WIP: Add duplicate pipeline error check

README.md

@@ -42,7 +42,7 @@ macros before including pcreader.hpp.
 The PC Writer utility performs dynamic memory allocations using the standard `new`
 and `delete` array operators.
 
-It also makes use of the `assert` and `memcpy` standard library functions.
+It also makes use of the `assert`, `memcpy`, and `memcmp` standard library functions.
 If a user of the library wishes to disable asserts or provide an alternative memcpy
-implementation this can be done by setting the `VKSC_ASSERT` and `VKSC_MEMCPY`
-macros before including pcwriter.hpp.
+and memcmp implementations this can be done by setting the `VKSC_ASSERT`, `VKSC_MEMCPY`,
+and `VKSC_MEMCMP` macros before including pcwriter.hpp.

pcwriter.hpp

@@ -29,6 +29,10 @@
 #include <cstring>
 #define VKSC_MEMCPY memcpy
 #endif // VKSC_MEMCPY
+#ifndef VKSC_MEMCMP
+#include <cstring>
+#define VKSC_MEMCMP memcmp
+#endif // VKSC_MEMCPY
 
 #include <vulkan/vulkan_sc_core.hpp>
 
@@ -145,6 +149,12 @@ class VKSCPipelineEntry
     VKSCPipelineEntry& operator=(VKSCPipelineEntry const& rhs) = delete; // copy assignment
     VKSCPipelineEntry& operator=(VKSCPipelineEntry&& rhs) = delete; // move assignment
 
+    // equality operator -- determined soley by equality of pipeline <identifier>
+    bool operator==(VKSCPipelineEntry const& rhs)
+    {
+        return (VKSC_MEMCMP(m_Identifier, rhs.m_Identifier, VK_UUID_SIZE) == 0);
+    }
+
     // destructor - delete any memory this class allocated
     ~VKSCPipelineEntry()
     {
@@ -446,7 +456,8 @@ class VKSCPipelineCacheHeaderWriter
     // write the Pipeline Index and all associated data at mPipelineIndexOffset bytes into <data>
     // param: <size> is the amount of memory in bytes for the pipeline cache memory
     // param: <data> is pointer to the beginning of the pipeline cache memory
-    // returns the offset in bytes into <data> which immediately follows the written information
+    // return: the offset in bytes into <data> which immediately follows the written information
+    // return: 0 if the pipeline cache contains duplicate identifiers, no data is written
     // precondition: the memory at [data,data+size) is writeable for the pipeline cache
     // No implementation-specific per-pipeline or per-stage metadata is written, but space is reserved if
     // setPipelineIndexStride and/or setStageIndexStride were called appropriately.
@@ -456,6 +467,13 @@ class VKSCPipelineCacheHeaderWriter
         uint64_t extraOffset = m_PipelineIndexOffset + indexSize;
         VKSC_ASSERT(size > extraOffset);
 
+        // cowardly refuse to create a pipeline cache with duplicate identifiers
+        if (checkDuplicatePipelineIdentifiers())
+        {
+            //VKSC_ASSERT(0 && "pipeline contains duplicates");
+            return 0;
+        }
+
         uint64_t currentOffset = m_PipelineIndexOffset;
         for (uint32_t i = 0U; i < m_PipelineCount; ++i)
         {
@@ -466,6 +484,25 @@ class VKSCPipelineCacheHeaderWriter
         return extraOffset;
     }
 
+    // A valid pipeline cache cannot contain duplicate pipeline identifiers, as it would be
+    // undefined which one would be used at runtime. It would also waste pipeline cache storage
+    // space, since they are presumably identical.
+    bool checkDuplicatePipelineIdentifiers() const
+    {
+        for (uint32_t i = 0U; i < m_PipelineCount; i++)
+        {
+            for (uint32_t j = i + 1U; j < m_PipelineCount; j++)
+            {
+                if (*m_PipelineIndex[i] == *m_PipelineIndex[j])
+                {
+                    std::cerr << "ERROR: pipelines " << i << " and " << j << " have identical pipeline identifiers." << std::endl;
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
     // return: the amount of space in bytes required for the pipeline index and all associated data.
     // includes pipeline index and all associated pipeline entry data (json, stage index, stage code).
     // Does NOT include the size of the initial VkPipelineCacheHeaderVersionSafetyCriticalOne header.

pipeline.cpp

@@ -193,6 +193,7 @@ int main(void)
 
         pcw.writeHeaderSafetyCriticalOne(cacheSize, cache.data());
         uint64_t end = pcw.writePipelineIndex(cacheSize, cache.data());
+        if (end == 0) std::cout << "pipeline write aborted due to duplicates" << std::endl;
         uint64_t pipelineIndexSize = pcw.getPipelineIndexSize();
 
         for (auto& entry : pipeStore)
@@ -238,6 +239,7 @@ int main(void)
             std::cout << "pie " << id << ": " << *pie << std::endl;
         } else {
             std::cout << "pie " << id << ": not found" << std::endl;
+            continue;
         }
         char const *jsonPtr = reinterpret_cast<char const *>(pcr.getJson(*pie));
         if (nullptr != jsonPtr)