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[108.35.55.112]) by smtp.gmail.com with ESMTPSA id l17sm1154080qtu.79.2022.01.25.14.50.30 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Tue, 25 Jan 2022 14:50:30 -0800 (PST) From: John Cai To: git@vger.kernel.org Cc: avarab@gmail.com, me@ttaylorr.com, phillip.wood123@gmail.com, John Cai Subject: [RFC v2] cat-file: add a --stdin-cmd mode Date: Tue, 25 Jan 2022 17:50:08 -0500 Message-Id: <20220125225008.45944-1-johncai86@gmail.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org This RFC patch proposes a new flag --stdin-cmd that works with git-cat-file --batch. Similar to git-update-ref --stdin, it will accept commands and arguments from stdin. The start of this idea was discussed in [1], where the original motivation was to be able to control when the buffer was flushed to stdout in --buffer mode. However, this can actually be much more useful in situations when git-cat-file --batch is being used as a long lived backend query process. At GitLab, we use a pair of cat-file processes. One for iterating over object metadata with --batch-check, and the other to grab object contents with --batch. However, if we had --stdin-cmd, we could get rid of the second --batch-check process, and just have one progress where we can flip between getting object info, and getting object contents. This can lead to huge savings. git cat-file --batch --stdin-cmd $ [arg1] [arg2] NL We can also add a -z mode to allow for NUL-terminated lines $ [arg1] [arg2] NUL This patch adds three commands: object, info, fflush $ object NL $ info NL $ fflush NL These three would be immediately useful in GitLab's context, but one can imagine this mode to be further extended for other things. For instance, a non-trivial part of "cat-file --batch" time is spent on parsing its argument and seeing if it's a revision, ref etc. So we could add a command that only accepts a full-length 40 character SHA-1. This would be the first step in adding such an interface to git-cat-file. [1] https://lore.kernel.org/git/pull.1124.git.git.1636149400.gitgitgadget@gmail.com/ Helped-by: Ævar Arnfjörð Bjarmason Signed-off-by: John Cai --- Changes from v1: - changed option name to batch-command. - changed command function interface to receive the whole line after the command name to put the onus of parsing arguments to each individual command function. - pass in whole line to batch_one_object in both parse_cmd_object and parse_cmd_info to support spaces in the object reference. - removed addition of -z to include in a separate patch series - added documentation. --- Documentation/git-cat-file.txt | 15 +++++ builtin/cat-file.c | 114 ++++++++++++++++++++++++++++++++- strvec.c | 23 +++++++ strvec.h | 8 +++ t/t1006-cat-file.sh | 32 +++++++++ 5 files changed, 191 insertions(+), 1 deletion(-) diff --git a/Documentation/git-cat-file.txt b/Documentation/git-cat-file.txt index bef76f4dd0..8aefa45e4c 100644 --- a/Documentation/git-cat-file.txt +++ b/Documentation/git-cat-file.txt @@ -96,6 +96,21 @@ OPTIONS need to specify the path, separated by whitespace. See the section `BATCH OUTPUT` below for details. +-batch-command:: + Enter a command mode that reads from stdin. May not be combined with any + other options or arguments except `--textconv` or `--filters`, in which + case the input lines also need to specify the path, separated by + whitespace. See the section `BATCH OUTPUT` below for details. + +object :: + Print object contents for object reference + +info :: + Print object info for object reference + +flush:: + Flush to stdout immediately when used with --buffer + --batch-all-objects:: Instead of reading a list of objects on stdin, perform the requested batch operation on all objects in the repository and diff --git a/builtin/cat-file.c b/builtin/cat-file.c index 7b3f42950e..30794284d5 100644 --- a/builtin/cat-file.c +++ b/builtin/cat-file.c @@ -16,6 +16,7 @@ #include "packfile.h" #include "object-store.h" #include "promisor-remote.h" +#include "strvec.h" struct batch_options { int enabled; @@ -26,7 +27,10 @@ struct batch_options { int unordered; int cmdmode; /* may be 'w' or 'c' for --filters or --textconv */ const char *format; + int stdin_cmd; + int end_null; }; +static char line_termination = '\n'; static const char *force_path; @@ -508,6 +512,102 @@ static int batch_unordered_packed(const struct object_id *oid, data); } +enum batch_state { + /* Non-transactional state open for commands. */ + BATCH_STATE_OPEN, +}; + +static void parse_cmd_object(struct batch_options *opt, + const char *line, + struct strbuf *output, + struct expand_data *data) +{ + opt->print_contents = 1; + batch_one_object(line, output, opt, data); +} + +static void parse_cmd_info(struct batch_options *opt, + const char *line, + struct strbuf *output, + struct expand_data *data) +{ + opt->print_contents = 0; + batch_one_object(line, output, opt, data); +} + +static void parse_cmd_fflush(struct batch_options *opt, + const char *line, + struct strbuf *output, + struct expand_data *data) +{ + fflush(stdout); +} + +typedef void (*parse_cmd_fn_t)(struct batch_options *, const char *, + struct strbuf *, struct expand_data *); + +static const struct parse_cmd { + const char *prefix; + parse_cmd_fn_t fn; + unsigned args; + enum batch_state state; +} commands[] = { + { "object", parse_cmd_object, 1, BATCH_STATE_OPEN }, + { "info", parse_cmd_info, 1, BATCH_STATE_OPEN }, + { "fflush", parse_cmd_fflush, 0, BATCH_STATE_OPEN }, +}; + +static void batch_objects_stdin_cmd(struct batch_options *opt, + struct strbuf *output, + struct expand_data *data) +{ + struct strbuf input = STRBUF_INIT; + enum batch_state state = BATCH_STATE_OPEN; + + /* Read each line dispatch its command */ + while (!strbuf_getwholeline(&input, stdin, line_termination)) { + int i; + const struct parse_cmd *cmd = NULL; + const char *p; + + if (*input.buf == line_termination) + die("empty command in input"); + else if (isspace(*input.buf)) + die("whitespace before command: %s", input.buf); + + for (i = 0; i < ARRAY_SIZE(commands); i++) { + const char *prefix = commands[i].prefix; + char c; + const char *cmd_name; + if (!skip_prefix(input.buf, prefix, &cmd_name)) + continue; + /* + * If the command has arguments, verify that it's + * followed by a space. Otherwise, it shall be followed + * by a line terminator. + */ + c = commands[i].args ? ' ' : line_termination; + if (input.buf[strlen(prefix)] != c) + continue; + + cmd = &commands[i]; + break; + } + if (!cmd) + die("unknown command: %s", input.buf); + + p = input.buf + strlen(cmd->prefix) + 1; + const char *pos = strstr(p, &line_termination); + + switch (state) { + case BATCH_STATE_OPEN: + break; + } + cmd->fn(opt, xstrndup(p, pos-p), output, data); + } + strbuf_release(&input); +} + static int batch_objects(struct batch_options *opt) { struct strbuf input = STRBUF_INIT; @@ -515,6 +615,7 @@ static int batch_objects(struct batch_options *opt) struct expand_data data; int save_warning; int retval = 0; + const int stdin_cmd = opt->stdin_cmd; if (!opt->format) opt->format = "%(objectname) %(objecttype) %(objectsize)"; @@ -590,7 +691,8 @@ static int batch_objects(struct batch_options *opt) save_warning = warn_on_object_refname_ambiguity; warn_on_object_refname_ambiguity = 0; - while (strbuf_getline(&input, stdin) != EOF) { + while (!stdin_cmd && + strbuf_getline(&input, stdin) != EOF) { if (data.split_on_whitespace) { /* * Split at first whitespace, tying off the beginning @@ -608,6 +710,9 @@ static int batch_objects(struct batch_options *opt) batch_one_object(input.buf, &output, opt, &data); } + if (stdin_cmd) + batch_objects_stdin_cmd(opt, &output, &data); + strbuf_release(&input); strbuf_release(&output); warn_on_object_refname_ambiguity = save_warning; @@ -636,6 +741,7 @@ static int batch_option_callback(const struct option *opt, bo->enabled = 1; bo->print_contents = !strcmp(opt->long_name, "batch"); + bo->stdin_cmd = !strcmp(opt->long_name, "batch-command"); bo->format = arg; return 0; @@ -683,6 +789,10 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix) N_("like --batch, but don't emit "), PARSE_OPT_OPTARG | PARSE_OPT_NONEG, batch_option_callback), + OPT_CALLBACK_F(0, "batch-command", &batch, N_(""), + N_("enters batch mode that accepts commands"), + PARSE_OPT_NOARG | PARSE_OPT_NONEG, + batch_option_callback), OPT_CMDMODE(0, "batch-all-objects", &opt, N_("with --batch[-check]: ignores stdin, batches all known objects"), 'b'), /* Batch-specific options */ @@ -738,6 +848,8 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix) /* Batch defaults */ if (batch.buffer_output < 0) batch.buffer_output = batch.all_objects; + if (batch.end_null) + line_termination = '\0'; /* Return early if we're in batch mode? */ if (batch.enabled) { diff --git a/strvec.c b/strvec.c index 61a76ce6cb..7dca04bf7a 100644 --- a/strvec.c +++ b/strvec.c @@ -85,6 +85,29 @@ void strvec_split(struct strvec *array, const char *to_split) } } +size_t strvec_split_delim(struct strvec *array, const char *string, + int delim, int maxsplit) +{ + size_t count = 0; + const char *p = string, *end; + + for (;;) { + count++; + if (maxsplit >= 0 && count > maxsplit) { + strvec_push(array, p); + return count; + } + end = strchr(p, delim); + if (end) { + strvec_push_nodup(array, xmemdupz(p, end - p)); + p = end + 1; + } else { + strvec_push(array, p); + return count; + } + } +} + void strvec_clear(struct strvec *array) { if (array->v != empty_strvec) { diff --git a/strvec.h b/strvec.h index 9f55c8766b..c474918b91 100644 --- a/strvec.h +++ b/strvec.h @@ -73,6 +73,14 @@ void strvec_pop(struct strvec *); /* Splits by whitespace; does not handle quoted arguments! */ void strvec_split(struct strvec *, const char *); +/** + * strvec_split_delim() is a split function that behaves more like its + * string_list_split() cousin than the whitespace-splitting + * strvec_split(). + */ +size_t strvec_split_delim(struct strvec *array, const char *string, + int delim, int maxsplit); + /** * Free all memory associated with the array and return it to the * initial, empty state. diff --git a/t/t1006-cat-file.sh b/t/t1006-cat-file.sh index 145eee11df..935ab1cd34 100755 --- a/t/t1006-cat-file.sh +++ b/t/t1006-cat-file.sh @@ -964,4 +964,36 @@ test_expect_success 'cat-file --batch-all-objects --batch-check ignores replace' test_cmp expect actual ' +F='%s\0' + +test_expect_success 'batch-command unknown command' ' + echo unknown_command >cmd && + test_expect_code 128 git cat-file --batch-command < cmd 2>err && + grep -E "^fatal:.*unknown command.*" err +' + +test_expect_success 'setup object data' ' + content="Object Data" && + size=$(strlen "$content") && + sha1=$(echo_without_newline "$content" | git hash-object -w --stdin) +' + +test_expect_success 'batch-command calling object works' ' + echo "object $sha1" | git cat-file --batch-command >actual && + echo "$sha1 blob $size" >expect && + echo `git cat-file -p "$sha1"` >>expect && + test_cmp expect actual +' + +test_expect_success 'batch-command calling info works' ' + echo "info $sha1" | git cat-file --batch-command >actual && + echo "$sha1 blob $size" >expect && + test_cmp expect actual +' + +test_expect_success 'batch-command fflush works' ' + printf "fflush\n" > cmd && + test_expect_code 0 git cat-file --batch-command < cmd 2>err +' + test_done