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Fix output report length bug

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On Windows, data shorter than the output report length must be padded.
This is because in the case of multiple reports, Windows expects the number
of bytes which are in the _longest_ report to be given to WriteFile() even
if the user is sending a report which has fewer bytes.

This allocates a temporary buffer in the case that the user passes in too
few bytes.

From: Vitali Lovich <vlovich@gmail.com>
Modified-by: Alan Ott <alan@signal11.us>
This commit is contained in:
Vitali Lovich
2011-12-31 02:47:35 +08:00
committed by Alan Ott
parent e44064cf6d
commit ee4ecc02ae
1 changed files with 31 additions and 3 deletions
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windows/hid.c
+31 -3
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@@ -125,6 +125,7 @@ extern "C" {
struct hid_device_ {
HANDLE device_handle;
BOOL blocking;
USHORT output_report_length;
size_t input_report_length;
void *last_error_str;
DWORD last_error_num;
@@ -138,6 +139,7 @@ static hid_device *new_hid_device()
hid_device *dev = (hid_device*) calloc(1, sizeof(hid_device));
dev->device_handle = INVALID_HANDLE_VALUE;
dev->blocking = TRUE;
dev->output_report_length = 0;
dev->input_report_length = 0;
dev->last_error_str = NULL;
dev->last_error_num = 0;
@@ -553,6 +555,7 @@ HID_API_EXPORT hid_device * HID_API_CALL hid_open_path(const char *path)
register_error(dev, "HidP_GetCaps");
goto err_pp_data;
}
dev->output_report_length = caps.OutputReportByteLength;
dev->input_report_length = caps.InputReportByteLength;
HidD_FreePreparsedData(pp_data);
@@ -574,15 +577,35 @@ int HID_API_EXPORT HID_API_CALL hid_write(hid_device *dev, const unsigned char *
BOOL res;
OVERLAPPED ol;
unsigned char *buf;
memset(&ol, 0, sizeof(ol));
res = WriteFile(dev->device_handle, data, length, NULL, &ol);
/* Make sure the right number of bytes are passed to WriteFile. Windows
expects the number of bytes which are in the _longest_ report (plus
one for the report number) bytes even if the data is a report
which is shorter than that. Windows gives us this value in
caps.OutputReportByteLength. If a user passes in fewer bytes than this,
create a temporary buffer which is the proper size. */
if (length >= dev->output_report_length) {
/* The user passed the right number of bytes. Use the buffer as-is. */
buf = (unsigned char *) data;
} else {
/* Create a temporary buffer and copy the user's data
into it, padding the rest with zeros. */
buf = (unsigned char *) malloc(dev->output_report_length);
memcpy(buf, data, length);
memset(buf + length, 0, dev->output_report_length - length);
length = dev->output_report_length;
}
res = WriteFile(dev->device_handle, buf, length, NULL, &ol);
if (!res) {
if (GetLastError() != ERROR_IO_PENDING) {
// WriteFile() failed. Return error.
register_error(dev, "WriteFile");
return -1;
bytes_written = -1;
goto end_of_function;
}
}
@@ -592,9 +615,14 @@ int HID_API_EXPORT HID_API_CALL hid_write(hid_device *dev, const unsigned char *
if (!res) {
// The Write operation failed.
register_error(dev, "WriteFile");
return -1;
bytes_written = -1;
goto end_of_function;
}
end_of_function:
if (buf != data)
free(buf);
return bytes_written;
}