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/*
* Copyright 2018 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "include/codec/SkEncodedOrigin.h"
#include "include/core/SkTypes.h"
#include "include/private/base/SkTo.h"
#include "src/codec/SkCodecPriv.h"
#include <algorithm>
#include <cstddef>
#include <cstdint>
static bool parse_encoded_origin(const uint8_t* exifData, size_t data_length, uint64_t offset,
bool littleEndian, bool is_root, SkEncodedOrigin* orientation) {
// Require that the marker is at least large enough to contain the number of entries.
if (data_length < offset + 2) {
return false;
}
uint32_t numEntries = get_endian_short(exifData + offset, littleEndian);
// Tag (2 bytes), Datatype (2 bytes), Number of elements (4 bytes), Data (4 bytes)
const uint32_t kEntrySize = 12;
const auto max = SkTo<uint32_t>((data_length - offset - 2) / kEntrySize);
numEntries = std::min(numEntries, max);
// Advance the data to the start of the entries.
auto data = exifData + offset + 2;
const uint16_t kOriginTag = 0x112;
const uint16_t kOriginType = 3;
const uint16_t kSubIFDOffsetTag = 0x8769;
const uint16_t kSubIFDOffsetType = 4;
for (uint32_t i = 0; i < numEntries; i++, data += kEntrySize) {
uint16_t tag = get_endian_short(data, littleEndian);
uint16_t type = get_endian_short(data + 2, littleEndian);
uint32_t count = get_endian_int(data + 4, littleEndian);
if (kOriginTag == tag && kOriginType == type && 1 == count) {
uint16_t val = get_endian_short(data + 8, littleEndian);
if (0 < val && val <= kLast_SkEncodedOrigin) {
*orientation = (SkEncodedOrigin)val;
return true;
}
} else if (kSubIFDOffsetTag == tag && kSubIFDOffsetType == type && 1 == count && is_root) {
uint32_t subifd = get_endian_int(data + 8, littleEndian);
if (0 < subifd && subifd < data_length) {
if (parse_encoded_origin(exifData, data_length, subifd, littleEndian, false,
orientation)) {
return true;
}
}
}
}
return false;
}
bool SkParseEncodedOrigin(const uint8_t* data, size_t data_length, SkEncodedOrigin* orientation) {
SkASSERT(orientation);
bool littleEndian;
// We need eight bytes to read the endian marker and the offset, below.
if (data_length < 8 || !is_valid_endian_marker(data, &littleEndian)) {
return false;
}
// Get the offset from the start of the marker.
// Though this only reads four bytes, use a larger int in case it overflows.
uint64_t offset = get_endian_int(data + 4, littleEndian);
return parse_encoded_origin(data, data_length, offset, littleEndian, true, orientation);
}
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