[FFmpeg-devel] [PATCH 1/6] lavu/mem: add av_realloc_reuse() as a replacement for av_fast_realloc()

[Anton Khirnov <anton@khirnov.net>]

It uses size_t rather than unsigned for the size and conforms to our
standard naming scheme.
---
 configure           |  5 ++++-
 doc/APIchanges      |  3 +++
 libavutil/mem.c     | 30 ++++++++++++++++++++++++++++++
 libavutil/mem.h     | 37 +++++++++++++++++++++++++++++++++++--
 libavutil/version.h |  3 ++-
 5 files changed, 74 insertions(+), 4 deletions(-)

diff --git a/configure b/configure
index 6712d045d9..fd0e6ae032 100755
--- a/configure
+++ b/configure
@@ -4360,7 +4360,10 @@ case "$toolchain" in
         target_exec_default="valgrind"
         case "$toolchain" in
             valgrind-massif)
-                target_exec_args="--tool=massif --alloc-fn=av_malloc --alloc-fn=av_mallocz --alloc-fn=av_calloc --alloc-fn=av_fast_padded_malloc --alloc-fn=av_fast_malloc --alloc-fn=av_realloc_f --alloc-fn=av_fast_realloc --alloc-fn=av_realloc"
+                target_exec_args="--tool=massif"
+                for func in av_malloc av_mallocz av_calloc av_fast_padded_malloc av_fast_malloc av_realloc_f av_fast_realloc av_realloc av_realloc_reuse; do
+                    target_exec_args="$target_exec_args --alloc-fn=$func"
+                done
                 ;;
             valgrind-memcheck)
                 target_exec_args="--error-exitcode=1 --malloc-fill=0x2a --track-origins=yes --leak-check=full --gen-suppressions=all --suppressions=$source_path/tests/fate-valgrind.supp"
diff --git a/doc/APIchanges b/doc/APIchanges
index b0a41c9e37..9a735c27e7 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -14,6 +14,9 @@ libavutil:     2021-04-27
 
 API changes, most recent first:
 
+2022-xx-xx - xxxxxxxxxx - lavu 57.38.100 - mem.h
+  Add av_realloc_reuse(), deprecate av_fast_realloc().
+
 2022-09-26 - xxxxxxxxxx - lavc 59.48.100 - avcodec.h
   Deprecate avcodec_enum_to_chroma_pos() and avcodec_chroma_pos_to_enum().
   Use av_chroma_location_enum_to_pos() or av_chroma_location_pos_to_enum()
diff --git a/libavutil/mem.c b/libavutil/mem.c
index 18aff5291f..51fdc9155f 100644
--- a/libavutil/mem.c
+++ b/libavutil/mem.c
@@ -502,6 +502,35 @@ void av_memcpy_backptr(uint8_t *dst, int back, int cnt)
     }
 }
 
+void *av_realloc_reuse(void *ptr, size_t *size, size_t min_size)
+{
+    size_t max_size;
+
+    if (min_size <= *size)
+        return ptr;
+
+    max_size = atomic_load_explicit(&max_alloc_size, memory_order_relaxed);
+
+    if (min_size > max_size) {
+        *size = 0;
+        return NULL;
+    }
+
+    min_size = FFMIN(max_size, FFMAX(min_size + min_size / 16 + 32, min_size));
+
+    ptr = av_realloc(ptr, min_size);
+    /* we could set this to the unmodified min_size but this is safer
+     * if the user lost the ptr and uses NULL now
+     */
+    if (!ptr)
+        min_size = 0;
+
+    *size = min_size;
+
+    return ptr;
+}
+
+#if FF_API_FAST_ALLOC
 void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size)
 {
     size_t max_size;
@@ -531,6 +560,7 @@ void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size)
 
     return ptr;
 }
+#endif
 
 static inline void fast_malloc(void *ptr, unsigned int *size, size_t min_size, int zero_realloc)
 {
diff --git a/libavutil/mem.h b/libavutil/mem.h
index d91174196c..deb440ca1a 100644
--- a/libavutil/mem.h
+++ b/libavutil/mem.h
@@ -264,7 +264,7 @@ void *av_mallocz_array(size_t nmemb, size_t size) av_malloc_attrib av_alloc_size
  * @warning Unlike av_malloc(), the returned pointer is not guaranteed to be
  *          correctly aligned. The returned pointer must be freed after even
  *          if size is zero.
- * @see av_fast_realloc()
+ * @see av_realloc_reuse()
  * @see av_reallocp()
  */
 void *av_realloc(void *ptr, size_t size) av_alloc_size(2);
@@ -346,6 +346,35 @@ av_alloc_size(2, 3) void *av_realloc_array(void *ptr, size_t nmemb, size_t size)
  */
 int av_reallocp_array(void *ptr, size_t nmemb, size_t size);
 
+/**
+ * Reallocate a data buffer, reusing the existing one if it is large enough.
+ *
+ * This function is similar to av_realloc(), but optimized for cases where the
+ * buffer may grow significantly and is not expected to shrink.
+ *
+ * @param[in] ptr Previously allocated buffer, or `NULL`. If `ptr` is `NULL`, a
+ * new uninitialized buffer is allocated. `ptr` is invalidated when this
+ * function returns non-`NULL` and must be replaced with its return value.
+ *
+ * @param[in,out] size Pointer to the allocated size of buffer `ptr`. This
+ * function updates `*size` to the new allocated size (which may be larger than
+ * `min_size`). `*size` is set to 0 on failure.
+ *
+ * @param[in] min_size Minimum size in bytes of the returned buffer.
+ *
+ * @return
+ * - An allocated buffer (to be freed with `av_free()`) that is large enough to
+ *   hold at least `min_size` bytes. The first `*size` (value on entry to this
+ *   function) bytes of the buffer remain the same as the data in `ptr`, the
+ *   rest is uninitialized.
+ * - `NULL` on failure, then `*size` is set to 0 and ptr remains untouched.
+ *
+ * @see av_realloc()
+ * @see av_fast_malloc()
+ */
+void *av_realloc_reuse(void *ptr, size_t *size, size_t min_size);
+
+#if FF_API_FAST_ALLOC
 /**
  * Reallocate the given buffer if it is not large enough, otherwise do nothing.
  *
@@ -377,13 +406,17 @@ int av_reallocp_array(void *ptr, size_t nmemb, size_t size);
  *         error
  * @see av_realloc()
  * @see av_fast_malloc()
+ *
+ * @deprecated use av_realloc_reuse()
  */
+attribute_deprecated
 void *av_fast_realloc(void *ptr, unsigned int *size, size_t min_size);
+#endif
 
 /**
  * Allocate a buffer, reusing the given one if large enough.
  *
- * Contrary to av_fast_realloc(), the current buffer contents might not be
+ * Contrary to av_realloc_reuse(), the current buffer contents might not be
  * preserved and on error the old buffer is freed, thus no special handling to
  * avoid memleaks is necessary.
  *
diff --git a/libavutil/version.h b/libavutil/version.h
index 9c44cef6aa..285a32f3d6 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -79,7 +79,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  57
-#define LIBAVUTIL_VERSION_MINOR  37
+#define LIBAVUTIL_VERSION_MINOR  38
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
@@ -115,6 +115,7 @@
 #define FF_API_OLD_CHANNEL_LAYOUT       (LIBAVUTIL_VERSION_MAJOR < 58)
 #define FF_API_AV_FOPEN_UTF8            (LIBAVUTIL_VERSION_MAJOR < 58)
 #define FF_API_PKT_DURATION             (LIBAVUTIL_VERSION_MAJOR < 58)
+#define FF_API_FAST_ALLOC               (LIBAVUTIL_VERSION_MAJOR < 58)
 
 /**
  * @}
-- 
2.35.1

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