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>

6 files changed, 191 insertions, 58 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 78e14fc132..314411332c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1200,6 +1200,12 @@ F: util/*coroutine*
 F: include/qemu/coroutine*
 F: tests/test-coroutine.c
 
+Buffers
+M: Daniel P. Berrange <berrange@redhat.com>
+S: Odd fixes
+F: util/buffer.c
+F: include/qemu/buffer.h
+
 Usermode Emulation
 ------------------
 Overall
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__ */
diff --git a/ui/vnc.c b/ui/vnc.c
index 1fa05506cc..faff0546e8 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -647,49 +647,6 @@ void vnc_framebuffer_update(VncState *vs, int x, int y, int w, int h,
     vnc_write_s32(vs, encoding);
 }
 
-void buffer_reserve(Buffer *buffer, size_t len)
-{
-    if ((buffer->capacity - buffer->offset) < len) {
-        buffer->capacity += (len + 1024);
-        buffer->buffer = g_realloc(buffer->buffer, buffer->capacity);
-    }
-}
-
-static int buffer_empty(Buffer *buffer)
-{
-    return buffer->offset == 0;
-}
-
-uint8_t *buffer_end(Buffer *buffer)
-{
-    return buffer->buffer + buffer->offset;
-}
-
-void buffer_reset(Buffer *buffer)
-{
-        buffer->offset = 0;
-}
-
-void buffer_free(Buffer *buffer)
-{
-    g_free(buffer->buffer);
-    buffer->offset = 0;
-    buffer->capacity = 0;
-    buffer->buffer = NULL;
-}
-
-void buffer_append(Buffer *buffer, const void *data, size_t len)
-{
-    memcpy(buffer->buffer + buffer->offset, data, len);
-    buffer->offset += len;
-}
-
-void buffer_advance(Buffer *buf, size_t len)
-{
-    memmove(buf->buffer, buf->buffer + len,
-            (buf->offset - len));
-    buf->offset -= len;
-}
 
 static void vnc_desktop_resize(VncState *vs)
 {
diff --git a/ui/vnc.h b/ui/vnc.h
index 4dd769cddb..2863f583aa 100644
--- a/ui/vnc.h
+++ b/ui/vnc.h
@@ -34,6 +34,7 @@
 #include "audio/audio.h"
 #include "qemu/bitmap.h"
 #include "crypto/tlssession.h"
+#include "qemu/buffer.h"
 #include <zlib.h>
 #include <stdbool.h>
 
@@ -56,13 +57,6 @@
  *
  *****************************************************************************/
 
-typedef struct Buffer
-{
-    size_t capacity;
-    size_t offset;
-    uint8_t *buffer;
-} Buffer;
-
 typedef struct VncState VncState;
 typedef struct VncJob VncJob;
 typedef struct VncRect VncRect;
@@ -535,14 +529,6 @@ ssize_t vnc_client_io_error(VncState *vs, ssize_t ret, int last_errno);
 void start_client_init(VncState *vs);
 void start_auth_vnc(VncState *vs);
 
-/* Buffer management */
-void buffer_reserve(Buffer *buffer, size_t len);
-void buffer_reset(Buffer *buffer);
-void buffer_free(Buffer *buffer);
-void buffer_append(Buffer *buffer, const void *data, size_t len);
-void buffer_advance(Buffer *buf, size_t len);
-uint8_t *buffer_end(Buffer *buffer);
-
 
 /* Misc helpers */
 
diff --git a/util/Makefile.objs b/util/Makefile.objs
index d8d7e7a919..1363d1fce8 100644
--- a/util/Makefile.objs
+++ b/util/Makefile.objs
@@ -21,3 +21,4 @@ util-obj-y += rcu.o
 util-obj-y += qemu-coroutine.o qemu-coroutine-lock.o qemu-coroutine-io.o
 util-obj-y += qemu-coroutine-sleep.o
 util-obj-y += coroutine-$(CONFIG_COROUTINE_BACKEND).o
+util-obj-y += buffer.o
diff --git a/util/buffer.c b/util/buffer.c
new file mode 100644
index 0000000000..cedd055680
--- /dev/null
+++ b/util/buffer.c
@@ -0,0 +1,65 @@
+/*
+ * 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/>.
+ *
+ */
+
+#include "qemu/buffer.h"
+
+void buffer_reserve(Buffer *buffer, size_t len)
+{
+    if ((buffer->capacity - buffer->offset) < len) {
+        buffer->capacity += (len + 1024);
+        buffer->buffer = g_realloc(buffer->buffer, buffer->capacity);
+    }
+}
+
+gboolean buffer_empty(Buffer *buffer)
+{
+    return buffer->offset == 0;
+}
+
+uint8_t *buffer_end(Buffer *buffer)
+{
+    return buffer->buffer + buffer->offset;
+}
+
+void buffer_reset(Buffer *buffer)
+{
+    buffer->offset = 0;
+}
+
+void buffer_free(Buffer *buffer)
+{
+    g_free(buffer->buffer);
+    buffer->offset = 0;
+    buffer->capacity = 0;
+    buffer->buffer = NULL;
+}
+
+void buffer_append(Buffer *buffer, const void *data, size_t len)
+{
+    memcpy(buffer->buffer + buffer->offset, data, len);
+    buffer->offset += len;
+}
+
+void buffer_advance(Buffer *buffer, size_t len)
+{
+    memmove(buffer->buffer, buffer->buffer + len,
+            (buffer->offset - len));
+    buffer->offset -= len;
+}