--- a/src/core/CMakeLists.txt	Mon Oct 05 09:17:11 2020 +0200
+++ b/src/core/CMakeLists.txt	Mon Oct 05 13:05:09 2020 +0200
@@ -84,6 +84,8 @@
 	${libcore_SOURCE_DIR}/panic.c
 	${libcore_SOURCE_DIR}/panic.h
 	${libcore_SOURCE_DIR}/plat.h
+	${libcore_SOURCE_DIR}/rbuf.c
+	${libcore_SOURCE_DIR}/rbuf.h
 	${libcore_SOURCE_DIR}/save.c
 	${libcore_SOURCE_DIR}/save.h
 	${libcore_SOURCE_DIR}/script.c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/core/rbuf.c	Mon Oct 05 13:05:09 2020 +0200
@@ -0,0 +1,57 @@
+/*
+ * rbuf.c -- basic utility for reading input buffers
+ *
+ * Copyright (c) 2020 David Demelier <markand@malikania.fr>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <assert.h>
+
+#include "rbuf.h"
+
+void
+rbuf_open(struct rbuf *rb, const void *data, size_t datasz)
+{
+	assert(rb);
+	assert(data);
+
+	rb->s = data;
+	rb->e = rb->s + datasz;
+}
+
+bool
+rbuf_readline(struct rbuf *rb, char *output, size_t outputsz)
+{
+	assert(rb);
+	assert(output);
+	assert(outputsz > 0);
+
+	if (rb->s == rb->e)
+		return false;
+
+	for (--outputsz; rb->s != rb->e && *rb->s != '\n' && outputsz; outputsz--)
+		*output++ = *rb->s++;
+
+	/* Not enough space? */
+	if (!outputsz && rb->s != rb->e && *rb->s != '\n')
+		return false;
+
+	/* Remove this '\n' if still present. */
+	if (rb->s != rb->e && *rb->s == '\n')
+		rb->s++;
+
+	*output = '\0';
+
+	return true;
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/core/rbuf.h	Mon Oct 05 13:05:09 2020 +0200
@@ -0,0 +1,81 @@
+/*
+ * rbuf.h -- basic utility for reading input buffers
+ *
+ * Copyright (c) 2020 David Demelier <markand@malikania.fr>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef MOLKO_RBUF_H
+#define MOLKO_RBUF_H
+
+/**
+ * \file rbuf.h
+ * \brief Basic utility for reading input buffers.
+ */
+
+#include <stdbool.h>
+#include <stddef.h>
+
+/**
+ * \brief Input object to store progression.
+ */
+struct rbuf {
+	const char *s;  /*!< (RO) Pointer to current character. */
+	const char *e;  /*!< (RO) Pointer to end of array. */
+};
+
+/**
+ * Open this input buffer.
+ *
+ * \pre rb != NULL
+ * \pre data != NULL
+ * \param rb the input object
+ * \param data the data to read
+ * \param datasz the size of buffer
+ */
+void
+rbuf_open(struct rbuf *rb, const void *data, size_t datasz);
+
+/**
+ * Read the next line from the input.
+ *
+ * This function writes at most outputsz - 1 and is always NULL terminated
+ * unless the function returns false which indicates either end of buffer or
+ * too small output size.
+ *
+ * Example of use (`some_data` is assumed to be a buffer).
+ *
+ * \code
+ * struct rbuf rb;
+ * char line[1024];
+ *
+ * rbuf_open(&rb, some_data, sizeof (some_data));
+ *
+ * while (rbuf_readline(&rb, line, sizeof (line))) {
+ *     printf("line contents: >[%s]<\n", line);
+ * }
+ * \endcode
+ *
+ * \pre rb != NULL
+ * \pre output != NULL
+ * \pre outputsz > 0
+ * \param rb the input object
+ * \param output the output buffer
+ * \param outputsz the output buffer size
+ * \return true if a line was read correctly
+ */
+bool
+rbuf_readline(struct rbuf *rb, char *output, size_t outputsz);
+
+#endif /* !MOLKO_RBUF_H */

--- a/tests/CMakeLists.txt	Mon Oct 05 09:17:11 2020 +0200
+++ b/tests/CMakeLists.txt	Mon Oct 05 13:05:09 2020 +0200
@@ -25,5 +25,6 @@
 # Maps will be revamped.
 # molko_define_test(TARGET map SOURCES test-map.c ASSETS ${tests_SOURCE_DIR}/)
 #
+molko_define_test(TARGET rbuf SOURCES test-rbuf.c)
 molko_define_test(TARGET save SOURCES test-save.c)
 molko_define_test(TARGET script SOURCES test-script.c)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/test-rbuf.c	Mon Oct 05 13:05:09 2020 +0200
@@ -0,0 +1,153 @@
+/*
+ * test-rbuf.c -- test error routines
+ *
+ * Copyright (c) 2020 David Demelier <markand@malikania.fr>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#define GREATEST_USE_ABBREVS 0
+#include <greatest.h>
+
+#include <rbuf.h>
+
+/* Don't use "" to avoid '\0' */
+const char data1[] = { 'a', 'b', 'c', '\n', 'd', 'e', 'f', '\n' };
+const char data2[] = { 'a', 'b', 'c', '\n', 'd', 'e', 'f' };
+const char data3[] = { 'a', 'b', 'c', '\n', '\n', 'd', 'e', 'f', '\n' };
+const char data4[] = { 'a', 'b', 'c', '\n', 'd', 'e', 'f', 'g', 'h', '\n' };
+
+GREATEST_TEST
+simple(void)
+{
+	struct rbuf rb;
+	char line[128];
+
+	rbuf_open(&rb, data1, sizeof (data1));
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(rbuf_readline(&rb, line, sizeof (line)));
+	GREATEST_ASSERT_STR_EQ("abc", line);
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(rbuf_readline(&rb, line, sizeof (line)));
+	GREATEST_ASSERT_STR_EQ("def", line);
+
+	GREATEST_PASS();
+}
+
+GREATEST_TEST
+simple_noeol(void)
+{
+	struct rbuf rb;
+	char line[128];
+
+	rbuf_open(&rb, data2, sizeof (data2));
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(rbuf_readline(&rb, line, sizeof (line)));
+	GREATEST_ASSERT_STR_EQ("abc", line);
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(rbuf_readline(&rb, line, sizeof (line)));
+	GREATEST_ASSERT_STR_EQ("def", line);
+
+	GREATEST_PASS();
+}
+
+GREATEST_TEST
+simple_emptylines(void)
+{
+	struct rbuf rb;
+	char line[128];
+
+	rbuf_open(&rb, data3, sizeof (data3));
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(rbuf_readline(&rb, line, sizeof (line)));
+	GREATEST_ASSERT_STR_EQ("abc", line);
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(rbuf_readline(&rb, line, sizeof (line)));
+	GREATEST_ASSERT_STR_EQ("", line);
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(rbuf_readline(&rb, line, sizeof (line)));
+	GREATEST_ASSERT_STR_EQ("def", line);
+
+	GREATEST_PASS();
+}
+
+GREATEST_SUITE(simple_suite)
+{
+	GREATEST_RUN_TEST(simple);
+	GREATEST_RUN_TEST(simple_noeol);
+	GREATEST_RUN_TEST(simple_emptylines);
+}
+
+GREATEST_TEST
+fail_toosmall(void)
+{
+	struct rbuf rb;
+	char line[4];
+
+	rbuf_open(&rb, data4, sizeof (data4));
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(rbuf_readline(&rb, line, sizeof (line)));
+	GREATEST_ASSERT_STR_EQ("abc", line);
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(!rbuf_readline(&rb, line, sizeof (line)));
+
+	GREATEST_PASS();
+}
+
+GREATEST_TEST
+fail_end(void)
+{
+	struct rbuf rb;
+	char line[128];
+
+	rbuf_open(&rb, data1, sizeof (data1));
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(rbuf_readline(&rb, line, sizeof (line)));
+	GREATEST_ASSERT_STR_EQ("abc", line);
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(rbuf_readline(&rb, line, sizeof (line)));
+	GREATEST_ASSERT_STR_EQ("def", line);
+
+	memset(line, '?', sizeof (line));
+	GREATEST_ASSERT(!rbuf_readline(&rb, line, sizeof (line)));
+
+	GREATEST_PASS();
+}
+
+GREATEST_SUITE(fail_suite)
+{
+	GREATEST_RUN_TEST(fail_toosmall);
+	GREATEST_RUN_TEST(fail_end);
+}
+
+GREATEST_MAIN_DEFS();
+
+int
+main(int argc, char **argv)
+{
+	GREATEST_MAIN_BEGIN();
+	GREATEST_RUN_SUITE(simple_suite);
+	GREATEST_RUN_SUITE(fail_suite);
+	GREATEST_MAIN_END();
+}