avformat/avio: Constify data pointees of write callbacks

They are currently non-const for reasons unknown, although
avio_write() accepts a const buffer.

Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

doc/APIchanges

@@ -2,6 +2,10 @@ The last version increases of all libraries were on 2023-02-09
 
 API changes, most recent first:
 
+2023-09-07 - xxxxxxxxxx - lavf 60.12.100 - avio.h
+  Constify the buffer pointees in the write_packet and write_data_type
+  callbacks of AVIOContext on the next major bump.
+
 2023-09-07 - xxxxxxxxxx - lavc 60.26.100 - defs.h
   Add AV_PROFILE_* and AV_LEVEL_* replacements in defs.h for the
   defines from avcodec.h. The latter are deprecated.

libavformat/avio.c

@@ -408,7 +408,11 @@ int ffurl_read_complete(URLContext *h, unsigned char *buf, int size)
     return retry_transfer_wrapper(h, buf, size, size, h->prot->url_read);
 }
 
+#if FF_API_AVIO_WRITE_NONCONST
 int ffurl_write2(void *urlcontext, uint8_t *buf, int size)
+#else
+int ffurl_write2(void *urlcontext, const uint8_t *buf, int size)
+#endif
 {
     URLContext *h = urlcontext;
 

libavformat/avio.h

@@ -238,7 +238,11 @@ typedef struct AVIOContext {
     void *opaque;           /**< A private pointer, passed to the read/write/seek/...
                                  functions. */
     int (*read_packet)(void *opaque, uint8_t *buf, int buf_size);
+#if FF_API_AVIO_WRITE_NONCONST
     int (*write_packet)(void *opaque, uint8_t *buf, int buf_size);
+#else
+    int (*write_packet)(void *opaque, const uint8_t *buf, int buf_size);
+#endif
     int64_t (*seek)(void *opaque, int64_t offset, int whence);
     int64_t pos;            /**< position in the file of the current buffer */
     int eof_reached;        /**< true if was unable to read due to error or eof */
@@ -286,8 +290,13 @@ typedef struct AVIOContext {
     /**
      * A callback that is used instead of write_packet.
      */
+#if FF_API_AVIO_WRITE_NONCONST
     int (*write_data_type)(void *opaque, uint8_t *buf, int buf_size,
                            enum AVIODataMarkerType type, int64_t time);
+#else
+    int (*write_data_type)(void *opaque, const uint8_t *buf, int buf_size,
+                           enum AVIODataMarkerType type, int64_t time);
+#endif
     /**
      * If set, don't call write_data_type separately for AVIO_DATA_MARKER_BOUNDARY_POINT,
      * but ignore them and treat them as AVIO_DATA_MARKER_UNKNOWN (to avoid needlessly
@@ -407,7 +416,11 @@ AVIOContext *avio_alloc_context(
                   int write_flag,
                   void *opaque,
                   int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
+#if FF_API_AVIO_WRITE_NONCONST
                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
+#else
+                  int (*write_packet)(void *opaque, const uint8_t *buf, int buf_size),
+#endif
                   int64_t (*seek)(void *opaque, int64_t offset, int whence));
 
 /**

libavformat/avio_internal.h

@@ -89,7 +89,11 @@ void ffio_init_context(FFIOContext *s,
                   int write_flag,
                   void *opaque,
                   int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
+#if FF_API_AVIO_WRITE_NONCONST
                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
+#else
+                  int (*write_packet)(void *opaque, const uint8_t *buf, int buf_size),
+#endif
                   int64_t (*seek)(void *opaque, int64_t offset, int whence));
 
 /**

libavformat/aviobuf.c

@@ -84,7 +84,11 @@ void ffio_init_context(FFIOContext *ctx,
                   int write_flag,
                   void *opaque,
                   int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
+#if FF_API_AVIO_WRITE_NONCONST
                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
+#else
+                  int (*write_packet)(void *opaque, const uint8_t *buf, int buf_size),
+#endif
                   int64_t (*seek)(void *opaque, int64_t offset, int whence))
 {
     AVIOContext *const s = &ctx->pub;
@@ -143,7 +147,11 @@ AVIOContext *avio_alloc_context(
                   int write_flag,
                   void *opaque,
                   int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
+#if FF_API_AVIO_WRITE_NONCONST
                   int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
+#else
+                  int (*write_packet)(void *opaque, const uint8_t *buf, int buf_size),
+#endif
                   int64_t (*seek)(void *opaque, int64_t offset, int whence))
 {
     FFIOContext *s = av_malloc(sizeof(*s));
@@ -165,12 +173,20 @@ static void writeout(AVIOContext *s, const uint8_t *data, int len)
     if (!s->error) {
         int ret = 0;
         if (s->write_data_type)
+#if FF_API_AVIO_WRITE_NONCONST
             ret = s->write_data_type(s->opaque, (uint8_t *)data,
+#else
+            ret = s->write_data_type(s->opaque, data,
+#endif
                                      len,
                                      ctx->current_type,
                                      ctx->last_time);
         else if (s->write_packet)
+#if FF_API_AVIO_WRITE_NONCONST
             ret = s->write_packet(s->opaque, (uint8_t *)data, len);
+#else
+            ret = s->write_packet(s->opaque, data, len);
+#endif
         if (ret < 0) {
             s->error = ret;
         } else {
@@ -1396,7 +1412,11 @@ typedef struct DynBuffer {
     uint8_t io_buffer[1];
 } DynBuffer;
 
+#if FF_API_AVIO_WRITE_NONCONST
 static int dyn_buf_write(void *opaque, uint8_t *buf, int buf_size)
+#else
+static int dyn_buf_write(void *opaque, const uint8_t *buf, int buf_size)
+#endif
 {
     DynBuffer *d = opaque;
     unsigned new_size;
@@ -1428,7 +1448,11 @@ static int dyn_buf_write(void *opaque, uint8_t *buf, int buf_size)
     return buf_size;
 }
 
+#if FF_API_AVIO_WRITE_NONCONST
 static int dyn_packet_buf_write(void *opaque, uint8_t *buf, int buf_size)
+#else
+static int dyn_packet_buf_write(void *opaque, const uint8_t *buf, int buf_size)
+#endif
 {
     unsigned char buf1[4];
     int ret;
@@ -1565,7 +1589,11 @@ void ffio_free_dyn_buf(AVIOContext **s)
     avio_context_free(s);
 }
 
+#if FF_API_AVIO_WRITE_NONCONST
 static int null_buf_write(void *opaque, uint8_t *buf, int buf_size)
+#else
+static int null_buf_write(void *opaque, const uint8_t *buf, int buf_size)
+#endif
 {
     DynBuffer *d = opaque;
 

libavformat/hdsenc.c

@@ -112,7 +112,11 @@ static int parse_header(OutputStream *os, const uint8_t *buf, int buf_size)
     return 0;
 }
 
+#if FF_API_AVIO_WRITE_NONCONST
 static int hds_write(void *opaque, uint8_t *buf, int buf_size)
+#else
+static int hds_write(void *opaque, const uint8_t *buf, int buf_size)
+#endif
 {
     OutputStream *os = opaque;
     if (os->out) {

libavformat/smoothstreamingenc.c

@@ -75,7 +75,11 @@ typedef struct SmoothStreamingContext {
     int nb_fragments;
 } SmoothStreamingContext;
 
+#if FF_API_AVIO_WRITE_NONCONST
 static int ism_write(void *opaque, uint8_t *buf, int buf_size)
+#else
+static int ism_write(void *opaque, const uint8_t *buf, int buf_size)
+#endif
 {
     OutputStream *os = opaque;
     if (os->out)

libavformat/url.h

@@ -194,7 +194,11 @@ static inline int ffurl_read(URLContext *h, uint8_t *buf, int size)
  */
 int ffurl_read_complete(URLContext *h, unsigned char *buf, int size);
 
+#if FF_API_AVIO_WRITE_NONCONST
 int ffurl_write2(void *urlcontext, uint8_t *buf, int size);
+#else
+int ffurl_write2(void *urlcontext, const uint8_t *buf, int size);
+#endif
 /**
  * Write size bytes from buf to the resource accessed by h.
  *
@@ -203,7 +207,11 @@ int ffurl_write2(void *urlcontext, uint8_t *buf, int size);
  */
 static inline int ffurl_write(URLContext *h, const uint8_t *buf, int size)
 {
+#if FF_API_AVIO_WRITE_NONCONST
     return ffurl_write2(h, (uint8_t*)buf, size);
+#else
+    return ffurl_write2(h, buf, size);
+#endif
 }
 
 int64_t ffurl_seek2(void *urlcontext, int64_t pos, int whence);

libavformat/version.h

@@ -31,7 +31,7 @@
 
 #include "version_major.h"
 
-#define LIBAVFORMAT_VERSION_MINOR  11
+#define LIBAVFORMAT_VERSION_MINOR  12
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \

libavformat/version_major.h

@@ -45,6 +45,7 @@
 #define FF_API_GET_END_PTS              (LIBAVFORMAT_VERSION_MAJOR < 61)
 #define FF_API_AVIODIRCONTEXT           (LIBAVFORMAT_VERSION_MAJOR < 61)
 #define FF_API_AVFORMAT_IO_CLOSE        (LIBAVFORMAT_VERSION_MAJOR < 61)
+#define FF_API_AVIO_WRITE_NONCONST      (LIBAVFORMAT_VERSION_MAJOR < 61)
 
 
 #define FF_API_R_FRAME_RATE            1