[Spice-devel] [vdagent-win PATCH v4 07/19] Allow one more character reading strings from registry

[Christophe de Dinechin]

> On 2 Jul 2018, at 09:43, Frediano Ziglio <fziglio at redhat.com> wrote:
> 
> The strings in the registry are usually NUL-terminated but this
> is not a requirement.
> Handle the case when the string, considering the terminator, fit
> into the reading buffer. In this case accept the string. In the
> case the string fit into the buffer but is not terminated
> returns ERROR_MORE_DATA (the error that would be returned if the
> string didn't fit in the buffer as there is no place to add the
> terminator).
> 
> Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
> ---
> vdagent/display_setting.cpp | 20 ++++++++++++++------
> 1 file changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/vdagent/display_setting.cpp b/vdagent/display_setting.cpp
> index b68ef1c..4b47276 100644
> --- a/vdagent/display_setting.cpp
> +++ b/vdagent/display_setting.cpp
> @@ -295,6 +295,20 @@ static bool RegReadString(HKEY key, const TCHAR *name, TCHAR *buffer, size_t buf
>     LONG status;
> 
>     status = RegQueryValueEx(key, name, NULL, &value_type, (LPBYTE)buffer, &value_size);
> +    if (status == ERROR_SUCCESS && value_type == REG_SZ) {
> +        // assure NUL-terminated

s/assure/ensure/ (see https://data.grammarbook.com/blog/definitions/assure-vs-ensure-vs-insure/)

> +        value_size /= sizeof(buffer[0]);
> +        if (value_size == buffer_len) {
> +            // full buffer but not terminated?
> +            if (buffer[value_size-1] != '\0') {
> +                status = ERROR_MORE_DATA;
> +            }
> +        } else {
> +            // append a NUL. If there's already a NUL character this
> +            // new one will be ignored
> +            buffer[value_size] = '\0';
> +        }
> +    }
>     if (status != ERROR_SUCCESS) {
>         vd_printf("RegQueryValueEx(%" PRIsTSTR ") : fail %ld", name, status);
>         return false;
> @@ -305,12 +319,6 @@ static bool RegReadString(HKEY key, const TCHAR *name, TCHAR *buffer, size_t buf
>         return false;
>     }
> 
> -    // assure NUL-terminated
> -    value_size /= sizeof(buffer[0]);
> -    if (!value_size || buffer[value_size - 1] != '\0') {
> -        buffer[value_size] = '\0';
> -    }
> -
>     return true;
> }
> 
> -- 
> 2.17.1
> 
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