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Write directly to a stream buffer

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This commit is contained in:
Victor Zverovich
2024-01-18 07:27:59 -08:00
parent b2cde48de5
commit 6b68dff901
4 changed files with 172 additions and 85 deletions
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91
test/scan.h
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@ -42,9 +42,9 @@ class scan_buffer {
: ptr_(ptr), end_(end), contiguous_(contiguous) {}
~scan_buffer() = default;
void set(string_view buf) {
ptr_ = buf.begin();
end_ = buf.end();
void set(span<const char> buf) {
ptr_ = buf.data;
end_ = buf.data + buf.size;
}
auto ptr() const -> const char* { return ptr_; }
@ -150,83 +150,6 @@ class string_scan_buffer : public scan_buffer {
: scan_buffer(s.begin(), s.end(), true) {}
};
#ifdef _WIN32
void flockfile(FILE* f) { _lock_file(f); }
void funlockfile(FILE* f) { _unlock_file(f); }
int getc_unlocked(FILE* f) { return _fgetc_nolock(f); }
#endif
// A FILE wrapper. F is FILE defined as a template parameter to make
// system-specific API detection work.
template <typename F> class file_base {
protected:
F* file_;
public:
file_base(F* file) : file_(file) {}
operator F*() const { return file_; }
// Reads a code unit from the stream.
auto get() -> int {
int result = getc_unlocked(file_);
if (result == EOF && ferror(file_) != 0)
FMT_THROW(system_error(errno, FMT_STRING("getc failed")));
return result;
}
// Puts the code unit back into the stream buffer.
void unget(char c) {
if (ungetc(c, file_) == EOF)
FMT_THROW(system_error(errno, FMT_STRING("ungetc failed")));
}
};
// A FILE wrapper for glibc.
template <typename F> class glibc_file : public file_base<F> {
public:
using file_base<F>::file_base;
// Returns the file's read buffer as a string_view.
auto buffer() const -> string_view {
return {this->file_->_IO_read_ptr,
to_unsigned(this->file_->_IO_read_end - this->file_->_IO_read_ptr)};
}
};
// A FILE wrapper for Apple's libc.
template <typename F> class apple_file : public file_base<F> {
public:
using file_base<F>::file_base;
auto buffer() const -> string_view {
return {reinterpret_cast<char*>(this->file_->_p),
to_unsigned(this->file_->_r)};
}
};
// A fallback FILE wrapper.
template <typename F> class fallback_file : public file_base<F> {
private:
char next_; // The next unconsumed character in the buffer.
bool has_next_ = false;
public:
using file_base<F>::file_base;
auto buffer() const -> string_view { return {&next_, has_next_ ? 1u : 0u}; }
auto get() -> int {
has_next_ = false;
return file_base<F>::get();
}
void unget(char c) {
file_base<F>::unget(c);
next_ = c;
has_next_ = true;
}
};
class file_scan_buffer : public scan_buffer {
private:
template <typename F, FMT_ENABLE_IF(sizeof(F::_IO_read_ptr) != 0)>
@ -243,19 +166,19 @@ class file_scan_buffer : public scan_buffer {
// Fills the buffer if it is empty.
void fill() {
string_view buf = file_.buffer();
if (buf.size() == 0) {
span<const char> buf = file_.get_read_buffer();
if (buf.size == 0) {
int c = file_.get();
// Put the character back since we are only filling the buffer.
if (c != EOF) file_.unget(static_cast<char>(c));
buf = file_.buffer();
buf = file_.get_read_buffer();
}
set(buf);
}
void consume() override {
// Consume the current buffer content.
size_t n = to_unsigned(ptr() - file_.buffer().begin());
size_t n = to_unsigned(ptr() - file_.get_read_buffer().data);
for (size_t i = 0; i != n; ++i) file_.get();
fill();
}