This image ..cannot be displayed because it contains errors
in [Unix Programming]
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From: Mr_John on 18 Jun 2008 19:01 im trying with web server i wrote in unix (Freebsd) to send file to mozilla client.it works fine with html,txt.. but when i try to send a jpeg, mozilla browser write: " This image 127.0.0.1:1024/pic.jpg cannot be displayed because it contains an error".where is my error in the code i think there could be some byte in the buffer it cannot read.but i can find where im wrong in the code..please someone can help me?thanks a lot char *risp; /*buffer when i put the file before sending*/ /* i get the n with getfilesize() correctly tested*/ risp=malloc(n); strncpy(msgb,"HTTP/1.0 200 OK\r\nContent-Type:image/jpeg\r\nContent- Length:21139\r\nServer: webserver/0.1 (FreeBSD)\r\n\r \n",sizeof(msgb)-1); /*i write an header just to try if works*/ msgb[199]='\0'; fp = fopen(uri,"r");/*uri is ok (tested) */ if(fp==NULL)printf("Error opening file"); else{ ret=fread(risp,1,n,fp); risp[n]='\0'; ret=send(cl_sk,msgb,strlen(msgb),0); ret=send(cl_sk,risp,strlen(risp),0); fclose(fp); free(risp);
From: Jens Thoms Toerring on 18 Jun 2008 19:24 Mr_John <lecter.hannibal(a)email.it> wrote: > im trying with web server i wrote in unix (Freebsd) to send file to > mozilla client.it works fine with html,txt.. but when i try to send a > jpeg, mozilla browser write: " This image 127.0.0.1:1024/pic.jpg > cannot be displayed because it contains an error".where is my error in > the code i think there could be some byte in the buffer it cannot > read.but i can find where im wrong in the code..please someone can > help me?thanks a lot > char *risp; /*buffer when i put the file before sending*/ > /* i get the n with getfilesize() correctly tested*/ > risp=malloc(n); > strncpy(msgb,"HTTP/1.0 200 OK\r\nContent-Type:image/jpeg\r\nContent- > Length:21139\r\nServer: webserver/0.1 (FreeBSD)\r\n\r > \n",sizeof(msgb)-1); /*i write an header just to try if works*/ > msgb[199]='\0'; > fp = fopen(uri,"r");/*uri is ok (tested) */ > if(fp==NULL)printf("Error opening file"); > else{ > ret=fread(risp,1,n,fp); > risp[n]='\0'; That's already problematic because you alllocated only 'n' bytes but now you write one more byte. Remember: if you write to risp[n] you assign to the (n+1)th element of the buffer. > ret=send(cl_sk,msgb,strlen(msgb),0); > ret=send(cl_sk,risp,strlen(risp),0); I guess what's going to be in 'risp' is data from the jpeg file. And that's not a string but binary data, which very well can contain '\0' characters all over the place. So adding a '\0' at the end of what you read and using strlen() on it doesn't make sense (strlen() stops at the first '\0' it encounters, not necessarily at the end of the file). Just do ret = send( cl_sk, risp, n, 0 ); instead if 'n' is the size of the file. Regards, Jens -- \ Jens Thoms Toerring ___ jt(a)toerring.de \__________________________ http://toerring.de
From: David Schwartz on 18 Jun 2008 20:25 On Jun 18, 4:01 pm, Mr_John <lecter.hanni...(a)email.it> wrote: > ret=fread(risp,1,n,fp); > risp[n]='\0'; > > ret=send(cl_sk,msgb,strlen(msgb),0); > ret=send(cl_sk,risp,strlen(risp),0); Umm, 'strlen' is for C-style strings, not for arbitrary data. DS
From: James Kanze on 19 Jun 2008 07:22 On Jun 19, 1:01 am, Mr_John <lecter.hanni...(a)email.it> wrote: > im trying with web server i wrote in unix (Freebsd) to send > file to mozilla client.it works fine with html,txt.. but when > i try to send a jpeg, mozilla browser write: " This image > 127.0.0.1:1024/pic.jpg cannot be displayed because it contains > an error".where is my error in the code i think there could be > some byte in the buffer it cannot read.but i can find where im > wrong in the code..please someone can help me?thanks a lot > char *risp; /*buffer when i put the file before sending*/ > /* i get the n with getfilesize() correctly tested*/ > risp=malloc(n); > strncpy(msgb,"HTTP/1.0 200 OK\r\nContent-Type:image/jpeg\r\nContent- > Length:21139\r\nServer: webserver/0.1 (FreeBSD)\r\n\r > \n",sizeof(msgb)-1); /*i write an header just to try if works*/ > msgb[199]='\0'; > fp = fopen(uri,"r");/*uri is ok (tested) */ Just a nit, but formally, you can't read binary data if you open the file in text mode (but it doesn't matter in Unix). > if(fp==NULL)printf("Error opening file"); > else{ > ret=fread(risp,1,n,fp); > risp[n]='\0'; > ret=send(cl_sk,msgb,strlen(msgb),0); > ret=send(cl_sk,risp,strlen(risp),0); And it makes no sense using strlen on binary data. Quite frankly, for binary data, I'd use open and read, then send the number of bytes returned from the read request. Text data is somewhat more complicated, because in theory, on the Internet you're supposed to use CRLF as line end, instead of just LF. In practice, however, most HTTP clients will be tolerant enough to accept either. > fclose(fp); > free(risp); -- James Kanze (GABI Software) email:james.kanze(a)gmail.com Conseils en informatique orientée objet/ Beratung in objektorientierter Datenverarbeitung 9 place Sémard, 78210 St.-Cyr-l'École, France, +33 (0)1 30 23 00 34
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