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Add user-defined type support to compilation

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This commit is contained in:
Victor Zverovich 2020-06-23 12:05:37 -07:00
parent 8bef1c3b3a
commit 1a83443e6c
2 changed files with 44 additions and 1 deletions
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37
include/fmt/compile.h
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@ -408,6 +408,23 @@ template <typename Char, typename T, int N> struct field {
template <typename Char, typename T, int N>
struct is_compiled_format<field<Char, T, N>> : std::true_type {};
// A replacement field that refers to argument N and has format specifiers.
template <typename Char, typename T, int N> struct spec_field {
using char_type = Char;
mutable formatter<T, Char> fmt;
template <typename OutputIt, typename... Args>
OutputIt format(OutputIt out, const Args&... args) const {
// This ensures that the argument type is convertile to `const T&`.
const T& arg = get<N>(args...);
basic_format_context<OutputIt, Char> ctx(out, {});
return fmt.format(arg, ctx);
}
};
template <typename Char, typename T, int N>
struct is_compiled_format<spec_field<Char, T, N>> : std::true_type {};
template <typename L, typename R> struct concat {
L lhs;
R rhs;
@ -456,6 +473,21 @@ constexpr auto parse_tail(T head, S format_str) {
}
}
template <typename T, typename Char> struct parse_specs_result {
formatter<T, Char> fmt;
size_t end;
};
template <typename T, typename Char>
constexpr parse_specs_result<T, Char> parse_specs(basic_string_view<Char> str,
size_t pos) {
str.remove_prefix(pos);
auto ctx = basic_format_parse_context<Char>(str);
auto f = formatter<T, Char>();
auto end = f.parse(ctx);
return {f, pos + (end - str.data()) + 1};
}
// Compiles a non-empty format string and returns the compiled representation
// or unknown_format() on unrecognized input.
template <typename Args, size_t POS, int ID, typename S>
@ -471,6 +503,11 @@ constexpr auto compile_format_string(S format_str) {
using type = get_type<ID, Args>;
return parse_tail<Args, POS + 2, ID + 1>(field<char_type, type, ID>(),
format_str);
} else if constexpr (str[POS + 1] == ':') {
using type = get_type<ID, Args>;
constexpr auto result = parse_specs<type>(str, POS + 2);
return parse_tail<Args, result.end, ID + 1>(
spec_field<char_type, type, ID>{result.fmt}, format_str);
} else {
return unknown_format();
}

8
test/compile-test.cc
View File

@ -127,7 +127,8 @@ struct formattable {};
FMT_BEGIN_NAMESPACE
template <> struct formatter<formattable> : formatter<const char*> {
auto format(formattable, format_context& ctx) -> decltype(ctx.out()) {
template <typename FormatContext>
auto format(formattable, FormatContext& ctx) -> decltype(ctx.out()) {
return formatter<const char*>::format("foo", ctx);
}
};
@ -154,6 +155,11 @@ TEST(CompileTest, FormatDefault) {
EXPECT_EQ("4.2", fmt::format(FMT_COMPILE("{}"), 4.2));
EXPECT_EQ("foo", fmt::format(FMT_COMPILE("{}"), "foo"));
EXPECT_EQ("foo", fmt::format(FMT_COMPILE("{}"), std::string("foo")));
EXPECT_EQ("foo", fmt::format(FMT_COMPILE("{}"), formattable()));
}
TEST(CompileTest, FormatSpecs) {
EXPECT_EQ("42", fmt::format(FMT_COMPILE("{:x}"), 0x42));
}
TEST(CompileTest, FormatTo) {