Encode type before header, simplify access to pixel data

CMakeLists.txt

@@ -61,7 +61,7 @@ set(PXCRYPT_QX_COMPONENTS
 
 include(OB/FetchQx)
 ob_fetch_qx(
-    REF "83e840ca996942c973f9bf5f9d9d6efc8cef029f"
+    REF "08d59b2aa53df3b53da44148740adfc39e1da5c1"
     COMPONENTS
         ${PXCRYPT_QX_COMPONENTS}
 )

lib/CMakeLists.txt

@@ -10,31 +10,42 @@ ob_add_standard_library(${LIB_TARGET_NAME}
         tools/bit_chunker.h
         tools/byte_compositer.h
         tools/ch_sequence_generator.h
+        tools/px_access_read.h
+        tools/px_access_write.h
         tools/px_sequence_generator.h
         tools/px_skimmer.h
         tools/px_weaver.h
     HEADERS_API
         COMMON "${PROJECT_NAMESPACE_LC}"
         FILES
+            _internal.h
             decode.h
             encdec.h
             encode.h
     IMPLEMENTATION
+        _internal.cpp
         decode.cpp
         encode.cpp
         encdec_p.cpp
         tools/bit_chunker.cpp
         tools/byte_compositer.cpp
         tools/ch_sequence_generator.cpp
+        tools/px_access_read.cpp
+        tools/px_access_write.cpp
         tools/px_sequence_generator.cpp
         tools/px_skimmer.cpp
         tools/px_weaver.cpp
     DOC_ONLY
         encdec.dox
     LINKS
+        PRIVATE
+            $<BUILD_INTERFACE:magic_enum::magic_enum>
         PUBLIC
             Qt6::Core
             Qt6::Gui
             Qx::Core
     CONFIG STANDARD
 )
+
+# Build interface wrapper for magic_enum is a workaround for a CMake limitation.
+# See https://github.com/oblivioncth/STARpp/blob/500d19354fe394ba5a1c84e56208d2186866c5e8/lib/CMakeLists.txt

lib/include/pxcrypt/_internal.h

@@ -0,0 +1,18 @@
+#ifndef _INTERNAL_H
+#define _INTERNAL_H
+
+// Qt Includes
+#include <QSize>
+
+// Shared Library Support
+#include "pxcrypt/pxcrypt_codec_export.h"
+
+/*! @cond */
+namespace _PxCrypt
+{
+//-Namespace Functions-------------------------------------------------------------------------------------------------
+PXCRYPT_CODEC_EXPORT quint64 calculateMaximumPayloadBits(const QSize& dim, quint16 tagSize, quint8 bpc);
+}
+/*! @endcond */
+
+#endif // _INTERNAL_H

lib/include/pxcrypt/decode.h

@@ -10,20 +10,10 @@
 // Qx Includes
 #include <qx/core/qx-genericerror.h>
 
-// Project Includes
-#include "pxcrypt/encdec.h"
-
 namespace PxCrypt
 {
-//-Namespace Types ---------------------------------------------------------------------------------------------
-struct DecodeSettings
-{
-    QByteArray psk;
-    EncType type = Absolute;
-};
-
 //-Namespace Functions-------------------------------------------------------------------------------------------------
-PXCRYPT_CODEC_EXPORT Qx::GenericError decode(QByteArray& dec, QString& tag, const QImage& enc, DecodeSettings set, const QImage& medium = QImage());
+PXCRYPT_CODEC_EXPORT Qx::GenericError decode(QByteArray& dec, QString& tag, const QImage& enc, QByteArrayView psk = QByteArrayView(), const QImage& medium = QImage());
 
 }
 

lib/include/pxcrypt/encdec.h

@@ -14,7 +14,7 @@ namespace PxCrypt
 //-Namespace Enums-----------------------------------------------------------------------------------------------------
 enum EncType : quint8 {
     Relative = 0,
-    Absolute = 1
+    Absolute = 4
 };
 
 }

lib/src/_internal.cpp

@@ -0,0 +1,22 @@
+// Unit Includes
+#include "pxcrypt/_internal.h"
+
+// Project Includes
+#include "encdec_p.h"
+
+namespace _PxCrypt
+{
+//-Namespace Functions-------------------------------------------------------------------------------------------------
+/*!
+ *  @warning This functions exists primarily for testing the library. The practical amount of storage
+ *  available within an image is always lower than this. Use calculateMaximumStorage() instead.
+ *
+ *  Returns the maximum number of bits that can be stored within an image of dimensions @a dim and tag of size
+ *  @a tagSize when using @a bpc bits per channel.
+ */
+quint64 calculateMaximumPayloadBits(const QSize& dim, quint16 tagSize, quint8 bpc)
+{
+    return PxCrypt::calcMaxPayloadBits(dim, tagSize, bpc);
+}
+
+}

lib/src/decode.cpp

@@ -4,13 +4,17 @@
 // Project Includes
 #include "pxcrypt/encdec.h"
 #include "encdec_p.h"
+#include "tools/px_access_read.h"
 #include "tools/px_skimmer.h"
 #include "tools/byte_compositer.h"
 
 // Qx Includes
 #include <qx/core/qx-bitarray.h>
 #include <qx/core/qx-integrity.h>
 
+// Magic Enum Include
+#include <magic_enum.hpp>
+
 /*!
  *  @file decode.h
  *
@@ -27,19 +31,18 @@ namespace
     // Errors
     const QString ERR_DECODING_FAILED = QSL("Decoding failed.");
     const QString ERR_INVALID_SOURCE = QSL("The encoded image is invalid.");
-    const QString ERR_MISSING_MEDIUM = QSL("The required medium image is invalid.");
+    const QString ERR_MISSING_MEDIUM = QSL("The encoded image requires a medium to be decoded but none was provided.");
     const QString ERR_DIMMENSION_MISTMATCH = QSL("The required medium image has different dimmensions than the encoded image.");
     const QString ERR_NOT_LARGE_ENOUGH = QSL("The provided image is not large enough to be an encoded image.");
-    const QString ERR_INVALID_HEADER = QSL("The provided image is not encoded, the wrong encoding type was specified,"
-                                           " or the password/medium are incorrect.");
+    const QString ERR_NOT_MAGIC = QSL("The provided image is not encoded or the password/medium are incorrect.");
     const QString ERR_LENGTH_MISMATCH = QSL("The encoded image's header indicates it contains more data than possible.");
     const QString ERR_UNEXPECTED_END = QSL("All pixels were skimmed before the expected payload size was reached.");
     const QString ERR_CHECKSUM_MISMATCH = QSL("The payload's checksum did not match the expected value.");
 
     //-Unit Private Functions ---------------------------------------------------------------------------------------------
     bool canFitHeader(const QSize& dim, quint8 bpc)
     {
-        int bits = (dim.width() * dim.height() - 1) * 3 * bpc; // -1 For bpp indicator
+        int bits = (dim.width() * dim.height() - META_PIXELS) * 3 * bpc;
         return bits >= HEADER_BYTES * 8;
     }
 }
@@ -50,25 +53,6 @@ namespace
 // DecodeSettings
 //===============================================================================================================
 
-/*!
- *  @struct DecodeSettings <pxcrypt/decode.h>
- *
- *  @brief The DecodeSettings struct holds tuning parameters that are required to properly decode
- *  data from an image.
- */
-
-/*!
- *  @var QByteArray DecodeSettings::psk
- *
- *  The key that was used when encoding the original data, if any.
- */
-
-/*!
- *  @var EncType DecodeSettings::type
- *
- *  The encoding strategy that was used when encoding the original data.
- */
-
 //-Namespace Functions-------------------------------------------------------------------------------------------------
 
 /*!
@@ -77,13 +61,13 @@ namespace
  *  @param[out] dec The original payload.
  *  @param[out] tag The image's/payload's tag
  *  @param[in] enc The image with the encoded data
- *  @param[in] set Tuneables for properly decoding the input image
+ *  @param[in] psk The key that was used when encoding the original data, if any.
  *  @param[in] medium The original medium used when encoding the payload. Ignored for encoding types other than EncType::Relative
  *  @return An error object that describes cause of failure if encoding fails.
  *
- *  @sa encode(), DecodeSettings.
+ *  @sa encode().
  */
-Qx::GenericError decode(QByteArray& dec, QString& tag, const QImage& enc, DecodeSettings set, const QImage& medium)
+Qx::GenericError decode(QByteArray& dec, QString& tag, const QImage& enc, QByteArrayView psk, const QImage& medium)
 {
     // Clear buffer
     dec.clear();
@@ -92,44 +76,52 @@ Qx::GenericError decode(QByteArray& dec, QString& tag, const QImage& enc, Decode
     if(enc.isNull())
         return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_INVALID_SOURCE);
 
-    // Ensure medium image is valid if applicable
-    if(set.type == EncType::Relative)
-    {
-        if(medium.isNull())
-            return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_MISSING_MEDIUM);
-
-        if(medium.size() != enc.size())
-            return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_DIMMENSION_MISTMATCH);
-    }
+    // Ensure image meets bare minimum space for meta pixels
+    if(enc.size().width() * enc.size().height() < META_PIXELS)
+        return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_NOT_LARGE_ENOUGH);
 
     // Ensure standard pixel format
     QImage encStd = enc; // Because of Qt's CoW system this occurs almost no penalty if the format is already correct
     if(encStd.format() != QImage::Format_RGBA8888)
         encStd.convertTo(QImage::Format_RGBA8888);
 
-    QImage mediumStd = medium;
-    if(!mediumStd.isNull() && mediumStd.format() != QImage::Format_RGBA8888)
-        mediumStd.convertTo(QImage::Format_RGBA8888);
+    // Prepare pixel access, automatically reads meta pixels
+    PxAccessRead pAccess(&encStd, !psk.isEmpty() ? psk : DEFAULT_SEED);
 
-    // Check BPC
-    Qx::BitArray bpcBits(3);
+    // Ensure BPC is valid
+    if(pAccess.bpc() < 1 || pAccess.bpc() > 7)
+        return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_NOT_MAGIC);
 
-    QRgb first = enc.pixel(0, 0);
-    bpcBits.setBit(0, qRed(first) & 0x01);
-    bpcBits.setBit(1, qGreen(first) & 0x01);
-    bpcBits.setBit(2, qBlue(first) & 0x01);
-    quint8 bpc = bpcBits.toInteger<quint8>();
+    // Ensure type is valid
+    if(!magic_enum::enum_contains(pAccess.type()))
+        return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_NOT_MAGIC);
 
     // Ensure at least header can fit
-    if(!canFitHeader(encStd.size(), bpc))
+    if(!canFitHeader(encStd.size(), pAccess.bpc()))
         return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_NOT_LARGE_ENOUGH);
 
     // Reserve space for header
     dec.reserve(HEADER_BYTES);
 
+    // Ensure medium image is valid if applicable
+    QImage mediumStd;
+    if(pAccess.type() == EncType::Relative)
+    {
+        mediumStd = medium;
+
+        if(mediumStd.isNull())
+            return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_MISSING_MEDIUM);
+
+        if(mediumStd.size() != encStd.size())
+            return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_DIMMENSION_MISTMATCH);
+
+        if(!mediumStd.isNull() && mediumStd.format() != QImage::Format_RGBA8888)
+            mediumStd.convertTo(QImage::Format_RGBA8888);
+    }
+
     // Prepare pixel skimmer and byte compositer
-    PxSkimmer pSkimmer(&encStd, &mediumStd, !set.psk.isEmpty() ? set.psk : DEFAULT_SEED, bpc, set.type);
-    ByteCompositer bCompositer(&dec, bpc);
+    PxSkimmer pSkimmer(&pAccess, &mediumStd);
+    ByteCompositer bCompositer(&dec, pAccess.bpc());
 
     // Read header
     while(dec.size() != HEADER_BYTES)
@@ -138,31 +130,20 @@ Qx::GenericError decode(QByteArray& dec, QString& tag, const QImage& enc, Decode
     // Extract header components
     QDataStream hs(dec);
     QByteArray hMagic(MAGIC_NUM.size(), Qt::Uninitialized);
-    EncType hType;
     quint32 hPayloadChecksum;
     quint16 hTagSize;
     quint32 hPayloadSize;
 
     hs.readRawData(hMagic.data(), hMagic.size());
-    hs >> hType;
     hs >> hPayloadChecksum;
     hs >> hTagSize;
     hs >> hPayloadSize;
 
     // Ensure header is valid
     if(hMagic != MAGIC_NUM)
-        return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_INVALID_HEADER);
-
-    if(hType != set.type)
-    {
-        /* NOTE: This should be impossible given the data would be garbage with
-         * the wrong encoding type, hence why this only causes a warning;
-         * however, potential future data types may require re-evaluating this check.
-         */
-        qWarning("mismatched encoding type!");
-    }
+        return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_NOT_MAGIC);
 
-    quint64 maxStorage = calcMaxPayloadSize(encStd.size(), hTagSize, bpc);
+    quint64 maxStorage = calcMaxPayloadBytes(encStd.size(), hTagSize, pAccess.bpc());
     if(hPayloadSize > maxStorage)
         return Qx::GenericError(Qx::GenericError::Critical, ERR_DECODING_FAILED, ERR_NOT_LARGE_ENOUGH);
 

lib/src/encdec_p.cpp

@@ -12,15 +12,20 @@ namespace PxCrypt
 /*! @cond */
 
 //-Namespace Functions-------------------------------------------------------------------------------------------------
-quint64 calcMaxPayloadSize(const QSize& dim, quint16 tagSize, quint8 bpc)
+quint64 calcMaxPayloadBits(const QSize& dim, quint16 tagSize, quint8 bpc)
 {
     // Returns 0 if no data can fit
-    quint64 pixles = dim.width() * dim.height() - 1; // -1 For bpp indicator
+    quint64 pixles = dim.width() * dim.height() - META_PIXELS;
     quint64 headerBits = HEADER_BYTES * 8;
-    quint64 tagBits = tagSize* 8;
+    quint64 tagBits = tagSize * 8;
     quint64 payloadBits = Qx::constrainedSub(pixles * bpc * 3, headerBits + tagBits);
 
-    return payloadBits / 8; // Truncate down
+    return payloadBits;
+}
+
+quint64 calcMaxPayloadBytes(const QSize& dim, quint16 tagSize, quint8 bpc)
+{
+    return calcMaxPayloadBits(dim, tagSize, bpc) / 8; // Truncate down
 }
 
 /*! @endcond */

lib/src/encdec_p.h

@@ -9,39 +9,37 @@
 // Qx Includes
 #include <qx/utility/qx-macros.h>
 
-// Project Includes
-#include "pxcrypt/encdec.h"
-
 namespace PxCrypt
 {
 /*! @cond */
 
 //-Namespace Enums-------------------------------------------------------------------------------------------------
 enum Channel : quint8{
     Red = 0,
-    Blue = 1,
-    Green = 2,
+    Green = 1,
+    Blue = 2,
     Alpha = 3
 };
 
 //-Namespace Variables-------------------------------------------------------------------------------------------------
 const QByteArray MAGIC_NUM = QBAL("PXC");
 
+const int META_PIXELS = 2; // BPC + EncType
+
 const int MAGIC_SIZE = MAGIC_NUM.size();
-const int TYPE_SIZE = sizeof(EncType);
 const int CHECKSUM_SIZE = sizeof(quint32);
 const int TAG_LENGTH_SIZE = sizeof(quint16);
 const int PAYLOAD_LENGTH_SIZE = sizeof(quint32);
 const int HEADER_BYTES = MAGIC_SIZE +
-                         TYPE_SIZE +
                          CHECKSUM_SIZE +
                          TAG_LENGTH_SIZE +
                          PAYLOAD_LENGTH_SIZE;
 
 static inline const QByteArray DEFAULT_SEED = QBAL("The best and most secure seed that is possible to exist!");
 
 //-Namespace Functions-------------------------------------------------------------------------------------------------
-quint64 calcMaxPayloadSize(const QSize& dim, quint16 tagSize, quint8 bpc);
+quint64 calcMaxPayloadBits(const QSize& dim, quint16 tagSize, quint8 bpc);
+quint64 calcMaxPayloadBytes(const QSize& dim, quint16 tagSize, quint8 bpc);
 
 /*! @endcond */
 }