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ircd::json: Use switch statement over enumeration in character_dfa. (related 24d73428c8)

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This commit is contained in:
Jason Volk 2020-05-23 07:34:35 -07:00
parent 24d73428c8
commit 4ca481a5fc
1 changed files with 66 additions and 64 deletions
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102
ircd/json.cc
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@ -277,7 +277,7 @@ ircd::json::printer
// string
struct string_state;
union character_state;
struct character_state;
using character_prototype = char(const string_view &, string_state &);
template<class context> static void character_dfa(char &, context &, bool &) noexcept;
const rule<character_prototype, locals<character_state>> character
@ -363,19 +363,21 @@ struct ircd::json::printer::string_state
bool escaped {0};
};
union ircd::json::printer::character_state
struct ircd::json::printer::character_state
{
static const char ctrl_tab[0x20][8];
uint64_t mode {0}; struct
enum mode
{
bool leave;
bool ctrl;
bool quote;
bool escape;
bool escaped;
uint8_t pos;
};
PASS,
LEAVE,
CTRL,
QUOTE,
ESCAPE,
ESCAPED,
}
mode {PASS};
uint8_t pos {0};
};
decltype(ircd::json::printer::character_state::ctrl_tab)
@ -406,72 +408,72 @@ ircd::json::printer::character_dfa(char &out,
bool &ret)
noexcept
{
__label__ Lpass, Lleave, Lctrl, Lquote, Lescape, Lescaped;
using mode = decltype(character_state::mode);
#if __has_builtin(__builtin_assume)
__builtin_assume(ret == true);
#endif
const string_view &str(attr_at<1>(g)); // Whole input string.
const char &in(attr_at<0>(g)); // Current character in input.
const uint8_t &in(attr_at<0>(g)); // Current character in input.
string_state &sst(attr_at<2>(g)); // Whole input string state.
auto &st(local_at<0>(g)); // Current character state.
st.ctrl |= !st.mode & (in < 0x20);
st.quote |= !st.mode & (in == '"');
st.escape |= !st.mode & (in == '\\');
goto *
(
st.leave? &&Lleave:
sst.escaped? &&Lescaped:
st.ctrl? &&Lctrl:
st.quote? &&Lquote:
st.escape? &&Lescape:
&&Lpass
);
Lpass:
out = in;
st.leave = true;
return;
st.mode =
st.mode != mode::PASS? st.mode:
sst.escaped? mode::ESCAPED:
in < 0x20U? mode::CTRL:
in == '"'? mode::QUOTE:
in == '\\'? mode::ESCAPE:
mode::PASS;
switch(st.mode)
{
[[likely]]
case mode::PASS:
st.mode = mode::LEAVE;
break; // mode::PASS
Lleave:
//assert(st.leave);
[[likely]]
case mode::LEAVE:
ret = false;
sst.pos++;
return;
assert(sst.pos <= str.size());
break; // mode::LEAVE
Lctrl:
out = st.ctrl_tab[uint8_t(in)][st.pos++];
case mode::CTRL:
out = st.ctrl_tab[in][st.pos++];
ret &= out != '\0'; // break loop at this iteration
sst.pos += !ret;
return;
assert(st.pos <= 8);
break; // mode::CTRL
Lquote:
case mode::QUOTE:
out = "\\\""_sv[st.pos++];
ret &= out != '\0'; // break loop at this iteration
sst.pos += !ret;
return;
assert(st.pos <= 8);
break; // mode::QUOTE
Lescape:
out = in;
case mode::ESCAPE:
st.mode = sst.pos + 1 < str.size()?
mode::LEAVE:
mode::PASS; // must spin if last char of string is esc
sst.escaped = true;
st.leave = sst.pos + 1 < str.size(); // must spin if last char of string is esc
return;
assert(sst.pos < str.size());
break; // mode::ESCAPE
Lescaped:
case mode::ESCAPED:
{
const auto ok
{
in == 'u' | in == '"' | in == '\\'
};
out = ok? in : '\\';
st.leave = ok;
const bool ok(in == 'u' | in == '"' | in == '\\');
sst.escaped = false;
return;
out = ok? out: '\\';
st.mode = ok?
mode::LEAVE:
mode::PASS;
break; // mode::ESCAPED
}
}
}