[SETUPLIB] Code re-organization in bootsup.c and fsutil.c.

- Move the actual VBR bootcode installation helpers into fsutil.c
  (they depend on the selected filesystem).

- Introduce InstallBootCodeToDisk() and InstallBootCodeToFile()
  and bootcode.c helpers, in order to replace the several functions
  that were duplicating the same code.

base/setup/lib/bootcode.c

@@ -0,0 +1,116 @@
+/*
+ * PROJECT:     ReactOS Setup Library
+ * LICENSE:     GPL-2.0+ (https://spdx.org/licenses/GPL-2.0+)
+ * PURPOSE:     BootCode support functions.
+ * COPYRIGHT:   Copyright 2020 Hermes Belusca-Maito
+ */
+
+/* INCLUDES *****************************************************************/
+
+#include "precomp.h"
+
+#include "bootcode.h"
+
+#define NDEBUG
+#include <debug.h>
+
+
+/* FUNCTIONS ****************************************************************/
+
+NTSTATUS
+ReadBootCodeByHandle(
+    IN OUT PBOOTCODE BootCodeInfo,
+    IN HANDLE FileHandle,
+    IN ULONG Length OPTIONAL)
+{
+    NTSTATUS Status;
+    PVOID BootCode;
+    IO_STATUS_BLOCK IoStatusBlock;
+    LARGE_INTEGER FileOffset;
+
+    ASSERT(BootCodeInfo);
+
+    /* Normalize the bootcode length */
+    if (Length == 0 || Length == (ULONG)-1)
+        Length = SECTORSIZE;
+
+    /* Allocate a buffer for the bootcode */
+    BootCode = RtlAllocateHeap(ProcessHeap, HEAP_ZERO_MEMORY, Length);
+    if (BootCode == NULL)
+        return STATUS_INSUFFICIENT_RESOURCES;
+
+    /* Read the bootcode from the file into the buffer */
+    FileOffset.QuadPart = 0ULL;
+    Status = NtReadFile(FileHandle,
+                        NULL,
+                        NULL,
+                        NULL,
+                        &IoStatusBlock,
+                        BootCode,
+                        Length,
+                        &FileOffset,
+                        NULL);
+    if (!NT_SUCCESS(Status))
+    {
+        RtlFreeHeap(ProcessHeap, 0, BootCode);
+        return Status;
+    }
+
+    /* Update the bootcode information */
+    if (BootCodeInfo->BootCode)
+        RtlFreeHeap(ProcessHeap, 0, BootCodeInfo->BootCode);
+    BootCodeInfo->BootCode = BootCode;
+    /**/ BootCodeInfo->Length = Length; /**/
+
+    return STATUS_SUCCESS;
+}
+
+NTSTATUS
+ReadBootCodeFromFile(
+    IN OUT PBOOTCODE BootCodeInfo,
+    IN PUNICODE_STRING FilePath,
+    IN ULONG Length OPTIONAL)
+{
+    NTSTATUS Status;
+    OBJECT_ATTRIBUTES ObjectAttributes;
+    IO_STATUS_BLOCK IoStatusBlock;
+    HANDLE FileHandle;
+
+    ASSERT(BootCodeInfo);
+
+    /* Open the file */
+    InitializeObjectAttributes(&ObjectAttributes,
+                               FilePath,
+                               OBJ_CASE_INSENSITIVE,
+                               NULL,
+                               NULL);
+    Status = NtOpenFile(&FileHandle,
+                        GENERIC_READ | SYNCHRONIZE,
+                        &ObjectAttributes,
+                        &IoStatusBlock,
+                        FILE_SHARE_READ | FILE_SHARE_WRITE, // Is FILE_SHARE_WRITE necessary?
+                        FILE_SYNCHRONOUS_IO_NONALERT);
+    if (!NT_SUCCESS(Status))
+        return Status;
+
+    Status = ReadBootCodeByHandle(BootCodeInfo, FileHandle, Length);
+
+    /* Close the file and return */
+    NtClose(FileHandle);
+    return Status;
+}
+
+VOID
+FreeBootCode(
+    IN OUT PBOOTCODE BootCodeInfo)
+{
+    ASSERT(BootCodeInfo);
+
+    /* Update the bootcode information */
+    if (BootCodeInfo->BootCode)
+        RtlFreeHeap(ProcessHeap, 0, BootCodeInfo->BootCode);
+    BootCodeInfo->BootCode = NULL;
+    /**/ BootCodeInfo->Length = 0; /**/
+}
+
+/* EOF */