util: pull Buffer code out of VNC module

The Buffer code in the VNC server is useful for the IO channel
code, so pull it out into a shared module, QIOBuffer.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

1 files changed, 118 insertions, 0 deletions

diff --git a/include/qemu/buffer.h b/include/qemu/buffer.h
new file mode 100644
index 0000000000..b380cec6fa
--- /dev/null
+++ b/include/qemu/buffer.h
@@ -0,0 +1,118 @@
+/*
+ * QEMU generic buffers
+ *
+ * Copyright (c) 2015 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef QEMU_BUFFER_H__
+#define QEMU_BUFFER_H__
+
+#include "qemu-common.h"
+
+typedef struct Buffer Buffer;
+
+/**
+ * Buffer:
+ *
+ * The Buffer object provides a simple dynamically resizing
+ * array, with separate tracking of capacity and usage. This
+ * is typically useful when buffering I/O or processing data.
+ */
+
+struct Buffer {
+    size_t capacity;
+    size_t offset;
+    uint8_t *buffer;
+};
+
+/**
+ * buffer_reserve:
+ * @buffer: the buffer object
+ * @len: the minimum required free space
+ *
+ * Ensure that the buffer has space allocated for at least
+ * @len bytes. If the current buffer is too small, it will
+ * be reallocated, possibly to a larger size than requested.
+ */
+void buffer_reserve(Buffer *buffer, size_t len);
+
+/**
+ * buffer_reset:
+ * @buffer: the buffer object
+ *
+ * Reset the length of the stored data to zero, but do
+ * not free / reallocate the memory buffer
+ */
+void buffer_reset(Buffer *buffer);
+
+/**
+ * buffer_free:
+ * @buffer: the buffer object
+ *
+ * Reset the length of the stored data to zero and also
+ * free the internal memory buffer
+ */
+void buffer_free(Buffer *buffer);
+
+/**
+ * buffer_append:
+ * @buffer: the buffer object
+ * @data: the data block to append
+ * @len: the length of @data in bytes
+ *
+ * Append the contents of @data to the end of the buffer.
+ * The caller must ensure that the buffer has sufficient
+ * free space for @len bytes, typically by calling the
+ * buffer_reserve() method prior to appending.
+ */
+void buffer_append(Buffer *buffer, const void *data, size_t len);
+
+/**
+ * buffer_advance:
+ * @buffer: the buffer object
+ * @len: the number of bytes to skip
+ *
+ * Remove @len bytes of data from the head of the buffer.
+ * The internal buffer will not be reallocated, so will
+ * have at least @len bytes of free space after this
+ * call completes
+ */
+void buffer_advance(Buffer *buffer, size_t len);
+
+/**
+ * buffer_end:
+ * @buffer: the buffer object
+ *
+ * Get a pointer to the tail end of the internal buffer
+ * The returned pointer is only valid until the next
+ * call to buffer_reserve().
+ *
+ * Returns: the tail of the buffer
+ */
+uint8_t *buffer_end(Buffer *buffer);
+
+/**
+ * buffer_empty:
+ * @buffer: the buffer object
+ *
+ * Determine if the buffer contains any current data
+ *
+ * Returns: true if the buffer holds data, false otherwise
+ */
+gboolean buffer_empty(Buffer *buffer);
+
+#endif /* QEMU_BUFFER_H__ */