diff options
Diffstat (limited to 'source/blender/blenlib/intern/filereader_memory.c')
-rw-r--r-- | source/blender/blenlib/intern/filereader_memory.c | 145 |
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; +} |