seems to work

include/aws/s3/private/s3_copy_object.h

@@ -7,6 +7,7 @@
  */
 
 #include "aws/s3/private/s3_meta_request_impl.h"
+#include <aws/common/uri.h>
 
 enum aws_s3_copy_object_request_tag {
     AWS_S3_COPY_OBJECT_REQUEST_TAG_GET_OBJECT_SIZE,
@@ -25,6 +26,8 @@ struct aws_s3_copy_object {
     /* Usable after the Create Multipart Upload request succeeds. */
     struct aws_string *upload_id;
 
+    struct aws_uri source_uri;
+
     /* Only meant for use in the update function, which is never called concurrently. */
     struct {
         uint32_t next_part_number;

include/aws/s3/private/s3_request_messages.h

@@ -136,7 +136,8 @@ struct aws_http_message *aws_s3_get_object_size_message_new(
 AWS_S3_API
 struct aws_http_message *aws_s3_get_source_object_size_message_new(
     struct aws_allocator *allocator,
-    struct aws_http_message *base_message);
+    struct aws_http_message *base_message,
+    struct aws_uri *source_uri);
 
 /* Add content-md5 header to the http message passed in. The MD5 will be computed from the input_buf */
 AWS_S3_API

include/aws/s3/s3_client.h

@@ -869,6 +869,9 @@ struct aws_s3_meta_request_options {
      * This is just used as an estimate, so it's okay to provide an approximate value if the exact size is unknown.
      */
     const uint64_t *object_size_hint;
+
+
+    const struct aws_byte_cursor copy_source_uri;
 };
 
 /* Result details of a meta request.

source/s3_copy_object.c

@@ -82,8 +82,7 @@ struct aws_s3_meta_request *aws_s3_meta_request_copy_object_new(
             copy_object,
             &s_s3_copy_object_vtable,
             &copy_object->base)) {
-        aws_mem_release(allocator, copy_object);
-        return NULL;
+        goto on_error;
     }
 
     aws_array_list_init_dynamic(
@@ -92,10 +91,20 @@ struct aws_s3_meta_request *aws_s3_meta_request_copy_object_new(
     copy_object->synced_data.content_length = UNKNOWN_CONTENT_LENGTH;
     copy_object->synced_data.total_num_parts = UNKNOWN_NUM_PARTS;
     copy_object->threaded_update_data.next_part_number = 1;
+    if(options->copy_source_uri.len != 0) {
+        if(aws_uri_init_parse(&copy_object->source_uri, allocator, &options->copy_source_uri)) {
+            // TODO: log
+            goto on_error;
+        }
+
+    }
 
     AWS_LOGF_DEBUG(AWS_LS_S3_META_REQUEST, "id=%p Created new CopyObject Meta Request.", (void *)&copy_object->base);
 
     return &copy_object->base;
+on_error:
+    aws_mem_release(allocator, copy_object);
+    return NULL;
 }
 
 static void s_s3_meta_request_copy_object_destroy(struct aws_s3_meta_request *meta_request) {
@@ -105,6 +114,7 @@ static void s_s3_meta_request_copy_object_destroy(struct aws_s3_meta_request *me
     struct aws_s3_copy_object *copy_object = meta_request->impl;
 
     aws_string_destroy(copy_object->upload_id);
+    aws_uri_clean_up(&copy_object->source_uri);
     copy_object->upload_id = NULL;
 
     for (size_t part_index = 0; part_index < aws_array_list_length(&copy_object->synced_data.part_list); ++part_index) {
@@ -364,7 +374,7 @@ static struct aws_future_void *s_s3_copy_object_prepare_request(struct aws_s3_re
         /* Prepares the GetObject HEAD request to get the source object size. */
         case AWS_S3_COPY_OBJECT_REQUEST_TAG_GET_OBJECT_SIZE: {
             message = aws_s3_get_source_object_size_message_new(
-                meta_request->allocator, meta_request->initial_request_message);
+                meta_request->allocator, meta_request->initial_request_message, &copy_object->source_uri);
             break;
         }
 

source/s3_request_messages.c

@@ -10,6 +10,7 @@
 #include <aws/common/byte_buf.h>
 #include <aws/common/encoding.h>
 #include <aws/common/string.h>
+#include <aws/common/uri.h>
 #include <aws/http/request_response.h>
 #include <aws/io/async_stream.h>
 #include <aws/io/stream.h>
@@ -457,8 +458,35 @@ static const struct aws_byte_cursor s_slash_char = AWS_BYTE_CUR_INIT_FROM_STRING
  */
 struct aws_http_message *aws_s3_get_source_object_size_message_new(
     struct aws_allocator *allocator,
-    struct aws_http_message *base_message) {
+    struct aws_http_message *base_message,
+    struct aws_uri *source_uri) {
     struct aws_http_message *message = NULL;
+
+    message = aws_http_message_new_request(allocator);
+    if (message == NULL) {
+        goto error_cleanup;
+    }
+
+    if (aws_http_message_set_request_method(message, g_head_method)) {
+        goto error_cleanup;
+    }
+    if (source_uri->self_size > 0) {
+        struct aws_byte_cursor host = *aws_uri_host_name(source_uri);
+        struct aws_byte_cursor path = *aws_uri_path(source_uri);
+        struct aws_http_header host_header = {
+            .name = g_host_header_name,
+            .value = host,
+        };
+        if (aws_http_message_add_header(message, host_header)) {
+            goto error_cleanup;
+        }
+
+        if (aws_http_message_set_request_path(message, path)) {
+            goto error_cleanup;
+        }
+        return message;
+    }
+
     struct aws_byte_buf head_object_host_header;
     AWS_ZERO_STRUCT(head_object_host_header);
 
@@ -529,15 +557,6 @@ struct aws_http_message *aws_s3_get_source_object_size_message_new(
         goto error_cleanup;
     }
 
-    message = aws_http_message_new_request(allocator);
-    if (message == NULL) {
-        goto error_cleanup;
-    }
-
-    if (aws_http_message_set_request_method(message, g_head_method)) {
-        goto error_cleanup;
-    }
-
     struct aws_http_header host_header = {
         .name = g_host_header_name,
         .value = aws_byte_cursor_from_buf(&head_object_host_header),