write line parser

Makefile

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+TESTS=test/input
+
+tests: $(TESTS)
+	for i in $(TESTS); do ./$$i; done
+
+TEST_INPUT=test/input.o input.o
+test/input: $(TEST_INPUT)
+	$(CC) -Wall $(TEST_INPUT) -o test/input
+.c.o:
+	$(CC) -std=c89 -Wall -c $< -o $@

README

@@ -0,0 +1,10 @@
+# libscomp -- Simple Control Protocol #
+
+This is a C89+ library for parsing and executing commands. It is written
+for a freestanding implementation, meaning that
+
+* It does no dynamic allocation
+* It does not require any standard library functions
+* It can run on anything with a C compiler
+
+This is designed for microcontrollers that take ASCII input from serial.

input.c

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+#include "input.h"
+
+enum { READ, DISCARD };
+
+void libscomm_reset(struct libscomm_input *in) {
+	in->state = READ;
+	in->len = 0;
+}
+
+static enum libscomm_input_r parse(struct libscomm_input *in,
+                                   struct libscomm_line *line) {
+	char *s = in->intbuf;
+
+	line->name = (*s == ':');
+	line->len = 0;
+
+	while (line->len < LIBSCOMM_MAXARG) {
+		line->buf[line->len++] = s;
+		for (; *s && *s != '\t'; s++);
+
+		if (!*s) {
+			return LIBSCOMM_COMPLETE;
+		} else {
+			*s = 0;
+			s++;
+		}
+	}
+
+	return LIBSCOMM_ARG_OVERFLOW;
+}
+
+enum libscomm_input_r libscomm_read(struct libscomm_input *in,
+                                    struct libscomm_inbuf *buf,
+                                    struct libscomm_line *line) {
+	char c;
+
+	while (buf->l > 0) {
+		buf->l--;
+		c = *buf->s++;
+
+		if (in->state == DISCARD) {
+			if (c == '\n') {
+				libscomm_reset(in);
+				return LIBSCOMM_OVERFLOW;
+			}
+		} else {
+			switch (c) {
+			case '\n':
+				in->intbuf[in->len] = 0;
+				return parse(in, line);
+			default:
+				in->intbuf[in->len++] = c;
+				if (in->len == LIBSCOMM_MAXBUF)
+					in->state = DISCARD;
+			}
+		}
+	}
+
+	return LIBSCOMM_MORE;
+}

input.h

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+#pragma once
+#include <stddef.h>
+
+#define LIBSCOMM_MAXARG 32
+#define LIBSCOMM_MAXBUF 1024
+
+struct libscomm_line {
+	size_t name;
+	char *buf[LIBSCOMM_MAXARG];
+	size_t len;
+};
+
+struct libscomm_inbuf {
+	const char *s;
+	size_t l;
+};
+
+struct libscomm_input {
+	int state;
+
+	char intbuf[LIBSCOMM_MAXBUF];
+	size_t len;
+};
+
+enum libscomm_input_r {
+	LIBSCOMM_MORE,
+	LIBSCOMM_OVERFLOW,
+	LIBSCOMM_ARG_OVERFLOW,
+	LIBSCOMM_COMPLETE
+};
+
+void libscomm_reset(struct libscomm_input *);
+enum libscomm_input_r libscomm_read(struct libscomm_input *,
+                                    struct libscomm_inbuf *,
+                                    struct libscomm_line *);

test/input.c

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+#include "greatest.h"
+#include "../input.h"
+
+#define s(x) {x, sizeof(x) - 1}
+
+TEST one_pass(void) {
+	struct libscomm_input in;
+	struct libscomm_inbuf b = s("Arg 1\tArg \r\v\t!\n");
+	struct libscomm_line l;
+
+	libscomm_reset(&in);
+	ASSERT_EQ(libscomm_read(&in, &b, &l), LIBSCOMM_COMPLETE);
+	ASSERT_EQ(l.len, 3);
+	ASSERT_EQ(l.name, 0);
+
+	ASSERT_STR_EQ(l.buf[0], "Arg 1");
+	ASSERT_STR_EQ(l.buf[1], "Arg \r\v");
+	ASSERT_STR_EQ(l.buf[2], "!");
+
+	PASS();
+}
+
+GREATEST_MAIN_DEFS();
+
+int main(int argc, char *argv[]) {
+	GREATEST_MAIN_BEGIN();
+	RUN_TEST(one_pass);
+	GREATEST_MAIN_END();
+}