Libguestfs - Dec 2018 - Re: [supermin PATCH] build: ignore empty files

Do not error out on empty files, just ignore them.
---
 src/mode_build.ml | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/mode_build.ml b/src/mode_build.ml
index b5f5fa6..9cd0a21 100644
--- a/src/mode_build.ml
+++ b/src/mode_build.ml
@@ -46,6 +46,7 @@ and file_content  | Packages
 | Hostfiles
 | Excludefiles
+| Empty
 
 let rec string_of_file_type = function
   | GZip c -> sprintf "gzip %s" (string_of_file_content c)
@@ -56,6 +57,7 @@ and string_of_file_content = function
   | Packages -> "packages"
   | Hostfiles -> "hostfiles"
   | Excludefiles -> "excludefiles"
+  | Empty -> "(empty)"
 
 let rec build debug
     (copy_kernel, format, host_cpu,
@@ -250,6 +252,8 @@ and read_appliance debug basedir appliance = function
     (* Depending on the file type, read or unpack the file. *)
     let appliance        match file_type with
+      | Uncompressed Empty | GZip Empty | XZ Empty ->
+        appliance
       | Uncompressed ((Packages|Hostfiles|Excludefiles) as t) ->
         let chan = open_in file in
         let lines = input_all_lines chan in
@@ -294,7 +298,7 @@ and update_appliance appliance lines = function
         String.sub path 1 (n-1)
     ) lines in
     { appliance with excludefiles = appliance.excludefiles @ lines }
-  | Base_image -> assert false
+  | Base_image | Empty -> assert false
 
 (* Determine the [file_type] of [file], or exit with an error. *)
 and get_file_type file @@ -331,6 +335,7 @@ and get_file_content file buf len   
else if len >= 2 && buf.[0] = '/' then Hostfiles
   else if len >= 2 && buf.[0] = '-' then Excludefiles
   else if len >= 1 && isalnum buf.[0] then Packages
+  else if len = 0 then Empty
   else error "%s: unknown file type in supermin directory" file
 
 and get_compressed_file_content zcat file -- 
2.17.2

On Mon, Dec 03, 2018 at 04:32:19PM +0100, Pino Toscano
wrote:
> Do not error out on empty files, just ignore them.
> ---
>  src/mode_build.ml | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/src/mode_build.ml b/src/mode_build.ml
> index b5f5fa6..9cd0a21 100644
> --- a/src/mode_build.ml
> +++ b/src/mode_build.ml
> @@ -46,6 +46,7 @@ and file_content >  | Packages
>  | Hostfiles
>  | Excludefiles
> +| Empty
>  
>  let rec string_of_file_type = function
>    | GZip c -> sprintf "gzip %s" (string_of_file_content c)
> @@ -56,6 +57,7 @@ and string_of_file_content = function
>    | Packages -> "packages"
>    | Hostfiles -> "hostfiles"
>    | Excludefiles -> "excludefiles"
> +  | Empty -> "(empty)"
>  
>  let rec build debug
>      (copy_kernel, format, host_cpu,
> @@ -250,6 +252,8 @@ and read_appliance debug basedir appliance = function
>      (* Depending on the file type, read or unpack the file. *)
>      let appliance >        match file_type with
> +      | Uncompressed Empty | GZip Empty | XZ Empty ->
> +        appliance
>        | Uncompressed ((Packages|Hostfiles|Excludefiles) as t) ->
>          let chan = open_in file in
>          let lines = input_all_lines chan in
> @@ -294,7 +298,7 @@ and update_appliance appliance lines = function
>          String.sub path 1 (n-1)
>      ) lines in
>      { appliance with excludefiles = appliance.excludefiles @ lines }
> -  | Base_image -> assert false
> +  | Base_image | Empty -> assert false
>  
>  (* Determine the [file_type] of [file], or exit with an error. *)
>  and get_file_type file > @@ -331,6 +335,7 @@ and get_file_content file
buf len >    else if len >= 2 && buf.[0] = '/' then
Hostfiles
>    else if len >= 2 && buf.[0] = '-' then Excludefiles
>    else if len >= 1 && isalnum buf.[0] then Packages
> +  else if len = 0 then Empty
>    else error "%s: unknown file type in supermin directory" file
>  
>  and get_compressed_file_content zcat file > -- 
This is fine, ACK.

Is there a situation where we have empty files in the supermin
directory?

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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On Monday, 3 December 2018 16:54:14 CET Richard W.M. Jones
wrote:
> Is there a situation where we have empty files in the supermin
> directory?
The bigger picture here is when creating an appliance, and none of the
packages has config files (it does not happen with libguestfs
appliances, while it can if you choose packages carefully).
The resulting base.tar.gz is not detected by Mode_build.get_file_type,
and I have a couple of patches fixing this.

This patch alone fixes the failure at --build time when touching an
empty file in the appliance directory.

-- 
Pino Toscano

On Mon, Dec 03, 2018 at 04:32:19PM +0100, Pino Toscano
wrote:
>Do not error out on empty files, just ignore them.
>---
> src/mode_build.ml | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
>diff --git a/src/mode_build.ml b/src/mode_build.ml
>index b5f5fa6..9cd0a21 100644
>--- a/src/mode_build.ml
>+++ b/src/mode_build.ml
>@@ -46,6 +46,7 @@ and file_content > | Packages
> | Hostfiles
> | Excludefiles
>+| Empty
>
> let rec string_of_file_type = function
>   | GZip c -> sprintf "gzip %s" (string_of_file_content c)
>@@ -56,6 +57,7 @@ and string_of_file_content = function
>   | Packages -> "packages"
>   | Hostfiles -> "hostfiles"
>   | Excludefiles -> "excludefiles"
>+  | Empty -> "(empty)"
>
> let rec build debug
>     (copy_kernel, format, host_cpu,
>@@ -250,6 +252,8 @@ and read_appliance debug basedir appliance = function
>     (* Depending on the file type, read or unpack the file. *)
>     let appliance >       match file_type with
>+      | Uncompressed Empty | GZip Empty | XZ Empty ->
>+        appliance
>       | Uncompressed ((Packages|Hostfiles|Excludefiles) as t) ->
>         let chan = open_in file in
>         let lines = input_all_lines chan in
>@@ -294,7 +298,7 @@ and update_appliance appliance lines = function
>         String.sub path 1 (n-1)
>     ) lines in
>     { appliance with excludefiles = appliance.excludefiles @ lines }
>-  | Base_image -> assert false
>+  | Base_image | Empty -> assert false
>
> (* Determine the [file_type] of [file], or exit with an error. *)
> and get_file_type file >@@ -331,6 +335,7 @@ and get_file_content file
buf len >   else if len >= 2 && buf.[0] = '/' then
Hostfiles
>   else if len >= 2 && buf.[0] = '-' then Excludefiles
>   else if len >= 1 && isalnum buf.[0] then Packages
>+  else if len = 0 then Empty
For me `zcat` outputs 10 KB of zeroes when ran with the empty base.tar.gz so
this is not enough.  The following works for me, but is probably not the right
way to approach it:

diff --git i/src/mode_build.ml w/src/mode_build.ml
index 9cd0a21d4c44..9fdfe7fb3729 100644
--- i/src/mode_build.ml
+++ w/src/mode_build.ml
@@ -336,6 +336,7 @@ and get_file_content file buf len    else if len >= 2
&& buf.[0] = '-' then Excludefiles
   else if len >= 1 && isalnum buf.[0] then Packages
   else if len = 0 then Empty
+  else if buf = String.make len '\000' then Empty
   else error "%s: unknown file type in supermin directory" file

 and get_compressed_file_content zcat file --
>   else error "%s: unknown file type in supermin directory" file
>
> and get_compressed_file_content zcat file >-- 
>2.17.2
>
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