commit c212578bf05138801597dcce23f52780c9b7dbb3 Author: Neel Chauhan neel@neelc.org Date: Fri Jul 24 18:14:15 2020 -0700

Introduce write_str_if_not_equal() --- src/feature/relay/router.c | 14 +++++--------- src/lib/fs/files.c | 20 ++++++++++++++++++++ src/lib/fs/files.h | 2 ++ 3 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/src/feature/relay/router.c b/src/feature/relay/router.c index 48f53a263d..25263468c8 100644 --- a/src/feature/relay/router.c +++ b/src/feature/relay/router.c @@ -870,15 +870,11 @@ router_write_fingerprint(int hashed, int ed25519_identity) tor_asprintf(&fingerprint_line, "%s %s\n", options->Nickname, fingerprint);

/* Check whether we need to write the (hashed-)fingerprint file. */ - - cp = read_file_to_str(keydir, RFTS_IGNORE_MISSING, NULL); - if (!cp || strcmp(cp, fingerprint_line)) { - if (write_str_to_file(keydir, fingerprint_line, 0)) { - log_err(LD_FS, "Error writing %s%s line to file", - hashed ? "hashed " : "", - ed25519_identity ? "ed25519 identity" : "fingerprint"); - goto done; - } + if (write_str_if_not_equal(keydir, fingerprint_line)) { + log_err(LD_FS, "Error writing %s%s line to file", + hashed ? "hashed " : "", + ed25519_identity ? "ed25519 identity" : "fingerprint"); + goto done; }

log_notice(LD_GENERAL, "Your Tor %s identity key %s fingerprint is '%s %s'", diff --git a/src/lib/fs/files.c b/src/lib/fs/files.c index a0b5a40aac..189d2cb646 100644 --- a/src/lib/fs/files.c +++ b/src/lib/fs/files.c @@ -718,6 +718,26 @@ read_file_to_str, (const char *filename, int flags, struct stat *stat_out)) return string; }

+/** Attempt to read a file <b>fname</b>. If the file's contents is + * equal to the string <b>str</b>, return 0. Otherwise, attempt to + * overwrite the file with the contents of <b>str</b> and return + * the value of write_str_to_file(). + */ +int +write_str_to_file_if_not_equal(const char *fname, const char *str) +{ + char *fstr = read_file_to_str(fname, RFTS_IGNORE_MISSING, NULL); + int rv; + + if (!fstr || strcmp(str, fstr)) { + rv = write_str_to_file(fname, str, 0); + } else { + rv = 0; + } + tor_free(fstr); + return rv; +} + #if !defined(HAVE_GETDELIM) || defined(TOR_UNIT_TESTS) #include "ext/getdelim.c" #endif diff --git a/src/lib/fs/files.h b/src/lib/fs/files.h index a109cd6248..62b79c4cd8 100644 --- a/src/lib/fs/files.h +++ b/src/lib/fs/files.h @@ -91,6 +91,8 @@ int append_bytes_to_file(const char *fname, const char *str, size_t len, int write_bytes_to_new_file(const char *fname, const char *str, size_t len, int bin);

+int write_str_to_file_if_not_equal(const char *fname, const char *str); + /** Flag for read_file_to_str: open the file in binary mode. */ #define RFTS_BIN 1 /** Flag for read_file_to_str: it's okay if the file doesn't exist. */