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/* SPDX-License-Identifier: GPL-2.0-or-later
* Copyright 2008 Blender Foundation. All rights reserved. */
/** \file
* \ingroup blendthumb
*
* Expose #blendthumb_create_thumb_from_file that creates the PNG data
* but does not write it to a file.
*/
#include <cstring>
#include "BLI_alloca.h"
#include "BLI_endian_defines.h"
#include "BLI_endian_switch.h"
#include "BLI_fileops.h"
#include "BLI_filereader.h"
#include "BLI_string.h"
#include "blendthumb.hh"
static bool blend_header_check_magic(const char header[12])
{
/* Check magic string at start of file. */
if (!BLI_str_startswith(header, "BLENDER")) {
return false;
}
/* Check pointer size and endianness indicators. */
if (!ELEM(header[7], '_', '-') || !ELEM(header[8], 'v', 'V')) {
return false;
}
/* Check version number. */
if (!isdigit(header[9]) || !isdigit(header[10]) || !isdigit(header[11])) {
return false;
}
return true;
}
static bool blend_header_is_version_valid(const char header[12])
{
/* Thumbnails are only in files with version >= 2.50 */
char num[4];
memcpy(num, header + 9, 3);
num[3] = 0;
return atoi(num) >= 250;
}
static int blend_header_pointer_size(const char header[12])
{
return header[7] == '_' ? 4 : 8;
}
static bool blend_header_is_endian_switch_needed(const char header[12])
{
return (((header[8] == 'v') ? L_ENDIAN : B_ENDIAN) != ENDIAN_ORDER);
}
static void thumb_data_vertical_flip(Thumbnail *thumb)
{
uint32_t *rect = (uint32_t *)thumb->data.data();
int x = thumb->width, y = thumb->height;
uint32_t *top = rect;
uint32_t *bottom = top + ((y - 1) * x);
uint32_t *line = (uint32_t *)malloc(x * sizeof(uint32_t));
y >>= 1;
for (; y > 0; y--) {
memcpy(line, top, x * sizeof(uint32_t));
memcpy(top, bottom, x * sizeof(uint32_t));
memcpy(bottom, line, x * sizeof(uint32_t));
bottom -= x;
top += x;
}
free(line);
}
static int32_t bytes_to_native_i32(const uint8_t bytes[4], bool endian_switch)
{
int32_t data;
memcpy(&data, bytes, 4);
if (endian_switch) {
BLI_endian_switch_int32(&data);
}
return data;
}
static bool file_read(FileReader *file, uint8_t *buf, size_t buf_len)
{
return (file->read(file, buf, buf_len) == buf_len);
}
static bool file_seek(FileReader *file, size_t len)
{
if (file->seek != nullptr) {
if (file->seek(file, len, SEEK_CUR) == -1) {
return false;
}
return true;
}
/* File doesn't support seeking (e.g. gzip), so read and discard in chunks. */
constexpr size_t dummy_data_size = 4096;
blender::Array<char> dummy_data(dummy_data_size);
while (len > 0) {
const size_t len_chunk = std::min(len, dummy_data_size);
if ((size_t)file->read(file, dummy_data.data(), len_chunk) != len_chunk) {
return false;
}
len -= len_chunk;
}
return true;
}
static eThumbStatus blendthumb_extract_from_file_impl(FileReader *file,
Thumbnail *thumb,
const size_t bhead_size,
const bool endian_switch)
{
/* Iterate over file blocks until we find the thumbnail or run out of data. */
uint8_t *bhead_data = (uint8_t *)BLI_array_alloca(bhead_data, bhead_size);
while (file_read(file, bhead_data, bhead_size)) {
/* Parse type and size from `BHead`. */
const int32_t block_size = bytes_to_native_i32(&bhead_data[4], endian_switch);
/* We're looking for the thumbnail, so skip any other block. */
switch (*((int32_t *)bhead_data)) {
case MAKE_ID('T', 'E', 'S', 'T'): {
uint8_t shape[8];
if (!file_read(file, shape, sizeof(shape))) {
return BT_INVALID_THUMB;
}
thumb->width = bytes_to_native_i32(&shape[0], endian_switch);
thumb->height = bytes_to_native_i32(&shape[4], endian_switch);
/* Verify that image dimensions and data size make sense. */
size_t data_size = block_size - 8;
const uint64_t expected_size = static_cast<uint64_t>(thumb->width) *
static_cast<uint64_t>(thumb->height) * 4;
if (thumb->width < 0 || thumb->height < 0 || data_size != expected_size) {
return BT_INVALID_THUMB;
}
thumb->data = blender::Array<uint8_t>(data_size);
if (!file_read(file, thumb->data.data(), data_size)) {
return BT_INVALID_THUMB;
}
return BT_OK;
}
case MAKE_ID('R', 'E', 'N', 'D'): {
if (!file_seek(file, block_size)) {
return BT_INVALID_THUMB;
}
/* Check the next block. */
break;
}
default: {
/* Early exit if there are no `TEST` or `REND` blocks.
* This saves scanning the entire blend file which could be slow. */
return BT_INVALID_THUMB;
}
}
}
return BT_INVALID_THUMB;
}
eThumbStatus blendthumb_create_thumb_from_file(FileReader *rawfile, Thumbnail *thumb)
{
/* Read header in order to identify file type. */
char header[12];
if (rawfile->read(rawfile, header, sizeof(header)) != sizeof(header)) {
rawfile->close(rawfile);
return BT_ERROR;
}
/* Rewind the file after reading the header. */
rawfile->seek(rawfile, 0, SEEK_SET);
/* Try to identify the file type from the header. */
FileReader *file = nullptr;
if (BLI_str_startswith(header, "BLENDER")) {
file = rawfile;
rawfile = nullptr;
}
else if (BLI_file_magic_is_gzip(header)) {
file = BLI_filereader_new_gzip(rawfile);
if (file != nullptr) {
rawfile = nullptr; /* The Gzip #FileReader takes ownership of raw-file. */
}
}
else if (BLI_file_magic_is_zstd(header)) {
file = BLI_filereader_new_zstd(rawfile);
if (file != nullptr) {
rawfile = nullptr; /* The Zstd #FileReader takes ownership of raw-file. */
}
}
/* Clean up rawfile if it wasn't taken over. */
if (rawfile != nullptr) {
rawfile->close(rawfile);
}
if (file == nullptr) {
return BT_ERROR;
}
/* Re-read header in case we had compression. */
if (file->read(file, header, sizeof(header)) != sizeof(header)) {
file->close(file);
return BT_ERROR;
}
/* Check if the header format is valid for a .blend file. */
if (!blend_header_check_magic(header)) {
file->close(file);
return BT_INVALID_FILE;
}
/* Check if the file is new enough to contain a thumbnail. */
if (!blend_header_is_version_valid(header)) {
file->close(file);
return BT_EARLY_VERSION;
}
/* Depending on where it was saved, the file can use different pointer size or endianness. */
int bhead_size = 16 + blend_header_pointer_size(header);
const bool endian_switch = blend_header_is_endian_switch_needed(header);
/* Read the thumbnail. */
eThumbStatus err = blendthumb_extract_from_file_impl(file, thumb, bhead_size, endian_switch);
file->close(file);
if (err != BT_OK) {
return err;
}
thumb_data_vertical_flip(thumb);
return BT_OK;
}
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