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mu-sexp: improve corner-cases, performance

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Some C++20 updates; use the new ascii/ctype functions. Avoid unlimited
recursion. Speed-up conversion to_string

Update unit-tests.
This commit is contained in:
Dirk-Jan C. Binnema
2026-07-21 16:54:52 +03:00
committed by Seth Ladygo
parent dfdd943817
commit da2995a768
2 changed files with 163 additions and 124 deletions
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227
lib/utils/mu-sexp.cc
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@ -21,47 +21,45 @@
#include "mu-sexp.hh"
#include "mu-utils.hh"
#include <atomic>
#include <sstream>
#include <array>
#include <charconv>
using namespace Mu;
/* avoid unbounded recursion (i.e., stack overflow) for pathological input */
constexpr size_t MaxDepth{1024};
template<typename...T> static Mu::Error
parsing_error(size_t pos, fmt::format_string<T...> frm, T&&... args)
{
const auto&& msg{fmt::format(frm, std::forward<T>(args)...)};
if (pos == 0)
return Mu::Error(Error::Code::Parsing, "{}", msg);
else
return Mu::Error(Error::Code::Parsing, "{}: {}", pos, msg);
return Mu::Error(Error::Code::Parsing, "{}: {}", pos, msg);
}
static size_t
skip_whitespace(const std::string& s, size_t pos)
{
while (pos != s.size()) {
if (s[pos] == ' ' || s[pos] == '\t' || s[pos] == '\n')
++pos;
else
break;
}
while (pos != s.size() && is_ascii_space(s[pos]))
++pos;
return pos;
}
static Result<Sexp> parse(const std::string& expr, size_t& pos);
static Result<Sexp> parse(const std::string& expr, size_t& pos, size_t depth);
static Result<Sexp>
parse_list(const std::string& expr, size_t& pos)
parse_list(const std::string& expr, size_t& pos, size_t depth)
{
if (expr[pos] != '(') // sanity check.
return Err(parsing_error(pos, "expected: '(' but got '{}", expr[pos]));
return Err(parsing_error(pos, "expected: '(' but got '{}'", expr[pos]));
if (depth >= MaxDepth)
return Err(parsing_error(pos, "parentheses nested too deeply"));
Sexp lst{};
++pos;
while (pos < expr.size() && expr[pos] != ')') {
if (auto&& item = parse(expr, pos); item)
if (auto&& item = parse(expr, pos, depth + 1); item)
lst.add(std::move(*item));
else
return Err(item.error());
@ -80,27 +78,30 @@ static Result<Sexp>
parse_string(const std::string& expr, size_t& pos)
{
if (expr[pos] != '"') // sanity check.
return Err(parsing_error(pos, "expected: '\"'' but got '{}", expr[pos]));
return Err(parsing_error(pos, "expected: '\"' but got '{}'", expr[pos]));
bool escape{};
std::string str;
for (++pos; pos != expr.size(); ++pos) {
auto kar = expr[pos];
if (escape && (kar == '"' || kar == '\\')) {
str += kar;
if (escape) {
// follow the elisp reader: '\n', '\t' are special,
// any other escaped character stands for itself.
switch (kar) {
case 'n': str += '\n'; break;
case 't': str += '\t'; break;
default: str += kar; break;
}
escape = false;
continue;
}
if (kar == '"')
break;
else if (kar == '\\')
} else if (kar == '\\')
escape = true;
else if (kar == '"')
break;
else
str += kar;
}
if (escape || expr[pos] != '"')
if (escape || pos == expr.size())
return Err(parsing_error(pos, "unterminated string '{}'", str));
++pos;
@ -111,54 +112,57 @@ parse_string(const std::string& expr, size_t& pos)
static Result<Sexp>
parse_integer(const std::string& expr, size_t& pos)
{
if (!isdigit(expr[pos]) && expr[pos] != '-') // sanity check.
return Err(parsing_error(pos, "expected: <digit> but got '{}", expr[pos]));
if (!is_ascii_digit(expr[pos]) && expr[pos] != '-') // sanity check.
return Err(parsing_error(pos, "expected: <digit> but got '{}'", expr[pos]));
std::string num; // negative number?
if (expr[pos] == '-') {
num = "-";
++pos;
}
auto end{pos + (expr[pos] == '-' ? 1U : 0U)};
while (end != expr.size() && is_ascii_digit(expr[end]))
++end;
for (; isdigit(expr[pos]); ++pos)
num += expr[pos];
Sexp::Number num{};
const auto res{std::from_chars(expr.data() + pos, expr.data() + end, num)};
if (res.ec != std::errc{} || res.ptr != expr.data() + end)
return Err(parsing_error(pos, "invalid number '{}'",
expr.substr(pos, end - pos)));
return Ok(Sexp{::atoi(num.c_str())});
pos = end;
return Ok(Sexp{num});
}
static Result<Sexp>
parse_symbol(const std::string& expr, size_t& pos)
{
if (!isalpha(expr[pos]) && expr[pos] != ':') // sanity check.
return Err(parsing_error(pos, "expected: <alpha>|: but got '{}", expr[pos]));
if (!is_ascii_alpha(expr[pos]) && expr[pos] != ':') // sanity check.
return Err(parsing_error(pos, "expected: <alpha>|: but got '{}'", expr[pos]));
std::string symb(1, expr[pos]);
for (++pos; isalnum(expr[pos]) || expr[pos] == '-'; ++pos)
symb += expr[pos];
const auto start{pos};
for (++pos; pos != expr.size() &&
(is_ascii_alnum(expr[pos]) || expr[pos] == '-'); ++pos)
;
return Ok(Sexp{Sexp::Symbol{symb}});
return Ok(Sexp{Sexp::Symbol{expr.substr(start, pos - start)}});
}
static Result<Sexp>
parse(const std::string& expr, size_t& pos)
parse(const std::string& expr, size_t& pos, size_t depth)
{
pos = skip_whitespace(expr, pos);
if (pos == expr.size())
return Err(parsing_error(pos, "expected: character '{}", expr[pos]));
return Err(parsing_error(pos, "unexpected end of input"));
const auto kar = expr[pos];
const auto sexp = std::invoke([&]() -> Result<Sexp> {
if (kar == '(')
return parse_list(expr, pos);
return parse_list(expr, pos, depth);
else if (kar == '"')
return parse_string(expr, pos);
else if (isdigit(kar) || kar == '-')
else if (is_ascii_digit(kar) || kar == '-')
return parse_integer(expr, pos);
else if (isalpha(kar) || kar == ':')
else if (is_ascii_alpha(kar) || kar == ':')
return parse_symbol(expr, pos);
else
return Err(parsing_error(pos, "unexpected character '{}", kar));
return Err(parsing_error(pos, "unexpected character '{}'", kar));
});
if (sexp)
@ -171,7 +175,7 @@ Result<Sexp>
Sexp::parse(const std::string& expr)
{
size_t pos{};
auto res = ::parse(expr, pos);
auto res = ::parse(expr, pos, 0/*depth*/);
if (!res)
return res;
else if (pos != expr.size())
@ -183,31 +187,39 @@ Sexp::parse(const std::string& expr)
std::string
Sexp::to_string(Format fopts) const
{
std::stringstream sstrm;
const auto splitp{any_of(fopts & Format::SplitList)};
const auto typeinfop{any_of(fopts & Format::TypeInfo)};
std::string str;
to_string_into(str, fopts);
return str;
}
void
Sexp::to_string_into(std::string& out, Format fopts) const
{
if (listp()) {
sstrm << '(';
out += '(';
bool first{true};
for(auto&& elm: list()) {
sstrm << (first ? "" : " ") << elm.to_string(fopts);
if (!first)
out += ' ';
elm.to_string_into(out, fopts);
first = false;
}
sstrm << ')';
if (splitp)
sstrm << '\n';
out += ')';
if (any_of(fopts & Format::SplitList))
out += '\n';
} else if (stringp())
sstrm << quote(string());
out += quote(string());
else if (numberp())
sstrm << number();
out += std::to_string(number());
else if (symbolp())
sstrm << symbol().name;
out += symbol().name;
if (typeinfop)
sstrm << '<' << Sexp::type_name(type()) << '>';
return sstrm.str();
if (any_of(fopts & Format::TypeInfo)) {
out += '<';
out += Sexp::type_name(type());
out += '>';
}
}
// LCOV_EXCL_START
@ -226,8 +238,15 @@ unix_tstamp(const Sexp& emacs_tstamp)
std::string
Sexp::to_json_string(Format fopts) const
{
std::stringstream sstrm;
std::string str;
to_json_string_into(str, fopts);
return str;
}
void
Sexp::to_json_string_into(std::string& out, Format fopts) const
{
const auto sym_name=[&](const std::string& sym) {
if (any_of(fopts & Format::NoColon) && sym[0] == ':')
return sym.substr(1); // remove colon
@ -239,60 +258,64 @@ Sexp::to_json_string(Format fopts) const
case Type::List: {
// property-lists become JSON objects
if (plistp()) {
sstrm << "{";
out += '{';
auto it{list().begin()};
bool first{true};
while (it != list().end()) {
const auto key{it->symbol().name};
sstrm << (first ? "" : ",")
<< quote(sym_name(key)) << ":";
if (!first)
out += ',';
out += quote(sym_name(key));
out += ':';
++it;
const auto emacs_tstamp{*it};
sstrm << emacs_tstamp.to_json_string(fopts);
const auto& propval{*it};
propval.to_json_string_into(out, fopts);
++it;
first = false;
// special-case: tstamp-fields also get a "unix" value,
// which are easier to work with than the "emacs" timestamps
if (key == ":date" || key == ":changed")
sstrm << "," << quote(sym_name(key) + "-unix")
<< ":"
<< unix_tstamp(emacs_tstamp);
if (key == ":date" || key == ":changed") {
out += ',';
out += quote(sym_name(key) + "-unix");
out += ':';
out += std::to_string(unix_tstamp(propval));
}
}
sstrm << "}";
out += '}';
if (any_of(fopts & Format::SplitList))
sstrm << '\n';
out += '\n';
} else { // other lists become arrays.
sstrm << '[';
out += '[';
bool first{true};
for (auto&& child : list()) {
sstrm << (first ? "" : ", ") << child.to_json_string(fopts);
if (!first)
out += ", ";
child.to_json_string_into(out, fopts);
first = false;
}
sstrm << ']';
out += ']';
if (any_of(fopts & Format::SplitList))
sstrm << '\n';
out += '\n';
}
break;
}
case Type::String:
sstrm << quote(string());
out += quote(string());
break;
case Type::Symbol:
if (nilp())
sstrm << "false";
out += "false";
else if (symbol() == "t")
sstrm << "true";
out += "true";
else
sstrm << quote(symbol().name);
out += quote(symbol().name);
break;
case Type::Number:
sstrm << number();
out += std::to_string(number());
break;
default:
break;
}
return sstrm.str();
}
@ -511,6 +534,21 @@ test_parser()
check_parse(R"("foo
bar")",
"\"foo\nbar\"");
// escapes: '\n'/'\t' are special; \\ and unknown escapes
// stand for the escaped character itself
check_parse(R"("hello\nworld")", "\"hello\nworld\"");
check_parse(R"("tab\there")", "\"tab\there\"");
check_parse(R"("back\\slash")", "\"back\\\\slash\"");
check_parse(R"("what\qever")", "\"whatqever\"");
// full int64 range
check_parse("4294967296", "4294967296");
check_parse("9223372036854775807", "9223372036854775807");
check_parse("-9223372036854775808", "-9223372036854775808");
// \r\n is whitespace, too
check_parse("(foo\r\nbar)", "(foo bar)");
}
static void
@ -522,6 +560,19 @@ test_parser_fail()
g_assert_false(!!Sexp::parse(")"));
g_assert_false(!!Sexp::parse("(hello (boo))))"));
// numbers that don't fit an int64, or aren't numbers at all
g_assert_false(!!Sexp::parse("99999999999999999999"));
g_assert_false(!!Sexp::parse("-"));
// trailing backslash
g_assert_false(!!Sexp::parse(R"("foo\)"));
// deeply-nested input gives an error, not a stack overflow
std::string deep(100000, '(');
deep += "a";
deep.append(100000, ')');
g_assert_false(!!Sexp::parse(deep));
g_assert_true(Sexp::type_name(static_cast<Sexp::Type>(-1)) == "<error>");
}