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Read from buffer not file

Posted on 2014-02-18
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Last Modified: 2014-02-18
Hello,
in my old code I worked with fread to read from an little text file some settings. This I want now replace with reading from a buffer (char).  The original ocde is:
	int val;
	fread(&val, sizeof(int), 1, f); DBFFTSize  = val;
	fread(&val, sizeof(int), 1, f); DBNumFFTs  = val;
	fread(&val, sizeof(int), 1, f); DBNumBins  = val;
	fread(&val, sizeof(int), 1, f); DBFirstBin = val;
	fread(DBOrgBuf, sizeof(float), 16, f);
	fclose(f);

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How to replace this while read from a char buffer.  I have a buffer that was filled before and that was initialized with:
char buff[100];
memset(buff,0,sizeof(buff));

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Thanks,

Ingo
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Question by:Ingo Foerster
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5 Comments
 
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Accepted Solution

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jkr earned 1600 total points
ID: 39868347
In this case, 'read' might not be the right term. You'd just interpret the buffer's content differently, i.e.

struct FFTVals {

  int DBFFTSize;
  int DBNumFFTs;
  int DBNumBins;
  int DBFirstBin;
  float DBOrgBuf[16];
};

// ...

char buff[100];
memset(buff,0,sizeof(buff));

// ...

FFTVals* pVals = (FFTVals*) buff; // consider 'buff' as 'read'

// copy values - or just use them directly from 'pVals'
  int DBFFTSize = pVals->DBFFTSize;
  int DBNumFFTs = pVals->DBNumFFTs;
  int DBNumBins = pVals->DBNumBins;
  int DBFirstBin = pVals->DBFirstBin;
  // etc.

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LVL 86

Expert Comment

by:jkr
ID: 39868426
BTW, the above would as well work to read your file in one single call, e.g.

fread(buff, 4 * sizeof(int) + 16* sizeof(float), 1, f);

FFTVals* pVals = (FFTVals*) buff;

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Author Comment

by:Ingo Foerster
ID: 39868481
ok, how to get the float to a existing float value:

existing:
float cinDBOrgBuf[16];
cinDBOrgBuf = pVals->DBOrgBuf; 

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do not work.
0
 
LVL 86

Expert Comment

by:jkr
ID: 39868500
That can be done like

float cinDBOrgBuf[16];
for (int i = 0; i < 16; ++i)
  cinDBOrgBuf[i] = pVals->DBOrgBuf[i]; 

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or simply like

float cinDBOrgBuf[16];
memcpy(cinDBOrgBuf,pVals->DBOrgBuf,16 * sizeof(float)); 

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But, as I wrote, there is no need to duplicate these values, you can use them directly from 'pVal'.
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Author Closing Comment

by:Ingo Foerster
ID: 39868719
Exact what I was looking for. Many thanks!
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