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101 lines
2.4 KiB
C++
101 lines
2.4 KiB
C++
// Formatting library for C++ - scanning API proof of concept
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//
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// Copyright (c) 2012 - 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 <climits>
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#include "fmt/format.h"
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#include "gmock.h"
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#include "gtest-extra.h"
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FMT_BEGIN_NAMESPACE
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namespace internal {
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struct scan_arg {
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int* value;
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// TODO: more types
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};
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template <typename Handler>
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void parse_scan_format(string_view format_str, Handler&& handler) {
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const char* p = format_str.data();
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const char* end = p + format_str.size();
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while (p != end) {
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char c = *p++;
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if (c != '{' || p == end || *p++ != '}')
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throw format_error("invalid format string");
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handler.on_arg();
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}
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}
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} // namespace internal
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struct scan_args {
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int size;
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const internal::scan_arg* data;
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template <size_t N>
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scan_args(const std::array<internal::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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namespace internal {
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struct scan_handler {
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const char* begin;
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const char* end;
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scan_args args;
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int next_arg_id;
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scan_handler(string_view input, scan_args args)
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: begin(input.data()),
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end(begin + input.size()),
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args(args),
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next_arg_id(0) {}
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void on_arg() {
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int value = 0;
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while (begin != end) {
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char c = *begin++;
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if (c < '0' || c > '9') throw format_error("invalid input");
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value = value * 10 + (c - '0');
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}
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if (next_arg_id >= args.size)
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throw format_error("argument index out of range");
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*args.data[0].value = value;
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}
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};
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} // namespace internal
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void vscan(string_view input, string_view format_str, scan_args args) {
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internal::parse_scan_format(format_str, internal::scan_handler(input, args));
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}
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template <typename... Args>
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std::array<internal::scan_arg, sizeof...(Args)> make_scan_args(Args&... args) {
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return std::array<internal::scan_arg, sizeof...(Args)>{&args...};
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}
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template <typename... Args>
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void scan(string_view input, string_view format_str, Args&... args) {
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vscan(input, format_str, make_scan_args(args...));
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}
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FMT_END_NAMESPACE
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TEST(ScanTest, ReadInt) {
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int n = 0;
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fmt::scan("42", "{}", n);
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EXPECT_EQ(n, 42);
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}
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TEST(ScanTest, InvalidFormat) {
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EXPECT_THROW_MSG(fmt::scan("", "{}"), fmt::format_error,
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"argument index out of range");
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EXPECT_THROW_MSG(fmt::scan("", "{"), fmt::format_error,
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"invalid format string");
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}
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