#ifndef ABSL_STRINGS_INTERNAL_STR_FORMAT_CHECKER_H_
#define ABSL_STRINGS_INTERNAL_STR_FORMAT_CHECKER_H_
#include "absl/base/attributes.h"
#include "absl/strings/internal/str_format/arg.h"
#include "absl/strings/internal/str_format/extension.h"
// Compile time check support for entry points.
#ifndef ABSL_INTERNAL_ENABLE_FORMAT_CHECKER
#if ABSL_HAVE_ATTRIBUTE(enable_if) && !defined(__native_client__)
#define ABSL_INTERNAL_ENABLE_FORMAT_CHECKER 1
#endif // ABSL_HAVE_ATTRIBUTE(enable_if) && !defined(__native_client__)
#endif // ABSL_INTERNAL_ENABLE_FORMAT_CHECKER
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace str_format_internal {
constexpr bool AllOf() { return true; }
template <typename... T>
constexpr bool AllOf(bool b, T... t) {
return b && AllOf(t...);
}
#ifdef ABSL_INTERNAL_ENABLE_FORMAT_CHECKER
constexpr bool ContainsChar(const char* chars, char c) {
return *chars == c || (*chars && ContainsChar(chars + 1, c));
}
// A constexpr compatible list of Convs.
struct ConvList {
const FormatConversionCharSet* array;
int count;
// We do the bound check here to avoid having to do it on the callers.
// Returning an empty FormatConversionCharSet has the same effect as
// short circuiting because it will never match any conversion.
constexpr FormatConversionCharSet operator[](int i) const {
return i < count ? array[i] : FormatConversionCharSet{};
}
constexpr ConvList without_front() const {
return count != 0 ? ConvList{array + 1, count - 1} : *this;
}
};
template <size_t count>
struct ConvListT {
// Make sure the array has size > 0.
FormatConversionCharSet list[count ? count : 1];
};
constexpr char GetChar(string_view str, size_t index) {
return index < str.size() ? str[index] : char{};
}
constexpr string_view ConsumeFront(string_view str, size_t len = 1) {
return len <= str.size() ? string_view(str.data() + len, str.size() - len)
: string_view();
}
constexpr string_view ConsumeAnyOf(string_view format, const char* chars) {
return ContainsChar(chars, GetChar(format, 0))
? ConsumeAnyOf(ConsumeFront(format), chars)
: format;
}
constexpr bool IsDigit(char c) { return c >= '0' && c <= '9'; }
// Helper class for the ParseDigits function.
// It encapsulates the two return values we need there.
struct Integer {
string_view format;
int value;
// If the next character is a '$', consume it.
// Otherwise, make `this` an invalid positional argument.
constexpr Integer ConsumePositionalDollar() const {
return GetChar(format, 0) == '$' ? Integer{ConsumeFront(format), value}
: Integer{format, 0};
}
};
constexpr Integer ParseDigits(string_view format, int value = 0) {
return IsDigit(GetChar(format, 0))
? ParseDigits(ConsumeFront(format),
10 * value + GetChar(format, 0) - '0')
: Integer{format, value};
}
// Parse digits for a positional argument.
// The parsing also consumes the '$'.
constexpr Integer ParsePositional(string_view format) {
return ParseDigits(format).ConsumePositionalDollar();
}
// Parses a single conversion specifier.
// See ConvParser::Run() for post conditions.
class ConvParser {
constexpr ConvParser SetFormat(string_view format) const {
return ConvParser(format, args_, error_, arg_position_, is_positional_);
}
constexpr ConvParser SetArgs(ConvList args) const {
return ConvParser(format_, args, error_, arg_position_, is_positional_);
}
constexpr ConvParser SetError(bool error) const {
return ConvParser(format_, args_, error_ || error, arg_position_,
is_positional_);
}
constexpr ConvParser SetArgPosition(int arg_position) const {
return ConvParser(format_, args_, error_, arg_position, is_positional_);
}
// Consumes the next arg and verifies that it matches `conv`.
// `error_` is set if there is no next arg or if it doesn't match `conv`.
constexpr ConvParser ConsumeNextArg(char conv) const {
return SetArgs(args_.without_front()).SetError(!Contains(args_[0], conv));
}
// Verify that positional argument `i.value` matches `conv`.
// `error_` is set if `i.value` is not a valid argument or if it doesn't
// match.
constexpr ConvParser VerifyPositional(Integer i, char conv) const {
return SetFormat(i.format).SetError(!Contains(args_[i.value - 1], conv));
}
// Parse the position of the arg and store it in `arg_position_`.
constexpr ConvParser ParseArgPosition(Integer arg) const {
return SetFormat(arg.format).SetArgPosition(arg.value);
}
// Consume the flags.
constexpr ConvParser ParseFlags() const {
return SetFormat(ConsumeAnyOf(format_, "-+ #0"));
}
// Consume the width.
// If it is '*', we verify that it matches `args_`. `error_` is set if it
// doesn't match.
constexpr ConvParser ParseWidth() const {
return IsDigit(GetChar(format_, 0))
? SetFormat(ParseDigits(format_).format)
: GetChar(format_, 0) == '*'
? is_positional_
? VerifyPositional(
ParsePositional(ConsumeFront(format_)), '*')
: SetFormat(ConsumeFront(format_))
.ConsumeNextArg('*')
: *this;
}
// Consume the precision.
// If it is '*', we verify that it matches `args_`. `error_` is set if it
// doesn't match.
constexpr ConvParser ParsePrecision() const {
return GetChar(format_, 0) != '.'
? *this
: GetChar(format_, 1) == '*'
? is_positional_
? VerifyPositional(
ParsePositional(ConsumeFront(format_, 2)), '*')
: SetFormat(ConsumeFront(format_, 2))
.ConsumeNextArg('*')
: SetFormat(ParseDigits(ConsumeFront(format_)).format);
}
// Consume the length characters.
constexpr ConvParser ParseLength() const {
return SetFormat(ConsumeAnyOf(format_, "lLhjztq"));
}
// Consume the conversion character and verify that it matches `args_`.
// `error_` is set if it doesn't match.
constexpr ConvParser ParseConversion() const {
return is_positional_
? VerifyPositional({ConsumeFront(format_), arg_position_},
GetChar(format_, 0))
: ConsumeNextArg(GetChar(format_, 0))
.SetFormat(ConsumeFront(format_));
}
constexpr ConvParser(string_view format, ConvList args, bool error,
int arg_position, bool is_positional)
: format_(format),
args_(args),
error_(error),
arg_position_(arg_position),
is_positional_(is_positional) {}
public:
constexpr ConvParser(string_view format, ConvList args, bool is_positional)
: format_(format),
args_(args),
error_(false),
arg_position_(0),
is_positional_(is_positional) {}
// Consume the whole conversion specifier.
// `format()` will be set to the character after the conversion character.
// `error()` will be set if any of the arguments do not match.
constexpr ConvParser Run() const {
return (is_positional_ ? ParseArgPosition(ParsePositional(format_)) : *this)
.ParseFlags()
.ParseWidth()
.ParsePrecision()
.ParseLength()
.ParseConversion();
}
constexpr string_view format() const { return format_; }
constexpr ConvList args() const { return args_; }
constexpr bool error() const { return error_; }
constexpr bool is_positional() const { return is_positional_; }
private:
string_view format_;
// Current list of arguments. If we are not in positional mode we will consume
// from the front.
ConvList args_;
bool error_;
// Holds the argument position of the conversion character, if we are in
// positional mode. Otherwise, it is unspecified.
int arg_position_;
// Whether we are in positional mode.
// It changes the behavior of '*' and where to find the converted argument.
bool is_positional_;
};
// Parses a whole format expression.
// See FormatParser::Run().
class FormatParser {
static constexpr bool FoundPercent(string_view format) {
return format.empty() ||
(GetChar(format, 0) == '%' && GetChar(format, 1) != '%');
}
// We use an inner function to increase the recursion limit.
// The inner function consumes up to `limit` characters on every run.
// This increases the limit from 512 to ~512*limit.
static constexpr string_view ConsumeNonPercentInner(string_view format,
int limit = 20) {
return FoundPercent(format) || !limit
? format
: ConsumeNonPercentInner(
ConsumeFront(format, GetChar(format, 0) == '%' &&
GetChar(format, 1) == '%'
? 2
: 1),
limit - 1);
}
// Consume characters until the next conversion spec %.
// It skips %%.
static constexpr string_view ConsumeNonPercent(string_view format) {
return FoundPercent(format)
? format
: ConsumeNonPercent(ConsumeNonPercentInner(format));
}
static constexpr bool IsPositional(string_view format) {
return IsDigit(GetChar(format, 0)) ? IsPositional(ConsumeFront(format))
: GetChar(format, 0) == '$';
}
constexpr bool RunImpl(bool is_positional) const {
// In non-positional mode we require all arguments to be consumed.
// In positional mode just reaching the end of the format without errors is
// enough.
return (format_.empty() && (is_positional || args_.count == 0)) ||
(!format_.empty() &&
ValidateArg(
ConvParser(ConsumeFront(format_), args_, is_positional).Run()));
}
constexpr bool ValidateArg(ConvParser conv) const {
return !conv.error() && FormatParser(conv.format(), conv.args())
.RunImpl(conv.is_positional());
}
public:
constexpr FormatParser(string_view format, ConvList args)
: format_(ConsumeNonPercent(format)), args_(args) {}
// Runs the parser for `format` and `args`.
// It verifies that the format is valid and that all conversion specifiers
// match the arguments passed.
// In non-positional mode it also verfies that all arguments are consumed.
constexpr bool Run() const {
return RunImpl(!format_.empty() && IsPositional(ConsumeFront(format_)));
}
private:
string_view format_;
// Current list of arguments.
// If we are not in positional mode we will consume from the front and will
// have to be empty in the end.
ConvList args_;
};
template <FormatConversionCharSet... C>
constexpr bool ValidFormatImpl(string_view format) {
return FormatParser(format,
{ConvListT<sizeof...(C)>{{C...}}.list, sizeof...(C)})
.Run();
}
#endif // ABSL_INTERNAL_ENABLE_FORMAT_CHECKER
} // namespace str_format_internal
ABSL_NAMESPACE_END
} // namespace absl
#endif // ABSL_STRINGS_INTERNAL_STR_FORMAT_CHECKER_H_