[PATCH v5 17/21] trace: move doc to trace.h

From

Heba Waly via GitGitGadget <gitgitgadget@gmail.com>

Date

Nov 17, 2019, 21:04 UTC

Message-ID

<f313d74e1ea0f5976a08bb3c1fe78e70937c1027.1574024701.git.gitgitgadget@gmail.com>

In-Reply-To

<pull.434.v5.git.1574024700.gitgitgadget@gmail.com>

From: Heba Waly <heba.waly@gmail.com>

Signed-off-by: Heba Waly <heba.waly@gmail.com>
---
 Documentation/technical/api-trace.txt | 140 --------------------------
 trace.h                               | 133 +++++++++++++++++++++++-
 2 files changed, 131 insertions(+), 142 deletions(-)
 delete mode 100644 Documentation/technical/api-trace.txt

diff --git a/Documentation/technical/api-trace.txt b/Documentation/technical/api-trace.txt
deleted file mode 100644
index fadb5979c4..0000000000
--- a/Documentation/technical/api-trace.txt
+++ /dev/null
@@ -1,140 +0,0 @@
-trace API
-=========
-
-The trace API can be used to print debug messages to stderr or a file. Trace
-code is inactive unless explicitly enabled by setting `GIT_TRACE*` environment
-variables.
-
-The trace implementation automatically adds `timestamp file:line ... \n` to
-all trace messages. E.g.:
-
-------------
-23:59:59.123456 git.c:312               trace: built-in: git 'foo'
-00:00:00.000001 builtin/foo.c:99        foo: some message
-------------
-
-Data Structures
----------------
-
-`struct trace_key`::
-
-	Defines a trace key (or category). The default (for API functions that
-	don't take a key) is `GIT_TRACE`.
-+
-E.g. to define a trace key controlled by environment variable `GIT_TRACE_FOO`:
-+
-------------
-static struct trace_key trace_foo = TRACE_KEY_INIT(FOO);
-
-static void trace_print_foo(const char *message)
-{
-	trace_printf_key(&trace_foo, "%s", message);
-}
-------------
-+
-Note: don't use `const` as the trace implementation stores internal state in
-the `trace_key` structure.
-
-Functions
----------
-
-`int trace_want(struct trace_key *key)`::
-
-	Checks whether the trace key is enabled. Used to prevent expensive
-	string formatting before calling one of the printing APIs.
-
-`void trace_disable(struct trace_key *key)`::
-
-	Disables tracing for the specified key, even if the environment
-	variable was set.
-
-`void trace_printf(const char *format, ...)`::
-`void trace_printf_key(struct trace_key *key, const char *format, ...)`::
-
-	Prints a formatted message, similar to printf.
-
-`void trace_argv_printf(const char **argv, const char *format, ...)``::
-
-	Prints a formatted message, followed by a quoted list of arguments.
-
-`void trace_strbuf(struct trace_key *key, const struct strbuf *data)`::
-
-	Prints the strbuf, without additional formatting (i.e. doesn't
-	choke on `%` or even `\0`).
-
-`uint64_t getnanotime(void)`::
-
-	Returns nanoseconds since the epoch (01/01/1970), typically used
-	for performance measurements.
-+
-Currently there are high precision timer implementations for Linux (using
-`clock_gettime(CLOCK_MONOTONIC)`) and Windows (`QueryPerformanceCounter`).
-Other platforms use `gettimeofday` as time source.
-
-`void trace_performance(uint64_t nanos, const char *format, ...)`::
-`void trace_performance_since(uint64_t start, const char *format, ...)`::
-
-	Prints the elapsed time (in nanoseconds), or elapsed time since
-	`start`, followed by a formatted message. Enabled via environment
-	variable `GIT_TRACE_PERFORMANCE`. Used for manual profiling, e.g.:
-+
-------------
-uint64_t start = getnanotime();
-/* code section to measure */
-trace_performance_since(start, "foobar");
-------------
-+
-------------
-uint64_t t = 0;
-for (;;) {
-	/* ignore */
-	t -= getnanotime();
-	/* code section to measure */
-	t += getnanotime();
-	/* ignore */
-}
-trace_performance(t, "frotz");
-------------
-
-Bugs & Caveats
---------------
-
-GIT_TRACE_* environment variables can be used to tell Git to show
-trace output to its standard error stream. Git can often spawn a pager
-internally to run its subcommand and send its standard output and
-standard error to it.
-
-Because GIT_TRACE_PERFORMANCE trace is generated only at the very end
-of the program with atexit(), which happens after the pager exits, it
-would not work well if you send its log to the standard error output
-and let Git spawn the pager at the same time.
-
-As a work around, you can for example use '--no-pager', or set
-GIT_TRACE_PERFORMANCE to another file descriptor which is redirected
-to stderr, or set GIT_TRACE_PERFORMANCE to a file specified by its
-absolute path.
-
-For example instead of the following command which by default may not
-print any performance information:
-
-------------
-GIT_TRACE_PERFORMANCE=2 git log -1
-------------
-
-you may want to use:
-
-------------
-GIT_TRACE_PERFORMANCE=2 git --no-pager log -1
-------------
-
-or:
-
-------------
-GIT_TRACE_PERFORMANCE=3 3>&2 git log -1
-------------
-
-or:
-
-------------
-GIT_TRACE_PERFORMANCE=/path/to/log/file git log -1
-------------
diff --git a/trace.h b/trace.h
index 9fa3e7a594..9826618b33 100644
--- a/trace.h
+++ b/trace.h
@@ -4,6 +4,82 @@
 #include "git-compat-util.h"
 #include "strbuf.h"
 
+/**
+ * The trace API can be used to print debug messages to stderr or a file. Trace
+ * code is inactive unless explicitly enabled by setting `GIT_TRACE*` environment
+ * variables.
+ *
+ * The trace implementation automatically adds `timestamp file:line ... \n` to
+ * all trace messages. E.g.:
+ *
+ * ------------
+ * 23:59:59.123456 git.c:312               trace: built-in: git 'foo'
+ * 00:00:00.000001 builtin/foo.c:99        foo: some message
+ * ------------
+ *
+ * Bugs & Caveats
+ * --------------
+ *
+ * GIT_TRACE_* environment variables can be used to tell Git to show
+ * trace output to its standard error stream. Git can often spawn a pager
+ * internally to run its subcommand and send its standard output and
+ * standard error to it.
+ *
+ * Because GIT_TRACE_PERFORMANCE trace is generated only at the very end
+ * of the program with atexit(), which happens after the pager exits, it
+ * would not work well if you send its log to the standard error output
+ * and let Git spawn the pager at the same time.
+ *
+ * As a work around, you can for example use '--no-pager', or set
+ * GIT_TRACE_PERFORMANCE to another file descriptor which is redirected
+ * to stderr, or set GIT_TRACE_PERFORMANCE to a file specified by its
+ * absolute path.
+ *
+ * For example instead of the following command which by default may not
+ * print any performance information:
+ *
+ * ------------
+ * GIT_TRACE_PERFORMANCE=2 git log -1
+ * ------------
+ *
+ * you may want to use:
+ *
+ * ------------
+ * GIT_TRACE_PERFORMANCE=2 git --no-pager log -1
+ * ------------
+ *
+ * or:
+ *
+ * ------------
+ * GIT_TRACE_PERFORMANCE=3 3>&2 git log -1
+ * ------------
+ *
+ * or:
+ *
+ * ------------
+ * GIT_TRACE_PERFORMANCE=/path/to/log/file git log -1
+ * ------------
+ *
+ */
+
+/**
+ * Defines a trace key (or category). The default (for API functions that
+ * don't take a key) is `GIT_TRACE`.
+ *
+ * E.g. to define a trace key controlled by environment variable `GIT_TRACE_FOO`:
+ *
+ * ------------
+ * static struct trace_key trace_foo = TRACE_KEY_INIT(FOO);
+ *
+ * static void trace_print_foo(const char *message)
+ * {
+ * 	trace_printf_key(&trace_foo, "%s", message);
+ * }
+ * ------------
+ *
+ * Note: don't use `const` as the trace implementation stores internal state in
+ * the `trace_key` structure.
+ */
 struct trace_key {
 	const char * const key;
 	int fd;
@@ -18,31 +94,84 @@ extern struct trace_key trace_perf_key;
 extern struct trace_key trace_setup_key;
 
 void trace_repo_setup(const char *prefix);
+
+/**
+ * Checks whether the trace key is enabled. Used to prevent expensive
+ * string formatting before calling one of the printing APIs.
+ */
 int trace_want(struct trace_key *key);
+
+/**
+ * Disables tracing for the specified key, even if the environment variable
+ * was set.
+ */
 void trace_disable(struct trace_key *key);
+
+/**
+ * Returns nanoseconds since the epoch (01/01/1970), typically used
+ * for performance measurements.
+ * Currently there are high precision timer implementations for Linux (using
+ * `clock_gettime(CLOCK_MONOTONIC)`) and Windows (`QueryPerformanceCounter`).
+ * Other platforms use `gettimeofday` as time source.
+ */
 uint64_t getnanotime(void);
+
 void trace_command_performance(const char **argv);
 void trace_verbatim(struct trace_key *key, const void *buf, unsigned len);
 uint64_t trace_performance_enter(void);
 
 #ifndef HAVE_VARIADIC_MACROS
 
+/**
+ * Prints a formatted message, similar to printf.
+ */
 __attribute__((format (printf, 1, 2)))
 void trace_printf(const char *format, ...);
 
 __attribute__((format (printf, 2, 3)))
 void trace_printf_key(struct trace_key *key, const char *format, ...);
 
+/**
+ * Prints a formatted message, followed by a quoted list of arguments.
+ */
 __attribute__((format (printf, 2, 3)))
 void trace_argv_printf(const char **argv, const char *format, ...);
 
+/**
+ * Prints the strbuf, without additional formatting (i.e. doesn't
+ * choke on `%` or even `\0`).
+ */
 void trace_strbuf(struct trace_key *key, const struct strbuf *data);
 
-/* Prints elapsed time (in nanoseconds) if GIT_TRACE_PERFORMANCE is enabled. */
+/**
+ * Prints elapsed time (in nanoseconds) if GIT_TRACE_PERFORMANCE is enabled.
+ *
+ * Example:
+ * ------------
+ * uint64_t t = 0;
+ * for (;;) {
+ * 	// ignore
+ * t -= getnanotime();
+ * // code section to measure
+ * t += getnanotime();
+ * // ignore
+ * }
+ * trace_performance(t, "frotz");
+ * ------------
+ */
 __attribute__((format (printf, 2, 3)))
 void trace_performance(uint64_t nanos, const char *format, ...);
 
-/* Prints elapsed time since 'start' if GIT_TRACE_PERFORMANCE is enabled. */
+/**
+ * Prints elapsed time since 'start' if GIT_TRACE_PERFORMANCE is enabled.
+ *
+ * Example:
+ * ------------
+ * uint64_t start = getnanotime();
+ * // code section to measure
+ * trace_performance_since(start, "foobar");
+ * ------------
+ */
 __attribute__((format (printf, 2, 3)))
 void trace_performance_since(uint64_t start, const char *format, ...);
 

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