Merge pull request #34205 from yuwata/pretty-print-buffering

pretty-print: introduce WITH_BUFFERED_STDERR macro to enable buffering

src/shared/pretty-print.c

@@ -460,7 +460,7 @@ bool shall_tint_background(void) {
         return cache != 0;
 }
 
-void draw_progress_bar_unbuffered(const char *prefix, double percentage) {
+void draw_progress_bar_impl(const char *prefix, double percentage) {
         fputc('\r', stderr);
         if (prefix) {
                 fputs(prefix, stderr);
@@ -516,7 +516,7 @@ void draw_progress_bar_unbuffered(const char *prefix, double percentage) {
 
 }
 
-void clear_progress_bar_unbuffered(const char *prefix) {
+void clear_progress_bar_impl(const char *prefix) {
         fputc('\r', stderr);
 
         if (terminal_is_dumb())
@@ -531,28 +531,14 @@ void clear_progress_bar_unbuffered(const char *prefix) {
 }
 
 void draw_progress_bar(const char *prefix, double percentage) {
-
         /* We are going output a bunch of small strings that shall appear as a single line to STDERR which is
          * unbuffered by default. Let's temporarily turn on full buffering, so that this is passed to the tty
          * as a single buffer, to make things more efficient. */
-        char buffer[LONG_LINE_MAX];
-        setvbuf(stderr, buffer, _IOFBF, sizeof(buffer));
-
-        draw_progress_bar_unbuffered(prefix, percentage);
-
-        fflush(stderr);
-
-        /* Disable buffering again */
-        setvbuf(stderr, NULL, _IONBF, 0);
+        WITH_BUFFERED_STDERR;
+        draw_progress_bar_impl(prefix, percentage);
 }
 
 void clear_progress_bar(const char *prefix) {
-        char buffer[LONG_LINE_MAX];
-        setvbuf(stderr, buffer, _IOFBF, sizeof(buffer));
-
-        clear_progress_bar_unbuffered(prefix);
-
-        fflush(stderr);
-
-        setvbuf(stderr, NULL, _IONBF, 0);
+        WITH_BUFFERED_STDERR;
+        clear_progress_bar_impl(prefix);
 }

src/shared/pretty-print.h

@@ -55,5 +55,34 @@ bool shall_tint_background(void);
 
 void draw_progress_bar(const char *prefix, double percentage);
 void clear_progress_bar(const char *prefix);
-void draw_progress_bar_unbuffered(const char *prefix, double percentage);
-void clear_progress_bar_unbuffered(const char *prefix);
+void draw_progress_bar_impl(const char *prefix, double percentage);
+void clear_progress_bar_impl(const char *prefix);
+
+static inline FILE* enable_buffering(FILE *f, char *buffer, size_t size) {
+        assert(f);
+        assert(buffer);
+        assert(size > 0);
+
+        if (setvbuf(f, buffer, _IOFBF, size) != 0)
+                return NULL;
+
+        return f;
+}
+
+static inline void fflush_and_disable_bufferingp(FILE **p) {
+        assert(p);
+
+        if (*p) {
+                fflush(*p);
+                setvbuf(*p, NULL, _IONBF, 0); /* Disable buffering again. */
+        }
+}
+
+/* Even though the macro below is slightly generic, but it may not work most streams except for stderr,
+ * as stdout is buffered and fopen() enables buffering by default. */
+#define _WITH_BUFFERED_STREAM(f, size, p)                               \
+        _unused_ _cleanup_(fflush_and_disable_bufferingp) FILE *p =     \
+                enable_buffering(f, (char[size]) {}, size)
+
+#define WITH_BUFFERED_STDERR                                            \
+        _WITH_BUFFERED_STREAM(stderr, LONG_LINE_MAX, UNIQ_T(p, UNIQ))