So, in theory this should be pretty straight forward to do right? Well I'm new to UDF's, so how mysql is passing the data to the UDF is a bit of a mystery. I'm hoping someone can help me understand this.

I'm selecting data from a BLOB field like this:

SELECT payload_time, SUBSTR(BINARY(frame_data), FLOOR(foffset/8)+1, CEIL((flength + (foffset %8 ))/8)) FROM RawMajorFrames WHERE raw_major_frame_id=rfid INTO ptime,fdata;

You can see that I'm only taking a portion of the string, but it is still in raw form.

Now I would like to pass it to my UDF function called toDoubleArray, to convert each 8 byte section to a double.

I call the function like this: (you can ignore conv_param) SELECT toDoubleArray(fdata,"%1.3E",conv_param) INTO fdata_string;

Well, I get a Lost Connection when the function is called. Here is the UDF:

my_bool toDoubleArray_init(UDF_INIT *initid, UDF_ARGS *args, char *message) { if (args->arg_count != 3) { strcpy(message,"Wrong arguments to toDouble: should be toDoubleArray(blob)"); return 1; } initid->max_length = strlen(args->args[0])/8 * 128; return 0;

} char * toDoubleArray(UDF_INIT *initid, UDF_ARGS *args, char *result, unsigned long *length,char *is_null,char *error) { int curr_buf_ptr =0; /* current length of FloatString */ char * data = args->args[0]; /* just to make it easier to reference the string */ char * f = args->args[1]; /* get the format string */ char format[15];

sprintf(format,"%s,",f); /* put a comma at the end of format for CSV format */

for(int i=0;i<strlen(data);i +=8){ sprintf(result + curr_buf_ptr,format,*((double *)(data +i))); curr_buf_ptr = strlen(result); } result[curr_buf_ptr -1] = '\0'; *length = strlen(result); return result; } This should return a comma delimited list of double values in a string format (ascii representation).

Like I said, I'm new to UDF's so it is likely I'm not aware of conventions to follow that are well known to others.

Any help would be great.

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