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TinyEXIF.cpp
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/*
TinyEXIF.cpp -- A simple ISO C++ library to parse basic EXIF and XMP
information from a JPEG file.
Copyright (c) 2015-2017 Seacave
cdc.seacave@gmail.com
All rights reserved.
Based on the easyexif library (2013 version)
https://github.com/mayanklahiri/easyexif
of Mayank Lahiri (mlahiri@gmail.com).
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY EXPRESS
OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
NO EVENT SHALL THE FREEBSD PROJECT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "TinyEXIF.h"
#ifndef TINYEXIF_NO_XMP_SUPPORT
#include <tinyxml2.h>
#endif // TINYEXIF_NO_XMP_SUPPORT
#include <cstdint>
#include <cstdio>
#include <cmath>
#include <cfloat>
#include <vector>
#include <algorithm>
#include <iostream>
#ifdef _MSC_VER
namespace {
int strcasecmp(const char* a, const char* b) {
return _stricmp(a, b);
}
}
#else
#include <string.h>
#endif
namespace Tools {
// search string inside a string, case sensitive
static const char* strrnstr(const char* haystack, const char* needle, size_t len) {
const size_t needle_len(strlen(needle));
if (0 == needle_len)
return haystack;
if (len <= needle_len)
return NULL;
for (size_t i=len-needle_len; i-- > 0; ) {
if (haystack[0] == needle[0] &&
0 == strncmp(haystack, needle, needle_len))
return haystack;
haystack++;
}
return NULL;
}
// split an input string with a delimiter and fill a string vector
static void strSplit(const std::string& str, char delim, std::vector<std::string>& values) {
values.clear();
std::string::size_type start(0), end(0);
while (end != std::string::npos) {
end = str.find(delim, start);
values.emplace_back(str.substr(start, end-start));
start = end + 1;
}
}
// make sure the given degrees value is between -180 and 180
static double NormD180(double d) {
return (d = fmod(d+180.0, 360.0)) < 0 ? d+180.0 : d-180.0;
}
} // namespace Tools
namespace TinyEXIF {
enum JPEG_MARKERS {
JM_START = 0xFF,
JM_SOF0 = 0xC0,
JM_SOF1 = 0xC1,
JM_SOF2 = 0xC2,
JM_SOF3 = 0xC3,
JM_DHT = 0xC4,
JM_SOF5 = 0xC5,
JM_SOF6 = 0xC6,
JM_SOF7 = 0xC7,
JM_JPG = 0xC8,
JM_SOF9 = 0xC9,
JM_SOF10 = 0xCA,
JM_SOF11 = 0xCB,
JM_DAC = 0xCC,
JM_SOF13 = 0xCD,
JM_SOF14 = 0xCE,
JM_SOF15 = 0xCF,
JM_RST0 = 0xD0,
JM_RST1 = 0xD1,
JM_RST2 = 0xD2,
JM_RST3 = 0xD3,
JM_RST4 = 0xD4,
JM_RST5 = 0xD5,
JM_RST6 = 0xD6,
JM_RST7 = 0xD7,
JM_SOI = 0xD8,
JM_EOI = 0xD9,
JM_SOS = 0xDA,
JM_DQT = 0xDB,
JM_DNL = 0xDC,
JM_DRI = 0xDD,
JM_DHP = 0xDE,
JM_EXP = 0xDF,
JM_APP0 = 0xE0,
JM_APP1 = 0xE1, // EXIF and XMP
JM_APP2 = 0xE2,
JM_APP3 = 0xE3,
JM_APP4 = 0xE4,
JM_APP5 = 0xE5,
JM_APP6 = 0xE6,
JM_APP7 = 0xE7,
JM_APP8 = 0xE8,
JM_APP9 = 0xE9,
JM_APP10 = 0xEA,
JM_APP11 = 0xEB,
JM_APP12 = 0xEC,
JM_APP13 = 0xED, // IPTC
JM_APP14 = 0xEE,
JM_APP15 = 0xEF,
JM_JPG0 = 0xF0,
JM_JPG1 = 0xF1,
JM_JPG2 = 0xF2,
JM_JPG3 = 0xF3,
JM_JPG4 = 0xF4,
JM_JPG5 = 0xF5,
JM_JPG6 = 0xF6,
JM_JPG7 = 0xF7,
JM_JPG8 = 0xF8,
JM_JPG9 = 0xF9,
JM_JPG10 = 0xFA,
JM_JPG11 = 0xFB,
JM_JPG12 = 0xFC,
JM_JPG13 = 0xFD,
JM_COM = 0xFE
};
// Parser helper
class EntryParser {
private:
const uint8_t* buf;
const unsigned len;
const unsigned tiff_header_start;
const bool alignIntel; // byte alignment (defined in EXIF header)
unsigned offs; // current offset into buffer
uint16_t tag, format;
uint32_t length;
public:
EntryParser(const uint8_t* _buf, unsigned _len, unsigned _tiff_header_start, bool _alignIntel)
: buf(_buf), len(_len), tiff_header_start(_tiff_header_start), alignIntel(_alignIntel), offs(0) {}
void Init(unsigned _offs) {
offs = _offs - 12;
}
void ParseTag() {
offs += 12;
tag = parse16(buf + offs, alignIntel);
format = parse16(buf + offs + 2, alignIntel);
length = parse32(buf + offs + 4, alignIntel);
}
const uint8_t* GetBuffer() const { return buf; }
unsigned GetOffset() const { return offs; }
bool IsIntelAligned() const { return alignIntel; }
uint16_t GetTag() const { return tag; }
uint32_t GetLength() const { return length; }
uint32_t GetData() const { return parse32(buf + offs + 8, alignIntel); }
uint32_t GetSubIFD() const { return tiff_header_start + GetData(); }
bool IsShort() const { return format == 3; }
bool IsLong() const { return format == 4; }
bool IsRational() const { return format == 5 || format == 10; }
bool IsSRational() const { return format == 10; }
bool IsFloat() const { return format == 11; }
bool IsUndefined() const { return format == 7; }
std::string FetchString() const {
return parseString(buf, length, GetData(), tiff_header_start, len, alignIntel);
}
bool Fetch(std::string& val) const {
if (format != 2 || length == 0)
return false;
val = FetchString();
return true;
}
bool Fetch(uint8_t& val) const {
if ((format != 1 && format != 2 && format != 6) || length == 0)
return false;
val = parse8(buf + offs + 8);
return true;
}
bool Fetch(uint16_t& val) const {
if (!IsShort() || length == 0)
return false;
val = parse16(buf + offs + 8, alignIntel);
return true;
}
bool Fetch(uint16_t& val, uint32_t idx) const {
if (!IsShort() || length <= idx)
return false;
val = parse16(buf + GetSubIFD() + idx*2, alignIntel);
return true;
}
bool Fetch(uint32_t& val) const {
if (!IsLong() || length == 0)
return false;
val = parse32(buf + offs + 8, alignIntel);
return true;
}
bool Fetch(float& val) const {
if (!IsFloat() || length == 0)
return false;
val = parseFloat(buf + offs + 8, alignIntel);
return true;
}
bool Fetch(double& val) const {
if (!IsRational() || length == 0)
return false;
val = parseRational(buf + GetSubIFD(), alignIntel, IsSRational());
return true;
}
bool Fetch(double& val, uint32_t idx) const {
if (!IsRational() || length <= idx)
return false;
val = parseRational(buf + GetSubIFD() + idx*8, alignIntel, IsSRational());
return true;
}
bool FetchFloat(double& val) const {
float _val;
if (!Fetch(_val))
return false;
val = _val;
return true;
}
public:
static uint8_t parse8(const uint8_t* buf) {
return buf[0];
}
static uint16_t parse16(const uint8_t* buf, bool intel) {
if (intel)
return ((uint16_t)buf[1]<<8) | buf[0];
return ((uint16_t)buf[0]<<8) | buf[1];
}
static uint32_t parse32(const uint8_t* buf, bool intel) {
if (intel)
return ((uint32_t)buf[3]<<24) |
((uint32_t)buf[2]<<16) |
((uint32_t)buf[1]<<8) |
buf[0];
return ((uint32_t)buf[0]<<24) |
((uint32_t)buf[1]<<16) |
((uint32_t)buf[2]<<8) |
buf[3];
}
static float parseFloat(const uint8_t* buf, bool intel) {
union {
uint32_t i;
float f;
} i2f;
i2f.i = parse32(buf, intel);
return i2f.f;
}
static double parseRational(const uint8_t* buf, bool intel, bool isSigned) {
const uint32_t denominator = parse32(buf+4, intel);
if (denominator == 0)
return 0.0;
const uint32_t numerator = parse32(buf, intel);
return isSigned ?
(double)(int32_t)numerator/(double)(int32_t)denominator :
(double)numerator/(double)denominator;
}
static std::string parseString(const uint8_t* buf,
unsigned num_components,
unsigned data,
unsigned base,
unsigned len,
bool intel)
{
std::string value;
if (num_components <= 4) {
value.resize(num_components);
char j = intel ? 0 : 24;
char j_m = intel ? -8 : 8;
for (unsigned i=0; i<num_components; ++i, j -= j_m)
value[i] = (data >> j) & 0xff;
if (value[num_components-1] == '\0')
value.resize(num_components-1);
} else
if (base+data+num_components <= len) {
const char* const sz((const char*)buf+base+data);
unsigned num(0);
while (num < num_components && sz[num] != '\0')
++num;
while (num && sz[num-1] == ' ')
--num;
value.assign(sz, num);
}
return value;
}
};
// Constructors
EXIFInfo::EXIFInfo() : Fields(FIELD_NA) {
}
EXIFInfo::EXIFInfo(EXIFStream& stream) {
parseFrom(stream);
}
EXIFInfo::EXIFInfo(std::istream& stream) {
parseFrom(stream);
}
EXIFInfo::EXIFInfo(const uint8_t* data, unsigned length) {
parseFrom(data, length);
}
// Parse tag as Image IFD
void EXIFInfo::parseIFDImage(EntryParser& parser, unsigned& exif_sub_ifd_offset, unsigned& gps_sub_ifd_offset) {
switch (parser.GetTag()) {
case 0x0102:
// Bits per sample
parser.Fetch(BitsPerSample);
break;
case 0x010e:
// Image description
parser.Fetch(ImageDescription);
break;
case 0x010f:
// Camera maker
parser.Fetch(Make);
break;
case 0x0110:
// Camera model
parser.Fetch(Model);
break;
case 0x0112:
// Orientation of image
parser.Fetch(Orientation);
break;
case 0x011a:
// XResolution
parser.Fetch(XResolution);
break;
case 0x011b:
// YResolution
parser.Fetch(YResolution);
break;
case 0x0128:
// Resolution Unit
parser.Fetch(ResolutionUnit);
break;
case 0x0131:
// Software used for image
parser.Fetch(Software);
break;
case 0x0132:
// EXIF/TIFF date/time of image modification
parser.Fetch(DateTime);
break;
case 0x1001:
// Original Image width
if (!parser.Fetch(RelatedImageWidth)) {
uint16_t _RelatedImageWidth;
if (parser.Fetch(_RelatedImageWidth))
RelatedImageWidth = _RelatedImageWidth;
}
break;
case 0x1002:
// Original Image height
if (!parser.Fetch(RelatedImageHeight)) {
uint16_t _RelatedImageHeight;
if (parser.Fetch(_RelatedImageHeight))
RelatedImageHeight = _RelatedImageHeight;
}
break;
case 0x8298:
// Copyright information
parser.Fetch(Copyright);
break;
case 0x8769:
// EXIF SubIFD offset
exif_sub_ifd_offset = parser.GetSubIFD();
break;
case 0x8825:
// GPS IFS offset
gps_sub_ifd_offset = parser.GetSubIFD();
break;
default:
// Try to parse as EXIF tag, as some images store them in here
parseIFDExif(parser);
break;
}
}
// Parse tag as Exif IFD
void EXIFInfo::parseIFDExif(EntryParser& parser) {
switch (parser.GetTag()) {
case 0x02bc:
#ifndef TINYEXIF_NO_XMP_SUPPORT
// XMP Metadata (Adobe technote 9-14-02)
if (parser.IsUndefined()) {
const std::string strXML(parser.FetchString());
parseFromXMPSegmentXML(strXML.c_str(), (unsigned)strXML.length());
}
#endif // TINYEXIF_NO_XMP_SUPPORT
break;
case 0x829a:
// Exposure time in seconds
parser.Fetch(ExposureTime);
break;
case 0x829d:
// FNumber
parser.Fetch(FNumber);
break;
case 0x8822:
// Exposure Program
parser.Fetch(ExposureProgram);
break;
case 0x8827:
// ISO Speed Rating
parser.Fetch(ISOSpeedRatings);
break;
case 0x9003:
// Original date and time
parser.Fetch(DateTimeOriginal);
break;
case 0x9004:
// Digitization date and time
parser.Fetch(DateTimeDigitized);
break;
case 0x9201:
// Shutter speed value
parser.Fetch(ShutterSpeedValue);
ShutterSpeedValue = 1.0/exp(ShutterSpeedValue*log(2));
break;
case 0x9202:
// Aperture value
parser.Fetch(ApertureValue);
ApertureValue = exp(ApertureValue*log(2)*0.5);
break;
case 0x9203:
// Brightness value
parser.Fetch(BrightnessValue);
break;
case 0x9204:
// Exposure bias value
parser.Fetch(ExposureBiasValue);
break;
case 0x9206:
// Subject distance
parser.Fetch(SubjectDistance);
break;
case 0x9207:
// Metering mode
parser.Fetch(MeteringMode);
break;
case 0x9208:
// Light source
parser.Fetch(LightSource);
break;
case 0x9209:
// Flash info
parser.Fetch(Flash);
break;
case 0x920a:
// Focal length
parser.Fetch(FocalLength);
break;
case 0x9214:
// Subject area
if (parser.IsShort() && parser.GetLength() > 1) {
SubjectArea.resize(parser.GetLength());
for (uint32_t i=0; i<parser.GetLength(); ++i)
parser.Fetch(SubjectArea[i], i);
}
break;
case 0x927c:
// MakerNote
parseIFDMakerNote(parser);
break;
case 0x9291:
// Fractions of seconds for DateTimeOriginal
parser.Fetch(SubSecTimeOriginal);
break;
case 0xa002:
// EXIF Image width
if (!parser.Fetch(ImageWidth)) {
uint16_t _ImageWidth;
if (parser.Fetch(_ImageWidth))
ImageWidth = _ImageWidth;
}
break;
case 0xa003:
// EXIF Image height
if (!parser.Fetch(ImageHeight)) {
uint16_t _ImageHeight;
if (parser.Fetch(_ImageHeight))
ImageHeight = _ImageHeight;
}
break;
case 0xa20e:
// Focal plane X resolution
parser.Fetch(LensInfo.FocalPlaneXResolution);
break;
case 0xa20f:
// Focal plane Y resolution
parser.Fetch(LensInfo.FocalPlaneYResolution);
break;
case 0xa210:
// Focal plane resolution unit
parser.Fetch(LensInfo.FocalPlaneResolutionUnit);
break;
case 0xa215:
// Exposure Index and ISO Speed Rating are often used interchangeably
if (ISOSpeedRatings == 0) {
double ExposureIndex;
if (parser.Fetch(ExposureIndex))
ISOSpeedRatings = (uint16_t)ExposureIndex;
}
break;
case 0xa404:
// Digital Zoom Ratio
parser.Fetch(LensInfo.DigitalZoomRatio);
break;
case 0xa405:
// Focal length in 35mm film
if (!parser.Fetch(LensInfo.FocalLengthIn35mm)) {
uint16_t _FocalLengthIn35mm;
if (parser.Fetch(_FocalLengthIn35mm))
LensInfo.FocalLengthIn35mm = (double)_FocalLengthIn35mm;
}
break;
case 0xa431:
// Serial number of the camera
parser.Fetch(SerialNumber);
break;
case 0xa432:
// Focal length and FStop.
if (parser.Fetch(LensInfo.FocalLengthMin, 0))
if (parser.Fetch(LensInfo.FocalLengthMax, 1))
if (parser.Fetch(LensInfo.FStopMin, 2))
parser.Fetch(LensInfo.FStopMax, 3);
break;
case 0xa433:
// Lens make.
parser.Fetch(LensInfo.Make);
break;
case 0xa434:
// Lens model.
parser.Fetch(LensInfo.Model);
break;
}
}
// Parse tag as MakerNote IFD
void EXIFInfo::parseIFDMakerNote(EntryParser& parser) {
const unsigned startOff = parser.GetOffset();
const uint32_t off = parser.GetSubIFD();
if (0 != strcasecmp(Make.c_str(), "DJI"))
return;
int num_entries = EntryParser::parse16(parser.GetBuffer()+off, parser.IsIntelAligned());
if (uint32_t(2 + 12 * num_entries) > parser.GetLength())
return;
parser.Init(off+2);
parser.ParseTag();
--num_entries;
std::string maker;
if (parser.GetTag() == 1 && parser.Fetch(maker)) {
if (0 == strcasecmp(maker.c_str(), "DJI")) {
while (--num_entries >= 0) {
parser.ParseTag();
switch (parser.GetTag()) {
case 3:
// SpeedX
parser.FetchFloat(GeoLocation.SpeedX);
break;
case 4:
// SpeedY
parser.FetchFloat(GeoLocation.SpeedY);
break;
case 5:
// SpeedZ
parser.FetchFloat(GeoLocation.SpeedZ);
break;
case 9:
// Camera Pitch
parser.FetchFloat(GeoLocation.PitchDegree);
break;
case 10:
// Camera Yaw
parser.FetchFloat(GeoLocation.YawDegree);
break;
case 11:
// Camera Roll
parser.FetchFloat(GeoLocation.RollDegree);
break;
}
}
}
}
parser.Init(startOff+12);
}
// Parse tag as GPS IFD
void EXIFInfo::parseIFDGPS(EntryParser& parser) {
switch (parser.GetTag()) {
case 1:
// GPS north or south
parser.Fetch(GeoLocation.LatComponents.direction);
break;
case 2:
// GPS latitude
if (parser.IsRational() && parser.GetLength() == 3) {
parser.Fetch(GeoLocation.LatComponents.degrees, 0);
parser.Fetch(GeoLocation.LatComponents.minutes, 1);
parser.Fetch(GeoLocation.LatComponents.seconds, 2);
}
break;
case 3:
// GPS east or west
parser.Fetch(GeoLocation.LonComponents.direction);
break;
case 4:
// GPS longitude
if (parser.IsRational() && parser.GetLength() == 3) {
parser.Fetch(GeoLocation.LonComponents.degrees, 0);
parser.Fetch(GeoLocation.LonComponents.minutes, 1);
parser.Fetch(GeoLocation.LonComponents.seconds, 2);
}
break;
case 5:
// GPS altitude reference (below or above sea level)
parser.Fetch((uint8_t&)GeoLocation.AltitudeRef);
break;
case 6:
// GPS altitude
parser.Fetch(GeoLocation.Altitude);
break;
case 7:
// GPS timestamp
if (parser.IsRational() && parser.GetLength() == 3) {
double h,m,s;
parser.Fetch(h, 0);
parser.Fetch(m, 1);
parser.Fetch(s, 2);
char buffer[256];
snprintf(buffer, 256, "%g %g %g", h, m, s);
GeoLocation.GPSTimeStamp = buffer;
}
break;
case 11:
// Indicates the GPS DOP (data degree of precision)
parser.Fetch(GeoLocation.GPSDOP);
break;
case 18:
// GPS geodetic survey data
parser.Fetch(GeoLocation.GPSMapDatum);
break;
case 29:
// GPS date-stamp
parser.Fetch(GeoLocation.GPSDateStamp);
break;
case 30:
// GPS differential indicates whether differential correction is applied to the GPS receiver
parser.Fetch(GeoLocation.GPSDifferential);
break;
}
}
//
// Locates the JM_APP1 segment and parses it using
// parseFromEXIFSegment() or parseFromXMPSegment()
//
int EXIFInfo::parseFrom(EXIFStream& stream) {
clear();
if (!stream.IsValid())
return PARSE_INVALID_JPEG;
// Sanity check: all JPEG files start with 0xFFD8 and end with 0xFFD9
// This check also ensures that the user has supplied a correct value for len.
const uint8_t* buf(stream.GetBuffer(2));
if (buf == NULL || buf[0] != JM_START || buf[1] != JM_SOI)
return PARSE_INVALID_JPEG;
// Scan for JM_APP1 header (bytes 0xFF 0xE1) and parse its length.
// Exit if both EXIF and XMP sections were parsed.
struct APP1S {
uint32_t& val;
inline APP1S(uint32_t& v) : val(v) {}
inline operator uint32_t () const { return val; }
inline operator uint32_t& () { return val; }
inline int operator () (int code=PARSE_ABSENT_DATA) const { return val&FIELD_ALL ? (int)PARSE_SUCCESS : code; }
} app1s(Fields);
while ((buf=stream.GetBuffer(2)) != NULL) {
// find next marker;
// in cases of markers appended after the compressed data,
// optional JM_START fill bytes may precede the marker
if (*buf++ != JM_START)
break;
uint8_t marker;
while ((marker=buf[0]) == JM_START && (buf=stream.GetBuffer(1)) != NULL);
// select marker
uint16_t sectionLength;
switch (marker) {
case 0x00:
case 0x01:
case JM_START:
case JM_RST0:
case JM_RST1:
case JM_RST2:
case JM_RST3:
case JM_RST4:
case JM_RST5:
case JM_RST6:
case JM_RST7:
case JM_SOI:
break;
case JM_SOS: // start of stream: and we're done
case JM_EOI: // no data? not good
return app1s();
case JM_APP1:
if ((buf=stream.GetBuffer(2)) == NULL)
return app1s(PARSE_INVALID_JPEG);
sectionLength = EntryParser::parse16(buf, false);
if (sectionLength <= 2 || (buf=stream.GetBuffer(sectionLength-=2)) == NULL)
return app1s(PARSE_INVALID_JPEG);
switch (int ret=parseFromEXIFSegment(buf, sectionLength)) {
case PARSE_ABSENT_DATA:
#ifndef TINYEXIF_NO_XMP_SUPPORT
switch (ret=parseFromXMPSegment(buf, sectionLength)) {
case PARSE_ABSENT_DATA:
break;
case PARSE_SUCCESS:
if ((app1s|=FIELD_XMP) == FIELD_ALL)
return PARSE_SUCCESS;
break;
default:
return app1s(ret); // some error
}
#endif // TINYEXIF_NO_XMP_SUPPORT
break;
case PARSE_SUCCESS:
if ((app1s|=FIELD_EXIF) == FIELD_ALL)
return PARSE_SUCCESS;
break;
default:
return app1s(ret); // some error
}
break;
default:
// skip the section
if ((buf=stream.GetBuffer(2)) == NULL ||
(sectionLength=EntryParser::parse16(buf, false)) <= 2 ||
!stream.SkipBuffer(sectionLength-2))
return app1s(PARSE_INVALID_JPEG);
}
}
return app1s();
}
int EXIFInfo::parseFrom(std::istream& stream) {
class EXIFStdStream : public EXIFStream {
public:
EXIFStdStream(std::istream& stream)
: stream(stream) {
// Would be nice to assert here that the stream was opened in binary mode, but
// apparently that's not possible: https://stackoverflow.com/a/224259/19254
}
bool IsValid() const override {
return !!stream;
}
const uint8_t* GetBuffer(unsigned desiredLength) override {
buffer.resize(desiredLength);
if (!stream.read(reinterpret_cast<char*>(buffer.data()), desiredLength))
return NULL;
return buffer.data();
}
bool SkipBuffer(unsigned desiredLength) override {
return (bool)stream.seekg(desiredLength, std::ios::cur);
}
private:
std::istream& stream;
std::vector<uint8_t> buffer;
};
EXIFStdStream streamWrapper(stream);
return parseFrom(streamWrapper);
}
int EXIFInfo::parseFrom(const uint8_t* buf, unsigned len) {
class EXIFStreamBuffer : public EXIFStream {
public:
explicit EXIFStreamBuffer(const uint8_t* buf, unsigned len)
: it(buf), end(buf+len) {}
bool IsValid() const override {
return it != NULL;
}
const uint8_t* GetBuffer(unsigned desiredLength) override {
const uint8_t* const itNext(it+desiredLength);
if (itNext >= end)
return NULL;
const uint8_t* const begin(it);
it = itNext;
return begin;
}
bool SkipBuffer(unsigned desiredLength) override {
return GetBuffer(desiredLength) != NULL;
}
private:
const uint8_t* it, * const end;
};
EXIFStreamBuffer stream(buf, len);
return parseFrom(stream);
}
//
// Main parsing function for an EXIF segment.
// Do a sanity check by looking for bytes "Exif\0\0".
// The marker has to contain at least the TIFF header, otherwise the
// JM_APP1 data is corrupt. So the minimum length specified here has to be:
// 6 bytes: "Exif\0\0" string
// 2 bytes: TIFF header (either "II" or "MM" string)
// 2 bytes: TIFF magic (short 0x2a00 in Motorola byte order)
// 4 bytes: Offset to first IFD
// =========
// 14 bytes
//
// PARAM: 'buf' start of the EXIF TIFF, which must be the bytes "Exif\0\0".
// PARAM: 'len' length of buffer
//
int EXIFInfo::parseFromEXIFSegment(const uint8_t* buf, unsigned len) {
unsigned offs = 6; // current offset into buffer
if (!buf || len < offs)
return PARSE_ABSENT_DATA;
if (!std::equal(buf, buf+offs, "Exif\0\0"))
return PARSE_ABSENT_DATA;
// Now parsing the TIFF header. The first two bytes are either "II" or
// "MM" for Intel or Motorola byte alignment. Sanity check by parsing
// the uint16_t that follows, making sure it equals 0x2a. The
// last 4 bytes are an offset into the first IFD, which are added to
// the global offset counter. For this block, we expect the following
// minimum size:
// 2 bytes: 'II' or 'MM'
// 2 bytes: 0x002a
// 4 bytes: offset to first IDF
// -----------------------------
// 8 bytes
if (offs + 8 > len)
return PARSE_CORRUPT_DATA;
const uint32_t _ONE32 = 1;
const bool IS_LITTLE_ENDIAN = reinterpret_cast<uint8_t const*>(&_ONE32)[0] == 1;
bool alignIntel;
if (buf[offs] == 'I' && buf[offs+1] == 'I')
alignIntel = IS_LITTLE_ENDIAN; // 1: Intel byte alignment
else
if (buf[offs] == 'M' && buf[offs+1] == 'M')
alignIntel = !IS_LITTLE_ENDIAN; // 0: Motorola byte alignment
else
return PARSE_UNKNOWN_BYTEALIGN;
EntryParser parser(buf, len, offs, alignIntel);
offs += 2;
if (0x2a != EntryParser::parse16(buf + offs, alignIntel))
return PARSE_CORRUPT_DATA;
offs += 2;
const unsigned first_ifd_offset = EntryParser::parse32(buf + offs, alignIntel);
offs += first_ifd_offset - 4;
if (offs >= len)
return PARSE_CORRUPT_DATA;
// Now parsing the first Image File Directory (IFD0, for the main image).
// An IFD consists of a variable number of 12-byte directory entries. The
// first two bytes of the IFD section contain the number of directory
// entries in the section. The last 4 bytes of the IFD contain an offset
// to the next IFD, which means this IFD must contain exactly 6 + 12 * num
// bytes of data.
if (offs + 2 > len)
return PARSE_CORRUPT_DATA;
int num_entries = EntryParser::parse16(buf + offs, alignIntel);
if (offs + 6 + 12 * num_entries > len)
return PARSE_CORRUPT_DATA;
unsigned exif_sub_ifd_offset = len;
unsigned gps_sub_ifd_offset = len;
parser.Init(offs+2);
while (--num_entries >= 0) {
parser.ParseTag();
parseIFDImage(parser, exif_sub_ifd_offset, gps_sub_ifd_offset);
}
// Jump to the EXIF SubIFD if it exists and parse all the information
// there. Note that it's possible that the EXIF SubIFD doesn't exist.
// The EXIF SubIFD contains most of the interesting information that a
// typical user might want.
if (exif_sub_ifd_offset + 4 <= len) {
offs = exif_sub_ifd_offset;
num_entries = EntryParser::parse16(buf + offs, alignIntel);
if (offs + 6 + 12 * num_entries > len)
return PARSE_CORRUPT_DATA;
parser.Init(offs+2);
while (--num_entries >= 0) {
parser.ParseTag();
parseIFDExif(parser);
}
}