Type Function BufferedReader [src]

Alias for std.io.buffered_reader.BufferedReader

Prototype

pub fn BufferedReader(comptime buffer_size: usize, comptime ReaderType: type) type

Parameters

buffer_size: usizeReaderType: type

Source

  pub fn BufferedReader(comptime buffer_size: usize, comptime ReaderType: type) type {
    return struct {
        unbuffered_reader: ReaderType,
        buf: [buffer_size]u8 = undefined,
        start: usize = 0,
        end: usize = 0,

        pub const Error = ReaderType.Error;
        pub const Reader = io.Reader(*Self, Error, read);

        const Self = @This();

        pub fn read(self: *Self, dest: []u8) Error!usize {
            // First try reading from the already buffered data onto the destination.
            const current = self.buf[self.start..self.end];
            if (current.len != 0) {
                const to_transfer = @min(current.len, dest.len);
                @memcpy(dest[0..to_transfer], current[0..to_transfer]);
                self.start += to_transfer;
                return to_transfer;
            }

            // If dest is large, read from the unbuffered reader directly into the destination.
            if (dest.len >= buffer_size) {
                return self.unbuffered_reader.read(dest);
            }

            // If dest is small, read from the unbuffered reader into our own internal buffer,
            // and then transfer to destination.
            self.end = try self.unbuffered_reader.read(&self.buf);
            const to_transfer = @min(self.end, dest.len);
            @memcpy(dest[0..to_transfer], self.buf[0..to_transfer]);
            self.start = to_transfer;
            return to_transfer;
        }

        pub fn reader(self: *Self) Reader {
            return .{ .context = self };
        }
    };
}  