hw: move fifo.[ch] to libqemuutil

fifo.c is generic code that can be easily unit tested.  So it
belongs in libqemuutil.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/qemu/fifo8.h

@@ -0,0 +1,99 @@
+#ifndef FIFO_H
+#define FIFO_H
+
+#include "migration/vmstate.h"
+
+typedef struct {
+    /* All fields are private */
+    uint8_t *data;
+    uint32_t capacity;
+    uint32_t head;
+    uint32_t num;
+} Fifo8;
+
+/**
+ * fifo8_create:
+ * @fifo: struct Fifo8 to initialise with new FIFO
+ * @capacity: capacity of the newly created FIFO
+ *
+ * Create a FIFO of the specified size. Clients should call fifo8_destroy()
+ * when finished using the fifo. The FIFO is initially empty.
+ */
+
+void fifo8_create(Fifo8 *fifo, uint32_t capacity);
+
+/**
+ * fifo8_destroy:
+ * @fifo: FIFO to cleanup
+ *
+ * Cleanup a FIFO created with fifo8_create(). Frees memory created for FIFO
+  *storage. The FIFO is no longer usable after this has been called.
+ */
+
+void fifo8_destroy(Fifo8 *fifo);
+
+/**
+ * fifo8_push:
+ * @fifo: FIFO to push to
+ * @data: data byte to push
+ *
+ * Push a data byte to the FIFO. Behaviour is undefined if the FIFO is full.
+ * Clients are responsible for checking for fullness using fifo8_is_full().
+ */
+
+void fifo8_push(Fifo8 *fifo, uint8_t data);
+
+/**
+ * fifo8_pop:
+ * @fifo: fifo to pop from
+ *
+ * Pop a data byte from the FIFO. Behaviour is undefined if the FIFO is empty.
+ * Clients are responsible for checking for emptyness using fifo8_is_empty().
+ *
+ * Returns: The popped data byte.
+ */
+
+uint8_t fifo8_pop(Fifo8 *fifo);
+
+/**
+ * fifo8_reset:
+ * @fifo: FIFO to reset
+ *
+ * Reset a FIFO. All data is discarded and the FIFO is emptied.
+ */
+
+void fifo8_reset(Fifo8 *fifo);
+
+/**
+ * fifo8_is_empty:
+ * @fifo: FIFO to check
+ *
+ * Check if a FIFO is empty.
+ *
+ * Returns: True if the fifo is empty, false otherwise.
+ */
+
+bool fifo8_is_empty(Fifo8 *fifo);
+
+/**
+ * fifo8_is_full:
+ * @fifo: FIFO to check
+ *
+ * Check if a FIFO is full.
+ *
+ * Returns: True if the fifo is full, false otherwise.
+ */
+
+bool fifo8_is_full(Fifo8 *fifo);
+
+extern const VMStateDescription vmstate_fifo8;
+
+#define VMSTATE_FIFO8(_field, _state) {                              \
+    .name       = (stringify(_field)),                               \
+    .size       = sizeof(Fifo8),                                     \
+    .vmsd       = &vmstate_fifo8,                                    \
+    .flags      = VMS_STRUCT,                                        \
+    .offset     = vmstate_offset_value(_state, _field, Fifo8),       \
+}
+
+#endif /* FIFO_H */