fread(..inf..skip) returns to many elements

[John W. Eaton]

On 27-Feb-2008, Alois Schloegl wrote:

| To: bug at octave.org
| Cc: a.schloegl at ieee.org
| Subject: bug in fread with skip
| --------
| Bug report for Octave 3.0.0+ configured for i686-pc-linux-gnu
| 
| Description:
| -----------
| 
| I came across a problem using a rather complex call to fread.
| The file contains some header (10752 bytes) and 40 data blocks with 
| 62976 bytes.
| This results in a file size of 2 555 904 bytes. When, I tried to read 
| the last 1536 bytes from each data block, using this command,
| [t,c] = fread(fid,inf,'1536*uint8',61440);
| 
| one gets 98304 bytes, this is much more than the expected 40*1536=61440.
| 
| 
| The problem appears in Octave 2.9.19 as well as in 3.0.0+ a recent CVS 
| snapshot (from Feb 24).
| 
| 
| 
| 
| Repeat-By:
| ---------
| 
| Here is a script for repeating the problem,
| 
| % generate test file with 2 555 904 bytes
| testfile='/tmp/test.bin';
| fid = fopen(testfile,'w');
| fwrite(fid,1:638976,'uint32');
| fclose(fid);
| 
| % read 1536 bytes and skip 61440 byes as long as data elements are available
| fid = fopen(testfile,'r');
| fseek(fid,10752+61440,'bof');
| [t,count] = fread(fid,inf,'1536*uint8',61440);
| fclose(fid);
| count,
| 
| length(t) and count have a value of 87552 instead of 61440.

Please try the following patch.

Thanks,

jwe


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