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Make format spec parsing constexpr

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This commit is contained in:
Victor Zverovich
2017-10-19 07:28:17 -07:00
parent bd5188c811
commit b83241ff4d
3 changed files with 95 additions and 25 deletions
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4
fmt/format.cc
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@ -58,9 +58,11 @@
# define FMT_CATCH(x) if (false)
#endif
#ifdef __GNUC__
// Disable the warning about declaration shadowing because it affects too
// many valid cases.
#pragma GCC diagnostic ignored "-Wshadow"
# pragma GCC diagnostic ignored "-Wshadow"
#endif
#ifdef _MSC_VER
# pragma warning(push)

37
fmt/format.h
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@ -3263,10 +3263,16 @@ template <typename Char>
struct arg_ref {
enum Kind { NONE, INDEX, NAME };
arg_ref() : kind(NONE) {}
constexpr arg_ref() : kind(NONE), index(0) {}
explicit arg_ref(unsigned index) : kind(INDEX), index(index) {}
explicit arg_ref(basic_string_view<Char> name) : kind(NAME), name(name) {}
constexpr arg_ref &operator=(unsigned index) {
kind = INDEX;
this->index = index;
return *this;
}
Kind kind;
union {
unsigned index;
@ -3361,13 +3367,14 @@ constexpr Iterator parse_arg_id(Iterator it, Handler& handler) {
// characters, possibly emulated via null_terminating_iterator, representing
// format specifiers.
template <typename Iterator, typename Handler>
Iterator parse_format_specs(Iterator it, Handler &handler) {
constexpr Iterator parse_format_specs(Iterator it, Handler &handler) {
using char_type = typename std::iterator_traits<Iterator>::value_type;
// Parse fill and alignment.
if (char_type c = *it) {
auto p = it + 1;
alignment align = ALIGN_DEFAULT;
int i = 1;
do {
auto p = it + i;
switch (*p) {
case '<':
align = ALIGN_LEFT;
@ -3395,7 +3402,7 @@ Iterator parse_format_specs(Iterator it, Handler &handler) {
} else ++it;
break;
}
} while (--p >= it);
} while (--i >= 0);
}
// Parse sign.
@ -3430,15 +3437,15 @@ Iterator parse_format_specs(Iterator it, Handler &handler) {
handler.on_width(parse_nonnegative_int(it));
} else if (*it == '{') {
struct width_handler {
explicit width_handler(Handler &h) : handler(h) {}
explicit constexpr width_handler(Handler &h) : handler(h) {}
void operator()() { handler.on_dynamic_width(auto_id()); }
void operator()(unsigned id) { handler.on_dynamic_width(id); }
void operator()(basic_string_view<char_type> id) {
constexpr void operator()() { handler.on_dynamic_width(auto_id()); }
constexpr void operator()(unsigned id) { handler.on_dynamic_width(id); }
constexpr void operator()(basic_string_view<char_type> id) {
handler.on_dynamic_width(id);
}
void on_error(const char *message) {
constexpr void on_error(const char *message) {
handler.on_error(message);
}
@ -3458,15 +3465,17 @@ Iterator parse_format_specs(Iterator it, Handler &handler) {
handler.on_precision(parse_nonnegative_int(it));
} else if (*it == '{') {
struct precision_handler {
explicit precision_handler(Handler &h) : handler(h) {}
explicit constexpr precision_handler(Handler &h) : handler(h) {}
void operator()() { handler.on_dynamic_precision(auto_id()); }
void operator()(unsigned id) { handler.on_dynamic_precision(id); }
void operator()(basic_string_view<char_type> id) {
constexpr void operator()() { handler.on_dynamic_precision(auto_id()); }
constexpr void operator()(unsigned id) {
handler.on_dynamic_precision(id);
}
constexpr void operator()(basic_string_view<char_type> id) {
handler.on_dynamic_precision(id);
}
void on_error(const char *message) {
constexpr void on_error(const char *message) {
handler.on_error(message);
}

79
test/format-test.cc
View File

@ -1582,7 +1582,7 @@ TEST(FormatTest, DynamicFormatter) {
format_error, "precision not allowed in integer format specifier");
}
struct TestHandler {
struct TestArgIDHandler {
enum Result { NONE, EMPTY, INDEX, NAME, ERROR };
Result result = NONE;
unsigned index = 0;
@ -1603,18 +1603,77 @@ struct TestHandler {
constexpr void on_error(const char *) { result = ERROR; }
};
constexpr TestHandler parse_arg_id(const char* id) {
TestHandler h;
fmt::internal::parse_arg_id(id, h);
constexpr TestArgIDHandler parse_arg_id(const char* s) {
TestArgIDHandler h;
fmt::internal::parse_arg_id(s, h);
return h;
}
TEST(FormatTest, ConstexprParseArgId) {
static_assert(parse_arg_id(":").result == TestHandler::EMPTY, "");
static_assert(parse_arg_id("}").result == TestHandler::EMPTY, "");
static_assert(parse_arg_id("42:").result == TestHandler::INDEX, "");
TEST(FormatTest, ConstexprParseArgID) {
static_assert(parse_arg_id(":").result == TestArgIDHandler::EMPTY, "");
static_assert(parse_arg_id("}").result == TestArgIDHandler::EMPTY, "");
static_assert(parse_arg_id("42:").result == TestArgIDHandler::INDEX, "");
static_assert(parse_arg_id("42:").index == 42, "");
static_assert(parse_arg_id("foo:").result == TestHandler::NAME, "");
static_assert(parse_arg_id("foo:").result == TestArgIDHandler::NAME, "");
static_assert(parse_arg_id("foo:").name.size() == 3, "");
static_assert(parse_arg_id("!").result == TestHandler::ERROR, "");
static_assert(parse_arg_id("!").result == TestArgIDHandler::ERROR, "");
}
struct TestFormatSpecsHandler {
enum Result { NONE, PLUS, MINUS, SPACE, HASH, ZERO, ERROR };
Result result = NONE;
fmt::alignment align = fmt::ALIGN_DEFAULT;
char fill = 0;
unsigned width = 0;
fmt::internal::arg_ref<char> width_ref;
unsigned precision = 0;
fmt::internal::arg_ref<char> precision_ref;
char type = 0;
constexpr void on_align(fmt::alignment align) { this->align = align; }
constexpr void on_fill(char fill) { this->fill = fill; }
constexpr void on_plus() { result = PLUS; }
constexpr void on_minus() { result = MINUS; }
constexpr void on_space() { result = SPACE; }
constexpr void on_hash() { result = HASH; }
constexpr void on_zero() { result = ZERO; }
constexpr void on_width(unsigned width) { this->width = width; }
constexpr void on_dynamic_width(fmt::internal::auto_id) {}
constexpr void on_dynamic_width(unsigned index) { width_ref = index; }
constexpr void on_dynamic_width(string_view) {}
constexpr void on_precision(unsigned precision) {
this->precision = precision;
}
constexpr void on_dynamic_precision(fmt::internal::auto_id) {}
constexpr void on_dynamic_precision(unsigned index) { precision_ref = index; }
constexpr void on_dynamic_precision(string_view) {}
constexpr void end_precision() {}
constexpr void on_type(char type) { this->type = type; }
constexpr void on_error(const char *) { result = ERROR; }
};
constexpr TestFormatSpecsHandler parse_specs(const char *s) {
TestFormatSpecsHandler h;
fmt::internal::parse_format_specs(s, h);
return h;
}
TEST(FormatTest, ConstexprParseFormatSpecs) {
static_assert(parse_specs("<").align == fmt::ALIGN_LEFT, "");
static_assert(parse_specs("*^").fill == '*', "");
static_assert(parse_specs("+").result == TestFormatSpecsHandler::PLUS, "");
static_assert(parse_specs("-").result == TestFormatSpecsHandler::MINUS, "");
static_assert(parse_specs(" ").result == TestFormatSpecsHandler::SPACE, "");
static_assert(parse_specs("#").result == TestFormatSpecsHandler::HASH, "");
static_assert(parse_specs("0").result == TestFormatSpecsHandler::ZERO, "");
static_assert(parse_specs("42").width == 42, "");
static_assert(parse_specs("{42}").width_ref.index == 42, "");
static_assert(parse_specs(".42").precision == 42, "");
static_assert(parse_specs(".{42}").precision_ref.index == 42, "");
static_assert(parse_specs("d").type == 'd', "");
static_assert(parse_specs("{<").result == TestFormatSpecsHandler::ERROR, "");
}