modules/zstd: Add raw block decoder

Internal-tag: [#51343]
Signed-off-by: Robert Winkler <[email protected]>

xls/modules/zstd/BUILD

@@ -139,3 +139,19 @@ cc_test(
         "@com_google_fuzztest//fuzztest:googletest_fixture_adapter",
     ],
 )
+
+xls_dslx_library(
+    name = "raw_block_dec_dslx",
+    srcs = [
+        "raw_block_dec.x",
+    ],
+    deps = [
+        ":buffer_dslx",
+        ":common_dslx",
+    ],
+)
+
+xls_dslx_test(
+    name = "raw_block_dec_dslx_test",
+    library = ":raw_block_dec_dslx",
+)

xls/modules/zstd/raw_block_dec.x

@@ -0,0 +1,96 @@
+// Copyright 2023 The XLS Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This file contains the implementation of RawBlockDecoder responsible for decoding
+// ZSTD Raw Blocks. More information about Raw Block's format can be found in:
+// https://datatracker.ietf.org/doc/html/rfc8878#section-3.1.1.2.2
+
+import xls.modules.zstd.common as common
+
+type BlockDataPacket = common::BlockDataPacket;
+type BlockData = common::BlockData;
+
+struct RawBlockDecoderState {
+    prev_id: u32, // ID of the previous block
+    prev_last: bool, // if the previous packet was the last one that makes up the whole block
+    prev_valid: bool, // if prev_id and prev_last contain valid data
+}
+
+const DATA_WIDTH = common::DATA_WIDTH;
+const ZERO_RAW_BLOCK_DECODER_STATE = zero!<RawBlockDecoderState>();
+
+// RawBlockDecoder is responsible for decoding Raw Blocks,
+// it should be a part of the ZSTD Decoder pipeline.
+pub proc RawBlockDecoder {
+    input_r: chan<BlockDataPacket> in;
+    output_s: chan<BlockDataPacket> out;
+
+    init { (ZERO_RAW_BLOCK_DECODER_STATE) }
+
+    config(
+        input_r: chan<BlockDataPacket> in,
+        output_s: chan<BlockDataPacket> out
+    ) {(input_r, output_s)}
+
+    next(tok: token, state: RawBlockDecoderState) {
+        let (tok, data) = recv(tok, input_r);
+        if state.prev_valid && (data.id != state.prev_id) && (state.prev_last == false) {
+            trace_fmt!("ID changed but previous packet have no last!");
+            fail!("no_last", ());
+        } else {};
+
+        let tok = send(tok, output_s, data);
+
+        RawBlockDecoderState {
+            prev_valid: true,
+            prev_id: data.id,
+            prev_last: data.last
+        }
+    }
+}
+
+#[test_proc]
+proc RawBlockDecoderTest {
+    terminator: chan<bool> out;
+    dec_input_s: chan<BlockDataPacket> out;
+    dec_output_r: chan<BlockDataPacket> in;
+
+    config(terminator: chan<bool> out) {
+        let (dec_input_s, dec_input_r) = chan<BlockDataPacket>;
+        let (dec_output_s, dec_output_r) = chan<BlockDataPacket>;
+        spawn RawBlockDecoder(dec_input_r, dec_output_s);
+        (terminator, dec_input_s, dec_output_r)
+    }
+
+    init {  }
+
+    next(tok: token, state: ()) {
+        let data_to_send: BlockDataPacket[5] = [
+            BlockDataPacket { id: u32:1, last: u1:false, last_block: u1:false, data: BlockData:1, length: u32:32 },
+            BlockDataPacket { id: u32:1, last: u1:false, last_block: u1:false, data: BlockData:2, length: u32:32 },
+            BlockDataPacket { id: u32:1, last: u1:true, last_block: u1:false, data: BlockData:3, length: u32:32 },
+            BlockDataPacket { id: u32:2, last: u1:false, last_block: u1:false, data: BlockData:4, length: u32:32 },
+            BlockDataPacket { id: u32:2, last: u1:true, last_block: u1:true, data: BlockData:5, length: u32:32 },
+        ];
+
+        let tok = for ((_, data), tok): ((u32, BlockDataPacket), token) in enumerate(data_to_send) {
+            let tok = send(tok, dec_input_s, data);
+            let (tok, received_data) = recv(tok, dec_output_r);
+            assert_eq(data, received_data);
+            (tok)
+        }(tok);
+
+        send(tok, terminator, true);
+    }
+}