greenplumn pg_get_line 源码
greenplumn pg_get_line 代码
文件路径：/src/common/pg_get_line.c
/*-------------------------------------------------------------------------
*
* 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_buf()
*
* This has similar behavior to pg_get_line(), and thence to fgets(),
* except that the collected data is returned in a caller-supplied
* StringInfo buffer. This is a convenient API for code that just
* wants to read and process one line at a time, without any artificial
* limit on line length.
*
* Returns true if a line was successfully collected (including the
* case of a non-newline-terminated line at EOF). Returns false if
* there was an I/O error or no data was available before EOF.
* (Check ferror(stream) to distinguish these cases.)
*
* In the false-result case, buf is reset to empty.
*/
bool
pg_get_line_buf(FILE *stream, StringInfo buf)
{
/* We just need to drop any data from the previous call */
resetStringInfo(buf);
return pg_get_line_append(stream, buf);
}
/*
* pg_get_line_append()
*
* This has similar behavior to pg_get_line(), and thence to fgets(),
* except that the collected data is appended to whatever is in *buf.
* This is useful in preference to pg_get_line_buf() if the caller wants
* to merge some lines together, e.g. to implement backslash continuation.
*
* Returns true if a line was successfully collected (including the
* case of a non-newline-terminated line at EOF). Returns false if
* there was an I/O error or no data was available before EOF.
* (Check ferror(stream) to distinguish these cases.)
*
* In the false-result case, the contents of *buf are logically unmodified,
* though it's possible that the buffer has been resized.
*/
bool
pg_get_line_append(FILE *stream, StringInfo buf)
{
int orig_len = buf->len;
/* 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 > orig_len && buf->data[buf->len - 1] == '\n')
return true;
/* Make some more room in the buffer, and loop to read more data */
enlargeStringInfo(buf, 128);
}
/* Check for I/O errors and EOF */
if (ferror(stream) || buf->len == orig_len)
{
/* Discard any data we collected before detecting error */
buf->len = orig_len;
buf->data[orig_len] = '\0';
return false;
}
/* No newline at EOF, but we did collect some data */
return true;
}
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