[Qemu-devel] [PATCH 1/2] qemu-char: Introduce Buffered driver

[Luiz Capitulino]

This driver handles in-memory qemu-char driver operations, that's,
all writes to this driver are stored in an internal buffer. The
driver doesn't talk to the external world in any way.

Right now it's very simple: it supports only writes. But it can
be easily extended to support more operations.

This driver is going to be used by the monitor subsystem, which
needs to 'emulate' a qemu-char device, so that monitor handlers
can be ran without a backing device and have their output stored.

TODO: Move buffer growth logic to cutils.

Signed-off-by: Luiz Capitulino <address@hidden>
---
 qemu-char.c |   68 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 qemu-char.h |    6 +++++
 2 files changed, 74 insertions(+), 0 deletions(-)

diff --git a/qemu-char.c b/qemu-char.c
index 6d2dce7..1ca9ccc 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -2279,6 +2279,74 @@ static CharDriverState *qemu_chr_open_socket(QemuOpts 
*opts)
     return NULL;
 }
 
+/***********************************************************/
+/* Buffered chardev */
+typedef struct {
+    size_t outbuf_size;
+    size_t outbuf_capacity;
+    uint8_t *outbuf;
+} BufferedDriver;
+
+static int buffered_chr_write(CharDriverState *chr, const uint8_t *buf, int 
len)
+{
+    BufferedDriver *d = chr->opaque;
+
+    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 0;
+}
+
+void qemu_chr_init_buffered(CharDriverState *chr)
+{
+    BufferedDriver *d;
+
+    d = qemu_mallocz(sizeof(BufferedDriver));
+    d->outbuf_capacity = 4096;
+    d->outbuf = qemu_mallocz(d->outbuf_capacity);
+
+    memset(chr, 0, sizeof(*chr));
+    chr->opaque = d;
+    chr->chr_write = buffered_chr_write;
+}
+
+QString *qemu_chr_buffered_to_qs(CharDriverState *chr)
+{
+    char *str;
+    QString *qs;
+    BufferedDriver *d = chr->opaque;
+
+    if (d->outbuf_size == 0) {
+        return NULL;
+    }
+
+    str = qemu_malloc(d->outbuf_size + 1);
+    memcpy(str, d->outbuf, d->outbuf_size);
+    str[d->outbuf_size] = '\0';
+
+    qs = qstring_from_str(str);
+    qemu_free(str);
+
+    return qs;
+}
+
+void qemu_chr_close_buffered(CharDriverState *chr)
+{
+    BufferedDriver *d = chr->opaque;
+
+    qemu_free(d->outbuf);
+    qemu_free(chr->opaque);
+    chr->opaque = NULL;
+    chr->chr_write = NULL;
+}
+
 QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
 {
     char host[65], port[33], width[8], height[8];
diff --git a/qemu-char.h b/qemu-char.h
index 18ad12b..4467641 100644
--- a/qemu-char.h
+++ b/qemu-char.h
@@ -6,6 +6,7 @@
 #include "qemu-option.h"
 #include "qemu-config.h"
 #include "qobject.h"
+#include "qstring.h"
 
 /* character device */
 
@@ -100,6 +101,11 @@ CharDriverState *qemu_chr_open_eventfd(int eventfd);
 
 extern int term_escape_char;
 
+/* buffered chardev */
+void qemu_chr_init_buffered(CharDriverState *chr);
+void qemu_chr_close_buffered(CharDriverState *chr);
+QString *qemu_chr_buffered_to_qs(CharDriverState *chr);
+
 /* async I/O support */
 
 int qemu_set_fd_handler2(int fd,
-- 
1.7.3.2.90.gd4c43