progress on os (on files)

code/os/os.c

@@ -0,0 +1,93 @@
+#ifdef INTELLISENSE_DIRECTIVES
+#	include "os.h"
+#endif
+
+// Copyright (c) 2024 Epic Games Tools
+// Licensed under the MIT license (https://opensource.org/license/mit/)
+
+////////////////////////////////
+//~ rjf: Filesystem Helpers (Helpers, Implemented Once)
+
+B32
+os_write_data_to_file_path(String8 path, String8 data)
+{
+	B32       good = 0;
+	OS_Handle file = os_file_open(OS_AccessFlag_Write, path);
+	if(! os_handle_match(file, os_handle_zero()))
+	{
+		good = 1;
+		os_file_write(file, r1u64(0, data.size), data.str);
+		os_file_close(file);
+	}
+	return good;
+}
+
+B32
+os_write_data_list_to_file_path(String8 path, String8List list)
+{
+	B32       good = 0;
+	OS_Handle file = os_file_open(OS_AccessFlag_Write, path);
+	if( ! os_handle_match(file, os_handle_zero()))
+	{
+		    good = 1;
+		U64 off  = 0;
+		for(String8Node* n = list.first; n != 0; n = n->next)
+		{
+			os_file_write(file, r1u64(off, off+n->string.size), n->string.str);
+			off += n->string.size;
+		}
+		os_file_close(file);
+	}
+	return good;
+}
+
+B32
+os_append_data_to_file_path(String8 path, String8 data)
+{
+	B32 good = 0;
+	if(data.size != 0)
+	{
+		OS_Handle file = os_file_open(OS_AccessFlag_Write|OS_AccessFlag_Append, path);
+		if( ! os_handle_match(file, os_handle_zero()))
+		{
+			good = 1;
+			U64 pos = os_properties_from_file(file).size;
+			os_file_write(file, r1u64(pos, pos+data.size), data.str);
+			os_file_close(file);
+		}
+	}
+	return good;
+}
+
+String8
+os_string_from_file_range(Arena* arena, OS_Handle file, Rng1U64 range)
+{
+	U64 pre_pos = arena_pos(arena);
+	String8 result;
+	result.size = dim_1u64(range);
+	result.str = push_array_no_zero(arena, U8, result.size);
+	U64 actual_read_size = os_file_read(file, range, result.str);
+	if(actual_read_size < result.size)
+	{
+		arena_pop_to(arena, pre_pos + actual_read_size);
+		result.size = actual_read_size;
+	}
+	return result;
+}
+
+String8
+os_string_from_file_range_alloc(AllocatorInfo ainfo, OS_Handle file, Rng1U64 range) {
+	String8 result;
+	result.size = dim_1u64(range);
+	result.str  = alloc_array_no_zero(ainfo, U8, result.size);
+	U64 actual_read_size = os_file_read(file, range, result.str);
+	if(actual_read_size < result.size)
+	{
+		// TODO(Ed): It may be better to actually wrap the alloation in an arena and then rewind it.
+		// This would ensure resize isn't doing an expensive shrink (from a bad heap realloc, or something else)
+		// That or we just leave it up to the user to make sure to pass in an arena.
+		resize(ainfo, result.str, result.size, result.str + actual_read_size);
+		result.size = actual_read_size;
+	}
+	return result;
+}