[PATCH] tftp: implement forward seeking

[PATCH] tftp: implement forward seeking

[Uwe Kleine-König]

Just abuse tftp_read to step forward.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 fs/tftp.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/fs/tftp.c b/fs/tftp.c
index 56d4365d773a..272a7106eb51 100644
--- a/fs/tftp.c
+++ b/fs/tftp.c
@@ -591,8 +591,29 @@ static int tftp_read(struct device_d *dev, FILE *f, void *buf, size_t insize)
 
 static loff_t tftp_lseek(struct device_d *dev, FILE *f, loff_t pos)
 {
-	/* not implemented in tftp protocol */
-	return -ENOSYS;
+	if (pos >= f->pos) {
+		char buf[1024];
+		int ret;
+		while (pos > f->pos) {
+			size_t len = min(sizeof(buf), (size_t)(pos - f->pos));
+			ret = tftp_read(dev, f, buf, len);
+
+			if (ret < 0)
+				return ret;
+			else if (!ret)
+				return -EINVAL;
+			f->pos += ret;
+
+			memory_display(buf, f->pos - len, 0x10, 4, 0);
+		}
+		return pos;
+	} else {
+		/*
+		 * We cannot seek backwards without reloading or caching the
+		 * file
+		 */
+		return -ENOSYS;
+	}
 }
 
 static DIR* tftp_opendir(struct device_d *dev, const char *pathname)
-- 
2.11.0


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Re: [PATCH] tftp: implement forward seeking

[Sascha Hauer]

On Thu, Mar 02, 2017 at 04:55:28PM +0100, Uwe Kleine-König wrote:
> Just abuse tftp_read to step forward.
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
>  fs/tftp.c | 25 +++++++++++++++++++++++--
>  1 file changed, 23 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/tftp.c b/fs/tftp.c
> index 56d4365d773a..272a7106eb51 100644
> --- a/fs/tftp.c
> +++ b/fs/tftp.c
> @@ -591,8 +591,29 @@ static int tftp_read(struct device_d *dev, FILE *f, void *buf, size_t insize)
>  
>  static loff_t tftp_lseek(struct device_d *dev, FILE *f, loff_t pos)
>  {
> -	/* not implemented in tftp protocol */
> -	return -ENOSYS;
> +	if (pos >= f->pos) {
> +		char buf[1024];

Better use an allocated buffer? 1KiB is quite large for allocating on
the stack.

> +		int ret;
> +		while (pos > f->pos) {
> +			size_t len = min(sizeof(buf), (size_t)(pos - f->pos));
> +			ret = tftp_read(dev, f, buf, len);
> +
> +			if (ret < 0)
> +				return ret;
> +			else if (!ret)
> +				return -EINVAL;
> +			f->pos += ret;
> +
> +			memory_display(buf, f->pos - len, 0x10, 4, 0);

debugging leftover?

Sascha

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