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Implement scan argument access
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@vitaut
vitaut committed Dec 31, 2023
1 parent 2382666 commit e33c156
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Showing 2 changed files with 84 additions and 65 deletions.
4 changes: 2 additions & 2 deletions include/fmt/core.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1622,8 +1622,8 @@ FMT_CONSTEXPR inline auto make_arg(T& val) -> basic_format_arg<Context> {
} // namespace detail
FMT_BEGIN_EXPORT

// A formatting argument. It is a trivially copyable/constructible type to
// allow storage in basic_memory_buffer.
// A formatting argument. Context is a template parameter for the compiled API
// where output can be unbuffered.
template <typename Context> class basic_format_arg {
private:
detail::value<Context> value_;
Expand Down
145 changes: 82 additions & 63 deletions test/scan.h
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Original file line number Diff line number Diff line change
Expand Up @@ -94,9 +94,7 @@ class scan_buffer {
value_ = *buf->ptr_;
}

friend scan_buffer& get_buffer(iterator it) {
return *it.buf_;
}
friend scan_buffer& get_buffer(iterator it) { return *it.buf_; }

public:
iterator() : ptr_(sentinel()), buf_(nullptr) {}
Expand Down Expand Up @@ -298,21 +296,6 @@ class scan_parse_context {
}
};

struct scan_context {
private:
detail::scan_buffer& buf_;

public:
using iterator = detail::scan_buffer::iterator;

explicit FMT_CONSTEXPR scan_context(detail::scan_buffer& buf) : buf_(buf) {}

auto begin() const -> iterator { return buf_.begin(); }
auto end() const -> iterator { return buf_.end(); }

void advance_to(iterator) { buf_.consume(); }
};

namespace detail {
enum class scan_type {
none_type,
Expand All @@ -325,13 +308,21 @@ enum class scan_type {
custom_type
};

template <typename Context>
struct custom_scan_arg {
void* value;
void (*scan)(void* arg, scan_parse_context& parse_ctx, scan_context& ctx);
void (*scan)(void* arg, scan_parse_context& parse_ctx, Context& ctx);
};
} // namespace detail

// A scan argument. Context is a template parameter for the compiled API where
// output can be unbuffered.
template <typename Context> class basic_scan_arg {
private:
using scan_type = detail::scan_type;

class scan_arg {
public:
// TODO: make private
scan_type type;
union {
int* int_value;
Expand All @@ -340,29 +331,34 @@ class scan_arg {
unsigned long long* ulong_long_value;
std::string* string;
fmt::string_view* string_view;
custom_scan_arg custom;
detail::custom_scan_arg<Context> custom;
// TODO: more types
};

FMT_CONSTEXPR scan_arg() : type(scan_type::none_type), int_value(nullptr) {}
FMT_CONSTEXPR scan_arg(int& value)
FMT_CONSTEXPR basic_scan_arg()
: type(scan_type::none_type), int_value(nullptr) {}
FMT_CONSTEXPR basic_scan_arg(int& value)
: type(scan_type::int_type), int_value(&value) {}
FMT_CONSTEXPR scan_arg(unsigned& value)
FMT_CONSTEXPR basic_scan_arg(unsigned& value)
: type(scan_type::uint_type), uint_value(&value) {}
FMT_CONSTEXPR scan_arg(long long& value)
FMT_CONSTEXPR basic_scan_arg(long long& value)
: type(scan_type::long_long_type), long_long_value(&value) {}
FMT_CONSTEXPR scan_arg(unsigned long long& value)
FMT_CONSTEXPR basic_scan_arg(unsigned long long& value)
: type(scan_type::ulong_long_type), ulong_long_value(&value) {}
FMT_CONSTEXPR scan_arg(std::string& value)
FMT_CONSTEXPR basic_scan_arg(std::string& value)
: type(scan_type::string_type), string(&value) {}
FMT_CONSTEXPR scan_arg(fmt::string_view& value)
FMT_CONSTEXPR basic_scan_arg(fmt::string_view& value)
: type(scan_type::string_view_type), string_view(&value) {}
template <typename T>
FMT_CONSTEXPR scan_arg(T& value) : type(scan_type::custom_type) {
FMT_CONSTEXPR basic_scan_arg(T& value) : type(scan_type::custom_type) {
custom.value = &value;
custom.scan = scan_custom_arg<T>;
}

constexpr explicit operator bool() const noexcept {
return type != scan_type::none_type;
}

template <typename Visitor>
auto visit(Visitor&& vis) -> decltype(vis(std::declval<int>())) {
switch (type) {
Expand Down Expand Up @@ -390,37 +386,60 @@ class scan_arg {
private:
template <typename T>
static void scan_custom_arg(void* arg, scan_parse_context& parse_ctx,
scan_context& ctx) {
Context& ctx) {
auto s = scanner<T>();
parse_ctx.advance_to(s.parse(parse_ctx));
ctx.advance_to(s.scan(*static_cast<T*>(arg), ctx));
}
};
} // namespace detail

class scan_context;
using scan_arg = basic_scan_arg<scan_context>;

struct scan_args {
int size;
const detail::scan_arg* data;
const scan_arg* data;

template <size_t N>
FMT_CONSTEXPR scan_args(const std::array<detail::scan_arg, N>& store)
FMT_CONSTEXPR scan_args(const std::array<scan_arg, N>& store)
: size(N), data(store.data()) {
static_assert(N < INT_MAX, "too many arguments");
}
};

class scan_context {
private:
detail::scan_buffer& buf_;
scan_args args_;

public:
using iterator = detail::scan_buffer::iterator;

explicit FMT_CONSTEXPR scan_context(detail::scan_buffer& buf, scan_args args)
: buf_(buf), args_(args) {}

FMT_CONSTEXPR auto arg(int id) const -> scan_arg {
return id < args_.size ? args_.data[id] : scan_arg();
}

auto begin() const -> iterator { return buf_.begin(); }
auto end() const -> iterator { return buf_.end(); }

void advance_to(iterator) { buf_.consume(); }
};

namespace detail {

const char* parse_scan_specs(
const char* begin, const char* end, format_specs<>& specs, scan_type) {
const char* parse_scan_specs(const char* begin, const char* end,
format_specs<>& specs, scan_type) {
while (begin != end) {
switch (to_ascii(*begin)) {
// TODO: parse scan format specifiers
case 'x':
specs.type = presentation_type::hex_lower;
break;
case '}':
return begin;
// TODO: parse scan format specifiers
case 'x':
specs.type = presentation_type::hex_lower;
break;
case '}':
return begin;
}
}
return begin;
Expand All @@ -433,8 +452,9 @@ struct arg_scanner {
iterator end;
const format_specs<>& specs;

template <typename T>
template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
auto operator()(T) -> iterator {
// TODO
return begin;
}
};
Expand All @@ -443,9 +463,7 @@ struct scan_handler : error_handler {
private:
scan_parse_context parse_ctx_;
scan_context scan_ctx_;
scan_args args_;
int next_arg_id_;
scan_arg arg_;

using iterator = scan_buffer::iterator;

Expand Down Expand Up @@ -492,7 +510,7 @@ struct scan_handler : error_handler {
public:
FMT_CONSTEXPR scan_handler(string_view format, scan_buffer& buf,
scan_args args)
: parse_ctx_(format), scan_ctx_(buf), args_(args), next_arg_id_(0) {}
: parse_ctx_(format), scan_ctx_(buf, args), next_arg_id_(0) {}

auto pos() const -> scan_buffer::iterator { return scan_ctx_.begin(); }

Expand All @@ -507,34 +525,34 @@ struct scan_handler : error_handler {

FMT_CONSTEXPR auto on_arg_id() -> int { return on_arg_id(next_arg_id_++); }
FMT_CONSTEXPR auto on_arg_id(int id) -> int {
if (id >= args_.size) on_error("argument index out of range");
arg_ = args_.data[id];
if (!scan_ctx_.arg(id)) on_error("argument index out of range");
return id;
}
FMT_CONSTEXPR auto on_arg_id(string_view id) -> int {
if (id.data()) on_error("invalid format");
return 0;
}

void on_replacement_field(int, const char*) {
void on_replacement_field(int arg_id, const char*) {
scan_arg arg = scan_ctx_.arg(arg_id);
auto it = scan_ctx_.begin(), end = scan_ctx_.end();
while (it != end && is_whitespace(*it)) ++it;
switch (arg_.type) {
switch (arg.type) {
case scan_type::int_type:
if (auto value = read_int(it)) *arg_.int_value = *value;
if (auto value = read_int(it)) *arg.int_value = *value;
break;
case scan_type::uint_type:
if (auto value = read_uint(it)) *arg_.uint_value = *value;
if (auto value = read_uint(it)) *arg.uint_value = *value;
break;
case scan_type::long_long_type:
if (auto value = read_int<long long>(it)) *arg_.long_long_value = *value;
if (auto value = read_int<long long>(it)) *arg.long_long_value = *value;
break;
case scan_type::ulong_long_type:
if (auto value = read_uint<unsigned long long>(it))
*arg_.ulong_long_value = *value;
*arg.ulong_long_value = *value;
break;
case scan_type::string_type:
while (it != end && *it != ' ') arg_.string->push_back(*it++);
while (it != end && *it != ' ') arg.string->push_back(*it++);
break;
case scan_type::string_view_type: {
auto range = to_contiguous(it);
Expand All @@ -543,7 +561,7 @@ struct scan_handler : error_handler {
auto p = range.begin;
while (p != range.end && *p != ' ') ++p;
size_t size = to_unsigned(p - range.begin);
*arg_.string_view = {range.begin, size};
*arg.string_view = {range.begin, size};
advance(it, size);
break;
}
Expand All @@ -554,20 +572,21 @@ struct scan_handler : error_handler {
scan_ctx_.advance_to(it);
}

auto on_format_specs(int, const char* begin, const char* end) -> const char* {
if (arg_.type == scan_type::custom_type) {
auto on_format_specs(int arg_id, const char* begin, const char* end) -> const
char* {
scan_arg arg = scan_ctx_.arg(arg_id);
if (arg.type == scan_type::custom_type) {
parse_ctx_.advance_to(begin);
arg_.custom.scan(arg_.custom.value, parse_ctx_, scan_ctx_);
arg.custom.scan(arg.custom.value, parse_ctx_, scan_ctx_);
return parse_ctx_.begin();
}
auto specs = format_specs<>();
begin = parse_scan_specs(begin, end, specs, arg_.type);
if (begin == end || *begin != '}')
on_error("missing '}' in format string");
begin = parse_scan_specs(begin, end, specs, arg.type);
if (begin == end || *begin != '}') on_error("missing '}' in format string");
auto s = arg_scanner{scan_ctx_.begin(), scan_ctx_.end(), specs};
// TODO: scan argument according to specs
(void)s;
//context.advance_to(visit_format_arg(s, arg));
// context.advance_to(visit_format_arg(s, arg));
return begin;
}

Expand All @@ -579,7 +598,7 @@ struct scan_handler : error_handler {
} // namespace detail

template <typename... T>
auto make_scan_args(T&... args) -> std::array<detail::scan_arg, sizeof...(T)> {
auto make_scan_args(T&... args) -> std::array<scan_arg, sizeof...(T)> {
return {{args...}};
}

Expand Down

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