[FFmpeg-devel] [PATCHv2 1/3] avformat/avio: add avio_print_n_strings and avio_print

[Marton Balint]

These functions can be used to print a variable number of strings consecutively
to the IO context. Unlike av_bprintf, no temporary buffer is necessary.

Signed-off-by: Marton Balint <cus at passwd.hu>
---
 doc/APIchanges        |  3 +++
 libavformat/avio.h    | 17 +++++++++++++++++
 libavformat/aviobuf.c | 12 ++++++++++++
 libavformat/version.h |  2 +-
 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/doc/APIchanges b/doc/APIchanges
index 6603a8229e..0b19fb067d 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -15,6 +15,9 @@ libavutil:     2017-10-21
 
 API changes, most recent first:
 
+2019-08-xx - xxxxxxxxxx - lavf 58.31.100 - avio.h
+  Add avio_print_n_strings and avio_print.
+
 2019-07-27 - xxxxxxxxxx - lavu 56.33.100 - tx.h
   Add AV_TX_DOUBLE_FFT and AV_TX_DOUBLE_MDCT
 
diff --git a/libavformat/avio.h b/libavformat/avio.h
index dcb8dcdf93..0c622f44bd 100644
--- a/libavformat/avio.h
+++ b/libavformat/avio.h
@@ -574,6 +574,23 @@ int avio_feof(AVIOContext *s);
 /** @warning Writes up to 4 KiB per call */
 int avio_printf(AVIOContext *s, const char *fmt, ...) av_printf_format(2, 3);
 
+/**
+ * Write nb_strings number of strings (const char *) to the context.
+ * This function is not to be used directly, use avio_print instead.
+ */
+void avio_print_n_strings(AVIOContext *s, int nb_strings, ...);
+
+/**
+ * Write strings (const char *) to the context.
+ * This is a macro around avio_print_n_strings but the number of strings to be
+ * written is determined automatically at compile time based on the number of
+ * parameters passed to this macro. For simple string concatenations this
+ * function is more performant than using avio_printf since it does not need a
+ * temporary buffer.
+ */
+#define avio_print(s, ...) \
+    avio_print_n_strings(s, sizeof((const char*[]){__VA_ARGS__}) / sizeof(const char*), __VA_ARGS__)
+
 /**
  * Force flushing of buffered data.
  *
diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
index 2d011027c9..4a37a13d7a 100644
--- a/libavformat/aviobuf.c
+++ b/libavformat/aviobuf.c
@@ -1225,6 +1225,18 @@ int avio_printf(AVIOContext *s, const char *fmt, ...)
     return ret;
 }
 
+void avio_print_n_strings(AVIOContext *s, int nb_strings, ...)
+{
+    va_list ap;
+
+    va_start(ap, nb_strings);
+    for (int i = 0; i < nb_strings; i++) {
+        const char *str = va_arg(ap, const char *);
+        avio_write(s, (const unsigned char *)str, strlen(str));
+    }
+    va_end(ap);
+}
+
 int avio_pause(AVIOContext *s, int pause)
 {
     if (!s->read_pause)
diff --git a/libavformat/version.h b/libavformat/version.h
index 45efaff9b9..feceaedc08 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -32,7 +32,7 @@
 // Major bumping may affect Ticket5467, 5421, 5451(compatibility with Chromium)
 // Also please add any ticket numbers that you believe might be affected here
 #define LIBAVFORMAT_VERSION_MAJOR  58
-#define LIBAVFORMAT_VERSION_MINOR  30
+#define LIBAVFORMAT_VERSION_MINOR  31
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
-- 
2.16.4