[FFmpeg-devel] [PATCH 1/2] Add av_fd_dump(): read from fd into buffer up to EOF

[Andrey Utkin]

---
 libavutil/file.c | 32 ++++++++++++++++++++++++++++++++
 libavutil/file.h | 30 ++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/libavutil/file.c b/libavutil/file.c
index 45fe853..1c664f2 100644
--- a/libavutil/file.c
+++ b/libavutil/file.c
@@ -184,6 +184,38 @@ int av_tempfile(const char *prefix, char **filename, int log_offset, void *log_c
     return fd; /* success */
 }
 
+int av_fd_dump(int fd, uint8_t **bufptr, size_t *size,
+        size_t spare_trailing_bytes, size_t buf_incr)
+{
+    int ret;
+    int should_free_on_failure;
+    int bufsize;
+    assert(bufptr && size);
+    should_free_on_failure = (*bufptr == NULL);
+    /* We don't pass explicitly current allocated size, but it is safe to
+     * assume it equal to the offset to start, i.e. *size */
+    bufsize = *size;
+    while (1) {
+        if (bufsize - *size <= spare_trailing_bytes) {
+            bufsize += buf_incr;
+            ret = av_reallocp(bufptr, bufsize);
+            if (ret)
+                break;
+        }
+        ret = read(fd, *bufptr + *size, bufsize - *size - spare_trailing_bytes);
+        if (!ret) {
+            break;
+        } else if (ret == -1) {
+            ret = AVERROR(errno);
+            break;
+        }
+        *size += ret;
+    }
+    if (ret && should_free_on_failure)
+        av_reallocp(*bufptr, 0);
+    return ret;
+}
+
 #ifdef TEST
 
 #undef printf
diff --git a/libavutil/file.h b/libavutil/file.h
index a7364fe..db585d4 100644
--- a/libavutil/file.h
+++ b/libavutil/file.h
@@ -63,4 +63,34 @@ void av_file_unmap(uint8_t *bufptr, size_t size);
  */
 int av_tempfile(const char *prefix, char **filename, int log_offset, void *log_ctx);
 
+/**
+ * Reads from fd up to EOF, saves data in *bufptr and updates *size.
+ *
+ * @note You MUST initialize *bufptr and *size to valid values. If you set them
+ * to NULL and 0, it will allocate the array for you and fill it with fd
+ * product. Otherwise you can set it to an address of some previously
+ * av_realloc()-ed buffer and the offset to proceed writing, and it will
+ * effectively append fd product to existing content of array. Array will get
+ * extended by av_reallocp() if needed.
+ *
+ * @note According to av_realloc() doc, it may work wrong if supplied with
+ * av_malloc()-ed buffer. Use av_realloc() to create pre-allocated buffer.
+ *
+ * @note fd is not closed by this function
+ *
+ * @param fd file descriptor to read from
+ * @param bufptr pointer to pointer to buffer, it must be initialized by caller.
+ * @param size pointer to amount of data written to buffer, it must be
+ * initialized by caller.
+ * @param spare_trailing_bytes how many allocated bytes to hold for later
+ * buffer finalization. Set to 0 if not needed, set to 1 if you need to
+ * null-terminate the buffer.
+ * @param buf_incr amount of bytes to increase the buffer size when needed
+ *
+ * @return zero on success, negative error code on failure
+ *
+ */
+int av_fd_dump(int fd, uint8_t **bufptr, size_t *size,
+        size_t spare_trailing_bytes, size_t buf_incr);
+
 #endif /* AVUTIL_FILE_H */
-- 
1.8.3.2