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665 lines
18 KiB
C++
665 lines
18 KiB
C++
// Formatting library for C++ - scanning API proof of concept
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//
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// Copyright (c) 2019 - present, Victor Zverovich
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// All rights reserved.
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//
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// For the license information refer to format.h.
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#include <array>
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#include <cassert>
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#include <climits>
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#include <tuple>
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#include "fmt/format-inl.h"
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FMT_BEGIN_NAMESPACE
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namespace detail {
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inline auto is_whitespace(char c) -> bool { return c == ' ' || c == '\n'; }
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// If c is a hex digit returns its numeric value, otherwise -1.
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inline auto to_hex_digit(char c) -> int {
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if (c >= '0' && c <= '9') return c - '0';
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if (c >= 'a' && c <= 'f') return c - 'a' + 10;
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if (c >= 'A' && c <= 'F') return c - 'A' + 10;
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return -1;
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}
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struct maybe_contiguous_range {
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const char* begin;
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const char* end;
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explicit operator bool() const { return begin != nullptr; }
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};
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class scan_buffer {
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private:
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const char* ptr_;
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const char* end_;
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bool contiguous_;
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protected:
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scan_buffer(const char* ptr, const char* end, bool contiguous)
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: ptr_(ptr), end_(end), contiguous_(contiguous) {}
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~scan_buffer() = default;
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void set(span<const char> buf) {
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ptr_ = buf.data;
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end_ = buf.data + buf.size;
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}
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auto ptr() const -> const char* { return ptr_; }
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public:
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scan_buffer(const scan_buffer&) = delete;
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void operator=(const scan_buffer&) = delete;
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// Fills the buffer with more input if available.
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virtual void consume() = 0;
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class sentinel {};
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class iterator {
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private:
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const char** ptr_;
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scan_buffer* buf_; // This could be merged with ptr_.
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char value_;
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static auto get_sentinel() -> const char** {
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static const char* ptr = nullptr;
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return &ptr;
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}
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friend class scan_buffer;
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friend auto operator==(iterator lhs, sentinel) -> bool {
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return *lhs.ptr_ == nullptr;
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}
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friend auto operator!=(iterator lhs, sentinel) -> bool {
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return *lhs.ptr_ != nullptr;
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}
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iterator(scan_buffer* buf) : buf_(buf) {
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if (buf->ptr_ == buf->end_) {
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ptr_ = get_sentinel();
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return;
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}
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ptr_ = &buf->ptr_;
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value_ = *buf->ptr_;
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}
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friend scan_buffer& get_buffer(iterator it) { return *it.buf_; }
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public:
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iterator() : ptr_(get_sentinel()), buf_(nullptr) {}
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auto operator++() -> iterator& {
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if (!buf_->try_consume()) ptr_ = get_sentinel();
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value_ = *buf_->ptr_;
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return *this;
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}
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auto operator++(int) -> iterator {
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iterator copy = *this;
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++*this;
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return copy;
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}
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auto operator*() const -> char { return value_; }
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auto base() const -> const char* { return buf_->ptr_; }
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friend auto to_contiguous(iterator it) -> maybe_contiguous_range;
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friend auto advance(iterator it, size_t n) -> iterator;
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};
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friend auto to_contiguous(iterator it) -> maybe_contiguous_range {
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if (it.buf_->is_contiguous()) return {it.buf_->ptr_, it.buf_->end_};
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return {nullptr, nullptr};
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}
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friend auto advance(iterator it, size_t n) -> iterator {
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FMT_ASSERT(it.buf_->is_contiguous(), "");
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const char*& ptr = it.buf_->ptr_;
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ptr += n;
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it.value_ = *ptr;
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if (ptr == it.buf_->end_) it.ptr_ = iterator::get_sentinel();
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return it;
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}
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auto begin() -> iterator { return this; }
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auto end() -> sentinel { return {}; }
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auto is_contiguous() const -> bool { return contiguous_; }
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// Tries consuming a single code unit. Returns true iff there is more input.
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auto try_consume() -> bool {
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FMT_ASSERT(ptr_ != end_, "");
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++ptr_;
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if (ptr_ != end_) return true;
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consume();
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return ptr_ != end_;
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}
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};
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using scan_iterator = scan_buffer::iterator;
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using scan_sentinel = scan_buffer::sentinel;
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class string_scan_buffer final : public scan_buffer {
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private:
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void consume() override {}
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public:
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explicit string_scan_buffer(string_view s)
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: scan_buffer(s.begin(), s.end(), true) {}
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};
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class file_scan_buffer final : public scan_buffer {
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private:
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template <typename F, FMT_ENABLE_IF(sizeof(F::_IO_read_ptr) != 0)>
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static auto get_file(F* f, int) -> glibc_file<F> {
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return f;
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}
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template <typename F, FMT_ENABLE_IF(sizeof(F::_p) != 0)>
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static auto get_file(F* f, int) -> apple_file<F> {
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return f;
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}
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static auto get_file(FILE* f, ...) -> fallback_file<FILE> { return f; }
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decltype(get_file(static_cast<FILE*>(nullptr), 0)) file_;
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// Fills the buffer if it is empty.
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void fill() {
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span<const char> buf = file_.get_read_buffer();
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if (buf.size == 0) {
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int c = file_.get();
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// Put the character back since we are only filling the buffer.
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if (c != EOF) file_.unget(static_cast<char>(c));
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buf = file_.get_read_buffer();
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}
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set(buf);
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}
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void consume() override {
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// Consume the current buffer content.
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size_t n = to_unsigned(ptr() - file_.get_read_buffer().data);
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for (size_t i = 0; i != n; ++i) file_.get();
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fill();
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}
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public:
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explicit file_scan_buffer(FILE* f)
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: scan_buffer(nullptr, nullptr, false), file_(f) {
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flockfile(f);
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fill();
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}
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~file_scan_buffer() { funlockfile(file_); }
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};
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} // namespace detail
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template <typename T, typename Char = char> struct scanner {
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// A deleted default constructor indicates a disabled scanner.
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scanner() = delete;
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};
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class scan_parse_context {
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private:
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string_view format_;
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public:
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using iterator = string_view::iterator;
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explicit FMT_CONSTEXPR scan_parse_context(string_view format)
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: format_(format) {}
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FMT_CONSTEXPR auto begin() const -> iterator { return format_.begin(); }
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FMT_CONSTEXPR auto end() const -> iterator { return format_.end(); }
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void advance_to(iterator it) {
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format_.remove_prefix(detail::to_unsigned(it - begin()));
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}
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};
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namespace detail {
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enum class scan_type {
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none_type,
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int_type,
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uint_type,
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long_long_type,
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ulong_long_type,
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string_type,
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string_view_type,
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custom_type
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};
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template <typename Context> struct custom_scan_arg {
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void* value;
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void (*scan)(void* arg, scan_parse_context& parse_ctx, Context& ctx);
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};
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} // namespace detail
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// A scan argument. Context is a template parameter for the compiled API where
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// output can be unbuffered.
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template <typename Context> class basic_scan_arg {
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private:
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using scan_type = detail::scan_type;
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scan_type type_;
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union {
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int* int_value_;
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unsigned* uint_value_;
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long long* long_long_value_;
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unsigned long long* ulong_long_value_;
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std::string* string_;
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string_view* string_view_;
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detail::custom_scan_arg<Context> custom_;
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// TODO: more types
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};
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template <typename T>
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static void scan_custom_arg(void* arg, scan_parse_context& parse_ctx,
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Context& ctx) {
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auto s = scanner<T>();
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parse_ctx.advance_to(s.parse(parse_ctx));
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ctx.advance_to(s.scan(*static_cast<T*>(arg), ctx));
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}
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public:
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FMT_CONSTEXPR basic_scan_arg()
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: type_(scan_type::none_type), int_value_(nullptr) {}
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FMT_CONSTEXPR basic_scan_arg(int& value)
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: type_(scan_type::int_type), int_value_(&value) {}
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FMT_CONSTEXPR basic_scan_arg(unsigned& value)
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: type_(scan_type::uint_type), uint_value_(&value) {}
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FMT_CONSTEXPR basic_scan_arg(long long& value)
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: type_(scan_type::long_long_type), long_long_value_(&value) {}
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FMT_CONSTEXPR basic_scan_arg(unsigned long long& value)
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: type_(scan_type::ulong_long_type), ulong_long_value_(&value) {}
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FMT_CONSTEXPR basic_scan_arg(std::string& value)
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: type_(scan_type::string_type), string_(&value) {}
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FMT_CONSTEXPR basic_scan_arg(string_view& value)
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: type_(scan_type::string_view_type), string_view_(&value) {}
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template <typename T>
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FMT_CONSTEXPR basic_scan_arg(T& value) : type_(scan_type::custom_type) {
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custom_.value = &value;
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custom_.scan = scan_custom_arg<T>;
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}
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constexpr explicit operator bool() const noexcept {
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return type_ != scan_type::none_type;
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}
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auto type() const -> detail::scan_type { return type_; }
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template <typename Visitor>
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auto visit(Visitor&& vis) -> decltype(vis(monostate())) {
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switch (type_) {
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case scan_type::none_type:
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break;
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case scan_type::int_type:
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return vis(*int_value_);
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case scan_type::uint_type:
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return vis(*uint_value_);
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case scan_type::long_long_type:
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return vis(*long_long_value_);
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case scan_type::ulong_long_type:
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return vis(*ulong_long_value_);
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case scan_type::string_type:
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return vis(*string_);
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case scan_type::string_view_type:
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return vis(*string_view_);
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case scan_type::custom_type:
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break;
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}
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return vis(monostate());
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}
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auto scan_custom(const char* parse_begin, scan_parse_context& parse_ctx,
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Context& ctx) const -> bool {
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if (type_ != scan_type::custom_type) return false;
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parse_ctx.advance_to(parse_begin);
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custom_.scan(custom_.value, parse_ctx, ctx);
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return true;
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}
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};
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class scan_context;
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using scan_arg = basic_scan_arg<scan_context>;
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struct scan_args {
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int size;
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const scan_arg* data;
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template <size_t N>
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FMT_CONSTEXPR scan_args(const std::array<scan_arg, N>& store)
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: size(N), data(store.data()) {
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static_assert(N < INT_MAX, "too many arguments");
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}
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};
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class scan_context {
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private:
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detail::scan_buffer& buf_;
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scan_args args_;
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public:
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using iterator = detail::scan_iterator;
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using sentinel = detail::scan_sentinel;
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explicit FMT_CONSTEXPR scan_context(detail::scan_buffer& buf, scan_args args)
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: buf_(buf), args_(args) {}
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FMT_CONSTEXPR auto arg(int id) const -> scan_arg {
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return id < args_.size ? args_.data[id] : scan_arg();
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}
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auto begin() const -> iterator { return buf_.begin(); }
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auto end() const -> sentinel { return {}; }
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void advance_to(iterator) { buf_.consume(); }
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};
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namespace detail {
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const char* parse_scan_specs(const char* begin, const char* end,
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format_specs& specs, scan_type) {
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while (begin != end) {
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switch (to_ascii(*begin)) {
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// TODO: parse more scan format specifiers
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case 'x':
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specs.type = presentation_type::hex;
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++begin;
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break;
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case '}':
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return begin;
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}
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}
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return begin;
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}
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template <typename T, FMT_ENABLE_IF(std::is_unsigned<T>::value)>
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auto read(scan_iterator it, T& value) -> scan_iterator {
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if (it == scan_sentinel()) return it;
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char c = *it;
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if (c < '0' || c > '9') report_error("invalid input");
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int num_digits = 0;
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T n = 0, prev = 0;
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char prev_digit = c;
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do {
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prev = n;
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n = n * 10 + static_cast<unsigned>(c - '0');
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prev_digit = c;
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c = *++it;
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++num_digits;
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if (c < '0' || c > '9') break;
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} while (it != scan_sentinel());
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// Check overflow.
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if (num_digits <= std::numeric_limits<int>::digits10) {
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value = n;
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return it;
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}
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unsigned max = to_unsigned((std::numeric_limits<int>::max)());
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if (num_digits == std::numeric_limits<int>::digits10 + 1 &&
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prev * 10ull + unsigned(prev_digit - '0') <= max) {
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value = n;
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} else {
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report_error("number is too big");
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}
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return it;
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}
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template <typename T, FMT_ENABLE_IF(std::is_unsigned<T>::value)>
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auto read_hex(scan_iterator it, T& value) -> scan_iterator {
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if (it == scan_sentinel()) return it;
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int digit = to_hex_digit(*it);
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if (digit < 0) report_error("invalid input");
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int num_digits = 0;
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T n = 0;
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do {
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n = (n << 4) + static_cast<unsigned>(digit);
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++num_digits;
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digit = to_hex_digit(*++it);
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if (digit < 0) break;
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} while (it != scan_sentinel());
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// Check overflow.
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if (num_digits <= (std::numeric_limits<T>::digits >> 2))
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value = n;
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else
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report_error("number is too big");
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return it;
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}
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template <typename T, FMT_ENABLE_IF(std::is_unsigned<T>::value)>
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auto read(scan_iterator it, T& value, const format_specs& specs)
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-> scan_iterator {
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if (specs.type == presentation_type::hex) return read_hex(it, value);
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return read(it, value);
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}
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template <typename T, FMT_ENABLE_IF(std::is_signed<T>::value)>
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auto read(scan_iterator it, T& value, const format_specs& specs = {})
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-> scan_iterator {
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bool negative = it != scan_sentinel() && *it == '-';
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if (negative) {
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++it;
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if (it == scan_sentinel()) report_error("invalid input");
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}
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using unsigned_type = typename std::make_unsigned<T>::type;
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unsigned_type abs_value = 0;
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it = read(it, abs_value, specs);
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auto n = static_cast<T>(abs_value);
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value = negative ? -n : n;
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return it;
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}
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auto read(scan_iterator it, std::string& value, const format_specs& = {})
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-> scan_iterator {
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while (it != scan_sentinel() && *it != ' ') value.push_back(*it++);
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return it;
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}
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auto read(scan_iterator it, string_view& value, const format_specs& = {})
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-> scan_iterator {
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auto range = to_contiguous(it);
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// This could also be checked at compile time in scan.
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if (!range) report_error("string_view requires contiguous input");
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auto p = range.begin;
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while (p != range.end && *p != ' ') ++p;
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size_t size = to_unsigned(p - range.begin);
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value = {range.begin, size};
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return advance(it, size);
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}
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auto read(scan_iterator it, monostate, const format_specs& = {})
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-> scan_iterator {
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return it;
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}
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// An argument scanner that uses the default format, e.g. decimal for integers.
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struct default_arg_scanner {
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scan_iterator it;
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template <typename T> FMT_INLINE auto operator()(T&& value) -> scan_iterator {
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return read(it, value);
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}
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};
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// An argument scanner with format specifiers.
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struct arg_scanner {
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scan_iterator it;
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const format_specs& specs;
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template <typename T> auto operator()(T&& value) -> scan_iterator {
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return read(it, value, specs);
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}
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};
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struct scan_handler {
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private:
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scan_parse_context parse_ctx_;
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scan_context scan_ctx_;
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int next_arg_id_;
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using sentinel = scan_buffer::sentinel;
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public:
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FMT_CONSTEXPR scan_handler(string_view format, scan_buffer& buf,
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scan_args args)
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: parse_ctx_(format), scan_ctx_(buf, args), next_arg_id_(0) {}
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auto pos() const -> scan_buffer::iterator { return scan_ctx_.begin(); }
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void on_text(const char* begin, const char* end) {
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if (begin == end) return;
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auto it = scan_ctx_.begin();
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for (; begin != end; ++begin, ++it) {
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if (it == sentinel() || *begin != *it) on_error("invalid input");
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}
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scan_ctx_.advance_to(it);
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}
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FMT_CONSTEXPR auto on_arg_id() -> int { return on_arg_id(next_arg_id_++); }
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FMT_CONSTEXPR auto on_arg_id(int id) -> int {
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if (!scan_ctx_.arg(id)) on_error("argument index out of range");
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return id;
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}
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FMT_CONSTEXPR auto on_arg_id(string_view id) -> int {
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if (id.data()) on_error("invalid format");
|
|
return 0;
|
|
}
|
|
|
|
void on_replacement_field(int arg_id, const char* begin) {
|
|
scan_arg arg = scan_ctx_.arg(arg_id);
|
|
if (arg.scan_custom(begin, parse_ctx_, scan_ctx_)) return;
|
|
auto it = scan_ctx_.begin();
|
|
while (it != sentinel() && is_whitespace(*it)) ++it;
|
|
scan_ctx_.advance_to(arg.visit(default_arg_scanner{it}));
|
|
}
|
|
|
|
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.scan_custom(begin, 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");
|
|
scan_ctx_.advance_to(arg.visit(arg_scanner{scan_ctx_.begin(), specs}));
|
|
return begin;
|
|
}
|
|
|
|
void on_error(const char* message) { report_error(message); }
|
|
};
|
|
|
|
void vscan(detail::scan_buffer& buf, string_view fmt, scan_args args) {
|
|
auto h = detail::scan_handler(fmt, buf, args);
|
|
detail::parse_format_string<false>(fmt, h);
|
|
}
|
|
|
|
template <size_t I, typename... T, FMT_ENABLE_IF(I == sizeof...(T))>
|
|
void make_args(std::array<scan_arg, sizeof...(T)>&, std::tuple<T...>&) {}
|
|
|
|
template <size_t I, typename... T, FMT_ENABLE_IF(I < sizeof...(T))>
|
|
void make_args(std::array<scan_arg, sizeof...(T)>& args,
|
|
std::tuple<T...>& values) {
|
|
using element_type = typename std::tuple_element<I, std::tuple<T...>>::type;
|
|
static_assert(std::is_same<remove_cvref_t<element_type>, element_type>::value,
|
|
"");
|
|
args[I] = std::get<I>(values);
|
|
make_args<I + 1>(args, values);
|
|
}
|
|
} // namespace detail
|
|
|
|
template <typename Range, typename... T> class scan_data {
|
|
private:
|
|
std::tuple<T...> values_;
|
|
Range range_;
|
|
|
|
public:
|
|
scan_data() = default;
|
|
scan_data(T... values) : values_(std::move(values)...) {}
|
|
|
|
auto value() const -> decltype(std::get<0>(values_)) {
|
|
return std::get<0>(values_);
|
|
}
|
|
|
|
auto values() const -> const std::tuple<T...>& { return values_; }
|
|
|
|
auto make_args() -> std::array<scan_arg, sizeof...(T)> {
|
|
auto args = std::array<scan_arg, sizeof...(T)>();
|
|
detail::make_args<0>(args, values_);
|
|
return args;
|
|
}
|
|
|
|
auto range() const -> Range { return range_; }
|
|
|
|
auto begin() const -> decltype(range_.begin()) { return range_.begin(); }
|
|
auto end() const -> decltype(range_.end()) { return range_.end(); }
|
|
};
|
|
|
|
template <typename... T>
|
|
auto make_scan_args(T&... args) -> std::array<scan_arg, sizeof...(T)> {
|
|
return {{args...}};
|
|
}
|
|
|
|
class scan_error {};
|
|
|
|
// A rudimentary version of std::expected for testing the API shape.
|
|
template <typename T, typename E> class expected {
|
|
private:
|
|
T value_;
|
|
bool has_value_ = true;
|
|
|
|
public:
|
|
expected(T value) : value_(std::move(value)) {}
|
|
|
|
explicit operator bool() const { return has_value_; }
|
|
|
|
auto operator->() const -> const T* { return &value_; }
|
|
|
|
auto error() -> E const { return E(); }
|
|
};
|
|
|
|
template <typename Range, typename... T>
|
|
using scan_result = expected<scan_data<Range, T...>, scan_error>;
|
|
|
|
auto vscan(string_view input, string_view fmt, scan_args args)
|
|
-> string_view::iterator {
|
|
auto&& buf = detail::string_scan_buffer(input);
|
|
detail::vscan(buf, fmt, args);
|
|
return input.begin() + (buf.begin().base() - input.data());
|
|
}
|
|
|
|
// Scans the input and stores the results (in)to args.
|
|
template <typename... T>
|
|
auto scan_to(string_view input, string_view fmt, T&... args)
|
|
-> string_view::iterator {
|
|
return vscan(input, fmt, make_scan_args(args...));
|
|
}
|
|
|
|
template <typename... T>
|
|
auto scan(string_view input, string_view fmt)
|
|
-> scan_result<string_view, T...> {
|
|
auto data = scan_data<string_view, T...>();
|
|
vscan(input, fmt, data.make_args());
|
|
return data;
|
|
}
|
|
|
|
template <typename Range, typename... T,
|
|
FMT_ENABLE_IF(!std::is_convertible<Range, string_view>::value)>
|
|
auto scan_to(Range&& input, string_view fmt, T&... args)
|
|
-> decltype(std::begin(input)) {
|
|
auto it = std::begin(input);
|
|
detail::vscan(get_buffer(it), fmt, make_scan_args(args...));
|
|
return it;
|
|
}
|
|
|
|
template <typename... T>
|
|
auto scan_to(FILE* f, string_view fmt, T&... args) -> bool {
|
|
auto&& buf = detail::file_scan_buffer(f);
|
|
detail::vscan(buf, fmt, make_scan_args(args...));
|
|
return buf.begin() != buf.end();
|
|
}
|
|
|
|
FMT_END_NAMESPACE
|