回复: Incorrect work of sox_open_memstream_write with memstream buffer and buffersize

[Sun Zhenliang <hisunzhenliang@xxxxxxxxxxx>]

here is a demo:

```

1. #include "sox.h"
2. #include "util.h"
3. #include <stdio.h>
4. #include <assert.h>
6. /* Example of reading and writing audio files stored in memory buffers
7.  * rather than actual files.
8.  *
9.  * Usage: example5 input output
10.  */
13. int main(int argc, char * argv[])
14. {
15.   static sox_format_t * in, * out;
16.   #define MAX_SAMPLES (size_t)2048
17.   sox_sample_t samples[MAX_SAMPLES];
18.   char * buffer;
19.   size_t buffer_size;
20.   size_t number_read;
22.   assert(argc == 3);
24.   assert(sox_init() == SOX_SUCCESS);
25.   assert((in = sox_open_read(argv[1], NULL, NULL, NULL)));
26.   sox_encodinginfo_t out_encoding = {
27.     SOX_ENCODING_ULAW,
28.     8,
29.     0,
30.     sox_option_default,
31.     sox_option_default,
32.     sox_option_default,
33.     sox_false
34.   };
35.   sox_signalinfo_t out_signal = {
36.     8000,
37.     1,
38.     0,
39.     0,
40.     NULL
41.   };
42.   assert(out = sox_open_memstream_write(&buffer, &buffer_size, &out_signal, &out_encoding, "wav", NULL));
43.   while ((number_read = sox_read(in, samples, MAX_SAMPLES)))
44.     assert(sox_write(out, samples, number_read) == number_read);
45.   sox_close(out);
46.   sox_close(in);
48.   printf("%ld\n", buffer_size);
50.   free(buffer);
51.   sox_quit();
52.   return 0;
53. }

```

$ ./example5 in.wav out.wav

$ 58

At this line 48: `printf("%ld\n", buffer_size);`

I take it for granted that it should be the length of the whole file，but due to the seek option，I can only get length of wav header.

I know it is feasible to get file data before sox_close through ft.fp, but at some situations I need get data from buff and buffsize.

---

发件人: Jan Stary <hans@xxxxxxxx>
发送时间: 2021年7月24日 18:43
收件人: sox-users@xxxxxxxxxxxxxxxxxxxxx <sox-users@xxxxxxxxxxxxxxxxxxxxx>
主题: Re: Incorrect work of sox_open_memstream_write with memstream buffer and buffersize

 

On Jul 23 01:43:36, hisunzhenliang@xxxxxxxxxxx wrote:
> Opened by sox_open_memstream_write function，the buffer and buffersize will work incorrectly when seeking back。
>
> For example， when opening buffer with sox_open_memstream_write to get a wav format output，wav handler's  stopwrite function will seek back to the beginning to rewrite wav header. In this situation，after closing ft，I assume that I can get whole data from buff and buffsize，but I can only get the wav header.
>
> I don't think it would be better to have seek back to the end when you need to rewrite data with a seek operation.

Without seeing the actual code,
it's hard to try to help.



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