path: root/src/android/jpeg/exif.cpp

/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2020, Google Inc.
 *
 * exif.cpp - EXIF tag creation using libexif
 */

#include "exif.h"

#include <map>
#include <uchar.h>

#include "libcamera/internal/log.h"
#include "libcamera/internal/utils.h"

using namespace libcamera;

LOG_DEFINE_CATEGORY(EXIF)

/*
 * List of EXIF tags that we set directly because they are not supported
 * by libexif version 0.6.21.
 */
enum class _ExifTag {
	OFFSET_TIME              = 0x9010,
	OFFSET_TIME_ORIGINAL     = 0x9011,
	OFFSET_TIME_DIGITIZED    = 0x9012,
};

/*
 * The Exif class should be instantiated and specific properties set
 * through the exposed public API.
 *
 * Once all desired properties have been set, the user shall call
 * generate() to process the entries and generate the Exif data.
 *
 * Calls to generate() must check the return code to determine if any error
 * occurred during the construction of the Exif data, and if successful the
 * data can be obtained using the data() method.
 */
Exif::Exif()
	: valid_(false), data_(nullptr), order_(EXIF_BYTE_ORDER_INTEL),
	  exifData_(0), size_(0)
{
	/* Create an ExifMem allocator to construct entries. */
	mem_ = exif_mem_new_default();
	if (!mem_) {
		LOG(EXIF, Error) << "Failed to allocate ExifMem Allocator";
		return;
	}

	data_ = exif_data_new_mem(mem_);
	if (!data_) {
		LOG(EXIF, Error) << "Failed to allocate an ExifData structure";
		return;
	}

	valid_ = true;

	exif_data_set_option(data_, EXIF_DATA_OPTION_FOLLOW_SPECIFICATION);
	exif_data_set_data_type(data_, EXIF_DATA_TYPE_COMPRESSED);

	/*
	 * Big-Endian: EXIF_BYTE_ORDER_MOTOROLA
	 * Little Endian: EXIF_BYTE_ORDER_INTEL
	 */
	exif_data_set_byte_order(data_, order_);

	setString(EXIF_IFD_EXIF, EXIF_TAG_EXIF_VERSION,
		  EXIF_FORMAT_UNDEFINED, "0231");

	/* Create the mandatory EXIF fields with default data. */
	exif_data_fix(data_);
}

Exif::~Exif()
{
	if (exifData_)
		free(exifData_);

	if (data_) {
		/*
		 * Reset thumbnail data to avoid getting double-freed by
		 * libexif. It is owned by the caller (i.e. PostProcessorJpeg).
		 */
		data_->data = nullptr;
		data_->size = 0;

		exif_data_unref(data_);
	}

	if (mem_)
		exif_mem_unref(mem_);
}

ExifEntry *Exif::createEntry(ExifIfd ifd, ExifTag tag)
{
	ExifContent *content = data_->ifd[ifd];
	ExifEntry *entry = exif_content_get_entry(content, tag);

	if (entry) {
		exif_entry_ref(entry);
		return entry;
	}

	entry = exif_entry_new_mem(mem_);
	if (!entry) {
		LOG(EXIF, Error) << "Failed to allocated new entry";
		valid_ = false;
		return nullptr;
	}

	exif_content_add_entry(content, entry);
	exif_entry_initialize(entry, tag);

	return entry;
}

ExifEntry *Exif::createEntry(ExifIfd ifd, ExifTag tag, ExifFormat format,
			     unsigned long components, unsigned int size)
{
	ExifContent *content = data_->ifd[ifd];

	/* Replace any existing entry with the same tag. */
	ExifEntry *existing = exif_content_get_entry(content, tag);
	exif_content_remove_entry(content, existing);

	ExifEntry *entry = exif_entry_new_mem(mem_);
	if (!entry) {
		LOG(EXIF, Error) << "Failed to allocated new entry";
		valid_ = false;
		return nullptr;
	}

	void *buffer = exif_mem_alloc(mem_, size);
	if (!buffer) {
		LOG(EXIF, Error) << "Failed to allocate buffer for variable entry";
		exif_mem_unref(mem_);
		valid_ = false;
		return nullptr;
	}

	entry->data = static_cast<unsigned char *>(buffer);
	entry->components = components;
	entry->format = format;
	entry->size = size;
	entry->tag = tag;

	exif_content_add_entry(content, entry);

	return entry;
}

void Exif::setShort(ExifIfd ifd, ExifTag tag, uint16_t item)
{
	ExifEntry *entry = createEntry(ifd, tag);
	if (!entry)
		return;

	exif_set_short(entry->data, order_, item);
	exif_entry_unref(entry);
}

void Exif::setLong(ExifIfd ifd, ExifTag tag, uint32_t item)
{
	ExifEntry *entry = createEntry(ifd, tag);
	if (!entry)
		return;

	exif_set_long(entry->data, order_, item);
	exif_entry_unref(entry);
}

void Exif::setRational(ExifIfd ifd, ExifTag tag, ExifRational item)
{
	ExifEntry *entry = createEntry(ifd, tag);
	if (!entry)
		return;

	exif_set_rational(entry->data, order_, item);
	exif_entry_unref(entry);
}

static const std::map<Exif::StringEncoding, std::array<uint8_t, 8>> stringEncodingCodes = {
	{ Exif::ASCII,     { 0x41, 0x53, 0x43, 0x49, 0x49, 0x00, 0x00, 0x00 } },
	{ Exif::Unicode,   { 0x55, 0x4e, 0x49, 0x43, 0x4f, 0x44, 0x45, 0x00 } },
};

void Exif::setString(ExifIfd ifd, ExifTag tag, ExifFormat format,
		     const std::string &item, StringEncoding encoding)
{
	std::string ascii;
	size_t length;
	const char *str;
	std::vector<uint8_t> buf;

	if (format == EXIF_FORMAT_ASCII) {
		ascii = utils::toAscii(item);
		str = ascii.c_str();

		/* Pad 1 extra byte to null-terminate the ASCII string. */
		length = ascii.length() + 1;
	} else {
		std::u16string u16str;

		auto encodingString = stringEncodingCodes.find(encoding);
		if (encodingString != stringEncodingCodes.end()) {
			buf = {
				encodingString->second.begin(),
				encodingString->second.end()
			};
		}

		switch (encoding) {
		case Unicode:
			u16str = utf8ToUtf16(item);

			buf.resize(8 + u16str.size() * 2);
			for (size_t i = 0; i < u16str.size(); i++) {
				if (order_ == EXIF_BYTE_ORDER_INTEL) {
					buf[8 + 2 * i] = u16str[i] & 0xff;
					buf[8 + 2 * i + 1] = (u16str[i] >> 8) & 0xff;
				} else {
					buf[8 + 2 * i] = (u16str[i] >> 8) & 0xff;
					buf[8 + 2 * i + 1] = u16str[i] & 0xff;
				}
			}

			break;

		case ASCII:
		case NoEncoding:
			buf.insert(buf.end(), item.begin(), item.end());
			break;
		}

		str = reinterpret_cast<const char *>(buf.data());

		/*
		 * Strings stored in different formats (EXIF_FORMAT_UNDEFINED)
		 * are not null-terminated.
		 */
		length = buf.size();
	}

	ExifEntry *entry = createEntry(ifd, tag, format, length, length);
	if (!entry)
		return;

	memcpy(entry->data, str, length);
	exif_entry_unref(entry);
}

void Exif::setMake(const std::string &make)
{
	setString(EXIF_IFD_0, EXIF_TAG_MAKE, EXIF_FORMAT_ASCII, make);
}

void Exif::setModel(const std::string &model)
{
	setString(EXIF_IFD_0, EXIF_TAG_MODEL, EXIF_FORMAT_ASCII, model);
}

void Exif::setSize(const Size &size)
{
	setLong(EXIF_IFD_EXIF, EXIF_TAG_PIXEL_Y_DIMENSION, size.height);
	setLong(EXIF_IFD_EXIF, EXIF_TAG_PIXEL_X_DIMENSION, size.width);
}

void Exif::setTimestamp(time_t timestamp)
{
	struct tm tm;
	localtime_r(&timestamp, &tm);

	char str[20];
	strftime(str, sizeof(str), "%Y:%m:%d %H:%M:%S", &tm);
	std::string ts(str);

	setString(EXIF_IFD_0, EXIF_TAG_DATE_TIME, EXIF_FORMAT_ASCII, ts);
	setString(EXIF_IFD_EXIF, EXIF_TAG_DATE_TIME_ORIGINAL, EXIF_FORMAT_ASCII, ts);
	setString(EXIF_IFD_EXIF, EXIF_TAG_DATE_TIME_DIGITIZED, EXIF_FORMAT_ASCII, ts);

	/* Query and set timezone information if available. */
	int r = strftime(str, sizeof(str), "%z", &tm);
	if (r > 0) {
		std::string tz(str);
		tz.insert(3, 1, ':');
		setString(EXIF_IFD_EXIF,
			  static_cast<ExifTag>(_ExifTag::OFFSET_TIME),
			  EXIF_FORMAT_ASCII, tz);
		setString(EXIF_IFD_EXIF,
			  static_cast<ExifTag>(_ExifTag::OFFSET_TIME_ORIGINAL),
			  EXIF_FORMAT_ASCII, tz);
		setString(EXIF_IFD_EXIF,
			  static_cast<ExifTag>(_ExifTag::OFFSET_TIME_DIGITIZED),
			  EXIF_FORMAT_ASCII, tz);
	}
}

void Exif::setOrientation(int orientation)
{
	int value;
	switch (orientation) {
	case 0:
	default:
		value = 1;
		break;
	case 90:
		value = 8;
		break;
	case 180:
		value = 3;
		break;
	case 270:
		value = 6;
		break;
	}

	setShort(EXIF_IFD_0, EXIF_TAG_ORIENTATION, value);
}

/*
 * The thumbnail data should remain valid until the Exif object is destroyed.
 * Failing to do so, might result in no thumbnail data being set even after a
 * call to Exif::setThumbnail().
 */
void Exif::setThumbnail(Span<const unsigned char> thumbnail,
			Compression compression)
{
	data_->data = const_cast<unsigned char *>(thumbnail.data());
	data_->size = thumbnail.size();

	setShort(EXIF_IFD_0, EXIF_TAG_COMPRESSION, compression);
}

/**
 * \brief Convert UTF-8 string to UTF-16 string
 * \param[in] str String to convert
 *
 * \return \a str in UTF-16
 */
std::u16string Exif::utf8ToUtf16(const std::string &str)
{
	mbstate_t state{};
	char16_t c16;
	const char *ptr = str.data();
	const char *end = ptr + str.size();

	std::u16string ret;
	while (size_t rc = mbrtoc16(&c16, ptr, end - ptr + 1, &state)) {
		if (rc == static_cast<size_t>(-2) ||
		    rc == static_cast<size_t>(-1))
			break;

		ret.push_back(c16);

		if (rc > 0)
			ptr += rc;
	}

	return ret;
}

[[nodiscard]] int Exif::generate()
{
	if (exifData_) {
		free(exifData_);
		exifData_ = nullptr;
	}

	if (!valid_) {
		LOG(EXIF, Error) << "Generated EXIF data is invalid";
		return -1;
	}

	exif_data_save_data(data_, &exifData_, &size_);

	LOG(EXIF, Debug) << "Created EXIF instance (" << size_ << " bytes)";

	return 0;
}