[PATCH] erofs-utils: list available compressors for help command

[Li Guifu]

Hi Gao Xiang

What do you think put the compressor's name into structure of 
erofs_compressor ?
So compressor's name will be matched to its implement not represented
at two place.


On 2019/10/22 12:20, Gao Xiang wrote:
> Users can get knowledge of supported compression
> algorithms then.
> 
> Signed-off-by: Gao Xiang <gaoxiang25 at huawei.com>
> ---
>   include/erofs/compress.h |  2 ++
>   lib/compressor.c         | 17 +++++++++++++++++
>   mkfs/main.c              | 15 +++++++++++++++
>   3 files changed, 34 insertions(+)
> 
> diff --git a/include/erofs/compress.h b/include/erofs/compress.h
> index e0abb8f1c422..fa918732b532 100644
> --- a/include/erofs/compress.h
> +++ b/include/erofs/compress.h
> @@ -21,5 +21,7 @@ int erofs_write_compressed_file(struct erofs_inode *inode);
>   int z_erofs_compress_init(void);
>   int z_erofs_compress_exit(void);
>   
> +const char *z_erofs_list_available_compressors(unsigned int i);
> +
>   #endif
>   
> diff --git a/lib/compressor.c b/lib/compressor.c
> index 8cc2f438479b..c593c769d46f 100644
> --- a/lib/compressor.c
> +++ b/lib/compressor.c
> @@ -36,6 +36,23 @@ int erofs_compress_destsize(struct erofs_compress *c,
>   	return ret;
>   }
>   
> +const char *z_erofs_list_available_compressors(unsigned int i)
> +{
> +	static const char *compressors[] = {
> +#if LZ4_ENABLED
> +#if LZ4HC_ENABLED
> +		"lz4hc",
> +#endif
> +		"lz4",
> +#endif
> +		NULL,
> +	};
> +
> +	if (i >= ARRAY_SIZE(compressors))
> +		return NULL;
> +	return compressors[i];
> +}
> +
>   int erofs_compressor_init(struct erofs_compress *c,
>   			  char *alg_name)
>   {
> diff --git a/mkfs/main.c b/mkfs/main.c
> index 31cf1c2408d1..1161b3f0f7cc 100644
> --- a/mkfs/main.c
> +++ b/mkfs/main.c
> @@ -29,6 +29,19 @@ static struct option long_options[] = {
>   	{0, 0, 0, 0},
>   };
>   
> +static void print_available_compressors(FILE *f, const char *delim)
> +{
> +	unsigned int i = 0;
> +	const char *s;
> +
> +	while ((s = z_erofs_list_available_compressors(i)) != NULL) {
> +		if (i++)
> +			fputs(delim, f);
> +		fputs(s, f);
> +	}
> +	fputc('\n', f);
> +}
> +
>   static void usage(void)
>   {
>   	fprintf(stderr, "usage: [options] FILE DIRECTORY\n\n");
> @@ -39,6 +52,8 @@ static void usage(void)
>   	fprintf(stderr, " -EX[,...] X=extended options\n");
>   	fprintf(stderr, " -T#       set a fixed UNIX timestamp # to all files\n");
>   	fprintf(stderr, " --help    display this help and exit\n");
> +	fprintf(stderr, "\nAvailable compressors are: ");
> +	print_available_compressors(stderr, ", ");
>   }
>   
>   static int parse_extended_opts(const char *opts)
>