Split out buf

adsbus/buf.c

@@ -0,0 +1,37 @@
+#include <assert.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "buf.h"
+
+void buf_init(struct buf *buf) {
+	buf->start = 0;
+	buf->length = 0;
+}
+
+ssize_t buf_fill(struct buf *buf, int fd) {
+	if (buf->start + buf->length == BUF_LEN_MAX) {
+		assert(buf->start > 0);
+		memmove(buf->buf, buf_at(buf, 0), buf->length);
+		buf->start = 0;
+	}
+
+	size_t space = BUF_LEN_MAX - buf->length - buf->start;
+	ssize_t in = read(fd, buf_at(buf, buf->length), space);
+	if (in <= 0) {
+		return in;
+	}
+	buf->length += in;
+	return in;
+}
+
+void buf_consume(struct buf *buf, size_t length) {
+	assert(buf->length >= length);
+
+	buf->length -= length;
+	if (buf->length) {
+		buf->start += length;
+	} else {
+		buf->start = 0;
+	}
+}