c read() causing bad file descriptor error -


context program reading through filestream, 4k chunks @ time, looking pattern. starts reading in 4k, , if doesn't find pattern there, starts loop reads in next 4k chunk (rinse , repeat until eof or pattern found). on many files code working properly, files getting errors.

the code below highly redacted, know might annoying, includes lines reference file descriptor or file itself. know don't want take word it, since i'm 1 problem...

having done little homework before crying help, i've found:

  1. the file descriptor happens = 6 (it's 6 files working), , number isn't getting changed through life of execution. don't know if that's useful info or not.

  2. by inserting print statements after every operation accesses file descriptor, i've found successful files go through following cycle "open-read-close-close" (i.e. pattern found in first 4k) unsuccessful files go "open-read-read error (bad file descriptor)-close." no premature close, , it's getting in first read successfully, second read causes bad file descriptor error.

.

int function(char *file) {  int len, fd, go = 0; char buf[4096];  if((fd = open(file, o_rdonly)) <= 0) {     my_error("error opening file %s: %s", file, strerror(errno));     return null; }  //first read if((len = read(fd, buf, 4096)) <= 0) {     my_error("error reading file %s: %s", file, strerror(errno));     close(fd); return null; }  //pattern-searching  if(/*conditions*/) {     /* found it, no need keep looking*/     close(fd); }  else {     //reading loop     while(!go)     {         if(/*conditions*/)         {             my_error("cannot locate pattern in file %s", file);             close(fd); return null;         }          //next read         if((len = read(fd, buf, 4096)) <= 0) /**** fails here *****/         {             my_error("error reading file, possible bad message %s: %s",                 file, strerror(errno));                 close(fd); return null;         }          if(/*conditions*/)         {             close(fd);             break;         }          //pattern searching          if(/*conditions*/)         {              /* found pattern */             go++; //break out of while loop              //stuff              close(fd);         }         else         {             //stuff, , loop again next chunk         }     } /*end while loop*/ }/*end else statement*/  close(fd); }

.

try not worry pattern-reading logic - operations done on char buffer, not on file, ought have no impact on problem.

eof returns 0 (falls if ... <= 0), not set errno, may have out of date code in it.

try testing 0 , negative (error, -1) values seperately.

regarding "strace": i've used little @ home, , in previous jobs. unfortunately, it's not installed in current work environment. useful tool, when it's available. here, took "let's read fine manual" (man read) approach questioner :-)


Comments

Post a Comment

Popular posts from this blog

c# - SharpSVN - How to get the previous revision? -

i trying find efficient way previous revision of file text comparison using sharpsvn. using (svnclient c = new svnclient()) { c.authentication.defaultcredentials = new networkcredential( configurationmanager.appsettings.get("svnserviceusername") , configurationmanager.appsettings.get("svnservicepassword") , configurationmanager.appsettings.get("svnservicedomain") ); c.authentication.sslservertrusthandlers += new eventhandler<svnsslservertrusteventargs>(authentication_sslservertrusthandlers); collection<svnfileversioneventargs> fileversioncollection = new collection<svnfileversioneventargs>(); svnrevisionrange range = new svnrevisionrange(0, this.hooks.revision); svnfileversionsargs args = new svnfileversionsargs(); args.retrieveproperties = true; args.range = range; foreach (svnchangeitem item in log.changedpaths) { string path = this.repositorypath + it...
Read more

c++ - Is it possible to compile a VST on linux? -

for class project i'm attempting write vst plugin backed cuda. current cuda workflow on linux box, i'd prefer compile , link there. according wikipedia , should possible (i couldn't find steinberg documentation relevant linux) can't find makefile or instructions on how build if aren't using xcode or visual studio. i'm vst 3 sdk doesn't support linux. when try compile plugin under linux, error: ./base/source/fatomic.cpp:39:30: fatal error: libkern/osatomic.h: no such file or directory this issue caused following code in "vst3 sdk/base/source/fatomic.cpp" #if mac #include <libkern/osatomic.h> #if mac_os_x_version_min_required > mac_os_x_version_10_4 #define native_atomic_type (volatile int32_t*) #else #define native_atomic_type (int32_t*) #endif #elif windows #include <windows.h> #endif but hope compiling under linux work vst sdk 2.4. reading. jvstwrapper seems run on lin...
Read more

url - Querystring manipulation of email Address in PHP -

i using third party application (email2http) send me emailid, body , message. unable retrieve email id due name appended on , enclosed < , >. here querystring getting. test.php?from=ajay+reddy &subject=cx&body=somebody when print variable in php returns name , not email id. $from = $_get['from']; echo $from; //output ajay reddy please suggest me how can emailid also. i dont want use post method due testing , debugging. it's working fine. forgot use htmlentities() in debugging.
Read more