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Diffstat (limited to 'source/blender/blenlib/intern/filereader_memory.c')
-rw-r--r--source/blender/blenlib/intern/filereader_memory.c145
1 files changed, 145 insertions, 0 deletions
diff --git a/source/blender/blenlib/intern/filereader_memory.c b/source/blender/blenlib/intern/filereader_memory.c
new file mode 100644
index 00000000000..150fed7d1cc
--- /dev/null
+++ b/source/blender/blenlib/intern/filereader_memory.c
@@ -0,0 +1,145 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2004-2021 Blender Foundation
+ * All rights reserved.
+ */
+
+/** \file
+ * \ingroup bli
+ */
+
+#include <string.h>
+
+#include "BLI_blenlib.h"
+#include "BLI_filereader.h"
+#include "BLI_mmap.h"
+
+#include "MEM_guardedalloc.h"
+
+/* This file implements both memory-backed and memory-mapped-file-backed reading. */
+typedef struct {
+ FileReader reader;
+
+ const char *data;
+ BLI_mmap_file *mmap;
+ size_t length;
+} MemoryReader;
+
+static ssize_t memory_read_raw(FileReader *reader, void *buffer, size_t size)
+{
+ MemoryReader *mem = (MemoryReader *)reader;
+
+ /* Don't read more bytes than there are available in the buffer. */
+ size_t readsize = MIN2(size, (size_t)(mem->length - mem->reader.offset));
+
+ memcpy(buffer, mem->data + mem->reader.offset, readsize);
+ mem->reader.offset += readsize;
+
+ return readsize;
+}
+
+static off64_t memory_seek(FileReader *reader, off64_t offset, int whence)
+{
+ MemoryReader *mem = (MemoryReader *)reader;
+
+ off64_t new_pos;
+ if (whence == SEEK_CUR) {
+ new_pos = mem->reader.offset + offset;
+ }
+ else if (whence == SEEK_SET) {
+ new_pos = offset;
+ }
+ else if (whence == SEEK_END) {
+ new_pos = mem->length + offset;
+ }
+ else {
+ return -1;
+ }
+
+ if (new_pos < 0 || new_pos > mem->length) {
+ return -1;
+ }
+
+ mem->reader.offset = new_pos;
+ return mem->reader.offset;
+}
+
+static void memory_close_raw(FileReader *reader)
+{
+ MEM_freeN(reader);
+}
+
+FileReader *BLI_filereader_new_memory(const void *data, size_t len)
+{
+ MemoryReader *mem = MEM_callocN(sizeof(MemoryReader), __func__);
+
+ mem->data = (const char *)data;
+ mem->length = len;
+
+ mem->reader.read = memory_read_raw;
+ mem->reader.seek = memory_seek;
+ mem->reader.close = memory_close_raw;
+
+ return (FileReader *)mem;
+}
+
+/* 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 memory_read_mmap(FileReader *reader, void *buffer, size_t size)
+{
+ MemoryReader *mem = (MemoryReader *)reader;
+
+ /* Don't read more bytes than there are available in the buffer. */
+ size_t readsize = MIN2(size, (size_t)(mem->length - mem->reader.offset));
+
+ if (!BLI_mmap_read(mem->mmap, buffer, mem->reader.offset, readsize)) {
+ return 0;
+ }
+
+ mem->reader.offset += readsize;
+
+ return readsize;
+}
+
+static void memory_close_mmap(FileReader *reader)
+{
+ MemoryReader *mem = (MemoryReader *)reader;
+ BLI_mmap_free(mem->mmap);
+ MEM_freeN(mem);
+}
+
+FileReader *BLI_filereader_new_mmap(int filedes)
+{
+ BLI_mmap_file *mmap = BLI_mmap_open(filedes);
+ if (mmap == NULL) {
+ return NULL;
+ }
+
+ MemoryReader *mem = MEM_callocN(sizeof(MemoryReader), __func__);
+
+ mem->mmap = mmap;
+ mem->length = BLI_lseek(filedes, 0, SEEK_END);
+
+ mem->reader.read = memory_read_mmap;
+ mem->reader.seek = memory_seek;
+ mem->reader.close = memory_close_mmap;
+
+ return (FileReader *)mem;
+}