WEBVTT 00:00.930 --> 00:05.790 We don't have to use just textfiles a lot of the time. 00:05.790 --> 00:14.710 All we want is to store some data in REPAK quickly not caring about the readability of the file itself. 00:15.420 --> 00:21.540 And binary files are the perfect complement to this. 00:21.540 --> 00:27.100 So what I've done here a start is I've created a structure. 00:27.120 --> 00:39.120 It has two members one in value two and it's integers and I've created a an array of this type and type 00:39.120 --> 00:47.370 data and there is just about 10 of them here Max is 10 and it is randomly stores and values into it. 00:47.450 --> 00:47.960 OK. 00:48.060 --> 00:50.080 And I'm just outputting the results. 00:50.230 --> 00:58.540 So you run this just randomly stores a bunch of Vout. 00:58.650 --> 00:59.660 OK. 01:00.140 --> 01:10.740 And I'm doing this because we're going to actually write out these values into a binary file and then 01:10.800 --> 01:14.330 read them back into a different array. 01:18.050 --> 01:24.560 So let's get started of how to write something right. 01:24.560 --> 01:26.050 File a binary file 01:28.830 --> 01:29.400 stream 01:32.740 --> 01:34.210 a file 01:36.770 --> 01:39.230 and when we opened the file 01:45.770 --> 01:48.210 it dated been this doesn't exist yet. 01:48.320 --> 01:49.830 Will. 01:50.080 --> 01:54.870 And when we open it will actually say it's a binary file. 01:56.000 --> 01:57.030 Like this. 01:57.140 --> 02:01.120 Use extreme and colon colon binary. 02:01.580 --> 02:02.220 OK. 02:02.480 --> 02:13.160 And so now that we have opened it in the binary kind of format We'll write to it and we can't just use 02:13.160 --> 02:16.850 the insertion operator like we do with Seow tour. 02:16.850 --> 02:23.600 What we did before we actually have to call a different function OK because the insertion operator really 02:23.600 --> 02:30.070 only works with Tex or possibly like integers just like just basic types like that. 02:30.190 --> 02:36.280 OK so what we're going to do is call out file dot right. 02:38.780 --> 02:50.210 And right actually we'll write code bytes essentially and we know that a character is one byte. 02:50.240 --> 02:59.810 So we're going to do is actually cast this to be the character character pointer and we're going to 02:59.810 --> 03:01.910 take the address of the array data 03:06.140 --> 03:08.210 and right to take. 03:08.210 --> 03:13.870 So this is the data that we're going to write to the file and write needs. 03:13.880 --> 03:18.710 The length of how much how many bytes to write. 03:19.220 --> 03:23.930 And to do that you use the size of orated 03:27.670 --> 03:28.470 k. 03:28.730 --> 03:32.280 So this is kind of interesting. 03:32.770 --> 03:41.330 If you take the size of the array and this array that's kind of static. 03:41.570 --> 03:43.820 Well it's made on the stack. 03:43.940 --> 03:44.470 OK. 03:44.510 --> 03:45.040 Right. 03:45.080 --> 03:47.410 This isn't dynamics that's made on the stack. 03:47.690 --> 03:54.530 So if you actually take a size of an array as create on the stack it'll actually give you how many bytes 03:54.530 --> 03:58.460 it is and total including each element. 03:59.940 --> 04:04.150 This wouldn't work if you used a dynamic array. 04:04.380 --> 04:08.520 If you use a dynamic array it'll just be the size of the pointer. 04:08.740 --> 04:21.840 OK so in this one his first parameter we're taking the address of the of the array. 04:22.280 --> 04:25.780 And then we're it to be this character pointer. 04:25.780 --> 04:31.850 So this looks a little bit complicated but really all it's saying is be that the first element and B 04:33.140 --> 04:36.660 type character pointer. 04:37.020 --> 04:38.730 That's that's really all this is saying. 04:38.730 --> 04:46.080 So it's really just it's kind of making a cursor and it's pointing at the very first bite of this radiate. 04:46.210 --> 04:48.490 So that's really all this is saying. 04:48.980 --> 04:54.020 Because cause right only works with bytes right. 04:54.320 --> 04:58.400 Each byte or this many bytes. 05:00.110 --> 05:12.850 And so now we will just close it for and what we're going to do is actually read it back in right now. 05:13.240 --> 05:14.990 But in a new array. 05:15.140 --> 05:19.470 So a new array of Max. 05:19.600 --> 05:23.560 So we're not going to use the same array data used for. 05:23.970 --> 05:26.930 And we're going to make a infile. 05:26.950 --> 05:47.070 So I have stream in file in file open loop in the same file open for binary reading. 05:47.130 --> 05:48.740 It's a binary reading. 05:48.790 --> 05:54.000 The last time and essentially we're going to use the same kind of signature. 05:54.010 --> 06:02.170 But this is this time it's not going you're right as can be read in file dot read 06:05.310 --> 06:07.600 you begin the same thing. 06:15.190 --> 06:22.850 Like this looks exactly the same as right but now is using right. 06:24.260 --> 06:25.910 And we just close it 06:31.520 --> 06:36.770 and now we're going to just loop through the new array and just output what we got. 06:36.780 --> 06:40.620 So hopefully they'll match up. 06:41.120 --> 06:44.790 Max plus 06:47.770 --> 06:51.420 put everything re 07:37.000 --> 07:37.790 k. 07:38.130 --> 07:41.410 So it's basically it I think. 07:41.410 --> 07:50.950 So again we're just filling the array data with some random values and then rewriting it in a binary 07:50.950 --> 07:51.520 way. 07:51.550 --> 07:56.930 And those that we're using it doesn't matter that these are structures. 07:57.360 --> 08:04.890 As long as it knows how big you can make or how many bytes it is. 08:05.310 --> 08:14.850 So it knows it because it's made on the stack so it knows that the size of this data is what 8 bytes. 08:14.850 --> 08:18.190 And there's 10 of them so it's 80 bytes right. 08:18.200 --> 08:19.350 Right right. 08:19.470 --> 08:24.560 So size of can actually do that calculation kind of Two-Step calculation. 08:24.820 --> 08:25.720 OK. 08:26.100 --> 08:36.470 So writing 80 bytes from this array to this fight then we're reading 80 bytes again into this new array. 08:36.510 --> 08:41.490 So you run this you will see. 08:41.820 --> 08:44.450 So it is. 08:44.500 --> 08:52.900 So this first one is first kind of 10 values here are all of this. 08:52.940 --> 08:59.460 So 29 to do 10 84 125 of 28 center etc.. 08:59.860 --> 09:02.590 And then now we're reading it back. 09:02.680 --> 09:07.760 So 9:31 for 125. 09:08.200 --> 09:09.150 Cetera. 09:09.220 --> 09:10.710 So it's working. 09:10.780 --> 09:20.990 So this really binary files are really good for making kind of smaller files on the disk. 09:21.260 --> 09:27.570 And it's also really faster to write and read it usually. 09:27.730 --> 09:35.800 And that's usually why we want to use binary files over text files because they're really fast to write 09:35.800 --> 09:41.800 out and they take up very little space because it's all kind of nicely packed together. 09:41.800 --> 09:49.210 And usually it's actually quite a bit easier to read in as well and really use three lines to write 09:49.210 --> 09:50.570 it out in three lines. 09:50.570 --> 09:52.640 Are you back in. 09:52.960 --> 09:58.540 So as long as you can get past what's happening here in this line. 09:58.780 --> 10:05.280 It's pretty simple to write out a binary file and then read it back and. 10:05.730 --> 10:11.810 And we'll be using them in kind of a mini project in the next lecture.