On Wed, Dec 02, 2020 at 12:32:40PM -0800, Nick Terrell wrote:
> From: Nick Terrell <terre...@fb.com>
>
> This patch:
> - Moves `include/linux/zstd.h` -> `lib/zstd/zstd.h`
> - Adds a new API in `include/linux/zstd.h` that is functionally
> equivalent to the in-use subset of the current API. Functions are
> renamed to avoid symbol collisions with zstd, to make it clear it is
> not the upstream zstd API, and to follow the kernel style guide.
> - Updates all callers to use the new API.
>
> There are no functional changes in this patch. Since there are no
> functional change, I felt it was okay to update all the callers in a
> single patch, since once the API is approved, the callers are
> mechanically changed.
[...]
> --- a/lib/decompress_unzstd.c
> +++ b/lib/decompress_unzstd.c
[...]
> static int INIT handle_zstd_error(size_t ret, void (*error)(char *x))
> {
> - const int err = ZSTD_getErrorCode(ret);
> -
> - if (!ZSTD_isError(ret))
> + if (!zstd_is_error(ret))
> return 0;
>
> - switch (err) {
> - case ZSTD_error_memory_allocation:
> - error("ZSTD decompressor ran out of memory");
> - break;
> - case ZSTD_error_prefix_unknown:
> - error("Input is not in the ZSTD format (wrong magic bytes)");
> - break;
> - case ZSTD_error_dstSize_tooSmall:
> - case ZSTD_error_corruption_detected:
> - case ZSTD_error_checksum_wrong:
> - error("ZSTD-compressed data is corrupt");
> - break;
> - default:
> - error("ZSTD-compressed data is probably corrupt");
> - break;
> - }
> + error("ZSTD decompression failed");
> return -1;
> }
This looses diagnostics specificity - is this intended? At least the
out-of-memory condition seems useful to distinguish.
> +size_t zstd_compress_stream(zstd_cstream *cstream,
> + struct zstd_out_buffer *output, struct zstd_in_buffer *input)
> +{
> + ZSTD_outBuffer o;
> + ZSTD_inBuffer i;
> + size_t ret;
> +
> + memcpy(&o, output, sizeof(o));
> + memcpy(&i, input, sizeof(i));
> + ret = ZSTD_compressStream(cstream, &o, &i);
> + memcpy(output, &o, sizeof(o));
> + memcpy(input, &i, sizeof(i));
> + return ret;
> +}
Is all this copying necessary? How is it different from type-punning by
direct pointer cast?
Best Regards
Michał Mirosław
