Move data streaming and formatting utils into new coral io module

This commit is contained in:
kayomn 2023-02-22 15:32:04 +00:00
parent d8b9a7e330
commit 809b45dc3c
2 changed files with 176 additions and 0 deletions

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@ -7,6 +7,7 @@ export module app;
import coral; import coral;
import coral.files; import coral.files;
import coral.image; import coral.image;
import coral.io;
import coral.math; import coral.math;
import oar; import oar;

175
source/coral/io.cpp Normal file
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@ -0,0 +1,175 @@
export module coral.io;
import coral;
export namespace coral {
/**
* Multiplexing byte-based ring buffer of `capacity` size that may be used for memory-backed
* I/O operations and lightweight data construction.
*/
template<usize capacity> struct fixed_buffer : public writer, public reader {
fixed_buffer(coral::u8 fill_value) : data{fill_value} {}
/**
* Returns the base pointer of the buffer data.
*/
u8 * begin() {
return this->data;
}
/**
* Returns the base pointer of the buffer data.
*/
u8 const * begin() const {
return this->data;
}
/**
* Returns the tail pointer of the buffer data.
*/
u8 * end() {
return this->data + this->cursor;
}
/**
* Returns the tail pointer of the buffer data.
*/
u8 const * end() const {
return this->data + this->cursor;
}
/**
* Returns `true` if the buffer has been completely filled with data.
*/
bool is_full() const {
return this->filled == capacity;
}
/**
* Reads whatever data is in the buffer into `data`, returning the number of bytes read
* from the buffer.
*/
expected<usize, io_error> read(slice<u8> const & data) override {
slice const readable_data{this->data, min(this->filled, data.length)};
this->filled -= readable_data.length;
for (usize index = 0; index < readable_data.length; index += 1) {
data[index] = this->data[this->read_index];
this->read_index = (this->read_index + 1) % capacity;
}
return readable_data.length;
}
/**
* Attempts to write `data` to the buffer, returning the number of bytes written or
* [io_error::unavailable] if it has been completely filled and no more bytes can be
* written.
*/
expected<usize, io_error> write(slice<u8 const> const & data) override {
if (this->is_full()) return io_error::unavailable;
slice const writable_data{data.sliced(0, min(data.length, this->filled))};
this->filled += writable_data.length;
for (usize index = 0; index < writable_data.length; index += 1) {
this->data[this->write_index] = data[index];
this->write_index = (this->write_index + 1) % capacity;
}
return writable_data.length;
}
private:
usize filled = 0;
usize read_index = 0;
usize write_index = 0;
u8 data[capacity];
};
/**
* Streams the data from `input` to `output`, using `buffer` as temporary transfer space.
*
* The returned [expected] can be used to introspect if `input` or `output` encountered any
* issues during streaming, otherwise it will contain the number of bytes streamed.
*
* *Note*: if `buffer` has a length of `0`, no data will be streamed as there is nowhere to
* temporarily place data during streaming.
*/
expected<usize, io_error> stream(writer & output, reader & input, slice<u8> const & buffer) {
usize total_bytes_written = 0;
expected bytes_read = input.read(buffer);
if (!bytes_read.is_ok()) return bytes_read.error();
usize read = bytes_read.value();
while (read != 0) {
expected const bytes_written = output.write(buffer.sliced(0, read));
if (!bytes_written.is_ok()) return bytes_read.error();
total_bytes_written += bytes_written.value();
bytes_read = input.read(buffer);
if (!bytes_read.is_ok()) return bytes_read.error();
read = bytes_read.value();
}
return total_bytes_written;
}
/**
* Returns a reference to a shared [allocator] which will always return `nullptr` on calls to
* [allocator::reallocate].
*/
allocator & null_allocator() {
static struct : public allocator {
u8 * reallocate(u8 * maybe_allocation, usize requested_size) override {
if (maybe_allocation != nullptr) unreachable();
return nullptr;
}
void deallocate(void * allocation) override {
if (allocation != nullptr) unreachable();
}
} a;
return a;
}
/**
* Attempts to format and print `value` as an unsigned integer out to `output`.
*
* The returned [expected] can be used to introspect if `output` encountered any issues during
* printing, otherwise it will contain the number of characters used to print `value` as text.
*/
expected<usize, io_error> print_unsigned(writer & output, u64 value) {
if (value == 0) return output.write(slice{"0"}.as_bytes());
u8 buffer[20]{0};
usize buffer_count{0};
while (value != 0) {
constexpr usize radix{10};
buffer[buffer_count] = static_cast<u8>((value % radix) + '0');
value = (value / radix);
buffer_count += 1;
}
usize const half_buffer_count{buffer_count / 2};
for (usize i = 0; i < half_buffer_count; i += 1)
swap(buffer[i], buffer[buffer_count - i - 1]);
return output.write({buffer, buffer_count});
}
}