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/*-------------------------------------------------------------------------
*
* pg_get_line.c
* fgets() with an expansible result buffer
*
* Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/common/pg_get_line.c
*
*-------------------------------------------------------------------------
*/
#ifndef FRONTEND
#include "postgres.h"
#else
#include "postgres_fe.h"
#endif
#include "common/string.h"
#include "lib/stringinfo.h"
/*
* pg_get_line()
*
* This is meant to be equivalent to fgets(), except that instead of
* reading into a caller-supplied, fixed-size buffer, it reads into
* a palloc'd (in frontend, really malloc'd) string, which is resized
* as needed to handle indefinitely long input lines. The caller is
* responsible for pfree'ing the result string when appropriate.
*
* As with fgets(), returns NULL if there is a read error or if no
* characters are available before EOF. The caller can distinguish
* these cases by checking ferror(stream).
*
* Since this is meant to be equivalent to fgets(), the trailing newline
* (if any) is not stripped. Callers may wish to apply pg_strip_crlf().
*
* Note that while I/O errors are reflected back to the caller to be
* dealt with, an OOM condition for the palloc'd buffer will not be;
* there'll be an ereport(ERROR) or exit(1) inside stringinfo.c.
*/
char *
pg_get_line(FILE *stream)
{
StringInfoData buf;
initStringInfo(&buf);
/* Read some data, appending it to whatever we already have */
while (fgets(buf.data + buf.len, buf.maxlen - buf.len, stream) != NULL)
{
buf.len += strlen(buf.data + buf.len);
/* Done if we have collected a newline */
if (buf.len > 0 && buf.data[buf.len - 1] == '\n')
return buf.data;
/* Make some more room in the buffer, and loop to read more data */
enlargeStringInfo(&buf, 128);
}
/* Did fgets() fail because of an I/O error? */
if (ferror(stream))
{
/* ensure that free() doesn't mess up errno */
int save_errno = errno;
pfree(buf.data);
errno = save_errno;
return NULL;
}
/* If we read no data before reaching EOF, we should return NULL */
if (buf.len == 0)
{
pfree(buf.data);
return NULL;
}
/* No newline at EOF ... so return what we have */
return buf.data;
}
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