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Refactor QUtil::hex_decode

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This commit is contained in:
m-holger 2023-03-23 18:51:28 +00:00
parent 0795b6952b
commit 5f4f553c35
1 changed files with 14 additions and 17 deletions
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31
libqpdf/QUtil.cc
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@ -783,28 +783,25 @@ std::string
QUtil::hex_decode(std::string const& input)
{
std::string result;
size_t pos = 0;
// We know result.size() <= 0.5 * input.size() + 1. However, reserving
// string space for this upper bound has a negative impact.
bool first = true;
char decoded;
for (auto ch: input) {
bool skip = false;
if ((ch >= 'A') && (ch <= 'F')) {
ch = QIntC::to_char(ch - 'A' + 10);
} else if ((ch >= 'a') && (ch <= 'f')) {
ch = QIntC::to_char(ch - 'a' + 10);
} else if ((ch >= '0') && (ch <= '9')) {
ch = QIntC::to_char(ch - '0');
} else {
skip = true;
}
if (!skip) {
if (pos == 0) {
result.push_back(static_cast<char>(ch << 4));
pos = 1;
ch = hex_decode_char(ch);
if (ch < '\20') {
if (first) {
decoded = static_cast<char>(ch << 4);
first = false;
} else {
result[result.length() - 1] |= ch;
pos = 0;
result.push_back(decoded | ch);
first = true;
}
}
}
if (!first) {
result.push_back(decoded);
}
return result;
}