1 files changed, 66 insertions, 2 deletions

diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index b61abd4ed06..2192e9a378f 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -68,6 +68,7 @@
 #include "BLI_math.h"
 #include "BLI_memarena.h"
 #include "BLI_mempool.h"
+#include "BLI_mmap.h"
 #include "BLI_threads.h"
 
 #include "BLT_translation.h"
@@ -1179,6 +1180,53 @@ static ssize_t fd_read_from_memory(FileData *filedata,
   return readsize;
 }
 
+/* Memory-mapped file reading.
+ * By using mmap(), we can map a file so that it can be treated like normal memory,
+ * meaning that we can just read from it with memcpy() etc.
+ * This avoids system call overhead and can significantly speed up file loading.
+ */
+
+static ssize_t fd_read_from_mmap(FileData *filedata,
+                                 void *buffer,
+                                 size_t size,
+                                 bool *UNUSED(r_is_memchunck_identical))
+{
+  /* don't read more bytes than there are available in the buffer */
+  size_t readsize = MIN2(size, (size_t)(filedata->buffersize - filedata->file_offset));
+
+  if (!BLI_mmap_read(filedata->mmap_file, buffer, filedata->file_offset, readsize)) {
+    return 0;
+  }
+
+  filedata->file_offset += readsize;
+
+  return readsize;
+}
+
+static off64_t fd_seek_from_mmap(FileData *filedata, off64_t offset, int whence)
+{
+  off64_t new_pos;
+  if (whence == SEEK_CUR) {
+    new_pos = filedata->file_offset + offset;
+  }
+  else if (whence == SEEK_SET) {
+    new_pos = offset;
+  }
+  else if (whence == SEEK_END) {
+    new_pos = filedata->buffersize + offset;
+  }
+  else {
+    return -1;
+  }
+
+  if (new_pos < 0 || new_pos > filedata->buffersize) {
+    return -1;
+  }
+
+  filedata->file_offset = new_pos;
+  return filedata->file_offset;
+}
+
 /* MemFile reading. */
 
 static ssize_t fd_read_from_memfile(FileData *filedata,
@@ -1306,6 +1354,8 @@ static FileData *blo_filedata_from_file_descriptor(const char *filepath,
 {
   FileDataReadFn *read_fn = NULL;
   FileDataSeekFn *seek_fn = NULL; /* Optional. */
+  size_t buffersize = 0;
+  BLI_mmap_file *mmap_file = NULL;
 
   gzFile gzfile = (gzFile)Z_NULL;
 
@@ -1322,14 +1372,21 @@ static FileData *blo_filedata_from_file_descriptor(const char *filepath,
     return NULL;
   }
 
-  BLI_lseek(file, 0, SEEK_SET);
-
   /* Regular file. */
   if (memcmp(header, "BLENDER", sizeof(header)) == 0) {
     read_fn = fd_read_data_from_file;
     seek_fn = fd_seek_data_from_file;
+
+    mmap_file = BLI_mmap_open(file);
+    if (mmap_file != NULL) {
+      read_fn = fd_read_from_mmap;
+      seek_fn = fd_seek_from_mmap;
+      buffersize = BLI_lseek(file, 0, SEEK_END);
+    }
   }
 
+  BLI_lseek(file, 0, SEEK_SET);
+
   /* Gzip file. */
   errno = 0;
   if ((read_fn == NULL) &&
@@ -1363,6 +1420,8 @@ static FileData *blo_filedata_from_file_descriptor(const char *filepath,
 
   fd->read = read_fn;
   fd->seek = seek_fn;
+  fd->mmap_file = mmap_file;
+  fd->buffersize = buffersize;
 
   return fd;
 }
@@ -1531,6 +1590,11 @@ void blo_filedata_free(FileData *fd)
       fd->buffer = NULL;
     }
 
+    if (fd->mmap_file) {
+      BLI_mmap_free(fd->mmap_file);
+      fd->mmap_file = NULL;
+    }
+
     /* Free all BHeadN data blocks */
 #ifndef NDEBUG
     BLI_freelistN(&fd->bhead_list);