From: Martin Ling <redacted>
Date: Fri, 24 Jan 2020 04:00:13 +0000 (+0000)
Subject: windows: Use correct variant of CreateFile.
X-Git-Url: https://sigrok.org/gitweb/?p=libserialport.git;a=commitdiff_plain;h=e47c7dcbffa04583d1e94d9c359784fc14a59d88

windows: Use correct variant of CreateFile.

When built with MSVC and unicode enabled, using CreateFile gave:

warning C4133: 'function': incompatible types - from 'char *' to 'LPCWSTR'

CreateFile is a macro expanding to either CreateFileW if unicode
mode is enabled, or CreateFileA if not.

For CreateFileW, the filename is a UTF-16 string. For CreateFileA
it is an 'ANSI' string, meaning 8-bit chars in the current Windows
code page.

We do need to stick to 8-bit strings for port names, since
sp_get_port_by_name() and sp_get_port_name() are defined with
char * types, and that is what we store in struct sp_port. So
CreateFileA is the correct version to use.

Since Windows serial port names are always just 'COM' and a digit,
with a '\\.\' prefix for higher numbers, encoding is fortunately
not an issue - ASCII, UTF-8 and all the Windows code pages seem to
be equivalent for these characters.

We should however explicitly document what the encoding of strings
accepted and returned by libserialport is.
---

diff --git a/serialport.c b/serialport.c
index b2e4a79..0a46688 100644
--- a/serialport.c
+++ b/serialport.c
@@ -488,7 +488,7 @@ SP_API enum sp_return sp_open(struct sp_port *port, enum sp_mode flags)
 	if (flags & SP_MODE_WRITE)
 		desired_access |= GENERIC_WRITE;
 
-	port->hdl = CreateFile(escaped_port_name, desired_access, 0, 0,
+	port->hdl = CreateFileA(escaped_port_name, desired_access, 0, 0,
 			 OPEN_EXISTING, flags_and_attributes, 0);
 
 	free(escaped_port_name);
diff --git a/windows.c b/windows.c
index 0521716..bc07e23 100644
--- a/windows.c
+++ b/windows.c
@@ -467,9 +467,9 @@ SP_PRIV enum sp_return get_port_details(struct sp_port *port)
 			if (!(escaped_port_name = malloc(strlen(port->name) + 5)))
 				RETURN_ERROR(SP_ERR_MEM, "Escaped port name malloc failed");
 			sprintf(escaped_port_name, "\\\\.\\%s", port->name);
-			handle = CreateFile(escaped_port_name, GENERIC_READ, 0, 0,
-			                    OPEN_EXISTING,
-			                    FILE_ATTRIBUTE_NORMAL|FILE_FLAG_OVERLAPPED, 0);
+			handle = CreateFileA(escaped_port_name, GENERIC_READ, 0, 0,
+			                     OPEN_EXISTING,
+			                     FILE_ATTRIBUTE_NORMAL|FILE_FLAG_OVERLAPPED, 0);
 			free(escaped_port_name);
 			CloseHandle(handle);