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/*
* Copyright (c) 2017 Intel Corporation
* Copyright (c) 2019 Paul Chaignon <paul.chaignon@gmail.com>
* Copyright (c) 2019-2021 The strace developers.
* All rights reserved.
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*/
/*
* open_memstream returns a FILE stream that allows writing to a
* dynamically growing buffer, that can be either copied to
* tcp->outf (syscall successful) or dropped (syscall failed)
*/
#include "defs.h"
struct staged_output_data {
char *memfptr;
size_t memfloc;
FILE *real_outf; /* Backup for real outf while staging */
};
FILE *
strace_open_memstream(struct tcb *tcp)
{
FILE *fp = NULL;
#ifdef HAVE_OPEN_MEMSTREAM
tcp->staged_output_data = xmalloc(sizeof(*tcp->staged_output_data));
fp = open_memstream(&tcp->staged_output_data->memfptr,
&tcp->staged_output_data->memfloc);
if (!fp)
perror_msg_and_die("open_memstream");
/*
* Call to fflush required to update tcp->memfptr,
* see open_memstream man page.
*/
fflush(fp);
/* Store the FILE pointer for later restoration. */
tcp->staged_output_data->real_outf = tcp->outf;
tcp->outf = fp;
#endif
return fp;
}
void
strace_close_memstream(struct tcb *tcp, bool publish)
{
#ifdef HAVE_OPEN_MEMSTREAM
if (!tcp->staged_output_data) {
debug_msg("memstream already closed");
return;
}
if (fclose(tcp->outf))
perror_msg("fclose(tcp->outf)");
tcp->outf = tcp->staged_output_data->real_outf;
if (tcp->staged_output_data->memfptr) {
if (publish)
fputs_unlocked(tcp->staged_output_data->memfptr,
tcp->outf);
else
debug_msg("syscall output dropped: %s",
tcp->staged_output_data->memfptr);
free(tcp->staged_output_data->memfptr);
tcp->staged_output_data->memfptr = NULL;
}
free(tcp->staged_output_data);
tcp->staged_output_data = NULL;
#endif
}
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