trace: add infrastructure to augment trace output with additional info

To be able to add a common prefix or suffix to all trace output (e.g.
a timestamp or file:line of the caller), factor out common setup and
cleanup tasks of the trace* functions.

When adding a common prefix, it makes sense that the output of each trace
call starts on a new line. Add '\n' in case the caller forgot.

Note that this explicitly limits trace output to line-by-line, it is no
longer possible to trace-print just part of a line. Until now, this was
just an implicit assumption (trace-printing part of a line worked, but
messed up the trace file if multiple threads or processes were involved).

Thread-safety / inter-process-safety is also the reason why we need to do
the prefixing and suffixing in memory rather than issuing multiple write()
calls. Write_or_whine_pipe() / xwrite() is atomic unless the size exceeds
MAX_IO_SIZE (8MB, see wrapper.c). In case of trace_strbuf, this costs an
additional string copy (which should be irrelevant for performance in light
of actual file IO).

While we're at it, rename trace_strbuf's 'buf' argument, which suggests
that the function is modifying the buffer. Trace_strbuf() currently is the
only trace API that can print arbitrary binary data (without barfing on
'%' or stopping at '\0'), so 'data' seems more appropriate.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/trace.c b/trace.c
index 8662b7980133eb900fde3bbb675e7a363f04cf1f..3d02bcc2393ae58e3af23c7566555ad04208ea49 100644 (file)
--- a/trace.c
+++ b/trace.c
@@ -85,17 +85,37 @@ void trace_disable(struct trace_key *key)
 static const char err_msg[] = "Could not trace into fd given by "
        "GIT_TRACE environment variable";
 
 static const char err_msg[] = "Could not trace into fd given by "
        "GIT_TRACE environment variable";
 

+static int prepare_trace_line(struct trace_key *key, struct strbuf *buf)
+{
+       if (!trace_want(key))
+               return 0;
+
+       set_try_to_free_routine(NULL);  /* is never reset */
+
+       /* add line prefix here */
+
+       return 1;
+}
+
+static void print_trace_line(struct trace_key *key, struct strbuf *buf)
+{
+       /* append newline if missing */
+       if (buf->len && buf->buf[buf->len - 1] != '\n')
+               strbuf_addch(buf, '\n');
+
+       write_or_whine_pipe(get_trace_fd(key), buf->buf, buf->len, err_msg);
+       strbuf_release(buf);
+}
+

 static void trace_vprintf(struct trace_key *key, const char *format, va_list ap)
 {
        struct strbuf buf = STRBUF_INIT;
 
 static void trace_vprintf(struct trace_key *key, const char *format, va_list ap)
 {
        struct strbuf buf = STRBUF_INIT;
 

-       if (!trace_want(key))
+       if (!prepare_trace_line(key, &buf))

                return;
 
                return;
 

-       set_try_to_free_routine(NULL);  /* is never reset */

        strbuf_vaddf(&buf, format, ap);
        strbuf_vaddf(&buf, format, ap);

-       trace_strbuf(key, &buf);
-       strbuf_release(&buf);
+       print_trace_line(key, &buf);

 }
 
 void trace_printf_key(struct trace_key *key, const char *format, ...)
 }
 
 void trace_printf_key(struct trace_key *key, const char *format, ...)


@@ -114,32 +134,31 @@ void trace_printf(const char *format, ...)
        va_end(ap);
 }
 
        va_end(ap);
 }
 

-void trace_strbuf(struct trace_key *key, const struct strbuf *buf)
+void trace_strbuf(struct trace_key *key, const struct strbuf *data)

 {
 {

-       int fd = get_trace_fd(key);
-       if (!fd)
+       struct strbuf buf = STRBUF_INIT;
+
+       if (!prepare_trace_line(key, &buf))

                return;
 
                return;
 

-       write_or_whine_pipe(fd, buf->buf, buf->len, err_msg);
+       strbuf_addbuf(&buf, data);
+       print_trace_line(key, &buf);

 }
 
 void trace_argv_printf(const char **argv, const char *format, ...)
 {
        struct strbuf buf = STRBUF_INIT;
        va_list ap;
 }
 
 void trace_argv_printf(const char **argv, const char *format, ...)
 {
        struct strbuf buf = STRBUF_INIT;
        va_list ap;

-       int fd = get_trace_fd(NULL);
-       if (!fd)
+
+       if (!prepare_trace_line(NULL, &buf))

                return;
 
                return;
 

-       set_try_to_free_routine(NULL);  /* is never reset */

        va_start(ap, format);
        strbuf_vaddf(&buf, format, ap);
        va_end(ap);
 
        sq_quote_argv(&buf, argv, 0);
        va_start(ap, format);
        strbuf_vaddf(&buf, format, ap);
        va_end(ap);
 
        sq_quote_argv(&buf, argv, 0);

-       strbuf_addch(&buf, '\n');
-       write_or_whine_pipe(fd, buf.buf, buf.len, err_msg);
-       strbuf_release(&buf);
+       print_trace_line(NULL, &buf);

 }
 
 static const char *quote_crnl(const char *path)
 }
 
 static const char *quote_crnl(const char *path)

diff --git a/trace.h b/trace.h
index d85ac4c6529ea1895a37847a009e17cbccf12735..28c10892df58602ef674d66e29d5d590726aca38 100644 (file)
--- a/trace.h
+++ b/trace.h
@@ -22,6 +22,6 @@ extern int trace_want(struct trace_key *key);
 extern void trace_disable(struct trace_key *key);
 __attribute__((format (printf, 2, 3)))
 extern void trace_printf_key(struct trace_key *key, const char *format, ...);
 extern void trace_disable(struct trace_key *key);
 __attribute__((format (printf, 2, 3)))
 extern void trace_printf_key(struct trace_key *key, const char *format, ...);

-extern void trace_strbuf(struct trace_key *key, const struct strbuf *buf);
+extern void trace_strbuf(struct trace_key *key, const struct strbuf *data);

 
 #endif /* TRACE_H */
 
 #endif /* TRACE_H */