Move data streaming and formatting utils into new coral io module

source/app.cpp

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

source/coral/io.cpp

@@ -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});
+	}
+}