Incorrect work of sox_open_memstream_write with memstream buffer and buffersize

Incorrect work of sox_open_memstream_write with memstream buffer and buffersize

[Sun Zhenliang]

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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.



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Re: Incorrect work of sox_open_memstream_write with memstream buffer and buffersize

[Jan Stary]

On Jul 23 01:43:36, hisunzhenliang@outlook.com 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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回复: Incorrect work of sox_open_memstream_write with memstream buffer and buffersize

[Sun Zhenliang]

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here is a demo:

```

  1.  #include "sox.h"
  2.  #include "util.h"
  3.  #include <stdio.h>
  4.  #include <assert.h>
  5.
  6.  /* Example of reading and writing audio files stored in memory buffers
  7.   * rather than actual files.
  8.   *
  9.   * Usage: example5 input output
  10.  */
  11.
  12.
  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;
  21.
  22.   assert(argc == 3);
  23.
  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);
  47.
  48.   printf("%ld\n", buffer_size);
  49.
  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@stare.cz>
发送时间: 2021年7月24日 18:43
收件人: sox-users@lists.sourceforge.net <sox-users@lists.sourceforge.net>
主题: Re: [SoX-users] Incorrect work of sox_open_memstream_write with memstream buffer and buffersize

On Jul 23 01:43:36, hisunzhenliang@outlook.com 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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