cdparanoia/buffering_write.c

   1 /* Eliminate teeny little writes.  patch submitted by
   2    Rob Ross <rbross@parl.ces.clemson.edu> --Monty 19991008 */
   3
   4 #include <string.h>
   5 #include <unistd.h>
   6 #include <errno.h>
   7 #include <stdio.h>
   8
   9 #define OUTBUFSZ 32*1024
  10
  11 #include "utils.h"
  12 extern long blocking_write(int outf, char *buffer, long num);
  13
  14
  15 /* GLOBALS FOR BUFFERING CALLS */
  16 static int  bw_fd  = -1;
  17 static long bw_pos = 0;
  18 static char bw_outbuf[OUTBUFSZ];
  19
  20
  21 /* buffering_write() - buffers data to a specified size before writing.
  22  *
  23  * Restrictions:
  24  * - MUST CALL BUFFERING_CLOSE() WHEN FINISHED!!!
  25  *
  26  */
  27 long buffering_write(int fd, char *buffer, long num)
  28 {
  29         if (fd != bw_fd) {
  30                 /* clean up after buffering for some other file */
  31                 if (bw_fd >= 0 && bw_pos > 0) {
  32                         if (blocking_write(bw_fd, bw_outbuf, bw_pos)) {
  33                                 perror("write (in buffering_write, flushing)");
  34                         }
  35                 }
  36                 bw_fd  = fd;
  37                 bw_pos = 0;
  38         }
  39
  40         if (bw_pos + num > OUTBUFSZ) {
  41                 /* fill our buffer first, then write, then modify buffer and num */
  42                 memcpy(&bw_outbuf[bw_pos], buffer, OUTBUFSZ - bw_pos);
  43                 if (blocking_write(fd, bw_outbuf, OUTBUFSZ)) {
  44                         perror("write (in buffering_write, full buffer)");
  45                         return(-1);
  46                 }
  47                 num -= (OUTBUFSZ - bw_pos);
  48                 buffer += (OUTBUFSZ - bw_pos);
  49                 bw_pos = 0;
  50         }
  51         /* save data */
  52         memcpy(&bw_outbuf[bw_pos], buffer, num);
  53         bw_pos += num;
  54
  55         return(0);
  56 }
  57
  58 /* buffering_close() - writes out remaining buffered data before closing
  59  * file.
  60  *
  61  */
  62 int buffering_close(int fd)
  63 {
  64         if (fd == bw_fd && bw_pos > 0) {
  65                 /* write out remaining data and clean up */
  66                 if (blocking_write(fd, bw_outbuf, bw_pos)) {
  67                         perror("write (in buffering_close)");
  68                 }
  69                 bw_fd  = -1;
  70                 bw_pos = 0;
  71         }
  72         return(close(fd));
  73 }