try to just load a page

Author: TingDaoK

include/aws/s3/private/aws_mmap.h

@@ -61,6 +61,7 @@ AWS_S3_API void *aws_mmap_context_map_content(
  * @return AWS_OP_SUCCESS on success, AWS_OP_ERR on error.
  **/
 AWS_S3_API int aws_mmap_context_unmap_content(void *mapped_addr, size_t len);
+AWS_S3_API int aws_mmap_context_get_fd(struct aws_mmap_context *context);
 
 AWS_EXTERN_C_END
 #endif /* AWS_MMAP_H */

source/aws_mmap.c

@@ -247,6 +247,12 @@ void *aws_mmap_context_map_content(
     return NULL;
 }
 
+int aws_mmap_context_get_fd(struct aws_mmap_context *context) {
+    AWS_PRECONDITION(context);
+    struct aws_mmap_context_posix_impl *impl = context->impl;
+    return impl->fd;
+}
+
 int aws_mmap_context_unmap_content(void *mapped_addr, size_t len) {
     if (!mapped_addr) {
         return AWS_OP_SUCCESS;

source/s3_parallel_input_stream.c

@@ -10,6 +10,18 @@
 
 #include <aws/io/future.h>
 #include <aws/io/stream.h>
+#ifdef _WIN32
+#    include <windows.h>
+#else
+#    include <errno.h>
+#    include <sys/mman.h>
+#    include <sys/stat.h>
+#    include <unistd.h>
+#endif /* _WIN32 */
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
 
 #include <errno.h>
 
@@ -252,6 +264,12 @@ struct aws_s3_mmap_part_streaming_input_stream_impl {
 
     struct aws_mmap_context *mmap_context;
     size_t offset;
+
+    long page_size;
+    void *page_address;
+    int page_offset;
+    size_t page_load_length;
+
     size_t total_length;
     size_t length_read;
 };
@@ -274,18 +292,39 @@ static int s_aws_s3_mmap_part_streaming_input_stream_read(struct aws_input_strea
     size_t read_length =
         aws_min_size(dest->capacity - dest->len, test_input_stream->total_length - test_input_stream->length_read);
 
-    void *content = aws_mmap_context_map_content(
-        test_input_stream->mmap_context,
-        read_length,
-        test_input_stream->offset + test_input_stream->length_read,
-        &out_start_addr);
-
+    if (test_input_stream->page_offset == -1) {
+        test_input_stream->page_load_length = aws_min_size(
+            test_input_stream->page_size, test_input_stream->total_length - test_input_stream->length_read);
+        size_t offset = test_input_stream->offset + test_input_stream->length_read;
+        long page_size = test_input_stream->page_size;
+        uint64_t number_pages = offset / page_size;
+        uint64_t page_starts_offset = page_size * number_pages;
+        uint64_t in_page_offset = offset - page_starts_offset;
+
+        void *mapped_data = mmap(
+            test_input_stream->page_address,
+            test_input_stream->page_load_length,
+            PROT_READ,
+            MAP_SHARED,
+            aws_mmap_context_get_fd(test_input_stream->mmap_context),
+            page_starts_offset);
+        test_input_stream->page_address = mapped_data;
+        test_input_stream->page_offset = in_page_offset;
+    }
+    read_length = aws_min_size(read_length, test_input_stream->page_size - test_input_stream->page_offset);
+    struct aws_byte_cursor page_cursor =
+        aws_byte_cursor_from_array((const uint8_t *)test_input_stream->page_address, test_input_stream->page_size);
+    aws_byte_cursor_advance(&page_cursor, test_input_stream->page_offset);
+    page_cursor.len = read_length;
+    int rt = aws_byte_buf_append(dest, &page_cursor);
+    test_input_stream->page_offset += read_length;
     test_input_stream->length_read += read_length;
-    AWS_FATAL_ASSERT(test_input_stream->length_read <= test_input_stream->total_length);
-    struct aws_byte_cursor content_cursor = aws_byte_cursor_from_array((const uint8_t *)content, read_length);
-    int rt = aws_byte_buf_append(dest, &content_cursor);
-    /* Release the content */
-    rt |= aws_mmap_context_unmap_content(out_start_addr, read_length);
+
+    if (test_input_stream->page_offset == test_input_stream->page_load_length) {
+        /* unmap the data */
+        munmap(test_input_stream->page_address, test_input_stream->page_load_length);
+        test_input_stream->page_offset = -1;
+    }
 
     return rt;
 }
@@ -350,5 +389,8 @@ struct aws_input_stream *aws_input_stream_new_from_mmap_context(
     mmap_input_stream->offset = offset;
     mmap_input_stream->length_read = 0;
     mmap_input_stream->mmap_context = mmap_context;
+    mmap_input_stream->page_size = sysconf(_SC_PAGE_SIZE);
+    mmap_input_stream->page_address = NULL;
+    mmap_input_stream->page_offset = -1;
     return &mmap_input_stream->base;
 }