feat: add skippable_frame

Author: SpringMT

ext/zstdruby/extconf.rb

@@ -1,6 +1,6 @@
 require "mkmf"
 
-$CFLAGS = '-I. -O3 -std=c99'
+$CFLAGS = '-I. -O3 -std=c99 -DZSTD_STATIC_LINKING_ONLY'
 $CPPFLAGS += " -fdeclspec" if CONFIG['CXX'] =~ /clang/
 
 Dir.chdir File.expand_path('..', __FILE__) do

ext/zstdruby/main.c

@@ -1,6 +1,7 @@
 #include <common.h>
 VALUE rb_mZstd;
 void zstd_ruby_init(void);
+void zstd_ruby_skippable_frame_init(void);
 void zstd_ruby_streaming_compress_init(void);
 void zstd_ruby_streaming_decompress_init(void);
 
@@ -13,6 +14,7 @@ Init_zstdruby(void)
 
   rb_mZstd = rb_define_module("Zstd");
   zstd_ruby_init();
+  zstd_ruby_skippable_frame_init();
   zstd_ruby_streaming_compress_init();
   zstd_ruby_streaming_decompress_init();
 }

ext/zstdruby/skippable_frame.c

@@ -0,0 +1,55 @@
+#include <common.h>
+
+extern VALUE rb_mZstd;
+
+static VALUE rb_write_skippable_frame(int argc, VALUE *argv, VALUE self)
+{
+  VALUE input_value;
+  VALUE skip_value;
+  rb_scan_args(argc, argv, "2", &input_value, &skip_value);
+
+  StringValue(input_value);
+  StringValue(skip_value);
+  char* input_data = RSTRING_PTR(input_value);
+  size_t input_size = RSTRING_LEN(input_value);
+  char* skip_data = RSTRING_PTR(skip_value);
+  size_t skip_size = RSTRING_LEN(skip_value);
+
+  size_t dst_size = input_size + ZSTD_SKIPPABLEHEADERSIZE + skip_size;
+  VALUE output = rb_str_new(input_data, dst_size);
+  char* output_data = RSTRING_PTR(output);
+  size_t output_size = ZSTD_writeSkippableFrame((void*)output_data, dst_size, (const void*)skip_data, skip_size, (unsigned)0);
+  if (ZSTD_isError(output_size)) {
+    rb_raise(rb_eRuntimeError, "%s: %s", "write skippable frame failed", ZSTD_getErrorName(output_size));
+  }
+
+  rb_str_resize(output, output_size);
+  return output;
+}
+
+static VALUE rb_read_skippable_frame(VALUE self, VALUE input_value)
+{
+  char* input_data = RSTRING_PTR(input_value);
+  size_t input_size = RSTRING_LEN(input_value);
+
+  if (ZSTD_isSkippableFrame(input_data, input_size) == 0) {
+    return Qnil;
+  }
+  // ref https://github.com/facebook/zstd/blob/321490cd5b9863433b3d44816d04012874e5ecdb/tests/fuzzer.c#L2096
+  size_t const skipLen = 129 * 1024;
+  VALUE output = rb_str_new(NULL, skipLen);
+  char* output_data = RSTRING_PTR(output);
+  size_t output_size = ZSTD_readSkippableFrame((void*)output_data, skipLen, (unsigned int*)0, (const void*)input_data, input_size);
+  if (ZSTD_isError(output_size)) {
+    rb_raise(rb_eRuntimeError, "%s: %s", "read skippable frame failed", ZSTD_getErrorName(output_size));
+  }
+  rb_str_resize(output, output_size);
+  return output;
+}
+
+void
+zstd_ruby_skippable_frame_init(void)
+{
+  rb_define_module_function(rb_mZstd, "write_skippable_frame", rb_write_skippable_frame, -1);
+  rb_define_module_function(rb_mZstd, "read_skippable_frame", rb_read_skippable_frame, 1);
+}

spec/zstd-skippable_frame_spec.rb

@@ -0,0 +1,25 @@
+require "spec_helper"
+require 'zstd-ruby'
+require 'securerandom'
+
+RSpec.describe Zstd do
+  describe 'read_skippable_frame' do
+    context 'simple string' do
+      it '' do
+        expect(Zstd.read_skippable_frame('abc')).to eq nil
+      end
+    end
+    context 'compressed string' do
+      it '' do
+        expect(Zstd.read_skippable_frame(Zstd.compress(SecureRandom.hex(150)))).to eq nil
+      end
+    end
+    context 'compressed string + skippable frame' do
+      it '' do
+        compressed_data = Zstd.compress(SecureRandom.hex(150))
+        compressed_data_with_skippable_frame = Zstd.write_skippable_frame(compressed_data, "sample data")
+        expect(Zstd.read_skippable_frame(compressed_data_with_skippable_frame)).to eq "sample data"
+      end
+    end
+  end
+end