post-scarcity/src/io/fopen.c

/*
 * fopen.c
 *
 * adapted from https://curl.haxx.se/libcurl/c/fopen.html.
 *
 * Modifications to read/write wide character streams by
 * Simon Brooke.
 *
 * Copyright (c) 2003, 2017 Simtec Electronics
 * Some portions (c) 2019 Simon Brooke <simon@journeyman.cc>
 *
 * 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 <stdio.h>
#include <string.h>
#ifndef WIN32
#  include <sys/time.h>
#endif
#include <stdlib.h>
#include <errno.h>

#include <curl/curl.h>

#include "fopen.h"

/* we use a global one for convenience */
static 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;
  size_t 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 succeeded 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, size_t want)
{
  fd_set fdread;
  fd_set fdwrite;
  fd_set fdexcep;
  struct timeval timeout;
  int rc;
  CURLMcode mc; /* curl_multi_fdset() return code */

  /* only attempt to fill buffer if transactions still running and buffer
   * doesn't 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 */
    mc = curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);

    if(mc != CURLM_OK) {
      fprintf(stderr, "curl_multi_fdset() failed, code %d.\n", mc);
      break;
    }

    /* On success the value of maxfd is guaranteed to be >= -1. We call
       select(maxfd + 1, ...); specially in case of (maxfd == -1) there are
       no fds ready yet so we call select(0, ...) --or Sleep() on Windows--
       to sleep 100ms, which is the minimum suggested value in the
       curl_multi_fdset() doc. */

    if(maxfd == -1) {
#ifdef _WIN32
      Sleep(100);
      rc = 0;
#else
      /* Portable sleep for platforms other than Windows. */
      struct timeval wait = { 0, 100 * 1000 }; /* 100ms */
      rc = select(0, NULL, NULL, NULL, &wait);
#endif
    }
    else {
      /* Note that on some platforms 'timeout' may be modified by select().
         If you need access to the original value save a copy beforehand. */
      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, size_t want)
{
  /* sort out buffer */
  if((file->buffer_pos - want) <= 0) {
    /* ditch buffer - write will recreate */
    free(file->buffer);
    file->buffer = NULL;
    free(file->wide_buffer);
    file->wide_buffer = NULL;
    file->buffer_pos = 0;
    file->buffer_len = 0;
    file->wide_cursor = 0;
  }
  else {
    /* move rest down make it available for later */
    memmove(file->buffer,
            &file->buffer[want],
            (file->buffer_pos - want));

    file->buffer_pos -= want;
    // TODO: something to adjust the wide_cursor
  }
  return 0;
}

URL_FILE *url_fopen(const char *url, const char *operation)
{
  /* this code could check for URLs or types in the 'url' and
     basically use the real fopen() for standard files */

  URL_FILE *file;
  (void)operation;

  file = calloc(1, sizeof(URL_FILE));
  if(!file)
    return NULL;

  file->handle.file = fopen(url, operation);
  if(file->handle.file)
    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;
  }

  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);

    /* check if there's 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, size_t size, URL_FILE *file)
{
  size_t want = size - 1;/* always need to leave room for zero termination */
  size_t loop;

  switch(file->type) {
  case CFTYPE_FILE:
    ptr = fgets(ptr, (int)size, file->handle.file);
    break;

  case CFTYPE_CURL:
    fill_buffer(file, want);

    /* check if there's 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;/* always 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*/
    free(file->buffer);
    file->buffer = NULL;
    file->buffer_pos = 0;
    file->buffer_len = 0;

    break;

  default: /* unknown or supported type - oh dear */
    break;
  }
}

/**
 * given this file handle f, return a new url_file handle wrapping it.
 *
 * @param f the file to be wrapped;
 * @return the new handle, or null if no such handle could be allocated.
 */
URL_FILE * file_to_url_file( FILE* f) {
  URL_FILE * result = (URL_FILE *)malloc(sizeof(URL_FILE));

  if ( result != NULL) {
    result->type = CFTYPE_FILE,
    result->handle.file = f;
  }

  return result;
}

/**
 * get one wide character from the buffer.
 *
 * @param file the stream to read from;
 * @return the next wide character on the stream, or zero if no more.
 */
wint_t url_fgetwc(URL_FILE *input) {
  wint_t result = 0;

  switch(input->type) {
  case CFTYPE_FILE:
    fwide( input->handle.file, 1 ); /* wide characters */
    result = fgetc(input->handle.file); /* passthrough */
    break;

  case CFTYPE_CURL:
    if (input.buffer_len != 0) {
      if ( input.wide_buffer == NULL) {
        /* not initialised */
        input.wide_buffer = calloc( input.buffer_len, sizeof(wint_t));
      }

      size_t len = wcslen(input.wide_buffer);
      if (input.still_running ||
          len == 0 ||
          len >= input.wide_cursor) {
        /* refresh the wide buffer */
        mbstowcs(input.wide_buffer, input.buffer, input.buffer_pos);
      }

      result = input.wide_buffer[input.wide_cursor] ++;

      /* do something to fread (advance) one utf character */
    }
    break;
  }

  return result;
}

/* #define FGETSFILE "fgets.test" */
/* #define FREADFILE "fread.test" */
/* #define REWINDFILE "rewind.test" */

/* /\* Small main program to retrieve 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; */

/*   size_t 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(FGETSFILE, "wb+"); */
/*   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(FREADFILE, "wb+"); */
/*   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(REWINDFILE, "wb+"); */
/*   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 *\/ */
/* } */