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Implement basic EMV highlighter for emv-viewer
QSyntaxHighlighter is designed to process one block at a time with very little context about other blocks. This is not ideal for EMV parsing but appears to be the only way to apply text formatting without impacting the undo/redo stack. Therefore, this implementation processes all blocks and reparses all of the EMV data when updating each block. This implementation also assumes that rehighlight() is called whenever the widget text changes because changes to later blocks may invalidate EMV field lengths specified in earlier blocks.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,183 @@ | ||
| /** | ||
| * @file emvhighlighter.cpp | ||
| * @brief QSyntaxHighlighter derivative that applies highlighting to EMV data | ||
| * | ||
| * Copyright 2024 Leon Lynch | ||
| * | ||
| * This program is free software: you can redistribute it and/or modify | ||
| * it under the terms of the GNU General Public License as published by | ||
| * the Free Software Foundation, either version 3 of the License, or | ||
| * (at your option) any later version. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * GNU General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU General Public License | ||
| * along with this program. If not, see <https://www.gnu.org/licenses/>. | ||
| */ | ||
|
|
||
| #include "emvhighlighter.h" | ||
| #include "iso8825_ber.h" | ||
|
|
||
| #include <QtCore/QString> | ||
| #include <QtCore/QByteArray> | ||
| #include <QtGui/QTextDocument> | ||
| #include <QtGui/QTextBlock> | ||
| #include <QtGui/QTextCharFormat> | ||
| #include <QtGui/QColor> | ||
|
|
||
| #include <cstddef> | ||
| #include <cctype> | ||
|
|
||
| static bool parseBerData( | ||
| const void* ptr, | ||
| std::size_t len, | ||
| std::size_t* validBytes | ||
| ) | ||
| { | ||
| int r; | ||
| struct iso8825_ber_itr_t itr; | ||
| struct iso8825_tlv_t tlv; | ||
| bool valid; | ||
|
|
||
| r = iso8825_ber_itr_init(ptr, len, &itr); | ||
| if (r) { | ||
| qWarning("iso8825_ber_itr_init() failed; r=%d", r); | ||
| return false; | ||
| } | ||
|
|
||
| while ((r = iso8825_ber_itr_next(&itr, &tlv)) > 0) { | ||
|
|
||
| if (iso8825_ber_is_constructed(&tlv)) { | ||
| // If the field is constructed, only consider the tag and length | ||
| // to be valid until the value has been parsed. The fields inside | ||
| // the value will be added when they are parsed. | ||
| *validBytes += (r - tlv.length); | ||
|
|
||
| // Recursively parse constructed fields | ||
| valid = parseBerData(tlv.value, tlv.length, validBytes); | ||
| if (!valid) { | ||
| qDebug("parseBerData() failed; validBytes=%zu", *validBytes); | ||
| return false; | ||
| } | ||
|
|
||
| } else { | ||
| // If the field is not constructed, consider all of the bytes to | ||
| // be valid BER encoded data | ||
| *validBytes += r; | ||
| } | ||
| } | ||
| if (r < 0) { | ||
| qDebug("iso8825_ber_itr_next() failed; r=%d", r); | ||
| return false; | ||
| } | ||
|
|
||
| return true; | ||
| } | ||
|
|
||
| class EmvTextBlockUserData : public QTextBlockUserData | ||
| { | ||
| public: | ||
| EmvTextBlockUserData(unsigned int startPos, unsigned int length) | ||
| : startPos(startPos), | ||
| length(length) | ||
| {} | ||
|
|
||
| public: | ||
| unsigned int startPos; | ||
| unsigned int length; | ||
| }; | ||
|
|
||
| void EmvHighlighter::highlightBlock(const QString& text) | ||
| { | ||
| // QSyntaxHighlighter is designed to process one block at a time with very | ||
| // little context about other blocks. This is not ideal for EMV parsing | ||
| // but appears to be the only way to apply text formatting without | ||
| // impacting the undo/redo stack. Therefore, this implementation processes | ||
| // all blocks and reparses all of the EMV data when updating each block. | ||
| // This implementation also assumes that rehighlight() is called whenever | ||
| // the widget text changes because changes to later blocks may invalidate | ||
| // EMV field lengths specified in earlier blocks. | ||
|
|
||
| // NOTE: If anyone knows a better way, please let me know. | ||
|
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| QTextDocument* doc = document(); | ||
| int strLen = 0; | ||
| unsigned int validLen; | ||
| QString str; | ||
| QByteArray data; | ||
| std::size_t validBytes = 0; | ||
|
|
||
| // Concatenate all blocks without whitespace and compute start position | ||
| // and length of current block within concatenated string | ||
| for (QTextBlock block = doc->begin(); block != doc->end(); block = block.next()) { | ||
| QString blockStr = block.text().simplified().remove(' '); | ||
| if (currentBlock() == block) { | ||
| block.setUserData(new EmvTextBlockUserData(strLen, blockStr.length())); | ||
| } | ||
|
|
||
| strLen += blockStr.length(); | ||
| str += blockStr; | ||
| } | ||
| if (strLen != str.length()) { | ||
| // Internal error | ||
| qWarning("strLen=%d; str.length()=%d", strLen, (int)str.length()); | ||
| strLen = str.length(); | ||
| } | ||
| validLen = strLen; | ||
|
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| // Ensure that hex string contains only hex digits | ||
| for (unsigned int i = 0; i < validLen; ++i) { | ||
| if (!std::isxdigit(str[i].unicode())) { | ||
| // Only parse up to invalid digit | ||
| validLen = i; | ||
| break; | ||
| } | ||
| } | ||
|
|
||
| // Ensure that hex string has even number of digits | ||
| if (validLen & 0x01) { | ||
| // Odd number of digits. Ignore last digit to see whether parsing can | ||
| // proceed regardless and highlight error later. | ||
| validLen -= 1; | ||
| } | ||
|
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| // Only decode valid hex digits to binary | ||
| data = QByteArray::fromHex(str.left(validLen).toUtf8()); | ||
|
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| // Parse BER encoded data and update number of valid characters | ||
| parseBerData(data.constData(), data.size(), &validBytes); | ||
| validLen = validBytes * 2; | ||
|
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| EmvTextBlockUserData* blockData = static_cast<decltype(blockData)>(currentBlockUserData()); | ||
| if (!blockData) { | ||
| // Internal error | ||
| qWarning("Block data missing for block number %d", currentBlock().blockNumber()); | ||
| return; | ||
| } | ||
|
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| if (validLen >= blockData->startPos + blockData->length) { | ||
| // All digits are valid | ||
| setFormat(0, currentBlock().length(), QTextCharFormat()); | ||
|
|
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| } else if (validLen <= blockData->startPos) { | ||
| // All digits are invalid | ||
| setFormat(0, currentBlock().length(), QColor(Qt::red)); | ||
| } else { | ||
| // Some digits are invalid | ||
| unsigned int digitIdx = 0; | ||
| for (int i = 0; i < text.length(); ++i) { | ||
| if (blockData->startPos + digitIdx < validLen) { | ||
| setFormat(i, 1, QTextCharFormat()); | ||
| } else { | ||
| setFormat(i, 1, QColor(Qt::red)); | ||
| } | ||
|
|
||
| if (std::isxdigit(text[i].unicode())) { | ||
| ++digitIdx; | ||
| } | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,41 @@ | ||
| /** | ||
| * @file emvhighlighter.h | ||
| * @brief QSyntaxHighlighter derivative that applies highlighting to EMV data | ||
| * | ||
| * Copyright 2024 Leon Lynch | ||
| * | ||
| * This program is free software: you can redistribute it and/or modify | ||
| * it under the terms of the GNU General Public License as published by | ||
| * the Free Software Foundation, either version 3 of the License, or | ||
| * (at your option) any later version. | ||
| * | ||
| * This program is distributed in the hope that it will be useful, | ||
| * but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| * GNU General Public License for more details. | ||
| * | ||
| * You should have received a copy of the GNU General Public License | ||
| * along with this program. If not, see <https://www.gnu.org/licenses/>. | ||
| */ | ||
|
|
||
| #ifndef EMV_HIGHLIGHTER_H | ||
| #define EMV_HIGHLIGHTER_H | ||
|
|
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| #include <QtGui/QSyntaxHighlighter> | ||
|
|
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| // Forward declarations | ||
| class QTextDocument; | ||
|
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| class EmvHighlighter : public QSyntaxHighlighter | ||
| { | ||
| Q_OBJECT | ||
|
|
||
| public: | ||
| explicit EmvHighlighter(QTextDocument* parent) | ||
| : QSyntaxHighlighter(parent) | ||
| {} | ||
|
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| virtual void highlightBlock(const QString& text) override; | ||
| }; | ||
|
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| #endif |