fread(..inf..skip) returns to many elements
Alois Schloegl
alois.schloegl at gmx.net
Wed Feb 27 15:45:52 CST 2008
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.
Configuration (please do not edit this section):
-----------------------------------------------
uname output: Linux edelweiss 2.6.22-3-k7 #1 SMP Sun Feb 10 21:04:14
UTC 2008 i686 GNU/Linux
configure opts:
Fortran compiler: g77
FFLAGS: -O -mieee-fp
F2C: @F2C@
F2CFLAGS: @F2CFLAGS@
FLIBS: -L/usr/lib/gcc/i486-linux-gnu/3.4.6
-L/usr/lib/gcc/i486-linux-gnu/3.4.6/../../../../lib
-L/usr/lib/gcc/i486-linux-gnu/3.4.6/../../.. -L/lib/../lib
-L/usr/lib/../lib -lhdf5 -lz -lfrtbegin -lg2c -lm
CPPFLAGS:
INCFLAGS: -I. -I. -I./liboctave -I./src -I./libcruft/misc
C compiler: gcc, version 4.2.3 (Debian 4.2.3-1)
CFLAGS: -g -O2
CPICFLAG: -fPIC
C++ compiler: g++, version 4.2.3
CXXFLAGS: -g -O2
CXXPICFLAG: -fPIC
LD_CXX: g++
LDFLAGS:
LIBFLAGS: -L.
RLD_FLAG: -Wl,-rpath -Wl,/usr/local/lib/octave-3.0.0+
BLAS_LIBS: -llapack -lblas
FFTW_LIBS: -lfftw3
LIBS: -lreadline -lncurses -ldl -lhdf5 -lz -lm
LEXLIB:
LIBGLOB:
SED: /bin/sed
DEFS:
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User-preferences (please do not edit this section):
--------------------------------------------------
EDITOR = emacs
EXEC_PATH =
/usr/local/libexec/octave/3.0.0+/site/exec/i686-pc-linux-gnu:/usr/local/libexec/octave/api-v32+/site/exec/i686-pc-linux-gnu:/usr/local/libexec/octave/site/exec/i686-pc-linux-gnu:/usr/local/libexec/octave/3.0.0+/exec/i686-pc-linux-gnu:/usr/local/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games:/usr/local/j2re1.4.2_01/bin
IMAGE_PATH = .:/usr/local/share/octave/3.0.0+/imagelib
PAGER = less
PS1 = \s:\#>
PS2 = >
PS4 = +
beep_on_error = 0
completion_append_char =
crash_dumps_octave_core = 1
echo_executing_commands = 0
fixed_point_format = 0
gnuplot_binary = gnuplot
# gnuplot_command_end = <no value or error in displaying it>
# gnuplot_command_plot = <no value or error in displaying it>
# gnuplot_command_replot = <no value or error in displaying it>
# gnuplot_command_splot = <no value or error in displaying it>
# gnuplot_command_title = <no value or error in displaying it>
# gnuplot_command_using = <no value or error in displaying it>
# gnuplot_command_with = <no value or error in displaying it>
history_file = /home/schloegl/.octave_hist
history_size = 1024
ignore_function_time_stamp = system
info_file = /usr/local/share/info/octave.info
info_program = info
makeinfo_program = makeinfo
max_recursion_depth = 256
output_max_field_width = 5
output_precision = 5
page_output_immediately = 0
page_screen_output = 1
# print_answer_id_name = <no value or error in displaying it>
print_empty_dimensions = 1
save_precision = 16
saving_history = 1
sighup_dumps_octave_core = 1
sigterm_dumps_octave_core = 1
silent_functions = 0
split_long_rows = 1
string_fill_char =
struct_levels_to_print = 2
suppress_verbose_help_message = 0
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