Merge pull request #3894 from crud89/master

Add export property to control blob names.

code/Common/Exporter.cpp

@@ -343,9 +343,11 @@ const aiExportDataBlob* Exporter::ExportToBlob( const aiScene* pScene, const cha
         delete pimpl->blob;
         pimpl->blob = nullptr;
     }
+    
+    auto baseName = pProperties ? pProperties->GetPropertyString(AI_CONFIG_EXPORT_BLOB_NAME, AI_BLOBIO_MAGIC) : AI_BLOBIO_MAGIC;
 
     std::shared_ptr<IOSystem> old = pimpl->mIOSystem;
-    BlobIOSystem* blobio = new BlobIOSystem();
+    BlobIOSystem *blobio = new BlobIOSystem(baseName);
     pimpl->mIOSystem = std::shared_ptr<IOSystem>( blobio );
 
     if (AI_SUCCESS != Export(pScene,pFormatId,blobio->GetMagicFileName(), pPreprocessing, pProperties)) {

include/assimp/BlobIOSystem.h

@@ -194,8 +194,14 @@ class BlobIOSystem : public IOSystem {
     friend class BlobIOStream;
     typedef std::pair<std::string, aiExportDataBlob *> BlobEntry;
 
+
 public:
-    BlobIOSystem() {
+    BlobIOSystem() :
+            baseName{AI_BLOBIO_MAGIC} {
+    }
+
+    BlobIOSystem(const std::string &baseName) :
+            baseName(baseName) {
     }
 
     virtual ~BlobIOSystem() {
@@ -207,27 +213,32 @@ public:
 public:
     // -------------------------------------------------------------------
     const char *GetMagicFileName() const {
-        return AI_BLOBIO_MAGIC;
+        return baseName.c_str();
     }
 
     // -------------------------------------------------------------------
     aiExportDataBlob *GetBlobChain() {
+        const auto magicName = std::string(this->GetMagicFileName());
+        const bool hasBaseName = baseName != AI_BLOBIO_MAGIC;
+
         // one must be the master
         aiExportDataBlob *master = nullptr, *cur;
+
         for (const BlobEntry &blobby : blobs) {
-            if (blobby.first == AI_BLOBIO_MAGIC) {
+            if (blobby.first == magicName) {
                 master = blobby.second;
+                master->name.Set(hasBaseName ? blobby.first : "");
                 break;
             }
         }
+
         if (!master) {
             ASSIMP_LOG_ERROR("BlobIOSystem: no data written or master file was not closed properly.");
             return nullptr;
         }
 
-        master->name.Set("");
-
         cur = master;
+
         for (const BlobEntry &blobby : blobs) {
             if (blobby.second == master) {
                 continue;
@@ -236,9 +247,13 @@ public:
             cur->next = blobby.second;
             cur = cur->next;
 
-            // extract the file extension from the file written
+            if (hasBaseName) {
-            const std::string::size_type s = blobby.first.find_first_of('.');
+                cur->name.Set(blobby.first);
-            cur->name.Set(s == std::string::npos ? blobby.first : blobby.first.substr(s + 1));
+            } else {
+                // extract the file extension from the file written
+                const std::string::size_type s = blobby.first.find_first_of('.');
+                cur->name.Set(s == std::string::npos ? blobby.first : blobby.first.substr(s + 1));
+            }
         }
 
         // give up blob ownership
@@ -283,6 +298,7 @@ private:
     }
 
 private:
+    std::string baseName;
     std::set<std::string> created;
     std::vector<BlobEntry> blobs;
 };

include/assimp/cexport.h

@@ -205,16 +205,22 @@ struct aiExportDataBlob {
     void *data;
 
     /** Name of the blob. An empty string always
-        indicates the first (and primary) blob,
+      * indicates the first (and primary) blob,
-        which contains the actual file data.
+      * which contains the actual file data.
-        Any other blobs are auxiliary files produced
+      * Any other blobs are auxiliary files produced
-        by exporters (i.e. material files). Existence
+      * by exporters (i.e. material files). Existence
-        of such files depends on the file format. Most
+      * of such files depends on the file format. Most
-        formats don't split assets across multiple files.
+      * formats don't split assets across multiple files.
-
+      *
-        If used, blob names usually contain the file
+      * If used, blob names usually contain the file
-        extension that should be used when writing
+      * extension that should be used when writing
-        the data to disc.
+      * the data to disc.
+      *
+      * The blob names generated can be influenced by
+      * setting the #AI_CONFIG_EXPORT_BLOB_NAME export
+      * property to the name that is used for the master
+      * blob. All other names are typically derived from
+      * the base name, by the file format exporter.
      */
     C_STRUCT aiString name;
 

include/assimp/config.h.in

@@ -1075,6 +1075,23 @@ enum aiComponent
  */
 #define AI_CONFIG_EXPORT_POINT_CLOUDS "EXPORT_POINT_CLOUDS"
 
+/**
+ * @brief Specifies the blob name, assimp uses for exporting.
+ * 
+ * Some formats require auxiliary files to be written, that need to be linked back into 
+ * the original file. For example, OBJ files export materials to a separate MTL file and
+ * use the `mtllib` keyword to reference this file.
+ * 
+ * When exporting blobs using #ExportToBlob, assimp does not know the name of the blob
+ * file and thus outputs `mtllib $blobfile.mtl`, which might not be desired, since the 
+ * MTL file might be called differently. 
+ * 
+ * This property can be used to give the exporter a hint on how to use the magic 
+ * `$blobfile` keyword. If the exporter detects the keyword and is provided with a name
+ * for the blob, it instead uses this name.
+ */
+#define AI_CONFIG_EXPORT_BLOB_NAME "EXPORT_BLOB_NAME"
+
 /**
  *  @brief  Specifies a gobal key factor for scale, float value
  */