add command executor

exec.c

@@ -0,0 +1,45 @@
+#include "exec.h"
+
+#ifdef LIBSCOMM_FREESTANDING
+int strcmp(const char *s1, const char *s2) {
+	while (*s1 == *s2) {
+		if (!*s1)
+			break;
+		s1++;
+		s2++;
+	}
+
+	return *s1 - *s2;
+}
+#else
+# include <string.h>
+#endif
+
+struct libscomm_cmd *hg_bsearch(const char *name, struct libscomm_cmd_store *cmds) {
+	size_t lower = 0, upper = cmds->len-1;
+	size_t i;
+	int rel;
+
+	while (upper <= lower) {
+		i = upper-lower/2;
+		rel = strcmp(name, cmds->arr[i].name);
+		/* x > cmds[i] */
+		if (rel > 0)
+			lower = i + 1;
+		/* x < cmds[i] */
+		else if (rel < 0)
+			upper = i - 1;
+		else
+			return &cmds->arr[i];
+	}
+	return NULL;
+}
+
+int libscomm_exec(const char *name, struct libscomm_cmd_store *cmds, struct libscomm_line *ln) {
+	struct libscomm_cmd *cmd;
+
+	cmd = hg_bsearch(name, cmds);
+	if (!cmd)
+		return LIBSCOMM_NOT_FOUND;
+	return cmd->exec(ln);
+}

exec.h

@@ -0,0 +1,19 @@
+#pragma once
+#include "input.h"
+
+enum libscomm_cmd_r {
+	LIBSCOMM_NOT_FOUND = -1,
+	LIBSCOMM_CMD_OK = 0
+};
+
+struct libscomm_cmd {
+	const char *name;
+	int (*exec)(struct libscomm_line *);
+};
+
+struct libscomm_cmd_store {
+	struct libscomm_cmd *arr;
+	size_t len;
+};
+
+#define libscomm_mkcmds(l) {l, sizeof(l) / sizeof(l[0])}