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Optimize unique serial number reading code for size -- remove atoi/toupper references, replace with hand-rolled code as the input has known size constraints.

This commit is contained in:
Dean Camera 2009-06-21 13:52:21 +00:00
parent 7d391eb04c
commit a34cccf099
1 changed files with 36 additions and 14 deletions
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50
LUFA/Drivers/USB/LowLevel/DevChapter9.c
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@ -182,27 +182,49 @@ static void USB_Device_GetDescriptor(void)
#if !defined(NO_INTERNAL_SERIAL) && (defined(USB_SERIES_6_AVR) || defined(USB_SERIES_7_AVR))
if (USB_ControlRequest.wValue == ((DTYPE_String << 8) | USE_INTERNAL_SERIAL))
{
uint8_t SignatureDescriptor[2 + (sizeof(int16_t) * 12)];
SignatureDescriptor[0] = sizeof(SignatureDescriptor);
SignatureDescriptor[1] = DTYPE_String;
uint16_t* SigUnicodeChars = (uint16_t*)&SignatureDescriptor[2];
for (uint8_t SerialByteNum = 0; SerialByteNum < 6; SerialByteNum++)
struct
{
char ConvSigString[3];
USB_Descriptor_Header_t Header;
int16_t UnicodeString[12];
} SignatureDescriptor;
itoa(boot_signature_byte_get(0x0E + SerialByteNum), ConvSigString, 16);
#if defined(USE_NONSTANDARD_DESCRIPTOR_NAMES)
SignatureDescriptor.Header.Size = sizeof(SignatureDescriptor);
SignatureDescriptor.Header.Type = DTYPE_String;
#else
SignatureDescriptor.Header.bLength = sizeof(SignatureDescriptor);
SignatureDescriptor.Header.bDescriptorType = DTYPE_String;
#endif
uint8_t SigReadAddress = 0x0E;
bool OddRead = false;
for (uint8_t SerialCharNum = 0; SerialCharNum < 12; SerialCharNum++)
{
uint8_t SerialByte = boot_signature_byte_get(SigReadAddress);
SigUnicodeChars[0] = toupper(ConvSigString[0]);
SigUnicodeChars[1] = toupper(ConvSigString[1]);
if (OddRead)
{
SerialByte >>= 4;
SigReadAddress++;
}
else
{
SerialByte &= 0x0F;
}
SigUnicodeChars += 2;
OddRead = !(OddRead);
if (SerialByte < 0x0A)
SerialByte += '0';
else
SerialByte += ('A' - 0x0A);
SignatureDescriptor.UnicodeString[SerialCharNum] = SerialByte;
}
Endpoint_ClearSETUP();
Endpoint_Write_Control_Stream_LE(SignatureDescriptor, sizeof(SignatureDescriptor));
Endpoint_Write_Control_Stream_LE(&SignatureDescriptor, sizeof(SignatureDescriptor));
Endpoint_ClearOUT();
return;