Replace external brotli.js with WASM

Removes brotli.js and polyfills used to decode .br files.
Instead, use existing libbrotlidec on C++ code, using adapted source from https://github.com/google/brotli/blob/7f740f1308336e9ec0afdb9434896307859f5dc9/go/cbrotli/reader.go (which we depend on).

This saves about 100 KiB or so, mostly extra dictionary size.

Author: WeebDataHoarder

Makefile

@@ -47,8 +47,6 @@ $(DIST_DIR)/lib/libexpat.a: build/lib/expat/configured
 	$(JSO_MAKE) install
 
 # Brotli
-build/lib/brotli/js/decode.js: build/lib/brotli/configured
-build/lib/brotli/js/polyfill.js: build/lib/brotli/configured
 build/lib/brotli/configured: lib/brotli $(wildcard $(BASE_DIR)build/patches/brotli/*.patch)
 	$(call PREPARE_SRC_PATCHED,brotli)
 	touch build/lib/brotli/configured
@@ -155,7 +153,7 @@ all-src:
 EMCC_COMMON_ARGS = \
 	$(LDFLAGS) \
 	-s AUTO_NATIVE_LIBRARIES=0 \
-	-s EXPORTED_FUNCTIONS="['_main', '_malloc']" \
+	-s EXPORTED_FUNCTIONS="['_main', '_malloc', '_free']" \
 	-s EXPORTED_RUNTIME_METHODS="['ccall', 'cwrap', 'getValue', 'FS_createPreloadedFile', 'FS_createPath']" \
 	--use-preload-plugins \
 	--preload-file assets/default.woff2 \
@@ -167,23 +165,20 @@ EMCC_COMMON_ARGS = \
 
 dist: src/subtitles-octopus-worker.bc dist/js/subtitles-octopus-worker.js dist/js/subtitles-octopus-worker-legacy.js dist/js/subtitles-octopus.js dist/js/COPYRIGHT
 
-dist/js/subtitles-octopus-worker.js: src/subtitles-octopus-worker.bc src/pre-worker.js src/SubOctpInterface.js src/post-worker.js build/lib/brotli/js/decode.js
+dist/js/subtitles-octopus-worker.js: src/subtitles-octopus-worker.bc src/pre-worker.js src/SubOctpInterface.js src/post-worker.js
 	mkdir -p dist/js
 	emcc src/subtitles-octopus-worker.bc $(OCTP_DEPS) \
 		--pre-js src/pre-worker.js \
-		--pre-js build/lib/brotli/js/decode.js \
 		--post-js src/SubOctpInterface.js \
 		--post-js src/post-worker.js \
 		-s WASM=1 \
 		$(EMCC_COMMON_ARGS)
 
-dist/js/subtitles-octopus-worker-legacy.js: src/subtitles-octopus-worker.bc src/polyfill.js src/pre-worker.js src/SubOctpInterface.js src/post-worker.js build/lib/brotli/js/decode.js build/lib/brotli/js/polyfill.js
+dist/js/subtitles-octopus-worker-legacy.js: src/subtitles-octopus-worker.bc src/polyfill.js src/pre-worker.js src/SubOctpInterface.js src/post-worker.js
 	mkdir -p dist/js
 	emcc src/subtitles-octopus-worker.bc $(OCTP_DEPS) \
 		--pre-js src/polyfill.js \
-		--pre-js build/lib/brotli/js/polyfill.js \
 		--pre-js src/pre-worker.js \
-		--pre-js build/lib/brotli/js/decode.js \
 		--post-js src/SubOctpInterface.js \
 		--post-js src/post-worker.js \
 		-s WASM=0 \

build/patches/brotli/0001-fix-brotli-js-for-webworkers.patch

@@ -3,7 +3,8 @@
 CXX = em++ -c
 CXXFLAGS = -O3 -g4
 LIBASS_CXXFLAGS = $(shell pkg-config --static --cflags "libass >= 0.14.0")
-LOCAL_CXXFLAGS  = -Wall -Wno-deprecated $(LIBASS_CXXFLAGS)
+BROTLI_CXXFLAGS = $(shell pkg-config --static --cflags "libbrotlidec")
+LOCAL_CXXFLAGS  = -Wall -Wno-deprecated $(LIBASS_CXXFLAGS) $(BROTLI_CXXFLAGS)
 
 all: subtitles-octopus-worker.bc
 

build/patches/brotli/0002-upstream_Enable-install-with-emscripten.patch renamed to build/patches/brotli/0001-upstream_Enable-install-with-emscripten.patch

@@ -10,6 +10,7 @@
 #include "../lib/libass/libass/ass.h"
 
 #include "libass.cpp"
+#include "brotli.cpp"
 
 #ifdef __EMSCRIPTEN__
 #include <emscripten.h>

src/Makefile

@@ -165,6 +165,12 @@ interface RenderBlendResult {
     attribute ByteString image;
 };
 
+[NoDelete]
+interface Brotli {
+    void Brotli();
+    ByteString decode([Const] ByteString encoded, unsigned long encoded_size, IntPtr decoded_size);
+};
+
 interface SubtitleOctopus {
     void SubtitleOctopus();
     attribute ASS_Track track;

src/SubtitleOctopus.cpp

@@ -0,0 +1,95 @@
+// Adjusted from go cbrotli reader https://github.com/google/brotli/blob/7f740f1308336e9ec0afdb9434896307859f5dc9/go/cbrotli/reader.go
+//
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Distributed under MIT license.
+// See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <string.h>
+#include <vector>
+#include <cstdint>
+
+#include <brotli/decode.h>
+
+static BrotliDecoderResult DecompressStream(BrotliDecoderState* s,
+                                            uint8_t* out, size_t out_len,
+                                            const uint8_t* in, size_t in_len,
+                                            size_t* bytes_written,
+                                            size_t* bytes_consumed) {
+  size_t in_remaining = in_len;
+  size_t out_remaining = out_len;
+  BrotliDecoderResult result = BrotliDecoderDecompressStream(
+      s, &in_remaining, &in, &out_remaining, &out, NULL);
+  *bytes_written = out_len - out_remaining;
+  *bytes_consumed = in_len - in_remaining;
+  return result;
+}
+
+#define BUF_SIZE 1024 * 64
+
+class Brotli {
+public:
+
+    static uint8_t* decode(const uint8_t* encoded, int encoded_size, int* decoded_size) {
+        *decoded_size = 0;
+
+        BrotliDecoderState* state = BrotliDecoderCreateInstance(NULL, NULL, NULL);
+        if (state == NULL){
+            return NULL;
+        }
+
+        size_t written, consumed;
+
+        const uint8_t* in = encoded;
+        size_t in_size = encoded_size;
+
+        std::vector<uint8_t> result_buf;
+        uint8_t* out_buf = (uint8_t*)malloc(BUF_SIZE);
+        if(out_buf == NULL){
+            BrotliDecoderDestroyInstance(state);
+            return NULL;
+        }
+
+        while(in_size > 0){
+            BrotliDecoderResult result = DecompressStream(state, out_buf, BUF_SIZE, in, in_size, &written, &consumed);
+
+            in += consumed;
+            in_size -= consumed;
+
+
+            if(written > 0){
+                result_buf.insert(result_buf.end(), out_buf, out_buf + written);
+            }
+
+            switch(result){
+                case BROTLI_DECODER_RESULT_SUCCESS:
+                    break;
+                case BROTLI_DECODER_RESULT_ERROR:
+                    free(out_buf);
+                    BrotliDecoderDestroyInstance(state);
+                    return NULL;
+                case BROTLI_DECODER_RESULT_NEEDS_MORE_OUTPUT:
+                    if(written == 0){
+                        free(out_buf);
+                        BrotliDecoderDestroyInstance(state);
+                        return NULL;
+                    }
+                    break;
+                case BROTLI_DECODER_RESULT_NEEDS_MORE_INPUT:
+                    break;
+            }
+        }
+
+        free(out_buf);
+        BrotliDecoderDestroyInstance(state);
+
+        uint8_t* decoded = (uint8_t*)malloc(result_buf.size());
+        std::copy(result_buf.begin(), result_buf.end(), decoded);
+        *decoded_size = result_buf.size();
+        return decoded;
+    }
+
+};

src/SubtitleOctopus.idl

@@ -103,14 +103,46 @@ self.freeTrack = function () {
     self.getRenderMethod()();
 };
 
+self.decodeBrotliArray = function (uint8array) {
+    //Allocate and copy brotli encoded input into the heap, using buf ptr as offset
+    var buf = Module._malloc(uint8array.length);
+    Module["HEAPU8"].set(uint8array, buf);
+
+    //Allocate return length memory
+    var decode_length_ptr = Module._malloc(4);
+
+    var br = new Module.Brotli();
+
+    //uint8_t* decoded;
+    var decoded = br.decode(buf, uint8array.length, decode_length_ptr);
+
+    //int decode_length = *decode_length_ptr
+    var decode_length = Module.getValue(decode_length_ptr, "i32");
+
+    //free input buffer and return length memory
+    Module._free(buf);
+    Module._free(decode_length_ptr);
+
+    if(decoded === 0){
+        //decode err
+        throw "could not decode brotli file";
+    }
+
+    //copy data from the decoded ptr in the heap to a slice, then copy it
+    var content = new Uint8Array(new Uint8Array(Module["HEAPU8"].buffer, decoded, decode_length));
+
+    Module._free(decoded);
+    return content;
+}
+
 /**
  * Set the subtitle track.
  * @param {!string} url the URL of the subtitle file.
  */
 self.setTrackByUrl = function (url) {
     var content = "";
     if (isBrotliFile(url)) {
-        content = Module["BrotliDecode"](readBinary(url))
+        content = self.decodeBrotliArray(readBinary(url));
     } else {
         content = read_(url);
     }

src/brotli.cpp

@@ -61,7 +61,7 @@ Module["preRun"].push(function () {
     if (!self.subContent) {
         // We can use sync xhr cause we're inside Web Worker
         if (isBrotliFile(self.subUrl)) {
-            self.subContent = Module["BrotliDecode"](readBinary(self.subUrl))
+            self.subContent = self.decodeBrotliArray(readBinary(self.subUrl));
         } else {
             self.subContent = read_(self.subUrl);
         }