Added version number to dehydrated SkSL files

This will allow us to catch cases where the dehydrated files were not
regenerated, and also provides a degree of future proofing.

Change-Id: I0e7d0e0d83099b78fc5d36c5c5fc1846d8bec467
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/499383
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>

src/sksl/SkSLDehydrator.cpp

@@ -592,11 +592,11 @@ void Dehydrator::write(const std::vector<std::unique_ptr<ProgramElement>>& eleme
 }
 
 void Dehydrator::finish(OutputStream& out) {
+    out.write16(Rehydrator::kVersion);
     String stringBuffer = fStringBuffer.str();
     String commandBuffer = fBody.str();
-
     out.write16(fStringBuffer.str().size());
-    fStringBufferStart = 2;
+    fStringBufferStart = 4;
     out.writeString(stringBuffer);
     fCommandStart = fStringBufferStart + stringBuffer.size();
     out.writeString(commandBuffer);

src/sksl/SkSLDehydrator.h

@@ -32,6 +32,7 @@ class SymbolTable;
 
 // The file has the structure:
 //
+// uint16 version
 // uint16 total string length
 // string data
 // symboltable

src/sksl/SkSLRehydrator.cpp

@@ -79,12 +79,16 @@ Rehydrator::Rehydrator(const Context* context,  std::shared_ptr<SymbolTable> sym
                        const uint8_t* src, size_t length)
                 : fContext(*context)
                 , fSymbolTable(std::move(symbolTable))
-                , fStart(src)
-    SkDEBUGCODE(, fEnd(fStart + length)) {
+    SkDEBUGCODE(, fEnd(src + length)) {
     SkASSERT(fSymbolTable);
     SkASSERT(fSymbolTable->isBuiltin());
-    // skip past string data
-    fIP = fStart;
+    fIP = src;
+    uint16_t version = this->readU16();
+    (void)version;
+    SkASSERTF(version == kVersion, "Dehydrated file is an unsupported version (current version is "
+            "%d, found version %d)", kVersion, version);
+    fStringStart = fIP;
+    // skip over string data
     fIP += this->readU16();
 }
 

src/sksl/SkSLRehydrator.h

@@ -32,6 +32,8 @@ class Type;
  */
 class Rehydrator {
 public:
+    static constexpr uint16_t kVersion = 1;
+
     enum Command {
         // uint16 id, Type componentType, uint8 count
         kArrayType_Command,
@@ -180,8 +182,8 @@ private:
 
     skstd::string_view readString() {
         uint16_t offset = this->readU16();
-        uint8_t length = *(uint8_t*) (fStart + offset);
-        const char* chars = (const char*) fStart + offset + 1;
+        uint8_t length = *(uint8_t*) (fStringStart + offset);
+        const char* chars = (const char*) fStringStart + offset + 1;
         return skstd::string_view(chars, length);
     }
 
@@ -223,7 +225,7 @@ private:
     std::shared_ptr<SymbolTable> fSymbolTable;
     std::vector<const Symbol*> fSymbols;
 
-    const uint8_t* fStart;
+    const uint8_t* fStringStart;
     const uint8_t* fIP;
     SkDEBUGCODE(const uint8_t* fEnd;)
 

src/sksl/generated/sksl_frag.dehydrated.sksl

@@ -1,4 +1,4 @@
-static uint8_t SKSL_INCLUDE_sksl_frag[] = {96,0,
+static uint8_t SKSL_INCLUDE_sksl_frag[] = {1,0,96,0,
 12,115,107,95,70,114,97,103,67,111,111,114,100,
 6,102,108,111,97,116,52,
 12,115,107,95,67,108,111,99,107,119,105,115,101,

src/sksl/generated/sksl_gpu.dehydrated.sksl

@@ -1,4 +1,4 @@
-static uint8_t SKSL_INCLUDE_sksl_gpu[] = {189,8,
+static uint8_t SKSL_INCLUDE_sksl_gpu[] = {1,0,189,8,
 7,100,101,103,114,101,101,115,
 8,36,103,101,110,84,121,112,101,
 7,114,97,100,105,97,110,115,

src/sksl/generated/sksl_public.dehydrated.sksl

@@ -1,4 +1,4 @@
-static uint8_t SKSL_INCLUDE_sksl_public[] = {227,3,
+static uint8_t SKSL_INCLUDE_sksl_public[] = {1,0,227,3,
 7,100,101,103,114,101,101,115,
 8,36,103,101,110,84,121,112,101,
 7,114,97,100,105,97,110,115,

src/sksl/generated/sksl_rt_shader.dehydrated.sksl

@@ -1,4 +1,4 @@
-static uint8_t SKSL_INCLUDE_sksl_rt_shader[] = {20,0,
+static uint8_t SKSL_INCLUDE_sksl_rt_shader[] = {1,0,20,0,
 12,115,107,95,70,114,97,103,67,111,111,114,100,
 6,102,108,111,97,116,52,
 47,1,0,

src/sksl/generated/sksl_vert.dehydrated.sksl

@@ -1,4 +1,4 @@
-static uint8_t SKSL_INCLUDE_sksl_vert[] = {82,0,
+static uint8_t SKSL_INCLUDE_sksl_vert[] = {1,0,82,0,
 12,115,107,95,80,101,114,86,101,114,116,101,120,
 11,115,107,95,80,111,115,105,116,105,111,110,
 6,102,108,111,97,116,52,