[Octave-bug-tracker] [bug #63968] fwrite writes incorrect number of bytes

[anonymous]

URL:
  <https://savannah.gnu.org/bugs/?63968>

                 Summary: fwrite writes incorrect number of bytes
                   Group: GNU Octave
               Submitter: None
               Submitted: Mon 27 Mar 2023 02:05:19 PM UTC
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: Michael Swamp
        Originator Email: mswamp@msrc.com
             Open/Closed: Open
                 Release: 8.1.0
         Discussion Lock: Any
        Operating System: Microsoft Windows
           Fixed Release: None
         Planned Release: None


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Follow-up Comments:


-------------------------------------------------------
Date: Mon 27 Mar 2023 02:05:19 PM UTC By: Anonymous
Seems to be a few bugs with fwrite.  Not only is it writing incorrect data
when you do binary writes with uint8, but it also seems to be writing an
incorrect number of bytes and not reporting a write error.

Run the following script.  It does not report a write error, but when you read
the data back it has a different amount of bytes.

display("Writing File");
ID = tic();
fid = fopen("TestWrite","w");
for i = 1:255
  for j = 1:254
    for k = 1:253
      CNT = fwrite(fid,uint8(k),"uint8");
      if (CNT == 0)
        display(sprintf("Index %d Index %d Index %d Write Failure\n",i,j,k));
        error("Write Error");
      endif
    endfor
  endfor
endfor
WRITE_FP = ftell(fid);
display(sprintf("Wrote %d bytes\n",i*j*k));
display(sprintf("File Pointer %d\n",WRITE_FP));
fclose(fid);
elapsed_time = toc(ID);
display(sprintf("Write took %f seconds\n",elapsed_time));
##
## Read back Data
##
display("Reading File");
ID = tic();
fid = fopen("TestWrite","r");
DATA = uint8(fread(fid,"uint8"));
READ_FP = ftell(fid);
fclose(fid);
elapsed_time = toc(ID);
display(sprintf("Read took %f seconds\n",elapsed_time));
display(sprintf("Read %d bytes\n",length(DATA)));
display(sprintf("File Pointer %d\n",READ_FP));
##
## Read Back Data - Method 2
display("Reading File");
ID = tic();
fid = fopen("TestWrite","r");
DATA2=uint8([]);
for i = 1:255
  for j = 1:254
    for k = 1:253
      [VAL, CNT] = fread(fid,1,"uint8");
      if (CNT == 0)
        READ2_FP = ftell(fid);
        display(sprintf("Index %d Index %d Index %d Read Failure\n",i,j,k));
        display(sprintf("File Pointer %d\n",READ2_FP));
        error("Invalid Read");
      endif
      DATA2(i*j+k) = uint8(VAL);
    endfor
  endfor
endfor
fclose(fid);
elapsed_time = toc(ID);
display(sprintf("Read took %f seconds\n",elapsed_time));
display(sprintf("Read %d bytes\n",length(DATA)));






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File Attachments:


-------------------------------------------------------
Date: Mon 27 Mar 2023 02:05:19 PM UTC  Name: TestWriteFile.m  Size: 2KiB   By:
None

<http://savannah.gnu.org/bugs/download.php?file_id=54532>

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