/cmd/rc/code.dep

(limited to 'sys/cmd/rc/code.dep')

diff --git a/sys/cmd/rc/code.dep b/sys/cmd/rc/code.dep
new file mode 100644
index 0000000..7fdd4bc
--- /dev/null
+++ b/sys/cmd/rc/code.dep
@@ -0,0 +1,166 @@
+#if 0
+// simple example code
+error
+cd(Args args)
+{
+    switch (args.len) {
+    case 0:
+        errorf("reached cd with no arguments!");
+        return 1;
+    case 1:
+    one:
+        errorf("sh: expected argument to command 'cd'");
+        return 1;
+    case 2:
+        if (args.a[1] == nil)
+            goto one;
+        break;
+    default:
+        errorf("sh: too many arguments to command 'cd'");
+        return 1;
+    }
+    if (chdir(args.a[1]))
+        errorf("cd fail: %s", strerror(errno));
+
+    return 0;
+}
+
+error
+quit(Args args)
+{
+    exit(0);
+}
+
+Builtin builtins[] = {
+    { "cd",   cd },
+    { "exit", quit },
+};
+
+void
+clear(Header *arr)
+{
+    arr->len = 0;
+}
+
+int
+readline(Code *code)
+{
+    int n, b;
+
+    n = code->len;
+getchar:
+    if (code->len >= code->cap) {
+        code->cap += 100;
+        code->s = realloc(code->s, code->cap);
+    }
+    /* TODO: unicode? */
+    switch ((b = getchar())) {
+    case EOF:
+        n = -1;
+        goto null;
+    case '\n':
+        n = code->len - n;
+    null:
+        code->s[code->len] = '\0';
+        break;
+    default:
+        code->s[code->len++] = b;
+        goto getchar;
+    }
+
+    return n;
+}
+
+/* TODO: unicode */
+int
+readargs(Code code, Args *args)
+{
+    if (args->a)
+        clear(&args->hdr);
+    else {
+        args->cap += 20;
+        args->a    = realloc(args->a, args->cap);
+    }
+
+    args->a[args->len++] = code.s;
+    while (*code.s) {
+        if (!isspace(*code.s++))
+            continue;
+
+        code.s[-1] = '\0';
+        /* consume all remaining space */
+        while (isspace(*code.s))
+            code.s++;
+
+        if (args->len >= args->cap-1) {
+            args->cap += 20;
+            args->a = realloc(args->a, args->cap);
+        }
+        args->a[args->len++] = code.s;
+    }
+    /* nil acts as a sentinel value */
+    args->a[args->len] = nil;
+
+    return args->len;
+}
+
+error
+execute(Args args)
+{
+    int i, status;
+    pid_t cid, wid;
+
+    for (i = 0; i < arrlen(builtins); i++) {
+        if (strcmp(args.a[0], builtins[i].cmd) == 0)
+            return builtins[i].func(args);
+    }
+
+    if ((cid = fork()) == 0) {
+        if (execvp(args.a[0], args.a) == -1)
+            errorf("exec failed: %s", strerror(errno));
+        exit(1);
+    } else if (cid > 0) 
+        do
+            wid = waitpid(cid, &status, WUNTRACED);
+        while (!WIFEXITED(status) && !WIFSIGNALED(status));
+    else
+        errorf("fork failed: %s", strerror(errno));
+
+    return status;
+}
+
+static
+void
+flush(void)
+{
+    io·flush(stdout);
+}
+
+static
+void
+prompt(void)
+{
+    printf(";");
+    flush();
+}
+
+int
+main(int argc, char *argv[])
+{
+    int  i, err, n;
+    Code code = {0};
+    Args args = {0};
+
+    ARGBEGIN {
+    } ARGEND;
+
+    do {
+        clear(&code.hdr);
+        prompt();
+
+        n = readline(&code);
+        readargs(code, &args);
+        err = execute(args);
+    } while (!err && n > 0);
+}
+#endif
-- 
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