kern/arg: new module

1 files changed, 162 insertions, 0 deletions

diff --git a/kern/arg.c b/kern/arg.c
new file mode 100644
index 00000000..02ed4b7b
--- /dev/null
+++ b/kern/arg.c
@@ -0,0 +1,162 @@
+/*
+ * Copyright (c) 2017 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <kern/arg.h>
+#include <kern/assert.h>
+#include <kern/init.h>
+#include <kern/macros.h>
+#include <kern/panic.h>
+
+/*
+ * Internally, all space characters are turned into null bytes so that
+ * values returned to callers directly point in the command line string,
+ * with no need for dynamic allocation.
+ */
+static char arg_cmdline[ARG_CMDLINE_MAX_SIZE] __initdata;
+static const char *arg_cmdline_end __initdata;
+
+void __init
+arg_setup(const char *cmdline)
+{
+    size_t i, length;
+
+    if (cmdline == NULL) {
+        arg_cmdline[0] = '\0';
+        return;
+    }
+
+    length = strlen(cmdline);
+
+    if ((length + 1) > ARRAY_SIZE(arg_cmdline)) {
+        panic("arg: command line too long");
+    }
+
+    memcpy(arg_cmdline, cmdline, length + 1);
+
+    for (i = 0; i < length; i++) {
+        if (arg_cmdline[i] == ' ') {
+            arg_cmdline[i] = '\0';
+        }
+    }
+
+    arg_cmdline_end = arg_cmdline + length;
+}
+
+void __init
+arg_info(void)
+{
+    printf("arg: %s\n", arg_cmdline);
+}
+
+static const char * __init
+arg_walk(const char *s)
+{
+    if (s == NULL) {
+        s = arg_cmdline;
+    } else {
+        for (;;) {
+            if (s >= arg_cmdline_end) {
+                return NULL;
+            }
+
+            if (*s == '\0') {
+                break;
+            }
+
+            s++;
+        }
+    }
+
+    for (;;) {
+        if (s >= arg_cmdline_end) {
+            return NULL;
+        }
+
+        if (*s != '\0') {
+            return s;
+        }
+
+        s++;
+    }
+}
+
+static const char * __init
+arg_find_name_end(const char *arg)
+{
+    const char *end;
+
+    end = strchr(arg, '=');
+
+    if (end == NULL) {
+        end = arg + strlen(arg);
+    }
+
+    return end;
+}
+
+static const char * __init
+arg_find(const char *name)
+{
+    const char *arg, *arg_name_end;
+    size_t arg_name_length, name_length;
+
+    name_length = strlen(name);
+    assert(name_length != 0);
+
+    for (arg = arg_walk(NULL); arg != NULL; arg = arg_walk(arg)) {
+        arg_name_end = arg_find_name_end(arg);
+        arg_name_length = arg_name_end - arg;
+
+        if ((arg_name_length == name_length)
+            && (memcmp(arg, name, name_length) == 0)) {
+            return arg;
+        }
+    }
+
+    return NULL;
+}
+
+bool __init
+arg_present(const char *name)
+{
+    return (arg_find(name) != NULL);
+}
+
+const char * __init
+arg_value(const char *name)
+{
+    const char *arg, *value;
+
+    arg = arg_find(name);
+
+    if (arg == NULL) {
+        return NULL;
+    }
+
+    value = strchr(arg, '=');
+
+    if (value == NULL) {
+        return "";
+    }
+
+    return value + 1;
+}