getting data from server in cycle - c

Question

my task is get from server data of an file with HTTP protocol
but problem is that i dont know the size of the content so i iterate through read func to get data from socked but it iterates every time only once i dont know really why
int res, len, total, boolk = 0, p=0;
while ((res = read(client_socket,bufferOut,4095)) > 0)
{
bufferOut[res]= '\0';
if(p==0)
{
buffer = calloc(strlen(bufferOut)+1,sizeof(char));
}
else
{
buffer = realloc(buffer,strlen(buffer)*sizeof(char)+strlen(bufferOut)+1*sizeof(char));
}
strcat(buffer,bufferOut);
if(isEnough(bufferOut)!=0 && boolk == 0)
{
index = getIndex(buffer);
kk = getCode(buffer);
len = getLen(buffer);
boolk = 1;
}
if(strlen(bufferOut)>=len+index && boolk == 1)
{
break;
}
p++;
}
function isEnough only looks if full http header arrived getIndex get lenght of header and getLen get length of that file so i wanted to iterate until buffer is same lenght as header file which should be

Answer 1

You're working much too hard.
int
read_until_enough(int client_socket, char **buf_out, size_t *buflen_out)
{
char *rdbuf = xmalloc(INITIAL_BUFFER_SIZE);
size_t buflen = 0, bufalloc = INITIAL_BUFFER_SIZE;
for (;;) {
ssize_t n = recv(client_socket, rdbuf + buflen, bufalloc - buflen);
if (n <= 0) goto recv_failure;
if (is_enough(rdbuf, buflen)) break;
buflen += n;
if (buflen == bufalloc) {
bufalloc *= 2;
rdbuf = xrealloc(rdbuf, bufalloc);
}
}
*rdbuf_out = rdbuf;
*buflen_out = buflen;
return 0;
recv_failure:;
int save_errno = errno;
free(rdbuf);
errno = save_errno;
*rdbuf_out = 0;
*buflen_out = 0;
return -1;
}
Please note that is_enough now takes the size of the received data as an argument, caller gets both the received data and its size, and the buffer is NOT nul-terminated. HTTP is a binary-transparent protocol; you MUST NOTrfc2119 assume that you never receive nul bytes.
Please also note that is_enough is stateless and is expected to do all of the parsing. This is better separation of concerns. Worry about the performance cost of re-parsing the HTTP headers each time around the loop only after you have everything working.
Finally, the functions xmalloc and xrealloc are wrappers around malloc and realloc that either succeed or crash the program. I am using them here to avoid cluttering up the example with error-recovery logic for memory allocation. You will have to decide whether they are appropriate for whatever you're doing.