LibCore: Rewrite Core::Stream::read_all_impl

The previous version relied on manually setting the amount of data to
read for the next chunk and was overall unclear. The new version uses
the Bytes API to vastly improve readability, and fixes a bug where
reading from files where a single read that wasn't of equal size to the
block size would cause the byte buffer to be incorrectly resized causing
corrupted output.

1 files changed, 10 insertions, 15 deletions

diff --git a/Userland/Libraries/LibCore/Stream.cpp b/Userland/Libraries/LibCore/Stream.cpp
index cfa6da77b4..22affc4bfa 100644
--- a/Userland/Libraries/LibCore/Stream.cpp
+++ b/Userland/Libraries/LibCore/Stream.cpp
@@ -55,26 +55,21 @@ ErrorOr<ByteBuffer> Stream::read_all(size_t block_size)
 ErrorOr<ByteBuffer> Stream::read_all_impl(size_t block_size, size_t expected_file_size)
 {
     ByteBuffer data;
-    data.ensure_capacity(file_size);
+    data.ensure_capacity(expected_file_size);
 
-    size_t total_read {};
-    size_t next_reading_size { block_size };
-    for (Span<u8> chunk; !is_eof();) {
-        if (next_reading_size == block_size)
-            chunk = TRY(data.get_bytes_for_writing(next_reading_size));
-        auto const nread = TRY(read(chunk)).size();
-
-        next_reading_size -= nread;
-
-        if (next_reading_size == 0)
-            next_reading_size = block_size;
+    size_t total_read = 0;
+    Bytes buffer;
+    while (!is_eof()) {
+        if (buffer.is_empty()) {
+            buffer = TRY(data.get_bytes_for_writing(block_size));
+        }
 
+        auto nread = TRY(read(buffer)).size();
         total_read += nread;
-
-        if (nread < block_size)
-            data.resize(total_read);
+        buffer = buffer.slice(nread);
     }
 
+    data.resize(total_read);
     return data;
 }