[PATCH] libfile: implement new pread_full

[Sascha Hauer]

On Fri, Mar 18, 2022 at 03:49:42PM +0100, Ahmad Fatoum wrote:
> We already have pwrite_full, add pread_full for symmetry.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
> ---
>  include/libfile.h |  1 +
>  lib/libfile.c     | 25 +++++++++++++++++++++++++
>  2 files changed, 26 insertions(+)

Applied, thanks

Sascha

> 
> diff --git a/include/libfile.h b/include/libfile.h
> index 3c2fe1714dcb..a353ccfa9ea9 100644
> --- a/include/libfile.h
> +++ b/include/libfile.h
> @@ -2,6 +2,7 @@
>  #ifndef __LIBFILE_H
>  #define __LIBFILE_H
>  
> +int pread_full(int fd, void *buf, size_t size, loff_t offset);
>  int pwrite_full(int fd, const void *buf, size_t size, loff_t offset);
>  int write_full(int fd, const void *buf, size_t size);
>  int read_full(int fd, void *buf, size_t size);
> diff --git a/lib/libfile.c b/lib/libfile.c
> index 6b373f05ca72..1f533133c593 100644
> --- a/lib/libfile.c
> +++ b/lib/libfile.c
> @@ -75,6 +75,31 @@ int write_full(int fd, const void *buf, size_t size)
>  }
>  EXPORT_SYMBOL(write_full);
>  
> +/*
> + * pread_full - read to filedescriptor at offset
> + *
> + * Like pread, but this function only returns less bytes than
> + * requested when the end of file is reached.
> + */
> +int pread_full(int fd, void *buf, size_t size, loff_t offset)
> +{
> +	size_t insize = size;
> +	int now;
> +
> +	while (size) {
> +		now = pread(fd, buf, size, offset);
> +		if (now == 0)
> +			break;
> +		if (now < 0)
> +			return now;
> +		size -= now;
> +		buf += now;
> +	}
> +
> +	return insize - size;
> +}
> +EXPORT_SYMBOL(pread_full);
> +
>  /*
>   * read_full - read from filedescriptor
>   *
> -- 
> 2.30.2
> 
> 
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