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Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver |
Date: |
Thu, 11 Nov 2010 16:30:26 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) |
Luiz Capitulino <address@hidden> writes:
> This driver handles in-memory chardev operations. That's, all writes
> to this driver are stored in an internal buffer and it 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 is going to be used by the monitor's "HMP passthrough via QMP"
> feature, which needs to run monitor handlers without a backing
> device.
>
> Signed-off-by: Luiz Capitulino <address@hidden>
> ---
> qemu-char.c | 66
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> qemu-char.h | 6 +++++
> 2 files changed, 72 insertions(+), 0 deletions(-)
>
> diff --git a/qemu-char.c b/qemu-char.c
> index 88997f9..896df14 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -2275,6 +2275,72 @@ static CharDriverState *qemu_chr_open_socket(QemuOpts
> *opts)
> return NULL;
> }
>
> +/***********************************************************/
> +/* Memory chardev */
> +typedef struct {
> + size_t outbuf_size;
> + size_t outbuf_capacity;
> + uint8_t *outbuf;
> +} MemoryDriver;
> +
> +static int mem_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
> +{
> + MemoryDriver *d = chr->opaque;
> +
> + /* 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) {
> + /* grown outbuf */
Used to say "grow" (sans n) here. Intentional change?
> + 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;
> +}
> +
> +#define DEFAULT_BUF_SIZE 4096
It's the *initial* buffer size, isn't it?
Doubt it's worth a #define (there's just one user), but that's a matter
of taste.
> +
> +void qemu_chr_init_mem(CharDriverState *chr)
> +{
> + MemoryDriver *d;
> +
> + d = qemu_malloc(sizeof(*d));
> + d->outbuf_size = 0;
> + d->outbuf_capacity = DEFAULT_BUF_SIZE;
> + d->outbuf = qemu_mallocz(d->outbuf_capacity);
> +
> + memset(chr, 0, sizeof(*chr));
> + chr->opaque = d;
> + chr->chr_write = mem_chr_write;
> +}
> +
> +/* assumes the stored data is a string */
What else could it be? Worrying about embedded '\0's?
> +QString *qemu_chr_mem_to_qs(CharDriverState *chr)
> +{
> + MemoryDriver *d = chr->opaque;
> +
> + if (d->outbuf_size == 0) {
> + return NULL;
> + }
Did you forget to change this? We agreed to return an empty QString
when chr contains an empty string.
> +
> + return qstring_from_substr((char *) d->outbuf, 0, d->outbuf_size - 1);
> +}
> +
> +/* NOTE: this driver can not be closed with qemu_chr_close()! */
> +void qemu_chr_close_mem(CharDriverState *chr)
> +{
> + MemoryDriver *d = chr->opaque;
> +
> + qemu_free(d->outbuf);
> + qemu_free(chr->opaque);
> + chr->opaque = NULL;
> + chr->chr_write = NULL;
> +}
> +
Unlike normal character drivers, this one can't be closed with
qemu_chr_close(). It probably explodes if you try. Please add a
suitable assertion to qemu_chr_close() to document the fact, and to
ensure misuse fails in a controlled, obvious manner.
> 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..c4e55b4 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;
>
> +/* memory chardev */
> +void qemu_chr_init_mem(CharDriverState *chr);
> +void qemu_chr_close_mem(CharDriverState *chr);
> +QString *qemu_chr_mem_to_qs(CharDriverState *chr);
> +
> /* async I/O support */
>
> int qemu_set_fd_handler2(int fd,
- [Qemu-devel] [PATCH v2 0/3]: QMP: Human Monitor passthrough, Luiz Capitulino, 2010/11/10
- [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver, Luiz Capitulino, 2010/11/10
- Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver,
Markus Armbruster <=
- Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver, Luiz Capitulino, 2010/11/11
- Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver, Markus Armbruster, 2010/11/11
- Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver, Luiz Capitulino, 2010/11/11
- Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver, Markus Armbruster, 2010/11/12
- Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver, Luiz Capitulino, 2010/11/12
- Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver, Markus Armbruster, 2010/11/12
- Re: [Qemu-devel] [PATCH 1/3] qemu-char: Introduce Memory driver, Luiz Capitulino, 2010/11/12
[Qemu-devel] [PATCH 2/3] QMP: Introduce Human Monitor passthrough command, Luiz Capitulino, 2010/11/10