1 files changed, 62 insertions, 0 deletions
diff --git a/qbuf.c b/qbuf.c
new file mode 100644
index 0000000..d225ce7
--- /dev/null
+++ b/qbuf.c
@@ -0,0 +1,62 @@
+#include <assert.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include "qbuf.h"
+
+void qbuf_init(struct qbuf *q, size_t length) {
+    assert(q && length);
+    memset(q, 0, sizeof(struct qbuf));
+
+    q->data = malloc(q->length = length*2);
+    assert(q->data);
+}
+
+void qbuf_done(struct qbuf *q) {
+    assert(q);
+    free(q->data);
+}
+
+static void move_to_front(struct qbuf *q) {
+    assert(q);
+
+    if (q->index+q->fill <= q->length/2)
+        return;
+
+    memmove(q->data, q->data+q->index, q->fill);
+    q->index = 0;
+}
+
+void* qbuf_push(struct qbuf *q, size_t *l) {
+    size_t m;
+    assert(q);
+
+    move_to_front(q);
+    m = q->length - q->fill - q->index;
+    *l = m;
+    return q->data + q->index + q->fill;
+}
+
+void qbuf_push_validate(struct qbuf *q, size_t l) {
+    assert(q);
+    q->fill += l;
+    assert(q->index+q->fill <= q->length);
+}
+
+void* qbuf_pull(struct qbuf *q, size_t *l) {
+    assert(q);
+    *l = q->fill;
+    return q->data + q->index;
+}
+
+void qbuf_pull_invalidate(struct qbuf *q, size_t l) {
+    assert(q);
+
+    assert(l <= q->fill);
+    q->fill -= l;
+    q->index += l;
+
+    assert(q->index+q->fill <= q->length);
+    if (!q->fill)
+        q->index = 0;
+}