[Qemu-devel] [PATCH 18/21] qom-chrdrv: add memory character driver

[Anthony Liguori <aliguori@us.ibm.com>]

This is used primarly by QMP.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
 chrdrv/Makefile       |    1 +
 chrdrv/Qconfig        |    7 +++++
 chrdrv/memchr.c       |   70 +++++++++++++++++++++++++++++++++++++++++++++++++
 include/qemu/memchr.h |   46 ++++++++++++++++++++++++++++++++
 4 files changed, 124 insertions(+), 0 deletions(-)
 create mode 100644 chrdrv/memchr.c
 create mode 100644 include/qemu/memchr.h

diff --git a/chrdrv/Makefile b/chrdrv/Makefile
index 43a51e7..6cfdd27 100644
--- a/chrdrv/Makefile
+++ b/chrdrv/Makefile
@@ -1 +1,2 @@
 chrdrv-obj-$(CONFIG_CHRDRV) := chrdrv.o
+chrdrv-obj-$(CONFIG_CHRDRV_MEM) += memchr.o
diff --git a/chrdrv/Qconfig b/chrdrv/Qconfig
index 845c205..f3f939e 100644
--- a/chrdrv/Qconfig
+++ b/chrdrv/Qconfig
@@ -3,3 +3,10 @@ config CHRDRV
        default y
        help
          Character layer
+
+config CHRDRV_MEM
+       bool "Memory character device"
+       default y
+       depends on CHRDRV
+       help
+         Character device that stores all written data to a memory buffer.
diff --git a/chrdrv/memchr.c b/chrdrv/memchr.c
new file mode 100644
index 0000000..3046d2e
--- /dev/null
+++ b/chrdrv/memchr.c
@@ -0,0 +1,70 @@
+#include "qemu/memchr.h"
+
+void memory_char_driver_initialize(MemoryCharDriver *d, const char *id)
+{
+    type_initialize(d, TYPE_MEMORY_CHAR_DRIVER, id);
+}
+
+void memory_char_driver_finalize(MemoryCharDriver *d)
+{
+    type_finalize(d);
+}
+
+static int memory_char_driver_write(CharDriver *chr, const uint8_t *buf,
+                                    int len)
+{
+    MemoryCharDriver *d = MEMORY_CHAR_DRIVER(chr);
+
+    /* TODO: the QString implementation has the same code, we should
+     * introduce a generic way to do this in cutils.c */
+    if (d->outbuf_capacity < d->outbuf_size + len) {
+        /* grow outbuf */
+        d->outbuf_capacity += len;
+        d->outbuf_capacity *= 2;
+        d->outbuf = qemu_realloc(d->outbuf, d->outbuf_capacity);
+    }
+
+    memcpy(d->outbuf + d->outbuf_size, buf, len);
+    d->outbuf_size += len;
+
+    return len;
+}
+
+size_t memory_char_driver_get_osize(MemoryCharDriver *d)
+{
+    return d->outbuf_size;
+}
+
+QString *memory_char_driver_get_qs(MemoryCharDriver *d)
+{
+    return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);
+}
+
+static void memory_char_driver_fini(TypeInstance *inst)
+{
+    MemoryCharDriver *d = MEMORY_CHAR_DRIVER(inst);
+
+    qemu_free(d->outbuf);
+}
+
+static void memory_char_driver_class_init(TypeClass *class)
+{
+    CharDriverClass *cdc = CHAR_DRIVER_CLASS(class);
+
+    cdc->write = memory_char_driver_write;
+}
+
+static TypeInfo memory_char_driver_type_info = {
+    .name = TYPE_MEMORY_CHAR_DRIVER,
+    .parent = TYPE_CHAR_DRIVER,
+    .instance_size = sizeof(MemoryCharDriver),
+    .class_init = memory_char_driver_class_init,
+    .instance_finalize = memory_char_driver_fini,
+};
+
+static void register_backends(void)
+{
+    type_register_static(&memory_char_driver_type_info);
+}
+
+device_init(register_backends);
diff --git a/include/qemu/memchr.h b/include/qemu/memchr.h
new file mode 100644
index 0000000..0744684
--- /dev/null
+++ b/include/qemu/memchr.h
@@ -0,0 +1,46 @@
+#ifndef CHAR_DRIVER_MEM_H
+#define CHAR_DRIVER_MEM_H
+
+#include "qemu/chrdrv.h"
+
+/**
+ * @MemoryCharDriver:
+ *
+ * A @CharDriver that stores all written data to memory.  This is useful for
+ * interfacing directly with objects that expect to work with a @CharDriver.
+ *
+ * The accumulated data can be obtained as a QString.
+ */
+typedef struct MemoryCharDriver
+{
+    CharDriver parent;
+
+    /* Private */
+    size_t outbuf_size;
+    size_t outbuf_capacity;
+    uint8_t *outbuf;
+} MemoryCharDriver;
+
+#define TYPE_MEMORY_CHAR_DRIVER "memory-char-driver"
+#define MEMORY_CHAR_DRIVER(obj) \
+    TYPE_CHECK(MemoryCharDriver, obj, TYPE_MEMORY_CHAR_DRIVER)
+
+void memory_char_driver_initialize(MemoryCharDriver *d, const char *id);
+void memory_char_driver_finalize(MemoryCharDriver *d);
+
+/**
+ * @memory_char_driver_get_osize:
+ *
+ * Returns:  The size of the output buffer.
+ */
+size_t memory_char_driver_get_osize(MemoryCharDriver *d);
+
+/**
+ * @memory_char_driver_get_qs:
+ *
+ * Returns:  A QString representing the output buffer.  The reference ownership
+ *           is transferred to the caller.
+ */
+QString *memory_char_driver_get_qs(MemoryCharDriver *d);
+
+#endif
-- 
1.7.4.1