command-line arguments

1 files changed, 64 insertions, 0 deletions

diff --git a/argparser.h b/argparser.h
new file mode 100644
index 0000000..6c97b42
--- /dev/null
+++ b/argparser.h
@@ -0,0 +1,64 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef struct {
+	int argc;
+	char **argv;
+	const char *options_with_value;
+
+	const char *option;
+	const char *value;
+
+	int i;
+	unsigned char no_option;
+} ArgParser;
+
+static int arg_parser_next(ArgParser *parser) {
+top:
+	if (parser->i <= 0)
+		parser->i = 1;
+	if (parser->i >= parser->argc)
+		return 0;
+	const char *const arg = parser->argv[parser->i++];
+	if (parser->no_option)
+		goto no_option;
+	if (arg[0] == '-') {
+		const char *option = arg + 1;
+		if (option[0] == '-') {
+			option += 1;
+		}
+		if (option[0] == '\0') {
+			parser->no_option = 1;
+			goto top;
+		}
+		int requires_arg = 0;
+		const char *p = parser->options_with_value;
+		while (p && *p) {
+			size_t n = strcspn(p, ",");
+			if (strncmp(p, option, n) == 0 && option[n] == 0) {
+				requires_arg = 1;
+				break;
+			}
+			p += n;
+			while (*p == ',')
+				p += 1;
+		}
+		if (requires_arg) {
+			parser->option = option;
+			if (parser->i >= parser->argc) {
+				fprintf(stderr, "Error: no value provided for option %s\n", option);
+				exit(EXIT_FAILURE);
+			}
+			parser->value = parser->argv[parser->i++];
+		} else {
+			parser->option = option;
+			parser->value = 0;
+		}
+		return 1;
+	}
+no_option:
+	parser->option = 0;
+	parser->value = arg;
+	return 1;
+}