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Improve EmvTreeItem rendering of field strings
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* Add raw value bytes to field strings when EMV decoding is disabled
* Add non-list description strings to field strings when EMV decoding is
  enabled

Both of the above improvements make emv-viewer look more similar to
emv-decode but it is intentional that they will likely never be
identical because each has an aesthestic that matches their respective
visual paradigms.
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@leonlynch
leonlynch committed Jul 7, 2024
1 parent 854c02e commit f70a152
Showing 1 changed file with 86 additions and 61 deletions.
147 changes: 86 additions & 61 deletions viewer/emvtreeitem.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -32,23 +32,29 @@
#include <QtCore/QStringList>

#include <cstddef>
#include <cstdint>

// Helper functions
static bool valueStrIsList(const QByteArray& str);
static QString buildSimpleFieldString(
unsigned int tag,
qsizetype length,
const std::uint8_t* value = nullptr
);
static QString buildDecodedFieldString(
unsigned int tag,
const struct emv_tlv_info_t& info,
const QByteArray& valueStr
);
static QString buildFieldString(
unsigned int tag,
const char* name = nullptr,
qsizetype length = -1
);
static bool valueStrIsList(const QByteArray& str);
static QTreeWidgetItem* addDescStringList(
EmvTreeItem* item,
const QByteArray& valueStr
);
static QTreeWidgetItem* addDescString(
EmvTreeItem* item,
const emv_format_t format,
const QByteArray& valueStr
);
static QTreeWidgetItem* addDescDol(
EmvTreeItem* item,
const void* ptr,
Expand Down Expand Up @@ -97,9 +103,8 @@ void EmvTreeItem::render(bool showDecoded)
setText(0, decodedFieldStr);

// Make decoded descriptions visible
// First child is length and raw bytes for primitive fields
if (!isConstructed && childCount() > 1) {
for (int i = 1; i < childCount(); ++i) {
if (!isConstructed) {
for (int i = 0; i < childCount(); ++i) {
child(i)->setHidden(false);
}
}
Expand All @@ -108,9 +113,8 @@ void EmvTreeItem::render(bool showDecoded)
setText(0, simpleFieldStr);

// Hide decoded descriptions
// First child is length and raw bytes for primitive fields
if (!isConstructed && childCount() > 1) {
for (int i = 1; i < childCount(); ++i) {
if (!isConstructed) {
for (int i = 0; i < childCount(); ++i) {
child(i)->setHidden(true);
}
}
Expand All @@ -129,17 +133,22 @@ void EmvTreeItem::setTlv(const struct iso8825_tlv_t* tlv, bool decode)
emv_tlv.ber = *tlv;
emv_tlv_get_info(&emv_tlv, &info, valueStr.data(), valueStr.size());
isConstructed = iso8825_ber_is_constructed(tlv);
simpleFieldStr = buildFieldString(tlv->tag);
decodedFieldStr = buildFieldString(tlv->tag, info.tag_name);
decodedFieldStr = buildDecodedFieldString(tlv->tag, info, valueStr);

if (!isConstructed) {
// Always add raw value bytes for primitive fields
if (isConstructed) {
// Add field length but omit raw value bytes from field strings for
// constructed fields
simpleFieldStr = buildSimpleFieldString(tlv->tag, tlv->length);
} else {
// Add field length and raw value bytes to simple field string for
// primitive fields
simpleFieldStr = buildSimpleFieldString(tlv->tag, tlv->length, tlv->value);

// Always add raw value bytes as first child for primitive fields
addDescRaw(this, tlv->value, tlv->length);

if (valueStrIsList(valueStr)) {
addDescStringList(this, valueStr);
} else if (valueStr[0]) {
addDescString(this, info.format, valueStr);
} else if (info.format == EMV_FORMAT_DOL) {
addDescDol(this, tlv->value, tlv->length);
} else if (info.format == EMV_FORMAT_TAG_LIST) {
Expand All @@ -151,6 +160,65 @@ void EmvTreeItem::setTlv(const struct iso8825_tlv_t* tlv, bool decode)
render(decode);
}

static bool valueStrIsList(const QByteArray& str)
{
if (!str[0]) {
return false;
}

// If the last character is a newline, assume that it is a string list
return str[qstrnlen(str.constData(), str.size()) - 1] == '\n';
}

static QString buildSimpleFieldString(
unsigned int tag,
qsizetype length,
const std::uint8_t* value
)
{
if (value) {
return
QString::asprintf("%02X : [%zu] ",
tag, static_cast<std::size_t>(length)
) +
// Create an uppercase hex string, with spaces, from the
// field's value bytes
QByteArray::fromRawData(
reinterpret_cast<const char*>(value),
length
).toHex(' ').toUpper().constData();
} else {
return QString::asprintf("%02X : [%zu]", tag, static_cast<std::size_t>(length));
}
}

static QString buildDecodedFieldString(
unsigned int tag,
const struct emv_tlv_info_t& info,
const QByteArray& valueStr
)
{
if (info.tag_name) {
QString fieldStr = QString::asprintf("%02X | %s", tag, info.tag_name);;
if (!valueStrIsList(valueStr) && valueStr[0]) {
if (info.format == EMV_FORMAT_A ||
info.format == EMV_FORMAT_AN ||
info.format == EMV_FORMAT_ANS
) {
fieldStr += QStringLiteral(" : \"") +
valueStr.constData() +
QStringLiteral("\"");
} else {
fieldStr += QStringLiteral(" : ") + valueStr.constData();
}
}
return fieldStr;

} else {
return QString::asprintf("%02X", tag);
}
}

static QString buildFieldString(
unsigned int tag,
const char* name,
Expand All @@ -172,16 +240,6 @@ static QString buildFieldString(
}
}

static bool valueStrIsList(const QByteArray& str)
{
if (!str[0]) {
return false;
}

// If the last character is a newline, assume it's a string list
return str[qstrnlen(str.constData(), str.size()) - 1] == '\n';
}

static QTreeWidgetItem* addDescStringList(
EmvTreeItem* item,
const QByteArray& valueStr
Expand All @@ -202,39 +260,6 @@ static QTreeWidgetItem* addDescStringList(
return descItem;
}

static QTreeWidgetItem* addDescString(
EmvTreeItem* item,
const emv_format_t format,
const QByteArray& valueStr
)
{
QString descStr;

if (!valueStr[0]) {
return nullptr;
}

// Use quotes for strings and parentheses for everything else
if (format == EMV_FORMAT_A ||
format == EMV_FORMAT_AN ||
format == EMV_FORMAT_ANS
) {
descStr = QStringLiteral("\"") +
valueStr.constData() +
QStringLiteral("\"");
} else {
descStr = QString::fromUtf8(valueStr);
}

QTreeWidgetItem* descItem = new QTreeWidgetItem(
item,
QStringList(descStr)
);
descItem->setFlags(Qt::ItemNeverHasChildren | Qt::ItemIsEnabled);

return descItem;
}

static QTreeWidgetItem* addDescDol(
EmvTreeItem* item,
const void* ptr,
Expand Down

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