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/* file_rd.c
*
* generic routines for reading and writing binary record-oriented
* files. */
#include "config.h"
#include <stdio.h>
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#include "common.h"
#include "file_rd.h"
/* Set up a file reader. */
struct file_rd_info *
file_reader_init (int record_size, int buffered_records, int backwards)
{
struct file_rd_info *new;
new = (struct file_rd_info *) xmalloc (sizeof (struct file_rd_info));
memset (new, 0, sizeof (struct file_rd_info));
new->record_size = record_size;
new->buffered_records = buffered_records;
new->buffer = (char *) xmalloc (record_size * buffered_records);
new->backwards = backwards;
return new;
}
/* Add a file to the list of files to process */
void
file_reader_add_file (struct file_rd_info *fri, char *name)
{
/* SNOC this file onto our list so that we process them in order. */
struct file_list *np, *new;
new = (struct file_list *) xmalloc (sizeof (struct file_list));
new->name = name;
new->next = NULL;
for (np = fri->the_files; (np != NULL) && (np->next != NULL); np = np->next)
/* spin */;
if (np == NULL)
{
/* This must be the first thing in the list! */
fri->the_files = new;
}
else
{
/* In every other case, np->next is NULL, so put NEW in its
place. */
np->next = new;
}
}
/* Do a buffered read of the file and return the next record in REC.
Return 0 if no more entries. */
char *
file_reader_get_entry (struct file_rd_info *fri)
{
extern int debugging_enabled;
/* If RECS_LEFT == 0, there's nothing in the buffer, so read another
block of records from the file. */
if (fri->recs_left == 0)
{
while (1)
{
/* If there's no file open, we should do so. */
if (fri->fp == NULL)
{
/* Open up the next file! First, check to see that there IS
another file... */
if (fri->the_files == NULL)
return 0; /* no more files == no more records */
fri->fp = file_open (fri->the_files->name, 0);
if (fri->fp == NULL)
{
/* make sure to free this list entry */
goto no_more_records_no_close;
}
if (fri->backwards)
fseek (fri->fp, 0, SEEK_END); /* go to end of file */
fri->rec_number = 0; /* start over! */
fri->name = fri->the_files->name;
}
/* We have to do things differently depending on our
direction of reading */
if (fri->backwards)
{
long offset, max_recs, recs_to_read;
if ((offset = ftell (fri->fp)) <= 0)
goto no_more_records;
/* Read as many records as possible, up to
FRI->BUFFERED_RECORDS */
max_recs = offset / (long) fri->record_size;
recs_to_read = ((max_recs < fri->buffered_records)
? max_recs
: fri->buffered_records);
/* Move back in the file */
fseek (fri->fp, -fri->record_size * recs_to_read,
SEEK_CUR);
if (debugging_enabled)
{
long new_offset = ftell (fri->fp);
fprintf (stddebug, "Did seek in file %ld --> %ld\n",
offset, new_offset);
}
if (fread ((void *) fri->buffer, fri->record_size,
recs_to_read, fri->fp) == -1)
fatal ("get_entry: couldn't read from file");
if (debugging_enabled)
fprintf (stddebug, "Got %ld records from file\n",
recs_to_read);
/* don't need to check this, because the above read was fine */
fseek (fri->fp, -fri->record_size * recs_to_read, SEEK_CUR);
/* Set up buffer position variables */
fri->recs_read = recs_to_read;
fri->recs_left = recs_to_read;
break; /* get out of this WHILE loop */
}
else
{
/* Reading forwards in the file */
int retval;
retval = fread ((void *) fri->buffer, fri->record_size,
fri->buffered_records, fri->fp);
if (retval == -1)
fatal ("get_entry: couldn't read from file");
else if (retval != 0)
{
fri->recs_read = retval;
fri->recs_left = retval;
break; /* get out of this loop */
}
}
/* If we got here, there were no more records in the file.
Close it, delete it from our list, and try again. */
no_more_records:
fclose (fri->fp);
no_more_records_no_close:
fri->fp = NULL;
fri->the_files = fri->the_files->next;
}
}
{
char *rec;
if (fri->backwards)
rec = (char *) fri->buffer + (--fri->recs_left * fri->record_size);
else
rec = (char *) fri->buffer + ((fri->recs_read - fri->recs_left--)
* fri->record_size);
fri->rec_number++;
return rec;
}
}
void
file_reader_print_file_and_line (FILE *out, struct file_rd_info *fri)
{
fprintf (out, "%s:%ld", fri->name ? fri->name : "NULL?", fri->rec_number);
}
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