/* buffers.c */

#include "or.h"

int buf_new(char **pbuf, size_t *pbuflen, size_t *pbuf_datalen) {

  if (!pbuf || !pbuflen || !pbuf_datalen) /* invalid parameters */
    return -1;

  *pbuf = (char *)malloc(MAX_BUF_SIZE);
  if(!*pbuf)
    return -1;
  memset(*pbuf,0,MAX_BUF_SIZE);
  *pbuflen = MAX_BUF_SIZE;
  *pbuf_datalen = 0;

  return 0;
}

int buf_free(char *buf) {

  free(buf);

  return 0;
}

int read_to_buf(int s, char **pbuf, size_t *pbuflen, size_t *pbuf_datalen, int *preached_eof) {

  /* grab from s, put onto buf, return how many bytes read */

  int read_result;
  char *buf;
  size_t buflen;
  size_t buf_datalen;

  if (!pbuf || !pbuflen || !pbuf_datalen || !preached_eof) /* invalid parameters */
    return -1 ;

  if(s<0) {
    log(LOG_DEBUG,"read_to_buf() received negative socket %d.",s);
    return -1;
  }

  /* this is the point where you would grow the buffer, if you want to */
  buf = *pbuf, buflen = *pbuflen, buf_datalen = *pbuf_datalen;

  if (!buf) /* invalid parameter */
    return -1;

  read_result = read(s, buf+buf_datalen, buflen - buf_datalen);
  if (read_result < 0) {
    if(errno!=EAGAIN) { /* it's a real error */
      return -1;
    }
    return 0;
  } else if (read_result == 0) {
    log(LOG_DEBUG,"read_to_buf(): Encountered eof");
    *preached_eof = 1;
    return 0;
  } else { /* we read some bytes */
    *pbuf_datalen = buf_datalen + read_result;
    log(LOG_DEBUG,"read_to_buf(): Read %d bytes. %d on inbuf.",read_result, *pbuf_datalen);
    return read_result;
  }

}

int flush_buf(int s, char **pbuf, size_t *pbuflen, size_t *pbuf_datalen) {

  /* push from buf onto s
   * then memmove to front of buf
   * return -1 or how many bytes remain on the buf */

  int write_result;
  char *buf;
  size_t buflen;
  size_t buf_datalen;

  if (!pbuf || !pbuflen || !pbuf_datalen) /* invalid parameters */
    return -1;

  if(s<0) {
    log(LOG_DEBUG,"flush_buf() received negative socket %d.",s);
    return -1;
  }


  if(*pbuf_datalen == 0) /* nothing to flush */
    return 0;

  /* this is the point where you would grow the buffer, if you want to */
  buf = *pbuf, buflen = *pbuflen, buf_datalen = *pbuf_datalen;

  if (!buf) /* invalid parameter */
    return -1;

  write_result = write(s, buf, buf_datalen);
  if (write_result < 0) {
    if(errno!=EAGAIN) { /* it's a real error */
      return -1;
    }
    log(LOG_DEBUG,"flush_buf(): write() would block, returning.");
    return 0;
  } else {
    *pbuf_datalen -= write_result;
    memmove(buf, buf+write_result, *pbuf_datalen);
    log(LOG_DEBUG,"flush_buf(): flushed %d bytes, %d remain.",write_result,*pbuf_datalen);
    return *pbuf_datalen;
  }

}

int write_to_buf(char *string, size_t string_len,
                 char **pbuf, size_t *pbuflen, size_t *pbuf_datalen) {

  /* append string to buf (growing as needed, return -1 if "too big")
   * return total number of bytes on the buf
   */

  char *buf;
  size_t buflen;
  size_t buf_datalen;

  if (!string || !pbuf || !pbuflen || !pbuf_datalen) /* invalid parameters */
    return -1;

  /* this is the point where you would grow the buffer, if you want to */
  buf = *pbuf, buflen = *pbuflen, buf_datalen = *pbuf_datalen;

  if (!buf) /* invalid parameter */
    return -1;

  if (string_len + buf_datalen > buflen) { /* we're out of luck */
    log(LOG_DEBUG, "write_to_buf(): buflen too small. Time to implement growing dynamic bufs.");
    return -1;
  }

  memcpy(buf+buf_datalen, string, string_len);
  *pbuf_datalen += string_len;
  log(LOG_DEBUG,"write_to_buf(): added %d bytes to buf (now %d total).",string_len, *pbuf_datalen);
  return *pbuf_datalen;

}

int fetch_from_buf(char *string, size_t string_len,
                 char **pbuf, size_t *pbuflen, size_t *pbuf_datalen) {

  /* if there is string_len bytes in buf, write them onto string,
   * then memmove buf back (that is, remove them from buf) */

  char *buf;
  size_t buflen;
  size_t buf_datalen;

  if (!string || !pbuf || !pbuflen || !pbuf_datalen) /* invalid parameters */
    return -1;

  /* this is the point where you would grow the buffer, if you want to */
  buf = *pbuf, buflen = *pbuflen, buf_datalen = *pbuf_datalen;

  if (!buf) /* invalid parameter */
    return -1;

  if(string_len > buf_datalen) /* we want too much. sorry. */
    return -1;
 
  memcpy(string,buf,string_len);
  *pbuf_datalen -= string_len;
  memmove(buf, buf+string_len, *pbuf_datalen);
  return *pbuf_datalen;

}