commit 05f45b21b72fdf738986ea428346f2fbec8444d8
author Mike Klein <mtklein@google.com> Thu Apr 25 12:13:03 2019 -0500
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Thu Apr 25 21:43:12 2019 +0000
tree 896f2d13a77a167b1f23dbd1b9e1db8f53235645
parent b14574924ab332c1b6ce9afabdc03820540aab1e

runtime registration for decoders

What do you think of this sort of thing for letting
users register codecs at runtime instead of at build time?

Change-Id: I448ea3466862326c283ad9b2f1b7eea56cffc80c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/210449
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>

src/codec/SkCodec.cpp

diff --git a/src/codec/SkCodec.cpp b/src/codec/SkCodec.cpp
index a09af36..49ec864 100644
--- a/src/codec/SkCodec.cpp
+++ b/src/codec/SkCodec.cpp
@@ -9,6 +9,8 @@
 #include "include/core/SkColorSpace.h"
 #include "include/core/SkData.h"
 #include "include/private/SkHalf.h"
+#include "include/private/SkMutex.h"
+#include "src/core/SkSharedMutex.h"
 #include "src/codec/SkBmpCodec.h"
 #include "src/codec/SkCodecPriv.h"
 #include "src/codec/SkFrameHolder.h"
@@ -35,27 +37,44 @@
     std::unique_ptr<SkCodec> (*MakeFromStream)(std::unique_ptr<SkStream>, SkCodec::Result*);
 };
 
-static constexpr DecoderProc gDecoderProcs[] = {
-#ifdef SK_HAS_JPEG_LIBRARY
-    { SkJpegCodec::IsJpeg, SkJpegCodec::MakeFromStream },
-#endif
-#ifdef SK_HAS_WEBP_LIBRARY
-    { SkWebpCodec::IsWebp, SkWebpCodec::MakeFromStream },
-#endif
-#ifdef SK_HAS_WUFFS_LIBRARY
-    { SkWuffsCodec_IsFormat, SkWuffsCodec_MakeFromStream },
-#else
-    { SkGifCodec::IsGif, SkGifCodec::MakeFromStream },
-#endif
-#ifdef SK_HAS_PNG_LIBRARY
-    { SkIcoCodec::IsIco, SkIcoCodec::MakeFromStream },
-#endif
-    { SkBmpCodec::IsBmp, SkBmpCodec::MakeFromStream },
-    { SkWbmpCodec::IsWbmp, SkWbmpCodec::MakeFromStream },
-#ifdef SK_HAS_HEIF_LIBRARY
-    { SkHeifCodec::IsHeif, SkHeifCodec::MakeFromStream },
-#endif
-};
+// Wish we had SK_DECLARE_STATIC_SHARED_MUTEX.
+static SkSharedMutex* decoders_mutex() {
+    static SkSharedMutex* mutex = new SkSharedMutex;
+    return mutex;
+}
+
+static std::vector<DecoderProc>* decoders() {
+    static auto* decoders = new std::vector<DecoderProc> {
+    #ifdef SK_HAS_JPEG_LIBRARY
+        { SkJpegCodec::IsJpeg, SkJpegCodec::MakeFromStream },
+    #endif
+    #ifdef SK_HAS_WEBP_LIBRARY
+        { SkWebpCodec::IsWebp, SkWebpCodec::MakeFromStream },
+    #endif
+    #ifdef SK_HAS_WUFFS_LIBRARY
+        { SkWuffsCodec_IsFormat, SkWuffsCodec_MakeFromStream },
+    #else
+        { SkGifCodec::IsGif, SkGifCodec::MakeFromStream },
+    #endif
+    #ifdef SK_HAS_PNG_LIBRARY
+        { SkIcoCodec::IsIco, SkIcoCodec::MakeFromStream },
+    #endif
+        { SkBmpCodec::IsBmp, SkBmpCodec::MakeFromStream },
+        { SkWbmpCodec::IsWbmp, SkWbmpCodec::MakeFromStream },
+    #ifdef SK_HAS_HEIF_LIBRARY
+        { SkHeifCodec::IsHeif, SkHeifCodec::MakeFromStream },
+    #endif
+    };
+    return decoders;
+}
+
+void SkCodec::Register(
+            bool                     (*peek)(const void*, size_t),
+            std::unique_ptr<SkCodec> (*make)(std::unique_ptr<SkStream>, SkCodec::Result*)) {
+    SkAutoExclusive lock{*decoders_mutex()};
+    decoders()->push_back(DecoderProc{peek, make});
+}
+
 
 std::unique_ptr<SkCodec> SkCodec::MakeFromStream(std::unique_ptr<SkStream> stream,
                                                  Result* outResult, SkPngChunkReader* chunkReader) {
@@ -105,7 +124,8 @@
     } else
 #endif
     {
-        for (DecoderProc proc : gDecoderProcs) {
+        SkAutoSharedMutexShared lock{*decoders_mutex()};
+        for (DecoderProc proc : *decoders()) {
             if (proc.IsFormat(buffer, bytesRead)) {
                 return proc.MakeFromStream(std::move(stream), outResult);
             }