On 7/24/2017 5:38 PM, Jonathan Tan wrote:
Refactor, into a common function, the version and capability negotiation
done when invoking a long-running process as a clean or smudge filter.
This will be useful for other Git code that needs to interact similarly
with a long-running process.
Christian Couder has been working on a similar refactoring for the perl
versions of very similar helper functions. They can be found in the
following patch series:
https://public-inbox.org/git/20170620075523.26961-1-chriscool@xxxxxxxxxxxxx/
In particular:
- Patches 02/49 to 08/49 create a Git/Packet.pm module by
refactoring "t0021/rot13-filter.pl". Functions from this new
module will be used later in test scripts.
Some differences I noticed: this patch does both the version and
capability negotiation and it lives in "sub-process.h/c" files. In the
perl script patch series, the version negotiation is in the new
"packet.pm" module but it does not include the capability negotiation.
It would make sense to me for these to have the same API and usage
behaviors. Perhaps pull them together into a single patch series so
that we can review and keep them in sync?
Signed-off-by: Jonathan Tan <jonathantanmy@xxxxxxxxxx>
---
This will be useful for anyone implementing functionality like that in
[1].
It is unfortunate that the code grew larger because it had to be more
generic, but I think this is better than having (in the future) 2 or
more separate handshake functions.
I'm always happy to see an effort to refactor common code into reusable
APIs. Its a good engineering practice that makes it easier to
stabilize, extend and maintain the code. The challenge is making sure
the common function supports all the requirements of the various callers
and that the increase in complexity doesn't outweigh the benefit of
centralizing the logic.
I also don't think that the protocol should be permissive - I think
things would be simpler if all protocol errors were fatal errors. As it
is, most parts are permissive, but packet_read_line() already dies
anyway upon a malformed packet, so it may not be too drastic a change to
change this. For reference, the original protocol comes from [2].
[1] https://public-inbox.org/git/20170714132651.170708-2-benpeart@xxxxxxxxxxxxx/
[2] edcc858 ("convert: add filter.<driver>.process option", 2016-10-17)
---
convert.c | 61 ++++-----------------------------
pkt-line.c | 19 -----------
pkt-line.h | 2 --
sub-process.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++
sub-process.h | 18 ++++++++++
t/t0021-conversion.sh | 2 +-
6 files changed, 120 insertions(+), 76 deletions(-)
diff --git a/convert.c b/convert.c
index deaf0ba7b..ec8ecc2ea 100644
--- a/convert.c
+++ b/convert.c
@@ -512,62 +512,15 @@ static struct hashmap subprocess_map;
static int start_multi_file_filter_fn(struct subprocess_entry *subprocess)
{
- int err;
+ static int versions[] = {2, 0};
+ static struct subprocess_capability capabilities[] = {
+ {"clean", CAP_CLEAN}, {"smudge", CAP_SMUDGE}, {NULL, 0}
+ };
struct cmd2process *entry = (struct cmd2process *)subprocess;
- struct string_list cap_list = STRING_LIST_INIT_NODUP;
- char *cap_buf;
- const char *cap_name;
- struct child_process *process = &subprocess->process;
- const char *cmd = subprocess->cmd;
-
- sigchain_push(SIGPIPE, SIG_IGN);
-
- err = packet_writel(process->in, "git-filter-client", "version=2", NULL);
- if (err)
- goto done;
-
- err = strcmp(packet_read_line(process->out, NULL), "git-filter-server");
- if (err) {
- error("external filter '%s' does not support filter protocol version 2", cmd);
- goto done;
- }
- err = strcmp(packet_read_line(process->out, NULL), "version=2");
- if (err)
- goto done;
- err = packet_read_line(process->out, NULL) != NULL;
- if (err)
- goto done;
-
- err = packet_writel(process->in, "capability=clean", "capability=smudge", NULL);
-
- for (;;) {
- cap_buf = packet_read_line(process->out, NULL);
- if (!cap_buf)
- break;
- string_list_split_in_place(&cap_list, cap_buf, '=', 1);
-
- if (cap_list.nr != 2 || strcmp(cap_list.items[0].string, "capability"))
- continue;
-
- cap_name = cap_list.items[1].string;
- if (!strcmp(cap_name, "clean")) {
- entry->supported_capabilities |= CAP_CLEAN;
- } else if (!strcmp(cap_name, "smudge")) {
- entry->supported_capabilities |= CAP_SMUDGE;
- } else {
- warning(
- "external filter '%s' requested unsupported filter capability '%s'",
- cmd, cap_name
- );
- }
-
- string_list_clear(&cap_list, 0);
- }
-
-done:
- sigchain_pop(SIGPIPE);
- return err;
+ return subprocess_handshake(subprocess, "git-filter-", versions, NULL,
+ capabilities,
+ &entry->supported_capabilities);
}
static int apply_multi_file_filter(const char *path, const char *src, size_t len,
diff --git a/pkt-line.c b/pkt-line.c
index 9d845ecc3..7db911957 100644
--- a/pkt-line.c
+++ b/pkt-line.c
@@ -171,25 +171,6 @@ int packet_write_fmt_gently(int fd, const char *fmt, ...)
return status;
}
-int packet_writel(int fd, const char *line, ...)
-{
While I found the writel functions useful, all my use cases were in
implementing the client/server version and capability handshake.
Hopefully, all those can be replaced with this new API.
I'm of the opinion that having a helper function that isn't actively
used just results in dead code that has to be maintained so it makes
sense to remove it.
- va_list args;
- int err;
- va_start(args, line);
- for (;;) {
- if (!line)
- break;
- if (strlen(line) > LARGE_PACKET_DATA_MAX)
- return -1;
- err = packet_write_fmt_gently(fd, "%s\n", line);
- if (err)
- return err;
- line = va_arg(args, const char*);
- }
- va_end(args);
- return packet_flush_gently(fd);
-}
-
static int packet_write_gently(const int fd_out, const char *buf, size_t size)
{
static char packet_write_buffer[LARGE_PACKET_MAX];
diff --git a/pkt-line.h b/pkt-line.h
index 450183b64..66ef610fc 100644
--- a/pkt-line.h
+++ b/pkt-line.h
@@ -25,8 +25,6 @@ void packet_buf_flush(struct strbuf *buf);
void packet_buf_write(struct strbuf *buf, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
int packet_flush_gently(int fd);
int packet_write_fmt_gently(int fd, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
-LAST_ARG_MUST_BE_NULL
-int packet_writel(int fd, const char *line, ...);
int write_packetized_from_fd(int fd_in, int fd_out);
int write_packetized_from_buf(const char *src_in, size_t len, int fd_out);
diff --git a/sub-process.c b/sub-process.c
index a3cfab1a9..1a3f39bdf 100644
--- a/sub-process.c
+++ b/sub-process.c
@@ -105,3 +105,97 @@ int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, co
hashmap_add(hashmap, entry);
return 0;
}
+
+int subprocess_handshake(struct subprocess_entry *entry,
+ const char *welcome_prefix,
+ int *versions,
+ int *chosen_version,
+ struct subprocess_capability *capabilities,
+ unsigned int *supported_capabilities) {
+ int version_scratch;
+ unsigned int capabilities_scratch;
+ struct child_process *process = &entry->process;
+ int i;
+ char *line;
+ const char *p;
+
+ if (!chosen_version)
+ chosen_version = &version_scratch;
+ if (!supported_capabilities)
+ supported_capabilities = &capabilities_scratch;
+
+ sigchain_push(SIGPIPE, SIG_IGN);
+
+ if (packet_write_fmt_gently(process->in, "%sclient\n",
+ welcome_prefix)) {
+ error("Could not write client identification");
+ goto error;
+ }
+ for (i = 0; versions[i]; i++) {
+ if (packet_write_fmt_gently(process->in, "version=%d\n",
+ versions[i])) {
+ error("Could not write requested version");
+ goto error;
+ }
+ }
+ if (packet_flush_gently(process->in))
+ goto error;
+
+ if (!(line = packet_read_line(process->out, NULL)) ||
+ !skip_prefix(line, welcome_prefix, &p) ||
+ strcmp(p, "server")) {
+ error("Unexpected line '%s', expected %sserver",
+ line ? line : "<flush packet>", welcome_prefix);
+ goto error;
+ }
+ if (!(line = packet_read_line(process->out, NULL)) ||
+ !skip_prefix(line, "version=", &p) ||
+ strtol_i(p, 10, chosen_version)) {
+ error("Unexpected line '%s', expected version",
+ line ? line : "<flush packet>");
+ goto error;
+ }
+ for (i = 0; versions[i]; i++) {
+ if (versions[i] == *chosen_version)
+ goto version_found;
+ }
This doesn't look like it supports negotiating a common version between
the client and server. If a client supports version 1, 2, and 3 and the
server only supports version 1 and 2, which version and capabilities
will be used?
+ error("Version %d not supported", *chosen_version);
+ goto error;
+version_found:
+ if ((line = packet_read_line(process->out, NULL))) {
+ error("Unexpected line '%s', expected flush", line);
+ goto error;
+ }
+
+ for (i = 0; capabilities[i].name; i++) {
+ if (packet_write_fmt_gently(process->in, "capability=%s\n",
+ capabilities[i].name)) {
+ error("Could not write requested capability");
+ goto error;
+ }
+ }
+ if (packet_flush_gently(process->in))
+ goto error;
+
+ while ((line = packet_read_line(process->out, NULL))) {
+ if (!skip_prefix(line, "capability=", &p))
+ continue;
+
+ for (i = 0; capabilities[i].name; i++) {
+ if (!strcmp(p, capabilities[i].name)) {
+ *supported_capabilities |= capabilities[i].flag;
+ goto capability_found;
+ }
+ }
+ warning("external filter requested unsupported filter capability '%s'",
+ p);
+capability_found:
+ ;
+ }
+
+ sigchain_pop(SIGPIPE);
+ return 0;
+error:
+ sigchain_pop(SIGPIPE);
+ return 1;
+}
diff --git a/sub-process.h b/sub-process.h
index 96a2cca36..a72e7f7cf 100644
--- a/sub-process.h
+++ b/sub-process.h
@@ -18,6 +18,11 @@ struct subprocess_entry {
struct child_process process;
};
+struct subprocess_capability {
+ const char *name;
+ unsigned int flag;
+};
+
/* subprocess functions */
extern int cmd2process_cmp(const void *unused_cmp_data,
@@ -41,6 +46,19 @@ static inline struct child_process *subprocess_get_child_process(
return &entry->process;
}
+/*
+ * Perform the handshake to a long-running process as described in the
+ * gitattributes documentation using the given requested versions and
+ * capabilities. The "versions" and "capabilities" parameters are arrays
+ * terminated by a 0 or blank struct.
+ */
+int subprocess_handshake(struct subprocess_entry *entry,
+ const char *welcome_prefix,
+ int *versions,
+ int *chosen_version,
+ struct subprocess_capability *capabilities,
+ unsigned int *supported_capabilities);
+
/*
* Helper function that will read packets looking for "status=<foo>"
* key/value pairs and return the value from the last "status" packet
diff --git a/t/t0021-conversion.sh b/t/t0021-conversion.sh
index 161f56044..d191a7228 100755
--- a/t/t0021-conversion.sh
+++ b/t/t0021-conversion.sh
@@ -697,7 +697,7 @@ test_expect_success PERL 'invalid process filter must fail (and not hang!)' '
cp "$TEST_ROOT/test.o" test.r &&
test_must_fail git add . 2>git-stderr.log &&
- grep "does not support filter protocol version" git-stderr.log
+ grep "expected git-filter-server" git-stderr.log
)
'
