/***************************************************************************** * * This example source code introduces a c library buffered I/O interface to * URL reads it supports fopen(), fread(), fgets(), feof(), fclose(), * rewind(). Supported functions have identical prototypes to their normal c * lib namesakes and are preceaded by url_ . * * Using this code you can replace your program's fopen() with url_fopen() * and fread() with url_fread() and it become possible to read remote streams * instead of (only) local files. Local files (ie those that can be directly * fopened) will drop back to using the underlying clib implementations * * See the main() function at the bottom that shows an app that retrives from a * specified url using fgets() and fread() and saves as two output files. * * Copyright (c) 2003 Simtec Electronics * * Re-implemented by Vincent Sanders with extensive * reference to original curl example code * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * * This example requires libcurl 7.9.7 or later. */ #include #include #ifndef WIN32 # include #endif #include #include #include enum fcurl_type_e { CFTYPE_NONE=0, CFTYPE_FILE=1, CFTYPE_CURL=2 }; struct fcurl_data { enum fcurl_type_e type; /* type of handle */ union { CURL *curl; FILE *file; } handle; /* handle */ char *buffer; /* buffer to store cached data*/ int buffer_len; /* currently allocated buffers length */ int buffer_pos; /* end of data in buffer*/ int still_running; /* Is background url fetch still in progress */ }; typedef struct fcurl_data URL_FILE; /* exported functions */ URL_FILE *url_fopen(const char *url,const char *operation); int url_fclose(URL_FILE *file); int url_feof(URL_FILE *file); size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file); char * url_fgets(char *ptr, int size, URL_FILE *file); void url_rewind(URL_FILE *file); /* we use a global one for convenience */ CURLM *multi_handle; /* curl calls this routine to get more data */ static size_t write_callback(char *buffer, size_t size, size_t nitems, void *userp) { char *newbuff; int rembuff; URL_FILE *url = (URL_FILE *)userp; size *= nitems; rembuff=url->buffer_len - url->buffer_pos; /* remaining space in buffer */ if(size > rembuff) { /* not enough space in buffer */ newbuff=realloc(url->buffer,url->buffer_len + (size - rembuff)); if(newbuff==NULL) { fprintf(stderr,"callback buffer grow failed\n"); size=rembuff; } else { /* realloc suceeded increase buffer size*/ url->buffer_len+=size - rembuff; url->buffer=newbuff; } } memcpy(&url->buffer[url->buffer_pos], buffer, size); url->buffer_pos += size; return size; } /* use to attempt to fill the read buffer up to requested number of bytes */ static int fill_buffer(URL_FILE *file,int want,int waittime) { fd_set fdread; fd_set fdwrite; fd_set fdexcep; struct timeval timeout; int rc; /* only attempt to fill buffer if transactions still running and buffer * doesnt exceed required size already */ if((!file->still_running) || (file->buffer_pos > want)) return 0; /* attempt to fill buffer */ do { int maxfd = -1; long curl_timeo = -1; FD_ZERO(&fdread); FD_ZERO(&fdwrite); FD_ZERO(&fdexcep); /* set a suitable timeout to fail on */ timeout.tv_sec = 60; /* 1 minute */ timeout.tv_usec = 0; curl_multi_timeout(multi_handle, &curl_timeo); if(curl_timeo >= 0) { timeout.tv_sec = curl_timeo / 1000; if(timeout.tv_sec > 1) timeout.tv_sec = 1; else timeout.tv_usec = (curl_timeo % 1000) * 1000; } /* get file descriptors from the transfers */ curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd); /* In a real-world program you OF COURSE check the return code of the function calls. On success, the value of maxfd is guaranteed to be greater or equal than -1. We call select(maxfd + 1, ...), specially in case of (maxfd == -1), we call select(0, ...), which is basically equal to sleep. */ rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout); switch(rc) { case -1: /* select error */ break; case 0: default: /* timeout or readable/writable sockets */ curl_multi_perform(multi_handle, &file->still_running); break; } } while(file->still_running && (file->buffer_pos < want)); return 1; } /* use to remove want bytes from the front of a files buffer */ static int use_buffer(URL_FILE *file,int want) { /* sort out buffer */ if((file->buffer_pos - want) <=0) { /* ditch buffer - write will recreate */ if(file->buffer) free(file->buffer); file->buffer=NULL; file->buffer_pos=0; file->buffer_len=0; } else { /* move rest down make it available for later */ memmove(file->buffer, &file->buffer[want], (file->buffer_pos - want)); file->buffer_pos -= want; } return 0; } URL_FILE *url_fopen(const char *url,const char *operation) { /* this code could check for URLs or types in the 'url' and basicly use the real fopen() for standard files */ URL_FILE *file; (void)operation; file = malloc(sizeof(URL_FILE)); if(!file) return NULL; memset(file, 0, sizeof(URL_FILE)); if((file->handle.file=fopen(url,operation))) file->type = CFTYPE_FILE; /* marked as URL */ else { file->type = CFTYPE_CURL; /* marked as URL */ file->handle.curl = curl_easy_init(); curl_easy_setopt(file->handle.curl, CURLOPT_URL, url); curl_easy_setopt(file->handle.curl, CURLOPT_WRITEDATA, file); curl_easy_setopt(file->handle.curl, CURLOPT_VERBOSE, 0L); curl_easy_setopt(file->handle.curl, CURLOPT_WRITEFUNCTION, write_callback); if(!multi_handle) multi_handle = curl_multi_init(); curl_multi_add_handle(multi_handle, file->handle.curl); /* lets start the fetch */ curl_multi_perform(multi_handle, &file->still_running); if((file->buffer_pos == 0) && (!file->still_running)) { /* if still_running is 0 now, we should return NULL */ /* make sure the easy handle is not in the multi handle anymore */ curl_multi_remove_handle(multi_handle, file->handle.curl); /* cleanup */ curl_easy_cleanup(file->handle.curl); free(file); file = NULL; } } return file; } int url_fclose(URL_FILE *file) { int ret=0;/* default is good return */ switch(file->type) { case CFTYPE_FILE: ret=fclose(file->handle.file); /* passthrough */ break; case CFTYPE_CURL: /* make sure the easy handle is not in the multi handle anymore */ curl_multi_remove_handle(multi_handle, file->handle.curl); /* cleanup */ curl_easy_cleanup(file->handle.curl); break; default: /* unknown or supported type - oh dear */ ret=EOF; errno=EBADF; break; } if(file->buffer) free(file->buffer);/* free any allocated buffer space */ free(file); return ret; } int url_feof(URL_FILE *file) { int ret=0; switch(file->type) { case CFTYPE_FILE: ret=feof(file->handle.file); break; case CFTYPE_CURL: if((file->buffer_pos == 0) && (!file->still_running)) ret = 1; break; default: /* unknown or supported type - oh dear */ ret=-1; errno=EBADF; break; } return ret; } size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file) { size_t want; switch(file->type) { case CFTYPE_FILE: want=fread(ptr,size,nmemb,file->handle.file); break; case CFTYPE_CURL: want = nmemb * size; fill_buffer(file,want,1); /* check if theres data in the buffer - if not fill_buffer() * either errored or EOF */ if(!file->buffer_pos) return 0; /* ensure only available data is considered */ if(file->buffer_pos < want) want = file->buffer_pos; /* xfer data to caller */ memcpy(ptr, file->buffer, want); use_buffer(file,want); want = want / size; /* number of items */ break; default: /* unknown or supported type - oh dear */ want=0; errno=EBADF; break; } return want; } char *url_fgets(char *ptr, int size, URL_FILE *file) { int want = size - 1;/* always need to leave room for zero termination */ int loop; switch(file->type) { case CFTYPE_FILE: ptr = fgets(ptr,size,file->handle.file); break; case CFTYPE_CURL: fill_buffer(file,want,1); /* check if theres data in the buffer - if not fill either errored or * EOF */ if(!file->buffer_pos) return NULL; /* ensure only available data is considered */ if(file->buffer_pos < want) want = file->buffer_pos; /*buffer contains data */ /* look for newline or eof */ for(loop=0;loop < want;loop++) { if(file->buffer[loop] == '\n') { want=loop+1;/* include newline */ break; } } /* xfer data to caller */ memcpy(ptr, file->buffer, want); ptr[want]=0;/* allways null terminate */ use_buffer(file,want); break; default: /* unknown or supported type - oh dear */ ptr=NULL; errno=EBADF; break; } return ptr;/*success */ } void url_rewind(URL_FILE *file) { switch(file->type) { case CFTYPE_FILE: rewind(file->handle.file); /* passthrough */ break; case CFTYPE_CURL: /* halt transaction */ curl_multi_remove_handle(multi_handle, file->handle.curl); /* restart */ curl_multi_add_handle(multi_handle, file->handle.curl); /* ditch buffer - write will recreate - resets stream pos*/ if(file->buffer) free(file->buffer); file->buffer=NULL; file->buffer_pos=0; file->buffer_len=0; break; default: /* unknown or supported type - oh dear */ break; } } /* Small main program to retrive from a url using fgets and fread saving the * output to two test files (note the fgets method will corrupt binary files if * they contain 0 chars */ int main(int argc, char *argv[]) { URL_FILE *handle; FILE *outf; int nread; char buffer[256]; const char *url; if(argc < 2) url="http://192.168.7.3/testfile";/* default to testurl */ else url=argv[1];/* use passed url */ /* copy from url line by line with fgets */ outf=fopen("fgets.test","w+"); if(!outf) { perror("couldn't open fgets output file\n"); return 1; } handle = url_fopen(url, "r"); if(!handle) { printf("couldn't url_fopen() %s\n", url); fclose(outf); return 2; } while(!url_feof(handle)) { url_fgets(buffer,sizeof(buffer),handle); fwrite(buffer,1,strlen(buffer),outf); } url_fclose(handle); fclose(outf); /* Copy from url with fread */ outf=fopen("fread.test","w+"); if(!outf) { perror("couldn't open fread output file\n"); return 1; } handle = url_fopen("testfile", "r"); if(!handle) { printf("couldn't url_fopen() testfile\n"); fclose(outf); return 2; } do { nread = url_fread(buffer, 1,sizeof(buffer), handle); fwrite(buffer,1,nread,outf); } while(nread); url_fclose(handle); fclose(outf); /* Test rewind */ outf=fopen("rewind.test","w+"); if(!outf) { perror("couldn't open fread output file\n"); return 1; } handle = url_fopen("testfile", "r"); if(!handle) { printf("couldn't url_fopen() testfile\n"); fclose(outf); return 2; } nread = url_fread(buffer, 1,sizeof(buffer), handle); fwrite(buffer,1,nread,outf); url_rewind(handle); buffer[0]='\n'; fwrite(buffer,1,1,outf); nread = url_fread(buffer, 1,sizeof(buffer), handle); fwrite(buffer,1,nread,outf); url_fclose(handle); fclose(outf); return 0;/* all done */ }