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Refactor JSON::encode_string

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m-holger 2023-02-03 14:28:45 +00:00 committed by Jay Berkenbilt
parent 1787d85096
commit 415e67951b
1 changed files with 52 additions and 32 deletions
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84
libqpdf/JSON.cc
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@ -220,41 +220,61 @@ JSON::unparse() const
std::string
JSON::encode_string(std::string const& str)
{
std::string result;
size_t len = str.length();
for (size_t i = 0; i < len; ++i) {
unsigned char ch = static_cast<unsigned char>(str.at(i));
switch (ch) {
case '\\':
result += "\\\\";
break;
case '\"':
result += "\\\"";
break;
case '\b':
result += "\\b";
break;
case '\f':
result += "\\f";
break;
case '\n':
result += "\\n";
break;
case '\r':
result += "\\r";
break;
case '\t':
result += "\\t";
break;
default:
if (ch < 32) {
result += "\\u" + QUtil::int_to_string_base(ch, 16, 4);
} else {
result.append(1, static_cast<char>(ch));
static auto constexpr hexchars = "0123456789abcdef";
auto begin = str.cbegin();
auto end = str.cend();
auto iter = begin;
while (iter != end) {
auto c = static_cast<unsigned char>(*iter);
if ((c > 34 && c != '\\') || c == ' ' || c == 33) {
// Optimistically check that no char in str requires escaping.
// Hopefully we can just return the input str.
++iter;
} else {
// We found a char that requires escaping. Initialize result to the
// chars scanned so far, append/replace the rest of str one char at
// a time, and return the result.
std::string result{begin, iter};
for (; iter != end; ++iter) {
auto ch = static_cast<unsigned char>(*iter);
if ((ch > 34 && ch != '\\') || ch == ' ' || ch == 33) {
// Check for most common case first.
result += *iter;
} else {
switch (ch) {
case '\\':
result += "\\\\";
break;
case '\"':
result += "\\\"";
break;
case '\b':
result += "\\b";
break;
case '\f':
result += "\\f";
break;
case '\n':
result += "\\n";
break;
case '\r':
result += "\\r";
break;
case '\t':
result += "\\t";
break;
default:
result += ch < 16 ? "\\u000" : "\\u001";
result += hexchars[ch % 16];
}
}
}
return result;
}
}
return result;
return str;
}
JSON